Alloying with Mn Enhances the Activity and Durability of the CoPt Catalyst toward the Methanol Oxidation Reaction

Abstract

To improve the catalytic performance and durability of Pt catalysts used for the methanol oxidation reaction (MOR) in direct methanol fuel cells (DMFCs), alloying of Pt with other transition metals such as Ru, Co, Ni, and Fe is considered an effective approach. Despite the significant progress made in the preparation of bimetallic alloys and their utilization for MOR, improving the activity and durability of the catalysts to make them commercially viable remains a stiff challenge. In this work, trimetallic Pt100–x (MnCo) x (16 < x < 41) catalysts were successfully synthesized via borohydride reduction followed by hydrothermal treatment at 150 °C. The electrocatalytic performance of the synthesized trimetallic Pt100–x (MnCo) x (16 < x < 41) catalysts toward MOR was studied using cyclic voltammetry and chronoamperometry. The results affirm that all Pt100–x (MnCo) x (16 < x < 41) alloys have superior MOR activity and durability as compared to bimetallic PtCo alloys and commercially available Pt/C (comm. Pt/C) catalysts. Among all the compositions studied, the Pt60Mn1.7Co38.3/C catalyst exhibited superior mass activity (1.3 and 1.9 times higher than those of Pt81Co19/C and comm. Pt/C, respectively) toward MOR. Furthermore, all the newly synthesized Pt100–x (MnCo) x /C (16 < x < 41) catalysts showed better CO tolerance when compared with comm. Pt/C. This improved performance of the Pt100–x (MnCo) x /C (16 < x < 41) catalyst can be attributed to the synergistic effect of Co and Mn on the Pt lattice.

Low-Pt Octahedral PtCuCo Nanoalloys: “One Stone, Four Birds” for Oxygen Reduction and Methanol Oxidation Reactions

“…The activity enhancement of the MOR could be explained by the electron effect (the strain effect caused by the mismatch of the lattice constant and the ligand effect caused by the electronic state change) and the synergistic/bifunctional effect of the alloying PtCuCo nanooctahedron. , On one hand, the electron effect (i.e., compressive strain and/or ligand effect) that was triggered by the introduction of Cu and Co favored a weakening of the adsorption strength of the carbon-containing intermediate species that were adsorbed on the Pt sites. On the other hand, the surface oxyphilic Cu and Co sites would activate water and provide more reactive oxygen species (Cu-OH ads and Co-OH ads ), which were expected to oxidize the strongly adsorbed CO ads species on adjacent Pt sites (Pt-CO ads ) by a so-called synergistic/bifunctional effect. , It was easier to oxidize CO on Pt 0.23 Cu 0.64 Co 0.13 /C than on Pt/C, which was confirmed by CO stripping experiments in both acidic and alkaline electrolytes. As shown in Figure f–i, the Pt 0.23 Cu 0.64 Co 0.13 /C had a much lower onset potential/peak potential than Pt/C: 0.812/0.848 V (in acid) and 0.474/0.646 V (in alkaline) versus 0.852/0.933 V (in acid) and 0.561/0.69 V (in alkaline), respectively.…”

“…On the other hand, the surface oxyphilic Cu and Co sites would activate water and provide more reactive oxygen species (Cu-OH ads and Co-OH ads ), which were expected to oxidize the strongly adsorbed CO ads species on adjacent Pt sites (Pt-CO ads ) by a so-called synergistic/bifunctional effect. 15,61 It was easier to oxidize CO on Pt 0.23 Cu 0.64 Co 0.13 /C than on Pt/C, which was confirmed by CO stripping experiments in both acidic and alkaline electrolytes. As shown in Figure 4f−i, the Pt 0.23 Cu 0.64 Co 0.13 /C had a much lower onset potential/peak potential than Pt/C: 0.812/0.848 V (in acid) and 0.474/0.646 V (in alkaline) versus 0.852/0.933 V (in acid) and 0.561/0.69 V (in alkaline), respectively.…”

MnO–Co@Pt nanowires encapsulated in N-doped porous carbon derived from MOFs for efficient electrocatalytic methanol oxidation reaction

“…The strong diffraction peaks of the synthesized Mn-BTC indicated a high level of crystallinity. 34–36 Compared with ZIF-67 and Mn-BTC, the XRD peaks of Mn-BTC@ZIF-67 were predominantly derived from ZIF-67, demonstrating the successful preparation of Mn-BTC@ZIF-67. Furthermore, the Pt content in the MnO–Co@Pt NPC 800 15% was determined using ICP-OES analysis (Table S1†), which revealed a Pt content of approximately 9.85 wt%.…”

High-Entropy Alloy PtCuNiCoMn Nanoparticles on rGO for Electrooxidation of Methanol and Formic Acid

“…These CV curves have significantly different shapes as compared to those obtained without methanol. Consider the CV curve of the PtCuNiCoMn/rGO catalyst as an example; in the forward scan, the current density has rapidly improved after the potential exceeds 0.2 V, and an anodic peak appears at about 0.60 V. Meanwhile, in the backward scan, another anodic peak appears at about 0.48 V. The anodic peak in the forward scan comes from the electrooxidation of methanol, and the other anodic peak in the backward scan comes from the electrooxidation of intermediates. − The mass activities are obtained from the peak current density in the forward scan, as shown in Figure d. The mass activities of PtCuNiCoMn/rGO, PtCuNiCo/rGO, PtCuNi/rGO, PtCu/rGO, Pt/rGO, and commercial Pt/C are 789.4, 346.4, 336.1, 238.2, 183.6, and 237.78 mA mg Pt –1 , respectively.…”