Oxygen Evolution Activity of Co–Ni Nanochain Alloys: Promotion by Electron Injection

Abstract

Metal alloy nanoparticles have shown promising applications in electrocatalysis. However, the nanoparticles usually suffer from limited charge‐transfer efficiency, which can be solved by preparing one‐dimensional materials. Herein, Co–Ni alloy nanochains are prepared by a direct‐current arc‐discharge method. The nanochains, comprised of mutually coupled uniform nanospheres, can range up to several micrometers in size. When the alloy is exposed to air or under the electro‐oxidation process, a metal–metal‐oxide heterostructure is obtained. The alloy can inject electrons into the oxide, which makes it more suitable for electrocatalysis. The composition of the samples can be changed by varying the ratio of Ni/Co (i.e., Co, Co₇Ni₃, Co₅Ni₅, Co₃Ni₇, Ni) in the synthesis process. The nanochains show good oxygen evolution performance that correlates with the Ni/Co ratio. Co₇Ni₃ demonstrates optimal activity with an onset point of 1.50 V vs. reversible hydrogen electrode (RHE) and overpotential of 350 mV at 10 mA cm⁻². The alloy nanochains also show excellent durability with 95.0 % current retention after a long‐term test for 12 h.