Facet-Dependent Lattice Oxygen Activation on Oxygen-Defective Co₃O₄ for Electrocatalytic Oxygen Evolution Reaction

Introducing oxygen vacancies into Co-based oxides with different surface structures can significantly affect their coordination environments and electronic structures, possibly contributing to the variation of the electrocatalytic oxygen evolution reaction (OER) activity. Herein, the oxygen vacancies were introduced into Co3O4 cubes and truncated octahedrons to uncover the effects of facets (001) and (111) on the intrinsic OER activity of oxygen-defective Co3O4. The (001)-faceted Co3O4 cubes with oxygen vacancies exhibited a lower onset overpotential of 298 mV than that of multifaceted truncated octahedrons (335 mV) because of the sufficient lattice oxygen participation in the OER process. Theoretical calculations revealed that oxygen vacancy on (001) surfaces can upshift the O 2p band center and trigger the lattice oxygen oxidation mechanism while oxygen vacancy on (111) surfaces matched well with the absorbate evolution mechanism. This work offers a new insight for designing OER electrocatalysts by selectively introducing oxygen defects on well-defined crystal facets.