Integration of earth-abundant cocatalysts for high-performance photoelectrochemical energy conversion

Abstract

Photoelectrochemical (PEC) energy conversion has emerged as a promising and efficient approach to sustainable energy harvesting and storage. By utilizing semiconductor photoelectrodes, PEC devices can harness solar energy and drive electrochemical reactions such as water splitting or carbon dioxide (CO₂) reduction to generate clean fuels and value-added chemicals. However, PEC energy conversion faces several challenges such as high overpotential, sluggish reaction kinetics, charge carrier recombination, and stability issues, which limit its practical implementation. Recently, significant research has been conducted to improve the overall conversion efficiency of PEC devices. One particularly promising approach is the use of cocatalysts, which involves introducing specific cocatalysts onto the photoelectrode surface to promote charge separation, improve reaction kinetics, and reduce the overpotential, thereby enhancing the overall performance of PEC energy conversion. This review provides a comprehensive overview of the recent developments in the earth-abundant cocatalysts for PEC water splitting and CO₂ reduction. The main earth-abundant catalysts for the PEC water splitting include transition-metal dichalcogenide (TMD)-based materials, metal phosphides/carbides, and metal oxides/hydroxides. Meanwhile, PEC-CO₂RR was divided into C₁ and C₂₊ based on the final product since various products could be produced, focusing on diverse earth-abundant materials-based cocatalysts. In addition, we provide and highlight key advancements achieved in the very recent reports on novel PEC system design engineering with cocatalysts. Finally, the current problems associated with PEC systems are discussed along with a suggested direction to overcome these obstacles.