Cocatalysts on Semiconductor Photocatalyst: A Mini Review

Recent progress in photocatalysts for sunlight energy conversion into chemical energy through water splitting, carbon dioxide (CO2) reduction, nitrogen fixation, etc. has witnessed the importance of cocatalysts in elevating the efficiency of the overall reaction systems. A cocatalyst can assist a semiconductor photocatalyst by promoting the transportation of photoexcited charges (electrons and holes). The improved shuttle of photoexcited charges has direct constructive impacts on the suppression of charge recombination, facilitation of redox reactions with reactants, and prevention of photo-corrosion (in certain photo-unstable semiconductor). Given the critical roles played by cocatalyst, the methodologies adopted in decorating such entities on a semiconductor photocatalyst would have influence in the surface and interfacial interaction between the two components, resulting in the tunability of reaction performance. In this mini review, we aim to summarize the structural configurations of cocatalyst-photocatalyst composites yielded via various loading methods. The implications of the resultant surface and interfacial interaction imposed by the cocatalysts are discussed to provide general guidance for tailoring an ideal photocatalytic system. Subsequently, we summarize the methodologies developed over years in loading of cocatalyst on semiconductor photocatalyst. The challenges presented at the end of this mini review serve as a platform of opportunity for this community to overcome or improve further.