Heterojunction-induced nickel-based oxygen vacancies on N-enriched porous carbons for enhanced alkaline hydrogen oxidation and oxygen reduction

Abstract

In an attempt to promote the commercialization of hydrogen fuel cells with a hydroxide-exchange membrane, a cost-efficient Ni/NiO/N-doped porous carbon (NC) catalyst with suitable Ni/NiO heterojunctions was fabricated by the fine calcination of a Ni-based metal–organic framework precursor. This in situ carbonization not only promotes the development of a heterointerface with a high content of oxygen vacancies, but also facilitates the formation of N-doped graphitic carbon with high conductivity. Benefiting from its favorable composition and the formed heterostructures, the resulting Ni/NiO/NC exhibits improved activity and durability for the hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) in an alkaline electrolyte, which makes it a promising electrode catalyst for hydroxide exchange membrane fuel cells. It is demonstrated that the abundant Ni/NiO interfaces and oxygen vacancies significantly improve the efficiency of hydrogen oxidation, and the large amount of pyridine-N atoms is considered to be the main factor responsible for the enhanced oxygen reduction capability. This work demonstrates the significant effect of heterointerfaces on the electrochemical reactions, thus providing novel inspiration for advanced electrocatalyst design.