A simple strategy to construct cobalt oxide-based high-efficiency electrocatalysts with oxygen vacancies and heterojunctions

Bare nonprecious metal oxides are generally considered to have low HER activity, but they have the advantages of abundant resources and low cost. Herein, a facile strategy to construct abundant oxygen vacancies with heterogeneous structures of oxygen-vacancies CoFe 2 O 4 /oxygen-vacancies cobalt oxides/nickel foam (Ov-CoFe 2 O 4 /CoO x /NF) is developed using gas-phase cation exchange. Benefiting from abundant oxygen vacancies, the strong interfacial coupling effects between oxygen-vacancies CoFe 2 O 4 (Ov-CoFe 2 O 4 ) and oxygen-vacancies cobalt oxides (Ov-CoO x ), a nanorod structure and the highly conductive nickel foam support, Ov-CoFe 2 O 4 /CoO x /NF exhibits a low overpotential of 59 mV and achieved a current density of 10 mA cm −2 in a 1 M KOH solution. Ov-CoFe 2 O 4 /CoO x /NF//Ov-CoFe 2 O 4 /CoO x /NF exhibits a low water splitting voltage of 1.51 V at 10 mA cm −2 . Density functional theory calculations suggest that oxygen vacancy and interfacial coupling effects can both improve conductivity of electrocatalysts . This study provides a facile design for simultaneous realization of oxygen vacancy modification and heterostructure, which may become a simple strategy to use oxides to improve HER performance.