Structure-dependent electronic modulation of Pt on perovskite surfaces: bifunctional oxygen catalysts for rechargeable Zn–air batteries

Abstract

The Zn–air batteries (ZABs) have emerged as promising candidates for advancing energy storage systems in the transition to a clean energy society. Nevertheless, the sluggishness of the oxygen reduction/evolution reaction (ORR/OER) on the air cathode is a prevalent problem in ZABs. Herein, we designed perovskite catalysts with platinum (Pt) loading to function as an oxygen electrocatalyst for the cathode to explore the modulation of their crystal and electronic structure with the goal of enhancing their catalytic performance. Barium titanate-based manganese-doped perovskites (BaTi_1−xMn_xO_3−δ) were designed, and their structural transitions (tetragonal → hexagonal → rhombohedral) were confirmed by Rietveld refinement analysis. With a low level of deposited Pt on the surface, the structural variation of perovskite led to changes in the electronic and chemical properties of surface Pt, thereby affecting its catalytic behaviour. In particular, hexagonal Pt–BaTi_0.8Mn_0.2O_3−δ exhibited the co-formation of metallic Pt⁰ and oxygen vacancies, which collectively promoted the O* spillover pathway during oxygen redox reactions, leading to an excellent bifunctional performance of ΔE = 1.02 V. For a ZAB application, this catalyst exhibited remarkable performance, with a specific capacity of 736 mA h g⁻¹ and maintained cyclic stability over 250 h and 1500 cycles, demonstrating that the electronic interactions between the perovskite and the surface Pt varies depending on the crystal structure. By proposing an efficient spillover-assisted reversible oxygen reaction mechanism, this work provides a design strategy for high-performance bifunctional electrocatalysts in ZABs.