Deciphering dynamic structural modulation of exogenous Fe3+ integrated into Ni-based anode toward oxygen electrocatalysis for rechargeable zinc-air batteries

Abstract

To promote the application of green energy technologies, the development of superior catalytic systems meeting both activity and stability requirements is urgently needed. Exogenous ions have been found to exhibit remarkable efficacy, while the fundamental way of their role remains ambiguous, and their implementation in devices such as zinc-air batteries (ZABs) has not been reported yet. Combined with quasi in-situ XAS, in-situ XPS, and operando Raman characterizations, we comprehensively monitor the dynamic assistance process of electrolytic Fe ions on the oxygen evolution reaction (OER) performance of NiO_x-based materials. Fe ions can rapidly couple with O sites, inducing benign distortion of the lattice motif of γ-NiOOH, directly forming O vacancies. Furthermore, they lengthen M-O bonds, and optimize the overall charge distribution state, hence reducing binding energies of oxygen-containing intermediates. Moreover, novel Fe⁴⁺ species can be generated, and the abundant valence states (2 +/3 +/4 +) of Fe ions enable them to donate or accept electrons from surrounding Ni sites, thereby enhancing catalytic flexibility. These benefits endow NiO_x@C-700/60 with remarkable OER activity with the TOF value reaching 17.83 s⁻¹ at an overpotential of 300 mV and exceptional ZAB performance with cycle durability of 1200 hours (3600 charge-discharge cycles), showing dazzling industrial application prospects.