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- Herausgeber: John Wiley & Sons
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
Comprehensive resource summarizing current approaches to generating hydrogen from water and reducing CO2 into various hydrocarbons Green Energy Harvesting: Materials for Hydrogen Generation and Carbon Dioxide Reduction provides an in-depth treatment of the subject by exploring the fundamentals required for the selection of the materials, their synthesis methods, and possible ways to modify them for higher efficiency and enhanced stability. The prospects of adopting these sustainable solutions at a commercial level are summarized. Special emphasis is given to the figure-of-merits for currently developed systems for hydrogen generation and CO2 reduction and to an assessment of available materials in terms of efficacy and efficiency. Green Energy Harvesting also includes information on: * Renewable energy in general, including the role of renewable hydrogen and hydrocarbon fuels, and possible renewable energy sources * A fundamental understanding hydrogen generation and CO2 reduction * Device development and deployment status for commercial usage and applications of H2 and hydrocarbon fuels in various sectors * Electrocatalysts, 2D materials, and hybrid materials for CO2 reduction and H2 generation Green Energy Harvesting is a highly useful guide for both novice and experienced researchers involved in renewable energy and carbon dioxide utilization that explains the current state of the field and discusses future perspectives.
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Green Energy Harvesting
Materials for Hydrogen Generation and Carbon Dioxide Reduction
Edited by
Pooja Devi
CSIR, DelhiIndia
This edition first published 2023
© 2023 John Wiley & Sons Ltd
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Contents
Cover
Title page
Copyright
List of Contributors
Preface
Acknowledgements
Abbreviations
1 Renewable Energy: Introduction, Current Status, and Future Prospects
2 Hydrogen and Hydrocarbons as Fuel
3 Fundamental Understanding and Figure of Merits for Electrocatalytic and Photoelectrocatalytic H
2
Production
4 Single Atom Catalysts for Hydrogen Production from Chemical Hydrogen Storage Materials
5 Non-Noble Metal Ion-Based Metal-Organic Framework Electrocatalyst for Electrochemical Hydrogen Generation
6 2D Materials for CO
2
Reduction and H
2
Generation
7 Hybrid Materials for CO
2
Reduction and H
2
Generation
8 Possible Ways for CO
2
Reduction into Hydrocarbons
9 MXenes for CO
2
Reduction and H
2
Generation
10 The Role of Transition Metal-Based Electrocatalyst Toward Efficient Electrochemical Hydrogen Fuel Generation
11 Devices Development and Deployment Status for Commercial Usage: H
2
Production and CO
2
Utilization
Index
End User License Agreement
List of Tables
CHAPTER 01
Table 1.1 RECAI scores...
Table 1.2 Technology-specific...
Table 1.3 Installed capacity...
CHAPTER 02
Table 2.1 Overall details...
CHAPTER 03
Table 3.1 Comparison of...
Table 3.2 Comparison of...
CHAPTER 04
Table 4.1 Comparison of...
CHAPTER 05
Table 5.1 Representation of...
Table 5.2 Representation of...
CHAPTER 07
Table 7.1 Hybrid materials...
Table 7.2 Hybrid materials...
CHAPTER 08
Table 8.1 Merits and...
Table 8.2 The CO...
CHAPTER 09
Table 9.1 Photocatalytic reduction...
Table 9.2 Comparative collection...
CHAPTER 11
Table 11.1 Challenges and...
List of Illustrations
CHAPTER 01
Figure 1.1 Geographical breakdown...
Figure 1.2 U.S...
Figure 1.3 CO...
Figure 1.4 Illustration of...
Figure 1.5 Illustration showing...
CHAPTER 02
Figure 2.1 Schematic representation...
Figure 2.2 Schematic representation...
Figure 2.3 Schematic representations...
Figure 2.4 Schematic representation...
Figure 2.5 Components of...
Figure 2.6 Schematic of...
Figure 2.7 Broad classification...
Figure 2.8 Schematic representation...
Figure 2.9 Schematic representation...
Figure 2.10 Polarization curve...
CHAPTER 03
Figure 3.1 (a) Source...
Figure 3.2 Advantages of...
Figure 3.3 (a) HER...
Figure 3.4 (a) Graphical...
Figure 3.5 (a) Diagram...
Figure 3.6 (a) Photocurrent...
CHAPTER 04
Figure 4.1 (a) HAADF...
Figure 4.2 HAADF-STEM...
Figure 4.3 Ac HAADF...
Figure 4.4 (a) ac...
Figure 4.5 (a) ac...
Figure 4.6 (a) Synthetic...
CHAPTER 05
Figure 5.1 Hydrogen production...
Figure 5.2 (a) Types...
Figure 5.3 Strategies for...
Figure 5.4 (a) Crystal...
CHAPTER 06
Figure 6.1 (a) Schematic...
Figure 6.2 Electrocatalytic activities...
Figure 6.3 (a) Schematic...
Figure 6.4 (a) TEM...
Figure 6.5 (a) SEM...
Figure 6.6 SEM, TEM...
CHAPTER 07
Figure 7.1 Impression of...
Figure 7.2 Schematic representation...
Figure 7.3 Schematic representation...
Figure 7.4 Representation of...
Figure 7.5 Research findings...
Figure 7.6 Schematic representation...
CHAPTER 08
Figure 8.1 (a) Mechanism...
Figure 8.2 (a) Yield...
CHAPTER 09
Figure 9.1 (a) MXenes...
Figure 9.2 (a) A...
CHAPTER 10
Figure 10.1 Mechanism of...
Figure 10.2 (a) SEM...
Figure 10.3 (a) TEM...
Figure 10.4 (a) The...
Figure 10.5 (a) Schematic...
CHAPTER 11
Figure 11.1 (a) Hydrogen...
Figure 11.2 (a) MoS...
Figure 11.3 (a–...
Figure 11.4 (a) Schematic...
Figure 11.5 Schematic of...
Figure 11.6 For PS...
Figure 11.7 (a) Illustration...
