Effect of Small Nb-doping Amount on the Performance of BaCoO3-δ-based Perovskite as Bifunctional Oxygen Catalysts

Perovskite oxides are of great interest as cost-effective replacements for noble metals and oxides employed in bifunctional electrocatalysts including the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). In this work, a series of Bi/Nb co-doped BaCoO3-delta-based perovskite oxides BaBi0.05Co0.95-xNbxO3-delta (BBC0.95-xNx, x=0.1, 0.15, 0.2) were synthesized and evaluated as oxygen electrocatalysts for ORR and OER. It is interesting to note that Nb-doping amount is related to the contents of surface oxygen vacancies and oxidation states of cobalt, subsequently inducing performance differences among BBC0.95-xNx. Results show that BBC0.95-xNx have bifunctional electrocatalytic activities toward both ORR and OER in alkaline media. Compared with the BBC0.85N0.1 and BBC0.8N0.15, BBC0.75N0.2 with the highest Nb-doping rate delivered a lowest total overpotential between the ORR and the OER. Moreover, the BBC0.95-xNx catalysts deliver outstanding durability and methanol tolerance for ORR, better than Pt/C. BBC0.95-xNx holding promising application as nonprecious bifunctional catalysts.