Effect of Iron Concentration and Annealing Conditions on the Catalytic Performance of Co–Mn Spinel Oxides with a Unique Nanowire–Nanosheet Coexisting Structure for Water Oxidation

In this work, cobalt–manganese–iron trimetallic oxide (CoMnFeO4) with a unique nanowire–nanosheet coexisting structure was synthesized by a hydrothermal method, followed by calcination. It is worth mentioning that the optimal iron concentration was 1.5 mmol and the suitable calcination temperature was 300 °C for 1 h in the Ar atmosphere. The as-prepared CoMnFeO4 showed outstanding oxygen evolution reaction (OER) performance in an alkaline medium with low overpotentials of 242 and 331 mV at a Tafel slope of 102 mv dec–1 to deliver current densities of 10 and 50 mA cm–2. The enhanced OER performance can be ascribed to the intrinsic electrocatalytic activity, which resulted from the porous nickel foam substrate, excellent structural stability, and the synergetic effect of multi-cations in the trimetallic catalyst, low solution resistance, fast electron transportation, and efficiently exposed active sites.