Guide
Cover
Title page
Copyright
List of Contributors
Preface
Acknowledgements
Abbreviations
Table of Contents
Begin Reading
Index
End User License Agreement
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List of Contributors
Chandraraj AlexCentre for Nano and Soft Matter Sciences, Shivanapura, Bengaluru,Karnataka, India
Soumen BasuSchool of Chemistry and Biochemistry, Thapar Institute of Engineering and Technology, Patiala, Punjab, [email protected]
Laxmidhar BesraMaterials Chemistry Department, CSIR-Institute of Minerals and Materials Technology, Bhubaneswar, Odisha,India
Rajani Kumar BorahInorganic and Physical Chemistry Laboratory (IPCL), Council of Scientific and Industrial Research (CSIR)-Central Leather Research Institute (CLRI), Chennai, India
Tribani BoruahInstitute of Nano Science and Technology (INST), Mohali, Punjab, India
Rapaka S. Chandra BoseCentre for Materials for Electronics Technology, Thrissur, Kerala,India
Sriparna ChatterjeeMaterials Chemistry Department, CSIR-Institute of Minerals and Materials Technology, Bhubaneswar, Odisha, [email protected]
Sampath ChinnamDepartment of Chemistry, M.S Ramaiah Institute of Technology (Affiliated to Visvesvaraya Technological University, Belgaum), Bengaluru, Karnakata, [email protected]
Tulsi Satyavir DabodiyaDepartment of Chemical and Materials Engineering, University of Alberta, Alberta,[email protected]
Pooja DeviMaterials Science and Sensor Application,Central Scientific Instruments Organisation,Chandigarh, Punjab, [email protected]
Ramendra Sundar DeyInstitute of Nano Science and Technology (INST), Mohali, Punjab, [email protected]
Adarsh P. FatrekarInorganic and Physical Chemistry Laboratory (IPCL), Council of Scientific and Industrial Research (CSIR)-Central Leather Research Institute (CLRI), Chennai, India
Twinkle GeorgeCentre for Nanoscience and Technology, Madanjeet School of Green Energy Technologies, Pondicherry University Kalapet, Puducherry, India
Demudu Babu GorleMaterials Research Centre, Indian Institute of Science, Bangalore, Karnataka, India
Neena S. JohnCentre for Nano and Soft Matter Sciences, Shivanapura, Bengaluru,Karnataka, [email protected]
KamleshAcademy of Scientific & Innovative Research (AcSIR), Ghaziabad, Uttar Pradesh, India
Maryam Sadat KiaiNano-Science and Nano-Engineering Program, Graduate School of Science, Engineering and Technology, Istanbul Technical University, Istanbul, Turkey
N. Usha KiranMaterials Chemistry Department, CSIR-Institute of Minerals and Materials Technology, Bhubaneswar, Odisha, India
Indu KumariDepartment of Biotechnology, Chandigarh College of Technology, Chandigarh Group of Colleges, Landran, Mohali, Punjab, India
A. Lakshman KumarCSIR-Central Electrochemical Research Institute, Karaikudi, Tamil Nādu,India
Rameez Ahmad MirDepartment of Materials Science Engineering, University of Toronto, Canada
Manish MudgalAcademy of Scientific & Innovative Research (AcSIR), Ghaziabad, Uttar Pradesh, India
Annapurna NowduriDepartment of Engineering Chemistry, Andhra University College of Engineering (A), Andhra University, Visakhapatnam, [email protected]
Swapna PahraMaterials Science and Sensor Application, Central Scientific Instruments Organisation, Chandigarh, Punjab,India
Panchami R.Inorganic and Physical Chemistry Laboratory (IPCL), Council of Scientific and Industrial Research (CSIR)-Central Leather Research Institute (CLRI), Chennai, India
O.P. PandeyCenter of Excellence for Emerging Materials (CEEMS)-Virginia Tech (VT), TIET, Patiala, Punjab, [email protected]
Srikanth PonnadaSustainable Materials and Catalysis Research Laboratory (SMCRL), Department of Chemistry, Indian Institute of Technology Jodhpur, Karwad, Jodhpur, India
Satya PrakashAcademy of Scientific & Innovative Research (AcSIR), Ghaziabad,India
Pankaj RaizdaSchool of Chemistry, Shoolini University, Himachal Pradesh, India
Rakesh K. SharmaSustainable Materials and Catalysis Research Laboratory (SMCRL), Department of Chemistry, Indian Institute of Technology Jodhpur,Jodhpur, [email protected]
Sweta SharmaAcademy of Scientific & Innovative Research (AcSIR), Ghaziabad,India
Archana SinghCSIR – Advanced Material and Processes Research Institute, Bhopal, [email protected]
Kapil Dev SinghDepartment of Material Science and Engineering, National Institute of Technology, Hamirpur, Himachal Pradesh, India
Pardeep SinghSchool of Chemistry, Shoolini University, Himachal Pradesh, India
Shelly SinglaSchool of Chemistry and Biochemistry, Thapar Institute of Engineering and Technology, Patiala, India
A.K. SrivastavaCSIR – Advanced Material and Processes Research Institute, Bhopal, India
Deepika TanwarAcademy of Scientific & Innovative Research (AcSIR), Ghaziabad, India
Anupma ThakurDiscipline of Chemical Engineering, Indian Institute of Technology Gandhinagar, Gujarat, [email protected]
Sanjay UpadhyaySchool of Physics and Materials Science (SPMS), Thapar Institute of Engineering and Technology, Patiala, India
Amit A. VernekarInorganic and Physical Chemistry Laboratory (IPCL), Council of Scientific and Industrial Research (CSIR)-Central Leather Research Institute (CLRI), Chennai, [email protected]
Arumugam Vadivel MuruganCentre for Nanoscience and Technology, Madanjeet School of Green Energy Technologies, Pondicherry UniversityKalapet, Puducherry, India
Preface
This book, Green Energy Harvesting: Materials for Hydrogen Generation and Carbon Dioxide Reduction, concisely summarises the possible ways to harvest hydrogen from water and also reduce CO2 into various hydrocarbons. A special emphasis is given to the figure-of-merits for the currently developed system/materials for hydrogen generation and CO2 reduction. We further have summarised the trends in materials innovation and the corresponding state of the art to achieve the desired efficiency and stability, while also considering the cost of production. Finally, the future prospects of this sustainable alternative fuel is summarized for the possible future strategy in adopting these sustainable solutions at the commercial level.
This book can be used to develop an understanding in this field in terms of fundamentals, materials advances, and devices deployment. The students and researchers from energy, environment, materials, chemistry, electrochemistry, and similar backgrounds will find it useful in their respective fields.
Acknowledgements
The kind permission of the Director of CSIO to execute this book project is highly acknowledged. All the reviewers who have reviewed the chapters in this book and suggested necessary improvements are also acknowledged.
