Homogenic boundary effect boosted oxygen evolution reaction in α/β-NiMoO${}_4$ for rechargeable aqueous Zn-air battery

Rechargeable Zn-air batteries (ZAB) represent a promising avenue for sustainable energy storage, boasting high energy density, cost-effectiveness, scalability, and environmental friendliness. However, the sluggish redox kinetics and limited cycle life of bifunctional oxygen evolution/reduction (OER/ORR) electrocatalysts impede the further practical development of ZABs. In this study, homogenic boundary effect within α/β-NiMoO${}_4$ is introduced as a superior electrocatalyst for ZAB. Through in situ poikilothermic X-ray diffraction, X-ray absorption spectroscopy, and theoretical investigations, the active Ni atoms exhibit more effective electron transfer at α/β-NiMoO${}_4$ due to the homogenic boundary effect is unveiled. Furthermore, the presence of oxygen vacancies and lattice distortions at these boundaries significantly reduces the thermodynamic barrier of OER to a mere 0.46 V. Consequently, α/β-NiMoO${}_4$ demonstrates a remarkably low overpotential of 270 mV at 10 mA cm${}^{-2}$ for the bottlenecked OER, along with prolonged durability (150 h) and a high specific capacity (745 mAh g${}^{-1}$ at 5 mA cm${}^{-2}$) for ZAB. This study underscores the efficacy of homogenic boundary effects in enhancing electrocatalytic activities, offering great promise for the advancement of sustainable energy systems. (© 2024 Wiley‐VCH GmbH)