Co/CoO heterojunction rich in oxygen vacancies introduced by O2 plasma embedded in mesoporous walls of carbon nanoboxes covered with carbon nanotubes for rechargeable zinc–air battery

Abstract

Abstract Herein, Co/CoO heterojunction nanoparticles (NPs) rich in oxygen vacancies embedded in mesoporous walls of nitrogen‐doped hollow carbon nanoboxes coupled with nitrogen‐doped carbon nanotubes (P–Co/CoOV@NHCNB@NCNT) are well designed through zeolite‐imidazole framework (ZIF‐67) carbonization, chemical vapor deposition, and O2 plasma treatment. As a result, the three‐dimensional NHCNBs coupled with NCNTs and unique heterojunction with rich oxygen vacancies reduce the charge transport resistance and accelerate the catalytic reaction rate of the P–Co/CoOV@NHCNB@NCNT, and they display exceedingly good electrocatalytic performance for oxygen reduction reaction (ORR, halfwave potential [EORR, 1/2 = 0.855 V vs. reversible hydrogen electrode]) and oxygen evolution reaction (OER, overpotential (ηOER, 10 = 377 mV@10 mA cm−2), which exceeds that of the commercial Pt/C + RuO2 and most of the formerly reported electrocatalysts. Impressively, both the aqueous and flexible foldable all‐solid‐state rechargeable zinc–air batteries (ZABs) assembled with the P–Co/CoOV@NHCNB@NCNT catalyst reveal a large maximum power density and outstanding long‐term cycling stability. First‐principles density functional theory calculations show that the formation of heterojunctions and oxygen vacancies enhances conductivity, reduces reaction energy barriers, and accelerates reaction kinetics rates. This work opens up a new avenue for the facile construction of highly active, structurally stable, and cost‐effective bifunctional catalysts for ZABs.

Keywords

• heterojunction
• oxygen evolution/reduction reaction
• oxygen vacancies
• rechargeable zinc–air battery
• three‐dimensional nitrogen‐doped hollow carbon nanoboxes