Rich Surface Oxygen Vacancies of MnO 2 for Enhancing Electrocatalytic Oxygen Reduction and Oxygen Evolution Reactions

Development of catalysts for the electrochemical oxygen reactions, namely, oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), is critical for the application of various renewable energy technologies. The aim of this work is to prepare low‐cost MnO 2 electrocatalyst with high activity for the ORR and OER via introduction of surface oxygen vacancies (OVs). Herein, the procedure of thermal heating treatment under air or H 2 has been demonstrated as an efficient way to create OVs on the surface of α‐MnO 2 and β‐MnO 2 nanorods, which are found to be highly active for both ORR and OER. The existence of surface OVs can modulate the intrinsic activity of α‐MnO 2 and β‐MnO 2 and improve their ORR and OER kinetics. More importantly, the H 2 ‐treated MnO 2 possesses much more surface OVs and thus exhibits much better catalytic performances for ORR and OER in comparison with MnO 2 obtained by common annealing treatments under air. Especially, the H 2 ‐treated α‐MnO 2 nanorods show the best activity for the ORR and OER. The results confirm that the heating treatment under H 2 reducing atmosphere can be a facile and efficient process to develop bifunctional Mn‐based electrocatalysts for electrochemical oxygen reactions.