Plasma-Treated Ultrathin Ternary FePSe₃ Nanosheets as a Bifunctional Electrocatalyst for Efficient Zinc–Air Batteries

Developing novel bifunctional electrocatalysts with advanced oxygen electrocatalytic activity is pivotal for next-generation energy-storage devices. Herein, we present ultrathin oxygen-doped FePSe 3 (FePSe 3 –O) nanosheets by Ar/O 2 plasma treatment, with remarkable surface atom reorganization. Such surface atom reorganization generates multiple crystalline–amorphous interfaces that benefit the kinetics of oxygen evolution reaction, achieving a low overpotential of only 261 mV at 10 mA cm –2 with a small Tafel slope of 41.13 mV dec –1 . Density functional theory calculation indicates that oxygen doping can also modulate the electrical states at the Fermi level with a decreased band gap responsible for the enhanced electrocatalytic performance. Such unique FePSe 3 –O nanosheets can be further fabricated as the air cathode in rechargeable liquid zinc–air batteries (ZABs), which deliver a high open circuit potential of 1.47 V, a small charge–discharge voltage gap of 0.80 V, and good cycling stability for more than 800 circles. As a proof of concept, the flexible solid-state ZABs assembled with FePSe 3 –O nanosheets as cathode also display a favorable charge–discharge performance, durable stability, and good bendability. This work sheds new insights into the rational design of defect-rich ternary thiophosphate nanosheets by plasma treatment toward enhanced oxygen electrocatalysts in metal–air batteries.