Study on Methanol Oxidation at Pt and PtRu Electrodes by Combining in situ Infrared Spectroscopy and Differential Electrochemical Mass Spectrometry

Methanol oxidation reaction (MOR) at Pt and Pt electrode surface deposited with various amounts of Ru (denoted as PtxRuy, nominal coverage y is 0.17, 0.27, and 0.44 ML) in 0.1 mol/L HClO4+0.5 mol/L MeOH has been studied under potentiostatic conditions by in situ FTIR spectroscopy in attenuated-total-reflection configuration and differential electrochemical mass spectrometry under controlled flow conditions. Results reveal that (1) CO is the only methanol-related adsorbate observed by IR spectroscopy at all the Pt and PtRu electrodes examined at potentials from 0.3 V to 0.6 V (vs. RHE); (ii) at Pt0.56Ru0.44, two IR bands, one from CO adsorbed at Ru islands and the other from COL at Pt substrate are detected, while at other electrodes, only a single band for COL adsorbed at Pt is observed; (iii) MOR activity decreases in the order of Pt0.73Ru0.27>Pt0.56Ru0.44>Pt0.83Ru0.17>Pt; (iv) at 0.5 V, MOR at Pt0.73Ru0.27 reaches a current efficiency of 50% for CO2 production, the turn-over frequency from CH3OH to CO2 is ca. 0.1 molecule/(site.sec). Suggestions for further improving of PtRu catalysts for MOR are provided.