Environmental degradation due to the carbon emissions from burning fossil fuels has triggered the need for sustainable and renewable energy. Hydrogen has the potential to meet the global energy requirement due to its high energy density; moreover, it is also clean burning. Photoelectrochemical (PEC) water splitting is a method that generates hydrogen from water by using solar radiation. Despite the advantages of PEC water splitting, its applications are limited by poor efficiency due to the recombination of charge carriers, high overpotential, and sluggish reaction kinetics. The synergistic effect of using different strategies with cocatalyst decoration is promising to enhance efficiency and stability. Transition metal-based cocatalysts are known to improve PEC efficiency by reducing the barrier to charge transfer. Recent developments in novel cocatalyst design have led to significant advances in the fundamental understanding of improved reaction kinetics and the mechanism of hydrogen evolution. To highlight key important advances in the understanding of surface reactions, this review provides a detailed outline of very recent reports on novel PEC system design engineering with cocatalysts. More importantly, the role of cocatalysts in surface passivation and photovoltage, and photocurrent enhancement are highlighted. Finally, some challenges and potential opportunities for designing efficient cocatalysts are discussed.
Developing
cost-effective noble metal-free co-catalysts as alternatives
to platinum group metals is an impeccable strategy to enhance photoelectrochemical
(PEC) water splitting. In this report, we successfully fabricated
CuInS2 nanosheet array-based photocathode modified with
CdS and co-catalyst MoS2 in a green approach to improve
water splitting under solar irradiation. The visible light absorption
of the modified hybrid photocathode (CIS/CdS/MoS2) was
significantly enhanced due to introducing CdS and MoS2.
Photoluminescence, impedance spectroscopy, and Mott–Schottky
analysis depicted improved separation of excited electron–hole
pairs, minimized resistance of charge transfer, and increased excited-state
charge carrier concentration, resulting in increased photocurrent.
Typical results indicated that composite photoelectrodes delivered
higher photocurrent (−1.75 mA/cm2 at 0 V vs RHE)
and HC-STH conversion efficiency (0.42% at 0.49 V vs RHE) than those
of CIS and CIS/CdS photoelectrodes. This improved PEC performance
is accredited to the synergetic impact of CdS in charge generation
and transfer and MoS2 as a cocatalyst with active surface
sites for proton reduction. This study not only reveals the promising
nature of CuInS2-based light absorber photocathodes for
solar energy utilization but also recommends the use of MoS2 as a cocatalyst for the proton reduction reactions for widespread
applications in solar to hydrogen conversion.
Developing efficient photocathodes with novel design is essential for enhancing the photoelectrodes functioning in photoelectrochemical(PEC) water splitting. The efficiency of solar-to-fuel conversion has been proven to improve by using suitable...
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