Synergistic Cu@CoOx core-cage structure on carbon layers as highly active and durable electrocatalysts for methanol oxidation

Abstract

Active and inexpensive electrocatalysts for methanol oxidation reaction (MOR) are highly required for the practical application of direct methanol fuel cells (DMFCs). However, efficient MOR is limited by using the expensive and rare noble metal-based catalysts. Here we report a Cu@CoOx core-cage nanostructure on carbon layers (CLs) for superior electrocatalysis of MOR in the alkaline media, which shows an excellent specific activity of 150.41 mA cm−2 and a high mass activity of 467.94 mA mg-1 at the potential of 0.8 V vs. SCE (1.85 V vs. RHE) in 1 M KOH + 1 M CH3OH. It represents the highest MOR activity ever reported for noble metal-free catalysts. Synchrotron radiation based in-situ X-ray absorption spectroscopy reveals that the outside CoOx cage can form a high Co4+ state to easily oxidize methanol, while the adsorption experiments indicate that Cu can act as the methanol adsorption center. The capture-catalysis process on the core-cage structure thus leads to the excellent MOR activity. The CLs can also anchor the Cu@CoOx particles and accelerate the charge transport to enhance the performance. The Cu@CoOx-CLs catalyst is economical, abundant, highly active and stable, which has the potential to act as a good alternate material for noble metal-based catalysts in DMFCs.