Impactful Role of Earth-Abundant Cocatalysts in Photocatalytic Water Splitting

Photocatalytic water splitting represents an attractive strategy for storing intermittent solar energy in the form of chemical bonds. Considerable efforts have been made to design efficient and stable semiconductor photocatalysts. However, the efficiencies of most developed photocatalysts are still unsatisfactory due to the severe charge recombination and sluggish surface reaction kinetics. Loading suitable cocatalysts can efficiently capture the photogenerated carriers to reduce charge recombination and provide surface reactive sites to accelerate the chemical reaction. Typically, developing earth-abundant cocatalysts to replace noble-metal-based ones is of great significance for the practical application. To understand the impactful role of cocatalysts in photocatalytic water splitting, this chapter first introduces the basic working principle of cocatalysts and then summarizes extensively studied earth-abundant cocatalysts. The effects of intrinsic characters of cocatalysts, such as morphology, crystallization, and composition are subsequently discussed. The influence of interfacial coupling of cocatalysts with host photocatalysts, such as cocatalyst location, built-in electric field, and contact manner, is further analyzed. To demonstrate the real active species of cocatalysts and clarify the reaction mechanism, some results using advanced characterization techniques are examined. Hopefully, this chapter can offer meaningful guidance to design cost-effective and highly efficient cocatalysts for photocatalytic water splitting.