Highly Efficient Methanol Oxidation Reaction Achieved by Cobalt Doping in Delafossite AgNi1–xCoxO2 Solid Solution

Abstract

Developing highly active and durable non-platinum catalysts for methanol oxidation is of great significance for direct methanol fuel cells. However, their electrocatalytic efficiency is still insufficient mainly due to their poor electrical conductivity and slow reaction kinetics. Herein, a non-Pt electrocatalyst AgNi0.8Co0.2O2 with a delafossite structure is facilely constructed via a cation-exchange strategy for the methanol oxidation reaction in alkaline media. The introduction of Co atoms is favorable to crystallization for boosting the synthesis procedure. Meanwhile, the uniform distribution of Co and Ni in the structure brings about additional oxygen vacancies in the materials, thereby improving the intrinsic methanol oxidation reaction activity of the catalysts, and the introduced Co atoms can help to oxidize intermediates such as formaldehyde. Therefore, the electrocatalyst exhibits excellent electrocatalytic performance (77.6 mA cm–2, 220 mA mg–1) and high selectivity, and it can effectively inhibit the oxygen evolution reaction (310 mV difference from the oxygen evolution reaction potential at 10 mA cm–2). This work not only provides a material system using cheap and effective non-Pt catalysts based on Ag-based delafossite oxides but also sheds light on the engineering of oxygen vacancies of electrocatalysts for developing high-performance direct methanol fuel cells.