Material Design and Surface/Interface Engineering of Photoelectrodes for Solar Water Splitting

Abstract

Photoelectrochemical (PEC) water splitting can convert solar energy into clean and renewable hydrogen energy, showing a promising application prospect. However, large‐scale implementation of PEC water splitting is now hampered by insufficient solar‐to‐hydrogen conversion efficiency, which requires the development of high‐performance photoelectrodes. Key processes that determine the water splitting performance of photoelectrodes are the light absorption, separation, and transport efficiency of photogenerated electrons and holes and the surface reaction of water oxidation/reduction. Concerning these three key processes, various material design and surface/interface engineering strategies have been explored to improve the performance of photoelectrodes. Herein, these strategies for photoelectrode optimization of the past decades are summarized and discussed in terms of micro‐ and nanostructuring, heterojunction construction, element doping, surface passivation, plasmonic metal coating, and electrocatalyst modification. Special attention is given to how these strategies play their roles in improving the performance of photoelectrodes, based on which it is hoped light is shed on the design principles and modification routes for high‐performance photoelectrodes.

Strategies for improving photoelectrochemical water splitting performance of Si‐based electrodes

“…With the aid of an electric field based on energy band engineering, the separation and transport of the photogenerated carriers could be successfully achieved. A high photovoltage can be obtained by engineering the interface energetics based on the work function difference of the contact materials 14,22,70‐72 . In this part, various surface/interface engineering strategies of Si‐based photoelectrodes are summarized and discussed in terms of homojunction and heterojunction.…”

“…Semiconductor/semiconductor heterojunctions can be classified into the p‐p heterojunction, n‐n heterojunction, and p‐n heterojunction. They all induce band bending at the contact interface, but the band bending degree of p‐n heterojunction is larger than that of the others because the Fermi‐level difference between p‐type and n‐type semiconductors is the largest before contact 14 …”

“…Solar energy‐driven water splitting to produce hydrogen is a promising and cost‐effective approach. Conversion of solar energy into hydrogen via water splitting can be achieved through various ways such as photovoltaic (PV)‐electrocatalytic (EC), 1‐4 photocatalytic, 5‐12 and photoelectrochemical/photoelectrocatalytic (PEC) water splitting, 13‐15 . Since PEC water splitting technology is technically and economically feasible, it stands out from various technologies for sustainable hydrogen production 16 …”

Photocatalytic Conversion of Plastic Waste: From Photodegradation to Photosynthesis

“…[49][50][51][52][53][54] The required potential energy to drive the overall water splitting reaction is at least 1.6 eV, larger than the theoretical thermodynamic requirement of water splitting (1.23 eV), due to the kinetic overpotentials from the H 2 evolution reaction (HER) and even more from the sluggish oxygen evolution reaction (OER). [55][56][57][58][59][60][61] Only 43% of the available solar photons have energy greater than 1.6 eV. Compared to water oxidation, plastic oxidation is much more facile due to the lower potential, thus reducing the overall potential requirement needed to couple with H 2 evolution.…”

Polydopamine and Nafion bi‐layer passivation modified CdS photoanode for photoelectrochemical hydrogen evolution

“…Photoelectrochemical (PEC) water splitting to produce hydrogen is a promising strategy for solving energy and environmental problems. [1][2][3] A variety of semiconductor catalysts, such as TiO 2 , 4 WO 3 , 5 ZnO, 6 Fe 2 O 3 , 7 BiVO 4 , 8 and CdS, 9 have been studied as photoanodes. Of these, CdS is regarded as one of the most prospective candidate materials due to its directly suitable bandgap (2.4 eV), low cost, and excellent electron mobility.…”