Abbreviations
AB
ammonia borane
ABPE
applied bias photon to current efficiency
ac
aberration-corrected
AC
activated carbon
AEL
alkaline electrolysis
AEM
alkaline exchange membrane
AFC
alkaline fuel cell
Ag
silver
Al
aluminum
ALD
atomic layer deposition
APCE
absorbed photon-to-current efficiency
Au
gold
B
boron
BASF
Baden Aniline and Soda Factory
BC
7
N
borocarbonitride
BDC
benzenedicarboxylic acid
BHT
benzene-1,2,3,4,5,6-hexathiol
C
3
N
4
carbon nitride
C
carbon
CA
California
CB
conduction band
CBE
conduction band edge
C
dl
double layer capacitance
CdS
cadmium sulfide
CH
4
methane
CNT
carbon nanotube
Co
cobalt
CO
carbon monoxide
CO
2
carbon dioxide
COD
Chemical Oxygen Demand
COOH
carboxyl intermediate
CoPC
Co phthalocyanine
CoPS
Co-phosphosulphides
CoP|S
Co-phosphosulfate nanoparticles
CO
2
RR
CO
2
reduction reaction
COVID-19
Coronavirus disease 2019
CS
catalytic selectivity
C
s
specific capacitance
CTF
covalent triazine framework
Cuf
copper foam
CUMS
coordinatively unsaturated metal sites
CV
cyclic voltammetry
CVD
chemical vapor deposition
1D
one-dimensional
2D
two-dimensional
3D
three-dimensional
DBD
dielectric barrier discharge
DFT
density functional theory
DMSO
dimethyl sulfoxide
DOE
Department of Energy
DOS
density of states
DRIFTS
CO-diffuse reflectance infrared Fourier transform spectroscopy
DTM
double transition-metal
EC
electrocatalyst
EC
electrochemical
ECSA
electrochemical active surface area
EELS
electron energy-loss spectroscopy
EF
energy efficiency
EG
ethylene glycol
EH
vac
H-vacancy energy
EIA
Energy Information Administration
EIS
electrochemical impedance spectroscopy
ENE-FARM
energy and farm
EV
electrovolts
EXAFS
extended X-ray absorption fine structure
EY
Ernst & Young Global Ltd
FA
formic acid
fcc
face-centred cubic
FCH JU
Fuel Cells and H
2
Joint Undertaking
FE
faradic efficiency
Fe
iron
FeO
x
iron oxide
FTO
conductive surface
ΔG
Gibbs’s free energy
GCE
glassy carbon electrode
GDL
gas diffusion layer
GGNR
graphene/graphene nanoribbon
GO
graphene oxide
Δh
enthalpy
Δs
entropy
2H
hydrogen
H
2
hydrogen
H
ads
hydrogen adsorption
HAADF
high-angle annular dark-field
h-BN
hexagonal boron nitride
HCN
heptazine-based crystalline carbon nitride
HCOOH
formic acid
hcp
hexagonal close packing
HDH
hetero-dimensional hybrid architecture
HDS
hydrodesulfurization
HEP
H
2
evolution photocatalyst
HER
hydrogen evolution reaction
HES
hydrogen energy storage
HF
hydrofluoric acid
HRTEM
high resolution transmission electron microscope
HSSA
high specific surface area
IC
ion chromatograph
ICP-AES
inductively coupled plasma atomic emission spectroscopy
IL
ionic liquid
i
-MAX
in-plane MAX
IPCC
Intergovernmental Panel on Climate Change
IPCE
Incident Photon-to-Current Efficiency
IPHE
International Partnership for H
2
and Fuel Cells in the Economy
i-PrA
isopropylamine
IQE
internal quantum efficiency
iR drop
ohmic potential drop
IrO
2
iridium oxide
j
o
exchange current density
KOH
potassium hydroxide
LB
Langmuir Blodgett
LBL
layer by layer
LDH
layered double hydroxide
LM Wind
Lunderskov Møbelfabrik
LOHC
liquid organic hydrogen carrier
LSV
linear sweep voltammetry
M
metal
MCFC
molten carbonate fuel cell
MD
molecular dynamic
MEA
membrane electrode assembly
MILD
minimally intensive layer delamination
Mo
molybdenum
Mo
2
C
molybdenum carbide
MOF
metal-organic framework
MoP
molybdenum phosphide
MoS
2
molybdenum disulfide
MoSe
2
molybdenum diselenide
MWCNT
multi-walled carbon nanotubes
MX
metal complex
N
nitrogen
N
2
O
nitrous oxide
NASA
National Aeronautics and Space Administration
Nb
niobium
ND
nanodisc
ND
nano-dots
NEXAFS
near edge X-ray absorption fine structure
NF
nanoflake
NG
N-doped graphene
NGO
N-doped graphene oxide
NH
4
HF
2
ammonium bifluoride
NHE
normal hydrogen electrode
Ni
nickel
NiCo-UMOFN
Ni-Co MOF nanosheet
Ni-G
Ni-graphene
NP
nanoparticle
O
2
oxygen
OEP
O
2
evolution photocatalyst
OER
oxygen evolution reaction
OH
hydroxyl
o
-MAX
out-of-plane MAX
OPEC
organic photoelectrochemical
ORR
oxygen reduction reaction
Os
osmium
Ov
oxygen vacancy
QD
quantum dots
P
phosphorus
PAFC
phosphoric acid fuel cell
PC
photocatalytic
PCE
photo-chemical-efficiency
PCG
porous conductive graphene
Pd
palladium
PDMS
polypyrrole, polydimethyl siloxane
PEC
photoelectrocatalyst
PEC
photoelectrochemical
PEC-HER
photoelectrochemical-hydrogen evolution reaction
PEM
(polymer) electrolyte membrane
PEM
proton exchange membrane
PEMEL
Proton Exchange Membrane Electrolysis
PEMFC
proton exchange fuel cell
PH
3
phosphine gas
PL
photoluminescence
PLD
pulsed laser deposition
POM
polyoxometalate
POMOF
polyoxometalate-based metal-organic framework
Pt
platinum
PV
photovoltaic
PVEC
photovoltaic electrocatalyst
PXRD
powder X-ray diffraction
QE
quantum efficiency
R
ct
charge transfer
R&D
Research and Development
RDS
rate determining step
RECAI
Renewable Energy Country Attractiveness Index
RES
renewable energy resources
rGO
reduced graphene oxide
RHE
reversible hydrogen electrode
Ru
ruthenium
S
sulfur
SA
surface area
SAA
single-atom alloy
SAC
single-atom catalyst
SCE
saturated calomel electrode
SCWG
supercritical water gasification
Se
selenium
SEM
scanning electron microscope
SFE
Solar-to-Fuel efficiency
SMR
steam methane reforming
SOEL
high-temperature solid oxide water electroysis
SOFC
solid oxide fuel cell
SPR
van der Waals
SSA
specific surface area
STEM
scanning transmission electron microscopy
STH
solar-to-hydrogen
Ta
tantalum
TA
terminal alkyne
TaS
2
tantalum disulfide
TBA
tetrabutylammonium
TEOA
triethanolamine
TNAOH
tetrabutylammonium hydroxide
TDOS
total density of states
TEM
transmission electron microscope
THT
triphenylene-2,3,6,7,10,11-hexathiolate (THT)
TM
transition metal
TMAOH
tetramethylammonium hydroxide
TMC
transition metal carbide
TMD
transition metal dichalcogenide
TMN
transition metal nitrides
TMO
transition metal oxide
TMP
transition metal phosphide
TMPS
TM-phosphosulphides
TOF
turnover frequency
TON
turnover number
TOP
trioctylphosphine
TV
television
TW
terawatt
UCLA
University of California, Los Angeles
UPS
UV photoelectron spectroscopy
USEPA
United States Environmental Protection Agency
UV
ultraviolet
VB
valance band
vdW
van der Waals
VO
2
vanadium dioxide
VS
2
vanadium sulfide
VSe
2
vanadium selenide
VS
2
s
vanadium sulfides
W
use.out
useful work output
W
rev.out
reversible work output
WC
tungsten carbide
WCHN
WSe
2
/CNTs hybrid network
WG
waved graphene
WGSR
water-gas shift reaction
WHO
World Health Organisation
φ
M
work function
φ
M
semiconductor work function
WS
2
tungsten disulfide
WSe
2
tungsten diselenide
XPS
X-ray photoelectron spectroscopy
XRD
X-ray diffraction
XANES
X-ray absorption near-edge spectroscopy
YSZ
yttria-stabilized zirconia
ZIF
zeolite imidazolate framework
1 Renewable Energy Introduction, Current Status, and Future Prospects
Srikanth Ponnada1, Indu Kumari2, Sampath Chinnam3, Maryam Sadat Kiai4, A. Lakshman Kumar5, Rapaka S. Chandra Bose6, Demudu Babu Gorle7, Annapurna Nowduri 8,* and Rakesh K. Sharma1,*
