Platinum-based metal alloys have been generally developed to provide high carbon monoxide resistance in the anodes of direct methanol fuel cells. We report the potential of bimetallic platinum/iridium electrocatalysts in preserving the outstanding carbon monoxide tolerance obtained from both experimental and theoretical studies, which represents the enhanced electrochemical performance of methanol oxidation and the in-depth and stepwise investigations for reaction mechanisms, respectively. In this study, the findings highlight the dual-enhancement characteristics of low carbon monoxide adsorption energy (electronic effect) and carbon monoxide oxidative removal (bifunctional effect) compared with various electrocatalysts such as platinum, iridium, and platinum/ruthenium alloys. In addition, the reaction affinity of platinum/iridium alloys for methanol dehydrogenation is also studied in accordance with atomistic properties, such as adsorption energy and electronic band gap, to understand the electrochemical performance compared to Pt. The results obtained indicate that the platinum/iridium alloy surface played diverse roles in terms of its multifunctional behaviors for carbon monoxide tolerance, including the favorable mechanism of methanol dehydrogenation. It turns out that throughout the theoretical in-depth studies, platinum/iridium alloys are promising candidates in terms of the extension for electrocatalytic material designs that differ from Ru in direct methanol fuel cells.
Keywords: bifunctional effect; carbon monoxide tolerance; density functional theory; iridium; methanol oxidation reaction; platinum.