Mo-Doped FeCoNiCu High-Entropy Alloys with Lattice Oxygen Activation for Stable Oxygen Evolution

The development of efficient and durable oxygen evolution reaction (OER) catalysts capable of operating at large current densities remains a critical challenge for renewable-energy technologies. Here, we report a Mo-doped FeCoNiCu high-entropy alloy (HEA) electrocatalyst that achieves enhanced OER activity and stability through high-valence Mo-induced lattice oxygen activation. The designed FeCoNiCuMo HEA nanoparticles exhibit low overpotentials of 340 mV at 100 mA cm–2, along with stability exceeding 650 h in alkaline media. Systematic studies reveal two key roles of Mo doping. It facilitates surface reconstruction by promoting lattice oxygen depletion and adsorbed oxygen generation. Meanwhile, it modulates the electronic structure of Ni sites to favor the formation of highly active β-NiOOH phases with shortened Ni–O bonds, a behavior distinctly different from Mo-free analogues. Furthermore, the FeCoNiCuMo HEA-based flexible zinc-air battery (FZAB) delivers a peak power density of 80 mW cm–2 with stable charge–discharge operation. This work offers a promising strategy for utilizing high-valence dopants to tailor the oxygen evolution pathway of HEAs for potential applications in energy conversion devices.