1 Sustainable Materials and Catalysis Research Laboratory (SMCRL, Department of Chemistry, Indian Institute of Technology Jodhpur, Karwad, Jodhpur 342037, India2 Department of Biotechnology, Chandigarh College of Technology, Chandigarh Group of Colleges, Landran, Mohali, Punjab 140307, India3 Department of Chemistry, M.S Ramaiah Institute of Technology (Affiliated to Visvesvaraya Technological University, Belgaum), Bengaluru, Karnataka 560054, India4 Nano-Science and Nano-Engineering Program, Graduate School of Science, Engineering and Technology, Istanbul Technical University, Istanbul 34469, Turkey5 CSIR-Central Electrochemical Research Institute, Karaikudi 630003, Tamil Nādu, India6 Centre for Materials for Electronics Technology, Thrissur 680581, Kerala, India7 Materials Research Centre, Indian Institute of Science, Bangalore 560012, India8 Department of Engineering Chemistry, Andhra University College of Engineering (A), Andhra University, Visakhapatnam 530003, India* Corresponding Author
1.1 Introduction
Continuous large-scale exploitation of our valuable natural resources, i.e., water, energy, and land has resulted in a drastic change in average global temperature [1]. While considering the world’s future needs, mitigating climate change without misusing these resources becomes the prime challenge of human civilization today. However, based on our former scrutiny of energy resources, it is possible to sustain and broaden a prosperous civilization by improving air quality, energy access, and energy security [2]. Energy resources mainly consist of three groups, i.e., fossil fuels, renewable resources, and nuclear resources [3]. Since the recovery of non-renewable resources (i.e., fossil fuels and nuclear resources) is not possible after their depletion, the demand of renewable energy resources (RES) increases.
Renewable energy is the form of sustainable energy that can be derived directly or indirectly from the environment and sources that are persistently replenished by nature. The main advantages of RES include no wastage, low maintenance cost, are economical, and no depletion. Renewable energy plays a major role in energy security and reducing greenhouse gas emissions. In general, roughly 8 billion metric tons of carbon are being consumed and dumped into the atmosphere each year; deforestation contributes to 1.5 billion, with 6.5 billion tons from fossil fuels [4]. The great consumption of fossil fuels has caused serious damage to the environment and disrupted the whole ecological cycle. According to the experts, nonrenewable resources will become depleted within 53 to 110 years and therefore are not sufficient to fulfill the world’s energy needs [5]. In addition, the burning of fossil fuels has led to poor air quality and global warming. According to the World Health Organisation (WHO), around 7 million deaths were recorded globally in 2016 due to household and ambient air pollution. In this data, around 94% of deaths were from low- and middle-income countries [6].
Thus, many countries have turned to renewable resources to meet their rising energy demands and to reduce air pollution. However, at present, RES provides only 14% of the total energy world energy demands [7], though several efforts have been taken up by countries worldwide. For instance, the binding target of 27% (by year 2030) has been adjusted by the European Union, that was earlier decided in 2014 to reach 32% by June 2018. According to this new target, by 2023, countries are going to discuss an even higher target [8]. The Government of India has also set an ambitious renewable energy target of 175 GW to be completed by 2022, consisting of 60 GW of wind and 100 GW of solar energy, and 10 GW of bio-power and 5 GW from small hydro-power [9]. In 2019, India was ranked fifth in wind power and solar power and fourth in renewable power installed capacity. The Government of India is planning to achieve 227 GW of renewable energy capacity by 2022, that includes 114 GW of solar capacity and 67 GW of wind power capacity, i.e., more than its 175 GW target [10]. Since July 2021, India holds 25.2% of the overall installed capacity of hydro projects and provides great options for green data centers’ development. The Government of India’s target is to establish a renewable energy capacity of 523 GW by 2030, including 73 GW from hydropower and about 280 GW expected from solar power. Throughout 2023, around 5000 compressed biogas plants are planned to be set up across India [11].
China, the largest energy producer and consumer, has a pivotal role in the global energy transition. China has also set targets to reduce carbon emissions per unit of gross domestic product by 60–65% from 2005 to 2030 [12]. In 2017, more than half of all global solar photovoltaic (PV) capacity additions of 94 GW were contributed by China. Also, solar PV deployment quotas were introduced by the Government of China in 2018 [13]. By the end of 2021, China and U.S. aimed to produce 600T Wh and 400 TWh, respectively, i.e., jointly representing more than half of the global wind power capacity. Figure 1.1 represents the geographical breakdown of the renewable power generation capacity additions, wherein China accounts for over one-third, followed by the United States, India, and the European Union [10].
Figure 1.1 Geographical breakdown of renewable power generation capacity additions, 2018–2050. Reproduced from [10] / With permission of Elsevier.
In 2021, the U.S. Energy Information Administration’s (EIA), with the recent invention of electricity generators, enabled power plant owners to generate 39.7 GW of new electricity capacity to start commercial operation [14], wherein solar accounts for the largest share of new capacity at 39% and wind accounts for 31% [14]. The U.S. primary energy consumption, in terms of energy source, is represented in Figure 1.2. According to the EIA, the tendency of large-scale battery storage more than quadrupled by late 2021. In Florida, the world’s largest solar powered battery was construction and scheduled to be operational by the end of 2021 [14].
Figure 1.2 U.S. primary energy consumption by energy source, 2020.
The main advantage of RES is its distribution over a wide range of geographical areas. The most common types of renewable resources include hydropower, biomass energy, geothermal power, wind energy, solar energy, and tidal energy (Scheme 1.1). These forms of energy are interconnected to each other in various ways. For instance, the Sun’s heat drives the winds, and wind turbines capture its energy. Then, the Sun’s heat and wind collectively lead to the evaporation of water that converts into rain or snow and finally flows downhill forming rivers or streams. Their energy can be utilized by hydroelectric power. In addition to rain and snow, sunlight is also responsible for the growth of plants and vegetation. The organic matter made by plants is the biomass that can be used for various purposes, such as transportation, fuel, electricity, or chemicals that lead to the generation of bioenergy. Hydrogen can be burned as a fuel or transformed into electricity. Though it is always found in combination with other elements, it can be used only after its separation from another element.
