Synergistic Cocatalytic Effect of Carbon Nanodots and Co3O4 Nanoclusters for the Photoelectrochemical Water Oxidation on Hematite

Cocatalysis plays an important role in enhancing the activity of semiconductor photocatalysts for solar water splitting. Compared to a single cocatalyst configuration, a cocatalytic system consisting of multiple components with different functions may realize outstanding enhancement through their interactions, yet limited research has been reported. Herein we describe the synergistic cocatalytic effect between carbon nanodots (CDots) and Co3O4, which promotes the photoelectrochemical water oxidation activity of the Fe2O3 photoanode with a 60mV cathodically shifted onset potential. The C/Co3O4-Fe2O3 photoanode exhibits a photocurrent density of 1.48mAcm(-2) at 1.23V (vs. reversible hydrogen electrode), 78% higher than that of the bare Fe2O3 photoanode. The slow reaction process on the single Co-III-OH site of the Co3O4 cocatalyst, oxidizing H2O to H2O2 with two photogenerated holes, could be accelerated by the timely H2O2 oxidation to O-2 catalyzed on CDots.