Methanol Oxidation Using Ternary Ordered Intermetallic Electrocatalysts: A DEMS Study

The sluggish methanol oxidation reaction (MOR) remains the biggest challenge for direct methanol fuel cells. To advance our understanding of the MOR mechanism, we have employed dual thin-layer differential electrochemical mass spectrometry (DEMS) to study reaction intermediates on a family of Pt-Fe-Cu ternary ordered intermetallics. We found that PtFe0.7Cu0.3/C exhibited the highest CO2 production efficiency, while PtFe0.5Cu0.5/C generated the largest proportion of methyl formate or formic acid. The different selectivity is partially ascribed to the difference in lattice compressive strain due to the incorporation of Fe and Cu atoms. We propose a dual-pathway mechanism in which the increase in lattice contraction can stabilize the intermediates forming methyl formate or formic acid, while a moderate lattice strain leads to the highest CO2 generation via COad intermediates. Our work on ternary catalysts may provide valuable insights for designing electrocatalysts for the MOR.