Sub‐2 nm Thiophosphate Nanosheets with Heteroatom Doping for Enhanced Oxygen Electrocatalysis

Abstract

Developing an efficient bifunctional electrocatalyst with accelerated kinetics is important but challenging for rechargeable metal‐air batteries. In this study, a series of anion‐regulated sub‐2 nm ultrathin thiophosphate nanosheets (NiPS 3–xSex NSs) is rationally designed and synthesized as bifunctional oxygen evolution/reduction reaction (OER/ORR) electrocatalysts for Zn‐air batteries. The increase of nominal Se dopants (0 ≤ x ≤ 0.5) leads to the expansion of (001) crystal plane spacing and partially disordered structure generation after the incorporation of Se to pristine NiPS 3. More importantly, electronic structures of active sites can be reasonably regulated via coordination of the interaction between anions and cations. Density functional theory calculations reveal that such tailored electronic structures reduce the overpotential of the thermodynamic barriers step for both OER and ORR as well as shorten energy bandgap, which can accelerate reaction kinetics in electrocatalytic processes and enhance electrical conductivity. Consequently, the obtained NiPS 3–xSex NSs exhibit low OER overpotential (250 mV) and positive ORR onset potential (0.94 V), large power density (152 mW cm−2), and robust stability (96 h cycle) for Zn‐air devices, far exceeding that of precious metal catalysts. This study provides a novel tactic to design earth‐abundant and highly efficient bifunctional electrocatalysts for metal‐air battery technologies.