Scheme 1.1 Schematic illustration of different types of renewable energy.
There is some RES available that does not come directly from Sun. For instance, geothermal energy uses the heat present inside the Earth and can be used in various applications, including electric power production and heating of buildings. Geothermal energy was first used for commercial purposes in 1900s by the Italians [15]. Turkey is known for its rich geothermal energy resources and ranked fifth after China, Japan, USA, and Iceland [16]. Additionally, the energy produced from the oceans’ tides can also be used as an RES. There are many sources available that can generate ocean energy. For instance, ocean energy can be generated from the the gravitational pull of the moon and Sun upon the Earth. Also, it can be driven by both the tides and winds [17].
Climate change and local air pollution are among the major factors responsible for energy transition worldwide. Countries such as China and India are greatly impacted by local air pollution. In Europe the rise in harmful health effects have been observed due to air pollution, largely related to energy supply and use. Thus, energy transition needs to lessen emissions substantially, whilst ensuring that sufficient energy is still available for economic growth. The data in Figure 1.3 shows that the CO2 emissions intensity of global economic activity needs to be reduced by 85% between 2015 and 2050, and CO2 emissions need to be lowered by more than 70% compared to the Reference Case in 2050. It is clear that renewable energy and energy efficiency measures can successfully attain 94% of the necessary emissions reductions by 2050, as compared to the Reference Case. The remaining 6% would be achieved via other options in terms of reduction of activities leading to CO2 emissions, i.e., fossil fuel switching, continued use of nuclear energy, and carbon capture and storage [10] (Figure 1.3).
Figure 1.3 CO2 emission reduction potential by technology in the Reference Case and REmap, 2010–2050. Note: the figure shows the breakdown of energy-related CO2 emissions by technology in the REmap Case compared to the Reference Case. The figure excludes emissions from non-energy use (feedstocks). Reproduced from [10] / With permission of Elsevier.
Renewable energy and sustainable development are very much related to each other. The development of renewable energy with reduced CO2 emissions has generated new interest in storage, thus it has become a chief component of sustainable development. Energy storage can improve the system flexibility, mitigate power variations, and enable the storage and transmission the electricity produced by different RES, including solar and wind energy. The various storage technologies are used in electric power systems such as chemical or electrochemical, mechanical, thermal, or electromagnetic storage [18]. For electrochemical storage, different batteries are available, including lithium-sulfur, nickel-cadmium, nickel-zinc, lead-acid, ZnO, etc. [18, 19a–c]. These batteries have remarkable properties; for example, high charge/discharge efficiency, long life, and low self-discharge. For hydrogen energy storage (HES), the energy is stored in the form of hydrogen where it is retransformed to electricity by a fuel cell to energize the power plants. Hydrogen can store energy for a long time by using various HES models such as compressed, liquefied, metal hydride, etc. [18]. Mechanical energy includes flywheel energy storage, pumped HES, and compressed air energy storage [18]. In thermal energy storage, the energy is stored by varying the temperature of the material such as by heating or cooling [18]. In India, it is predicted that about 49% of the total electricity will be produced by renewable energy owing to the more efficient batteries for the storage of electricity, which will further cut the solar energy by 66% as compared to present costs [18, 19].
Based on the above discussion, the renewable concept has been accepted worldwide and is now a central energy policy unit. Though the RES has numerous advantages, the concept might even be hazardous toward the efforts taken to combat climate change or power sustainable development [20]. This is because of the dependency of these solutions on geographical sites and climatic conditions. The careful planning, measures, and location selection can help to eliminate these limitation of RES. Among the different types of RES, many organizations have discussed the exceptional role of biomass combustion in various renewable energy strategies and scenarios [21, 22]. However, it has few environmental issues, such as biomass energy being an insufficient source of energy when compared with fossil fuels, growing and harvesting biomass, transportation to the power plant, and combustion, all of which can add to global warming emissions.
In the case of hydropower, major disadvantages include high costs of facilities, changes in stream regimens (where it can affect plants, fish, and wildlife by changing stream levels, flow patterns, and temperature), dependence on precipitation, deluge of land and wildlife habitat, and dislocation of people living in the vicinity of the reservoir [23]. Among RES, solar power is considered the true renewable resource and the most abundant renewable resource on the Earth. However, solar sources provide basic power, out of which humans consume only 0.04% due to the high cost of PV panels, which are more expensive than burning fossil fuels. Apart from its advantages, such as no wastage and no emission of greenhouse gases, its main disadvantages are the costs involved, and dependency on sunshine [15]. Like other RES, wind energy also has some limitations; for example, high maintenance and transmission costs, the irregular and unpredictable nature of wind power, noise pollution, interruption of TV and radio signals, killing of migratory birds, and requirement of large geographical areas for the setups [15, 24]. Similarly, the drawbacks of geothermal energy resources include finding a suitable location for the setup; safety issues, such as volcanoes concentrated near geothermal energy sources and earthquakes at these points being more frequent; relatively lesser energy than other RES; and the steam can include toxic materials such as mercury, ammonia, arsenic, etc. [15, 25]. Thus, more attention has to be paid toward these issues, and energy policies are much needed that should focus on solving such disadvantages of RES.
1.2 Impact of COVID-19 on Renewable Energy Resources
The ongoing COVID-19 pandemic is having a major impact on the renewable power sector around the world. During the pandemic, the full-lockdown measures ordered by governments worldwide resulted in depressed electricity demand (~15–30%) in many countries with the generation of an oversupply of existing power capacity.
As the crisis hit, a huge drop in global energy investment became apparent with spending plunging in each main sector in 2020 [26]. For instance, a wind power plant in North Dakota was closed due to the spread of the pandemic [27]. In Spain, LM Wind and Siemens Gamesa, top competitors in the wind energy market when the government announced a nationwide lockdown, stopped their wind turbine blade plant production [28]. The same effects have been observed in the solar industry; for example, delays in the supply chain and difficulties in tax stock markets [29]. India, the world’s fourth largest in the wind sector, was also affected by the outbreak of the pandemic. Its chief aims of generating 60 GW of energy by the end of 2022 and 450 GW by 2030, both were affected by these unforeseen situations [30]. Reports show that around 600 MW of new wind power addition is expected to overcome 2.60 GW of loss in the coming few years. In 2019, nations such as China, the U.S., India, the UK, and Spain had accounted for 70% of new wind power additions; however, at present they are among the countries most affected by the pandemic [31]. Additionally, many thermal plants were closed during the lockdown period [32]. Thus, the RES has faced various obstacles due to the pandemic; however, followed by new capacity additions, the energy sector has disregarded the pandemic and sustained its growth.
