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

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/CoO_V@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/CoO_V@NHCNB@NCNT, and they display exceedingly good electrocatalytic performance for oxygen reduction reaction (ORR, halfwave potential [E_{ORR, 1/2} = 0.855 V vs. reversible hydrogen electrode]) and oxygen evolution reaction (OER, overpotential (η_OER, 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/CoO_V@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

Author summay

Leijun Ye and Weiheng Chen contributed equally.