Facet-dependent activity and stability of Co₃O₄ nanocrystals towards the oxygen evolution reaction.

The electrocatalytic activities and stabilities of spinel cobalt oxides with different morphologies have been investigated for the oxygen evolution reaction (OER) in an alkaline environment. Spinel cobalt oxide nanoparticles with well-defined cubic and octahedral morphologies were prepared, which predominantly expose the (100) and (111) surfaces, respectively. The OER activity of spinel cobalt oxide, measured in terms of current density, increases with higher relative proportion of the (111) surface, which can be attributed to the higher density of cobalt ions on the (111) surface compared to that on the (100) surface. The surfaces of cobalt oxide nanocubes are slighted reduced compared to those of nanooctahedra prior to OER testing. Based on chronoamperometry experiments, the nanocubes exhibited higher stability compared to the nanooctahedra, which could be due to the lower surface energy of the (100) surface compared to the (111) surface. The dependence of OER activity and stability on spinel cobalt oxide crystal facets demonstrates the importance of surface orientation in catalyst performance optimization.