A critical study of the generality of the two step two electron pathway for water splitting by application of a C3N4/MnO2 photocatalyst

Abstract

A novel C₃N₄–CDot composite photocatalyst was very recently shown to be highly efficient and very stable in water splitting by solar radiation without using any sacrificial reagent (J. Liu, et al., Science, 2015, 347(6225), 970). This photocatalyst utilizes a two-electron/two-step process in which the production of H₂O₂ and H₂ is photocatalyzed by using C₃N₄ in the first step and H₂O₂ is decomposed by using CDots in the second step. The present work is a study on the generality of this approach by application of a C₃N₄/MnO₂ catalyst. This new catalyst indeed splits water by a two step process in a stable way, without any sacrificial agent. It was however found that though the absorbance of the new catalyst in the visible range of 500–600 nm is much larger than that of the C₃N₄–CDot catalyst, its water splitting efficiency is much lower. These findings add insight into and assist in the further optimization of this new class of photocatalysts to meet the requirements of commercial water splitting systems.