Chapter 16
Transition Metal Phosphide As Cocatalysts
for Semiconductor-Based Photocatalytic
Hydrogen Evolution Reaction
16.1 Introduction
The increasing global energy supply and extreme climate change and related environmental issues are complex technological challenges that are being faced by
scientists in the twenty-first century [1]. The rate of global energy consumption
averaged 15–17 TW in 2010, and this number will likely increase to 25–27 TW due
to the increasing global population and production [2, 3]. It is especially noteworthy
that human productions and livings heavily rely on nonrenewable fossil fuels, such
as coal, oil, and natural gas [4]. Furthermore, the combustion of these fossil fuels has
generated a series of environmental issues, including air and water contamination
and global warming [5]. Thus, it is extremely urgent to search for sustainable and
environmentally friendly alternative energy to replace exhaustible fossil resource.
Solar energy is a clean, stable, and renewable energy source [6–9]. Today resourcepoor around the world, the highly efficient conversion of solar energy into usable
energy is increasingly showing a bright future. Photocatalytic water reduction
represents a promising strategy for a clean, non-contaminative, and low-cost production of H 2 [10–12]. As an energy medium, hydrogen still has too much potential
(highest gravimetric energy density compared with other fuels) to shuffle quietly off
the dependence on coal [13, 14].
In general, the photocatalytic hydrogen reaction is composed of three major steps:
(i) absorption of light by semiconductor to generate electron–hole pairs, (ii) charge
separation and migration to semiconductor’s surface, and (iii) surface reduction
reaction for H 2 evolution (Fig. 16.1). The efficiency of photocatalytic hydrogen
evolution reaction is determined by the synergetic effect of thermodynamics and
kinetics of the above three steps [4]. To date, much significant progress has been
achieved to develop photocatalysts with the broad absorption of solar light (step i)
and high charge separation efficiency (step ii). For instance, a plenty of strategies
have been employed to extend the light absorption of photocatalyst, such as bandgap
reduction (metal or nonmetal element doping) [15–17], coupling with narrow
© Springer Nature Singapore Pte Ltd. 2018
J. Zhang et al., Photocatalysis, Lecture Notes in Chemistry 100,
https://doi.org/10.1007/978-981-13-2113-9_16
375
Transition Metal Phosphide As Cocatalysts
for Semiconductor-Based Photocatalytic
Hydrogen Evolution Reaction
16.1 Introduction
The increasing global energy supply and extreme climate change and related environmental issues are complex technological challenges that are being faced by
scientists in the twenty-first century [1]. The rate of global energy consumption
averaged 15–17 TW in 2010, and this number will likely increase to 25–27 TW due
to the increasing global population and production [2, 3]. It is especially noteworthy
that human productions and livings heavily rely on nonrenewable fossil fuels, such
as coal, oil, and natural gas [4]. Furthermore, the combustion of these fossil fuels has
generated a series of environmental issues, including air and water contamination
and global warming [5]. Thus, it is extremely urgent to search for sustainable and
environmentally friendly alternative energy to replace exhaustible fossil resource.
Solar energy is a clean, stable, and renewable energy source [6–9]. Today resourcepoor around the world, the highly efficient conversion of solar energy into usable
energy is increasingly showing a bright future. Photocatalytic water reduction
represents a promising strategy for a clean, non-contaminative, and low-cost production of H 2 [10–12]. As an energy medium, hydrogen still has too much potential
(highest gravimetric energy density compared with other fuels) to shuffle quietly off
the dependence on coal [13, 14].
In general, the photocatalytic hydrogen reaction is composed of three major steps:
(i) absorption of light by semiconductor to generate electron–hole pairs, (ii) charge
separation and migration to semiconductor’s surface, and (iii) surface reduction
reaction for H 2 evolution (Fig. 16.1). The efficiency of photocatalytic hydrogen
evolution reaction is determined by the synergetic effect of thermodynamics and
kinetics of the above three steps [4]. To date, much significant progress has been
achieved to develop photocatalysts with the broad absorption of solar light (step i)
and high charge separation efficiency (step ii). For instance, a plenty of strategies
have been employed to extend the light absorption of photocatalyst, such as bandgap
reduction (metal or nonmetal element doping) [15–17], coupling with narrow
© Springer Nature Singapore Pte Ltd. 2018
J. Zhang et al., Photocatalysis, Lecture Notes in Chemistry 100,
https://doi.org/10.1007/978-981-13-2113-9_16
375