1.3 Green Hydrogen as Promising RES
Among different types of RES, hydrogen energy is one of the very versatile forms of energy that can be used in liquid or gaseous form. Hydrogen exists in abundant amounts and its supply is almost unlimited. Hydrogen can be produced or transported anywhere and can store large amounts of electricity for extensive periods of time. Every year, around 70 million metric tons of hydrogen is manufactured globally that is used in different areas; for example, food processing, steel manufacturing, ammonia production, chemical and fertilizer production, metallurgy, etc. It is predicted that in the universe, around 90% of all atoms are hydrogen, more than any other element. However, hydrogen atoms are not present in nature by themselves. Thus, hydrogen atoms need to be decoupled from other elements or molecules with which they occur to produce hydrogen. The sustainability of hydrogen energy depends on the method of decoupling used.
Hydrogen energy can be transformed into electricity or fuel and various methods are available for its production. However, hydrogen can be generated at very low cost from entirely carbon-free sources by means of wind and solar energy. Based on the process and source of production, H2 is classified into four different categories (Figure 1.4) [33, 34].
Figure 1.4 Illustration of types of hydrogen and its sources.
1.3.1 Types of Hydrogen
Grey Hydrogen: H2 produced from fossil fuels (i.e., hydrogen produced from methane using steam methane reforming (SMR) or coal gasification) is categorized as “greyH2.” Production of grey H2 results in CO2 emission. The majority of H2 produced globally is grey H2.
Blue Hydrogen: H2 produced from fossil fuels, where the generated carbon emissions are captured or utilized, is considered “blue H2.” Hydrogen produced from nuclear energy is also considered as blue H2 due to the small amount of carbon emissions.
Turquoise Hydrogen: H2 that makes use of natural gas as a feedstock while emitting no CO2. The carbon in methane is converted to solid carbon black by the pyrolysis process. Since there is already a market for carbon black, this provides an extra revenue source. Carbon black can be stored more easily than CO2. Production of Turquoise hydrogen is still in the pilot stage.
Green Hydrogen: H2 generated from hydrocarbon-free renewable resources or excess process heat via a non-fossil process such as electrolysis of water is “green H2,” with very low carbon emissions (illustrated in Figure 1.4).
1.3.2 Need for Green Hydrogen Production?
As already discussed in previous sections, global warming is a major challenge for the entire world. A growing number of countries have pledged to achieve net-zero carbon dioxide (CO2) emissions by the middle of this century (2050), with the objective of keeping global warming to 1.5°C. This necessitates a significant change in electricity generation from fossil fuels to renewable sources such as solar and wind energy. Nature offers various renewable sources such as solar energy, wind energy, tidal energy, biomass energy, etc. (Scheme 1.1). However, such energy sources suffer from discontinuous availability due to regional or seasonal factors [35]. As a result, in conjunction with the exploration of renewable energy sources for large-scale use, an efficient energy conversion and storage system is also required [36]. This requirement is the primary driving force behind numerous innovations in energy conversion and storage systems. Hydrogen production from electrolysis of water, fuel cells for converting hydrogen to electricity, and lithium-ion or metal-air batteries for energy storage have all received a lot of attention in recent decades [37]. For the battery-based energy storage systems, it is increasingly difficult to store excess electricity generated from a large-scale production facility, which is very expensive and also needs a large facility area. Hence, large-scale solar or wind-generated electricity require alternate energy storage pathways. Green hydrogen generation using electricity-driven water splitting has emerged as a promising approach for converting huge amounts of excess electrical energy from renewable energy sources into clean fuel hydrogen. When this is used as a fuel in the hydrogen fuel cell, it not only converts energy efficiently but also creates no pollution because it only emits water as a by-product. As a result, the development of green hydrogen production from renewable sources has become a global push toward a future power package that is both sustainable and affordable. This advancement is paving the way for many of the difficult issues encountered during conversion and storage of renewable energy.
In addition, approximately 4 billion tonnes of hydrogen is required annually, with 95% of hydrogen production derived from fossil fuel [38]. Around 830 million tonnes of CO2 are emitted annually when hydrogen gas is produced using fossil fuels. Hence, swapping to production of green hydrogen utilizing renewable energy sources will reduce the CO2 emissions to a greater extent in the next few decades and will become independent of fossil energy carriers.
1.3.3 Uses and Limitations of Green Hydrogen
Generally, hydrogen can be generated using the electrolysis of water releasing oxygen as a by-product. In electrolysis, the electric current is used to split water into hydrogen and oxygen in an electrolyzer. Among different types of hydrogen energy, green hydrogen is generated by electrolysis, wherein the electricity is generated by using renewable sources; for example, solar or wind. Here, electricity is fed to an electrolyzer which requires water and electricity for the production of hydrogen and oxygen, with zero carbon emissions (Scheme 1.2) [33]. The main advantage of green hydrogen is that it only needs water and electricity to produce more electricity or heat. It can be used in industry and can be transported in gas pipelines to power household appliances. The green hydrogen produced could be directly blended and added to natural gas networks up to a definite percentage. This results in less consumption of natural gas as compared to the case of no green hydrogen. Additionally, synthetic methane can be produced via steam methane reforming process and can be directly added to gas networks. This is a proficient method for the reduction of carbon dioxide emission. Green hydrogen can be stored and used in aviation, marine, and other transportation systems via the hydrogen supply chain. Figure 1.5 illustrates the production of green hydrogen, its conversion into numerous beneficial compounds, transport, and multiple end uses across the energy system [34]. The total cost of hydrogen generation changed from $6/kg in 2015 to an estimated figure of $2/kg by 2025 by using cheap renewable energy. This fast decline in cost of renewable energy is one of the chief reasons for the growing interest in green hydrogen worldwide. The current decade is critical for green hydrogen technology development as one of the most promising options for the long duration storage of electricity. By this, the aim of 40% share of electricity in the worldwide energy portfolio in 2050 would be reached and therefore the Paris Agreement regarding the decarbonized energy will likely be accomplished [39]. Green hydrogen is basically considered as an alternative fuel produced with clean energy and thus identified as the clean energy source that could meet the world’s future energy demands and transform the world with net-zero emissions. However, the economics of green hydrogen are challenging today due to the underlying costs and that the availability of renewable energy sources vary widely [40].
Scheme 1.2 Production of green hydrogen.
Figure 1.5 Illustration showing the production of green hydrogen, its transformation, transport, and end uses across the energy system. Image from [34]. https://www.irena.org/publications/2020/Nov/Green-hydrogen.
