Evaluation of a V8C7 Anode for Oxygen Evolution in Alkaline Media: Unusual Morphological Behavior

Metallic vanadium carbide (V8C7) with cubic symmetry is examined as an oxygen evolution reaction (OER) precatalyst in alkaline media. Herein, we used quasi in situ scanning electron microscopy and energy-dispersive X-ray spectrometry to investigate the structural transformation of the precatalyst V8C7 microparticles during extended cyclic voltammetric (CV) OER testing. Interestingly, an anisotropic morphological transformation (from a distorted sphere to a cuboid) of V8C7 was observed. Our theoretical and experimental results strongly suggest that this morphological change happens due to the selective self-oxidation and dissolution of the V8C7(110) and (111) surfaces and the subsequent exposure of the relatively stable (100), (010), and (001) surfaces. These results also suggest that these stable facets are preferable for the OER, and a current density of 10 mA·cm–2 was delivered at an overpotential of 503 mV after the extended CV OER testing.