Promoting the catalytic properties of the medium-entropy Co-Fe-Ni alloy toward water splitting and methanol oxidation by introducing a small amount of Cu and Al

Multi-component alloys attract significant attentions as the efficient electrocatalysts due to the synergistic effects of their compositions. However, these multi-component alloys are difficult to synthesize under the mild conditions and generally do not possess the multi-functional electrocatalytic properties. In this work, a simple electrodeposition method is proposed to synthesize a medium-entropy CoFeNi alloy containing a small amount of Cu and Al on nickel foam (NF-CoFeNiCuAl). NF-CoFeNiCuAl has an amorphous structure and exhibits a porous microsphere morphology. Notably, owing to the synergistic interactions among various metal elements and special microstructural features, NF-CoFeNiCuAl has the excellent multi-functional electrocatalytic activities, and its potentials for the oxygen evolution, hydrogen evolution, and methanol oxidation reactions (OER, HER and MOR) at a current density of 100 mA cm ⁻² reach 1.486, 0.095 and 1.37 V, respectively. Moreover, the electrolyzer with NF-CoFeNiCuAl as both cathode and anode not only has a low electrolysis voltage (1.73 V) for alkaline water splitting but also exhibits the superior long-term stability at 100 mA cm ⁻². Replacing OER by MOR, the water splitting voltage can be further reduced to 1.67 V, and the high value-added formate can be prepared with high selectivity (98.7 %). Our work introduces a new approach for developing multi-component alloys with highly efficient and multi-functional electrocatalytic activities.