Although green hydrogen is gaining popularity across industries, it still faces the future power systems with numerous challenges in the planning and operational phases. Several factors such as market, public, demand uncertainty, and environmental constraints may impose further pressures on the network. There is less knowledge on optimum demand and return on investment, therefore limited bankability. In order to fulfil market demands, organizations have to scale up and advance their green hydrogen plant designs. However, optimizing plant designs and green hydrogen systems can be expensive and complex on the basis of limited market demand. Though green hydrogen will generate numerous new opportunities, so many individuals still need the essential training and skills to support the hydrogen economy. The best way forward seems to incorporate hydrogen generation to dedicated solar or wind power plants that can reach suitable annual load factors in chosen locations. Moreover, green hydrogen is expensive to store and transport, thus requiring high operational costs in specialized pipelines and carriers [41]. In addition to this, high energy loss at every point in the supply chain of green hydrogen is also a major concern. Around 30–35% of the energy utilized for the generation of hydrogen is lost during the electrolysis process, liquefying, or transforming hydrogen to other carriers; for example, ammonia, and this results in a 13–25% energy loss. Around 10–12% of the extra energy is required in the transporting of hydrogen [42]. Such inefficiencies will need significant renewable energy deployment to nourish green hydrogen electrolyzers that can compete with electrification. Apart from these challenges, another major challenge is the way to monetize green hydrogen. The condition of geographical area for green hydrogen creates a requirement for dedicated pipelines with all linked lead times and costs.
Transition to green hydrogen is one of the key requirements to reduce emissions, especially in the hard-to-abate areas. The Government of India has set a target of production of 5 million tonnes of green hydrogen before 2030. Thus, they have considered different policy measures to assist transition from fossil fuels to green hydrogen, both as energy carriers and chemical feedstock for different sectors [43]. The U.S. hydrogen economy could generate $140 billion and support 700,000 jobs. There are numerous green energy projects in the U.S. and around the world attempting to deal with these challenges and support hydrogen adoption. California is planning to invest $230 million on hydrogen projects before 2023. In Lancaster, CA, the world’s largest green hydrogen project is located. This plant uses waste gasification, combusting 42,000 tonnes of recycled paper waste annually to generate green hydrogen. European countries including Germany, Spain, and France announced the installation of 4, 5, and 6.5 GW of green hydrogen by 2030, respectively [44]. Green hydrogen national targets of France, Portugal, Germany, Netherlands, and Spain contributed to more than 50% of the European Union’s targeted 40 GW of installed electrolyzer capacity in 2030.
1.3.4 Green Hydrogen Production Pathways from Renewable Energy Sources and Their Current Level of Maturity
Various technology choices are available for creating hydrogen from renewable energy sources [39]. Water electrolysis is the most well-established technology choice for creating green hydrogen from RES. Biomass gasification and pyrolysis, thermochemical water splitting, photocatalysis, biomass supercritical water gasification, and coupled dark fermentation and anaerobic digestion are less developed routes. In this chapter, we restrict our discussion to the production of green hydrogen through electrolysis of water using renewable energy resources.
Currently, there are three main types of electrolysis technologies: (1) proton exchange membrane electrolysis (PEMEL); (2) alkaline electrolysis (AEL); and (3) high-temperature solid oxide water electrolysis (SOEL). While the low-temperature technologies, AEL and PEM, both provide high-technology readiness levels, the high-temperature SOEL technology is still in the development stage [38].
Alkaline water electrolysis uses concentrated lye as an electrolyte, and a gas-impermeable separator is required to keep the resultant gases from mixing. Non-noble metals, such as nickel, are used as electrodes with an electrocatalytic coating. The electrolyte in PEMEL is a humidified polymer membrane, and the electrocatalysts are noble metals like platinum and iridium oxide. Both systems can function at temperatures ranging from 50 to 80°C and at pressures up to 30 bar. Both technologies have a nominal stack efficiency of roughly 70% [45, 46]. SOEL is also known as high-temperature or steam electrolysis. Here gaseous water is transformed into hydrogen and oxygen at temperatures between 700 and 900°C. Due to beneficial thermodynamic effects on power usage at higher temperatures, stack efficiencies of 100% are theoretically possible. However, for cost-effective operation, the increased thermal demand needs a sufficient waste heat supply from the chemical, metallurgical, or thermal power generation industries. Moreover, the corrosive environment demands further material development [46, 47]. As a result, compared to 6 MW for AEL and 2 MW for PEMEL, SOEL only offers tiny stack capacities below 10 kW [46].
Generally, the overall water electrolysis reaction can be divided into two half-cell reactions: hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). During HER, water is reduced at the cathode to produce H2, and during OER, water is oxidized at the anode to produce O2. One of the critical barriers that keep water splitting from being of practical use is the sluggish reaction kinetics of OER and HER due to high overpotentials [48], a measure of the kinetic energy barriers. A broad range of highly effective catalysts are developed to minimize the overpotentials for OER and HER toward efficient H2 and O2 production. Platinum (Pt) is the most advanced catalyst for HER and OER at this time, and noble-metal-based catalysts continue to be the most efficient catalysts for HER and OER [49–52]. The creation of earth-abundant catalysts with high activity, as a result, becomes one of the most important tasks in the development of cost-effective and efficient water electrolysis systems. There have been numerous reports of earth-abundant catalysts with significant catalytic activity toward OER and, in particular, HER [53–60]. A great deal has been done in the field of HER research on transition metal dichalcogenides (TMDs) [61–66], transition metal phosphides (TMPs) [67–70], carbides [71–73], and nitrides [74, 75]. Several heterostructured catalysts have recently emerged from the crowd, demonstrating superior catalytic performance in electrochemical water splitting compared to their conventional equivalents [76–80]. By depositing MoS2 on the surface of CoSe2, for example, Gao et al. developed a MoS2/CoSe2 heterostructure catalyst that was effective. When tested in 0.5 m H2SO4, the MoS2/CoSe2 heterostructure had excellent HER performance. It displayed a high overpotential of 68 mV at 10 mA cm–2, a Tafel slope of 36 mV dec–1, and good performance durability [81]. In one study, Chen et al. synthesized a 3D core/shell catalyst composed of metallic Co cores and amorphous Co3O4 shells, and the Co/Co3O4 heterostructure delivered 10 mA cm–2 at a low overpotential of only 90 mV in 1 m potassium hydroxide (KOH) [82]. Most heterostructured catalysts, including active/active and active/nonactive types of heterostructures, exhibit higher HER activities than their single counterparts [83].
