Optimization of the Facet Structure of Cobalt Oxide Catalysts for Enhanced Hydrogen Evolution Reaction

The structure-property relationship plays a crucial role in further exploring the mechanism of hydrogen production by photocatalytic water splitting. Here, we utilize a simple hydrothermal method to synthesize three Co3O4 catalysts with different exposed crystal facets to elucidate their catalytic mechanism at the atomic level. Co3O4 microflowers, nanotruncated octahedra and nanorods have mainly exposed {112}, {011} and {001} crystal planes, respectively, and the concentration and distribution of Co2+ and Co3+ active sites on the surface are different. Further results indicate that the {112} and {011} planes with abundant Co3+ sites exhibit catalytic activity superior to that of the {001} plane. Surface atomic configuration and EPR studies manifest that the presence of octahedral coordinated Co3+ sites optimizes the photocatalytic hydrogen evolution activity. This work reveals the importance of regulating surface atomic configuration and catalytic active sites, and opens a new avenue for the development of solar-driven water splitting.