Enhancing the activity and stability by coupling Ni-M bimetals and TaN for methanol oxidation reaction in alkaline media

Abstract

Developing the efficient and durable non-platinum based electrocatalysts for methanol oxidation reaction is critical for the application of direct methanol fuel cells (DMFCs). Here, a series of Ni-based catalysts are synthesized via the microwave-assisted ethylene glycol reduction method, which couples the oxyphile metals with transition metal nitrides (TaN), to study the electrocatalytic behavior for methanol oxidation reaction in alkaline media. The results of transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) indicate that the existence of geometric and electronic effects among Ni, Cu/Sn and TaN. Electrochemical measurements indicate that NiCu-TaN/C and NiSn-TaN/C exhibit high activity with 256.02 and 224.03 mA·cm−2, high surface coverage of redox species, abundant active sites, long-term durability and fast reaction kinetics. In situ ATR-SEIRAS results imply that methanol oxidation reaction mainly goes through the direct pathway on the synthesized catalysts. Combined with the structural characterization and electrochemical measurements, it can be found that the enhanced catalytic performance of bimetallic catalysts can be ascribed to the synergistic effect with coupling the oxyphile metals with TaN. The introduction of Cu/Sn and TaN will change the electronic structure of Ni and coverage of Ni(OH)2/NiOOH redox species on the catalyst surface, which modify the adsorption characteristic of reaction intermediates and formation of HCOO, CO2 and OH species following the direct path in alkaline MOR.