Development of α‐MnO2 Nanowire with Ni and (Ni, Co) – Cation Doping as an Efficient Bifunctional Oxygen Evolution and Oxygen Reduction Reaction Catalysts

Selvakumar, Karuppiah, Duraisamy, Velu, Venkateshwaran, Selvaraj, Arumugam, Natarajan, Abdulrahman I., Almansour, Wang, Yucheng, Liu, Xiaoteng and Kumar, Sakkarapalayam Murugesan Senthil (2022) Development of α‐MnO2 Nanowire with Ni and (Ni, Co) – Cation Doping as an Efficient Bifunctional Oxygen Evolution and Oxygen Reduction Reaction Catalysts. ChemElectroChem, 9 (2). e202101303. ISSN 2196-0216

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Abstract

Manganese oxides (MnO 2 ) with nanowire morphology materials are a promising candidate 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 in order 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 of 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.

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