Development of α‐MnO<sub>2</sub> Nanowire with Ni‐ and (Ni, Co)‐Cation Doping as an Efficient Bifunctional Oxygen Evolution and Oxygen Reduction Reaction Catalyst
Karuppiah Selvakumar, Velu Duraisamy, Selvaraj Venkateshwaran, Natarajan Arumugam, Abdulrahman I. Almansour, Yucheng Wang, Xiaoteng Liu, Sakkarapalayam Murugesan Senthil Kumar
Abstract
Abstract Manganese oxides (MnO 2 ) with nanowire morphology materials are promising candidates for improving oxygen evolution and oxygen reduction reaction (OER/ORR) performance. In this work, we developed transition metal cation doping strategy into the α‐MnO 2 tunnel structure to tune the Mn oxidation states and control the uniform nanowire morphology, crystalline structure to investigate the effect of doping over bifunctional activity. The single Ni 2+ cation doping in α‐MnO 2 with various loading concentrations resulted in 8Ni−MnO 2 exhibiting remarkable OER and ORR activity owing to their excessive concentration of Mn 3+ and Mn 4+ octahedral sites respectively. Further, Co 2+ cation doping in 8Ni−MnO 2 leads to an enhanced synergistic effect that significantly improves the fraction of Mn 3+ quantity which is confirmed by average oxidation state. For electrochemical OER performance, 8Co−8Ni−MnO 2 exhibits a potential of 1.77 V, Tafel slope value of 68 mV dec −1 and lower charge transfer resistance and it is active in ORR with more positive onset potential of 0.90 V, half‐wave potential of 0.80 V, better current density (4.7 mA cm −2 ) and a four‐electron pathway. Moreover, bifunctional activity (ΔE=E OER @10 mA cm −2 – ORR@E 1/2 ) of 8Co−8Ni−MnO 2 demonstrated 0.97 V, indicates an excellent activity in alkaline electrolyte solution.