Nanoporous Au-Cu-Pt As a Superior Electro-Catalyst for the Methanol Oxidation Reaction

Abstract

Among fuel cells, the direct methanol fuel cell (DMFC) has attracted great attention and has been considered a very promising power source because of the ease of methanol transportation and its high energy density. A major limiting factor hindering DMFC’s commercial application is the poor catalytic performance in the anode (methanol oxidation reaction). The methanol oxidation reaction (MOR) requires (OH-) from water dissociation as an oxygen donor for the reaction; however, the slow water dissociation on Pt limits the rate of MOR. In addition to the sluggish catalytic activity, the other major impediment for Pt catalysts is the generation of carbon monoxide (CO) during the MOR process.In order to improve the catalytic performance of MOR catalysts, a variety of catalyst design strategies have been devised. The interesting way of carrying out the MOR catalytic process is the non-CO pathway which takes place on Pt-Au bimetallic catalysts, thus eliminating CO poisoning. However, the overall activity of Pt-Au alloys in MOR is relatively low, which ultimately limits the application of Pt-Au catalysts.In this study, a nanoporous (np) Au-Cu-Pt thin-film catalyst with a fine structure and tunable composition is synthesized by using a facile method involving successive electrodeposition and de-alloying. SEM, SEM-EDX and ICP have been used for morphology characterization and composition assessment. Pb under-potential deposition (UPD), H UPD and CO stripping tests have been employed to determine the electrochemical active surface area (ECSA) and to probe the Pt active sites specifically. Also, cyclic voltammetry (CV) tests have been performed to assess the catalytic performance in MOR. Finally, long-term CV and chronoamperometry (constant potential) tests have been used to study and evaluate the durability of accordingly synthesized catalyst for MOR.The prepared np Au-Cu-(8% in the precursor alloy)Pt catalyst exhibits outstanding mass and specific activity toward the MOR, which is approximately six- and nine-times higher than the activity of a commercial Pt/C(40%) counterpart, respectively. A negative 75 mV onset potential shift upon the MOR anodic scan on the np Au-Cu-(8 %)Pt catalyst in comparison with Pt/C(40%) corroborates its higher catalytic activity. Furthermore, the alloy catalyst demonstrates better durability than the Pt/C(40%) counterpart in a three-hour constant potential test and exhibits full post-factum recovery of its cycling activity. In addition, it retains more than 60% of its original activity after 3000 cycles of an accelerated degradation test.Reference:Xie, Y., Li, C., Razek, S.A., Fang, J. and Dimitrov, N., 2020. Synthesis of Nanoporous Au− Cu− Pt Alloy as a Superior Catalyst for the Methanol Oxidation Reaction. ChemElectroChem, 7(2), pp.569-580.