Ar/NH₃ Plasma Etching of Cobalt‐Nickel Selenide Microspheres Rich in Selenium Vacancies Wrapped with Nitrogen Doped Carbon Nanotubes as Highly Efficient Air Cathode Catalysts for Zinc‐Air Batteries

Abstract

This work utilizes defect engineering, heterostructure, pyridine N‐doping, and carbon supporting to enhance cobalt‐nickel selenide microspheres' performance in the oxygen electrode reaction. Specifically, microspheres mainly composed of CoNiSe₂ and Co₉Se₈ heterojunction rich in selenium vacancies (V_Se·) wrapped with nitrogen‐doped carbon nanotubes (p‐CoNiSe/NCNT@CC) are prepared by Ar/NH₃ radio frequency plasma etching technique. The synthesized p‐CoNiSe/NCNT@CC shows high oxygen reduction reaction (ORR) performance (half‐wave potential (E_1/2) = 0.878 V and limiting current density (J_L) = 21.88 mA cm⁻²). The J_L exceeds the 20 wt% Pt/C (19.34 mA cm⁻²) and the E_1/2 is close to the 20 wt% Pt/C (0.881 V). It also possesses excellent oxygen evolution reaction (OER) performance (overpotential of 324 mV@10 mA cm⁻²), which even exceeds that of the commercial RuO₂ (427 mV@10 mA cm⁻²). The density functional theory calculation indicates that the enhancement of ORR performance is attributed to the synergistic effect of plasma‐induced V_Se· and the CoNiSe₂‐Co₉Se₈ heterojunction. The p‐CoNiSe/NCNT@CC electrode assembled Zinc‐air batteries (ZABs) show a peak power density of 138.29 mW cm⁻², outperforming the 20 wt% Pt/C+RuO₂ (73.9 mW cm⁻²) and other recently reported catalysts. Furthermore, all‐solid‐state ZAB delivers a high peak power density of 64.83 mW cm⁻² and ultra‐robust cycling stability even under bending.