Preparation of reduced tantalum pentoxide by electrochemical technique for oxygen reduction reaction

A non-Pt based electrocatalyst, tantalum oxide (TaOx) deposited on glassy carbon, for oxygen reduction reaction (ORR) in acidic solutions was prepared by electrochemical technique. The tantalum pentoxide (Ta2O5) formed on the as-prepared deposits was electrochemically reduced to generate its reduced species which conventionally need a heat treatment under H2 atmosphere. The reduced Ta2O5 shows a fairly high onset potential of ORR (0.87 V vs. RHE) in comparison with that (0.98 V) at a commercially available Pt/C catalyst. The ORR performance of the TaOx was investigated using a rotating ring-disk electrode voltammetry showing that a four-electron ORR takes place actually at potential above ca. 0.8 V and a two-electron ORR becomes significant gradually as the potential is increased negatively.