Ar/NH 3 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 2 and Co 9 Se 8 heterojunction rich in selenium vacancies (V Se· ) wrapped with nitrogen-doped carbon nanotubes (p-CoNiSe/NCNT@CC) are prepared by Ar/NH 3 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 RuO 2 (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 CoNiSe 2 -Co 9 Se 8 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+RuO 2 (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.