Crystal‐Plane‐Dependent Activity of Spinel Co3O4 Towards Water Splitting and the Oxygen Reduction Reaction

Abstract Insights into the relationship between the crystal planes of metal oxides and the catalytic activity of the oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and hydrogen evolution reaction (HER) are essential for developing efficient renewable energy technologies. Herein, spinel Co 3 O 4 nanomaterials were synthesized controllably with the specified morphologies of nanocubes, nanosheets, and nanoplates with different exposed planes of {100}, {110}, and {111}, respectively. The effects of the crystal planes of Co 3 O 4 on the activity for the OER, ORR, and HER were subsequently investigated in alkaline media. Different electrocatalytic performances are possibly attributed to the abundance ratios of Co 3+ /Co 2+ over the different exposed planes. The surface Co 3+ ions exhibit higher activity for the OER and HER, whereas the surface Co 2+ ions exhibit better performance for the ORR; moreover, higher electroconductivity enhances the polarization current for ORR and HER except OER.