Electronic structure regulation of cobalt oxide clusters for promoting photocatalytic hydrogen evolution

Abstract

Photocatalysis for water decomposition under solar light is a promising route to produce clean hydrogen energy. Although both single atom catalysts (SACs) and atomic cluster catalysts effectively improve photocatalytic hydrogen evolution, their performances are different in different applications. In this study, we used the electrochemical method to deposit single atoms, clusters, and nanoparticles of cobalt on carbon nitride (CN) by adjusting the deposition time. It was found that among the three catalysts, atomic cluster catalysts showed the best photocatalytic hydrogen production performance, up to 129 μmol g⁻¹ h⁻¹ than that of 87.2 μmol g⁻¹ h⁻¹ for Co₁/CN SACs, and 110.3 μmol g⁻¹ h⁻¹ for CoO_x-nanoparticle/CN. DFT calculations suggested that the electronic structure of the load species can be regulated by CN through the interaction between cobalt species and CN substrate. When the cluster is loaded on CN, the charge of the cluster can flow to the CN. As the cluster size increases, this charge flow can be suppressed. When the cluster with an appropriate size is loaded on CN, the electronic structure would be regulated to an optimal state for photocatalytic hydrogen evolution. These results provide a new understanding of the influence of the interaction between CN substrate and loading species on photocatalytic activities and may inspire further developments in the conversion of solar energy to hydrogen energy.