Ar/NH 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.

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 CoNiSe and CoSe heterojunction rich in selenium vacancies (V) wrapped with nitrogen-doped carbon nanotubes (p-CoNiSe/NCNT@CC) are prepared by Ar/NH radio frequency plasma etching technique. The synthesized p-CoNiSe/NCNT@CC shows high oxygen reduction reaction (ORR) performance (half-wave potential (E) = 0.878 V and limiting current density (J) = 21.88 mA cm). The J exceeds the 20 wt% Pt/C (19.34 mA cm) and the E 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), which even exceeds that of the commercial RuO (427 mV@10 mA cm). The density functional theory calculation indicates that the enhancement of ORR performance is attributed to the synergistic effect of plasma-induced V and the CoNiSe-CoSe heterojunction. The p-CoNiSe/NCNT@CC electrode assembled Zinc-air batteries (ZABs) show a peak power density of 138.29 mW cm, outperforming the 20 wt% Pt/C+RuO (73.9 mW cm) and other recently reported catalysts. Furthermore, all-solid-state ZAB delivers a high peak power density of 64.83 mW cm and ultra-robust cycling stability even under bending.