Enhanced Electrocatalytic Activity of Murdochite-Type Ni₆MnO₈ for Water Oxidation via Surface Reconstruction

Ni-Mn-based binary oxides are deemed as prospective electrocatalysts for water oxidation. Here, a murdochite-type Ni₆MnO₈ electrocatalyst for water oxidation is reported. Murdochite-type Ni₆MnO₈ with hollow sphere (NMO-HS) and microflower (NMO-MF) structures has been controllably synthesized. After an in-situ activation process, the NMO-MF affords a superior activity for oxygen evolution reaction in 0.1 M KOH. A low overpotential of 370 mV at 10 mA cm^-2 is obtained, and the mass activity of activated NMO-MF is 1.96 times that of commercial IrO₂/C. As revealed by in-situ Raman spectra, Ni species in activated NMO-MF act as intrinsic active sites, and the in-situ formed NiOOH on the surface during the activation process is identified to contribute to the significantly enhanced catalytic activity. The Zn-air battery assembled with a NMO-MF cathode showed an exceptional power density (0.228 W cm^-2) and long-term cycling stability (148 h).