Investigating the physical and electrochemical effects of cathodic polarization treatment on TaOx

In the development of non-noble metal electrocatalysts, tantalum oxide (TaOx)-based materials possess promising potential due to their high corrosion resistance. In the stoichiometric and bulk form, however, the oxide is extremely inactive. Here, we explored the effects of electrochemical reduction treatment on the physical and electrochemical properties of TaOx. The oxide was electrochemically deposited on a glassy carbon electrode. The treatment employed a cyclic voltammetry technique in sulfuric acid solution and required no heat treatment. The X-ray photoelectron spectroscopy (XPS) measurements demonstrated that the stoichiometric Ta2O5 is reduced generating the oxides with a predominant oxidation state of 4+. Remarkably, the electrochemically reduced TaOx showed high activity in hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR). These findings suggest that the electrochemically reductive treatment is an effective way to activate TaOx for the electrocatalytic reactions which could be originated from the suboxide species, i.e., Ta4+.