Since the first study of photochemical H2 evolution from water splitting on TiO2, single crystal electrodes utilizing photoelectrochemistry was published in 1972 [84], and photochemical H2 evolution from water splitting has remained a hot topic for both academic and industrial researchers. It is possible to divide photochemical H2 evolution processes into two categories based on the reaction mechanism they use: (1) photoelectrocatalytic H2 evolution, and (2) photocatalytic H2 evolution. Photoelectrocatalytic methods employ photocatalysts as electrodes in addition to light irradiation, and necessitate the application of an additional bias voltage in order to prevent recombination of the photo-generated carriers. Because of its great efficiency, photoelectrocatalytic H2 evolution is frequently used in industry. However, it requires additional energy, and hence will not be discussed in detail in this chapter. Photocatalysis, on the other hand, directly utilizes the abundant solar energy to split water into H2 through a four-electron or two-electron process, which can successfully avoid environmental contamination as well as the consumption of additional energy. It is the quickest and most straightforward method of water splitting, and it produces H2 at a low cost and on a huge scale. It can easily be seen that the number of studies focusing on the creation of photocatalysts that do not contain noble metals (also known as non-noble metal photocatalysts) has expanded dramatically in recent years. However, they are still insignificant in comparison to the photocatalysts containing noble metals, which have a far higher number of active sites (named as noble-metal photocatalysts). Noble metals have the potential to be used as effective redox co-catalysts in general because of their good physicochemical and electrical properties, as well as their high catalytic activity [85, 86]. But due to the low abundance of noble metal elements in noble-metal photocatalysts, they are expensive and have only a few practical uses in the field of water splitting. However, because of their low cost and high efficiency, non-noble-metal photocatalysts are an attractive candidate for water-splitting applications due to their low toxicity. Non-noble-metal photocatalysts, on the other hand, have excellent stability and do not suffer from deactivation under particular conditions, in contrast to Pt-based photocatalysts (noble-metal photocatalysts), which suffer from Pt deactivation in the presence of halide ions. It follows that photocatalysts made of non-noble metals are acceptable for the conversion of wastewater to H2. All of the lanthanides, as well as the other elements in the s, p, and d regions of the periodic table, are stated to be capable of generating H2 [87]. The photocatalytic H2 evolution process can be classified into three steps that are followed by each other: (1) when a semiconductor absorbs high-energy photons with a wavelength greater than the bandgap, electrons in the valence band (VB) are excited and transmitted to the conduction band (CB), resulting in the generation of holes in the VB; (2) the induced electron–hole pairs separate and transfer to the surface of the material; and (3) the electrons in the CB reduce the adsorbed H+ to H2, and the holes in the VB oxidize water to oxygen. However, a prerequisite must be met for H2 production according to the following redox reactions [88]:
A lower than 0 V (E(H+/H2) CB energy level under the Normal Hydrogen Electrode (NHE) is required in order for the H2 evolution reaction to proceed under the normal hydrogen electrode (HER). In addition, the VB energy level should be more than 1.23 V (E(O2/H2O)) in order for the reduction process of H2O to proceed [89]. The production of H2 on non-noble-metal photocatalysts is hampered primarily by their weak visible light sensitivity, rapid recombination of the photo-generated carriers, low surface reaction rate, and high thermodynamic potential barriers, among other characteristics. There have been a variety of ways taken to circumvent the restrictions mentioned above. These include energy band engineering, heterojunction building [90], and reactive activity improvement [91]. It is possible to immobilize the co-catalyst on semiconductor photocatalysts, which is a potential strategy for overcoming the constraints outlined above. Co-catalysts are categorized into three categories based on the type of material they are made of: metallic, non-metallic, and semiconducting. Metallic co-catalysts can be further divided into two categories: precious metal catalysts and non-noble (base) metal catalysts, which are distinguished by the cost of the metal used [92]. The use of noble metals as efficient co-catalysts for hydrogen production has increased dramatically in recent decades, with the most common being Ru [93], Rh [94], Pd [95], Ag [96], Pt [97], and Au [98]. With the inclusion of precious metal co-catalysts, the activity of the photocatalyst can be dramatically increased. The usage of noble-metal co-catalysts, on the other hand, is not suited for large-scale applications due to the high cost and restricted storage space associated with them. So, the development of high-performance photocatalytic materials including nonprecious metals is a promising strategy for the sustainable and large-scale production of hydrogen from water splitting.
1.4 Current Scenario of RES in India
Over the past few years, India has developed a sustainable path for its energy supply and emerged as one of the top leaders in the world’s most attractive renewable energy sectors. India is the world’s third largest producer and consumer of electricity with 38% of total installed energy capacity in 2020 from RES [99]. India occupies the third position after the U.S. and China as per the Ernst & Young Global Ltd. (EY) 2021 Renewable Energy Country Attractiveness Index (RECAI) [40].
To meet the future nation’s energy needs, the Government of India has taken several initiatives. For instance, from FY 2016/17 to FY 2020/21, wind energy capacity in India has been augmented by 2.2 times. In March 2021, solar power capacity has increased by more than five times in the last five years from 6.7 to 40 GW [100]. On 16 June 2021, the installed renewable energy capacity was raised by over two and half times and stands at more than 141 GW, which is almost equal to 37% of the country’s total capacity [100]. At the same time, the installed solar energy capacity has augmented by over 15 times and stands at 41.09 GW. By 31 June 2021, the total installed energy capacity for renewable was 96.95 GW [100].
From 2020 to 2021, a decrease in the utility power generation by 0.8% has been observed along with the decline in power generation from fossil fuels by 1%. During the year 2020/2021, India exported more electricity than it imported from bordering countries. India’s grid-connection electricity generation capacity reached 100 GW from non-conventional renewable technologies and 46.21 GW from conventional renewable power or major hydroelectric power plants in 2021 [101].
The EY’s RECAI ranking (in July 2021) [99] in terms of installed capacity and investment in renewable energy is as shown in Table 1.1.
Table 1.1 RECAI scores and rank in July 2021.
Country
Score
RECAI Rank
U.S.
70.1
1
China
68.7
2
India
66.2
3
The technology-specific RECAI scores (and rank) [102, 103] for 2021 are tabulated in Table 1.2.
Table 1.2 Technology-specific RECAI scores (and rank).
Technology
U.S.
China
India
Solar PV
57.6
60.3
62.7 (1)
Onshore wind power
58.1
55.7
54.2 (6)
Offshore wind power
55.6
60.6
28.6 (29)
Biofuels
45.3
52.8
47.4 (10)
Hydroelectricity
57.6
60.3
46.4 (3)
Solar CSP power plants
46.2
54.3
09.2 (4)
Geothermal power
46.0
31.7
23.2 (16)
By 12 August 2021, India achieved the target of installing 100 GW of renewable energy capacity according to the Union Ministry of New and Renewable Energy. This data does not involve the large hydroelectricity capacities installed in the country. India has set a target of 459 GW renewable energy capacity to be installed by 2030. This value of installed renewable energy capacity can be increased by 146 GW if large hydroelectricity capacity is included. The world’s largest renewable energy park with 30 GW capacity solar wind hybrid project is in the pipeline in Gujarat [104]. The installed capacity of non-conventional non-renewable power [105] is tabulated in Table 1.3.
Table 1.3 Installed capacity of non-conventional non-renewable power.
Wind Power
39,870.45
Solar Power – Ground Mounted
39,347.92
Solar Power – Roof Top
5574.12
SPV Systems (Off-grid)
1353.10
Small Hydro Power
4809.81
Biomass (Bagasse) Cogeneration)
9403.56
Biomass (non-Bagasse) Cogeneration)/Captive Power
772.05
Waste to Power
168.64
Waste to Energy (Off-grid)
233.20
Total
101,532.85
