Abstract
Solar-driven water-splitting has been considered as a promising technology for large-scale generation of sustainable energy for succeeding generations. Recent intensive efforts have led to the discovery of advanced multi-element-compound water-splitting electrocatalysts with very small overpotentials in anticipation of their application to solar cell-assisted water electrolysis. Although photocatalytic and photoelectrochemical water-splitting systems are more attractive approaches for scaling up without much technical complexity and high investment costs, improving their efficiencies remains a huge challenge. Hybridizing photocatalysts or photoelectrodes with cocatalysts has been an effective scheme to enhance their overall solar energy conversion efficiencies. However, direct integration of highly-active electrocatalysts as cocatalysts introduces critical factors that require careful consideration. These additional requirements limit the design principle for cocatalysts compared with electrocatalysts, decelerating development of cocatalyst materials. This perspective first summarizes the recent advances in electrocatalyst materials and the effective strategies to assemble cocatalyst/photoactive semiconductor composites, and further discusses the core principles and tools that hold the key in designing advanced cocatalysts and generating a deeper understanding on how to further push the limits of water-splitting efficiency.
Highlights
Reducing the amount of CO2 emitted from burning fossil fuels is essential to mitigate global warming.[1]
By exploiting the transformation phenomenon of ECs during catalysis, we demonstrated that applying potential for oxygen evolution reaction (OER) to a NiPx@FePyOz NP-loaded electrode transformed the NPs into highly OER active NiFeOOH lm while simultaneously removing their organic ligands (Fig. 8).[148]
We believe that the colloidal approach using NPs of active EC materials with controllable sizes and compositions represents a promising solution to bridge the studies of ECs and CCs
Summary
Hydrogen is the most abundant element on earth, the dihydrogen molecule rarely exists in nature; H2 must be produced arti cially. The direct decomposition of water through photocatalysis represents a promising alternative approach owing to its technical simplicity and low associated investment costs.[10,11] Scaling up a photocatalytic system is relatively much easier because water splitting can proceed by immersing semiconductor photocatalyst (PC) powder in water under light irradiation.[12] Recently, a large-scale experiment (100 m2 scale) demonstrated that immobilizing powdered PCs on panels could lead to the production of about 600 L of H2 on a sunny day.[13] Such photoactive semiconductors can be used as light-absorbing layer of photoelectrodes (PEs) for photoelectrochemical (PEC) water-splitting cells.[14] These electrodes are usually placed in separate compartments which are electrically connected through an external circuit This con guration makes PEC systems more complex in terms of design, higher STH efficiencies have been achieved due to easier product collection and elimination of potential back-reactions.[15] For example, a tandem-type PEC cell reached an STH of. We hope this perspective will inspire researchers in pursuit of bridging the gap between the developments of highly-active EC and CC materials, which have only been studied separately to date (Fig. 1)
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