Optimizing the catalytic activity of PtRuM (M = Fe, Co, Ni) nanoparticles on mesoporous carbon Vulcan–multiwalled carbon nanotubes support for direct methanol fuel cells by controlling third-metal type and content

PtRu/C material is one of the most well-known and efficient anode catalysts in direct methanol fuel cells (DMFCs). Nevertheless, new anode catalysts with even higher performance and lower cost are indispensable for the further development of this fuel cell technology. The present study reports the synthesis and characterization of ternary alloy catalysts of Pt 1 Ru 1 M x (M = Fe, Co, Ni; x = 1, 3)/C-MWCNTs and Pt 1 Ru 1 Co y (y = 0, 0.5, 1, 2, 3, 4)/C-MWCNTs to optimize the material composition toward the enhanced methanol oxidation activity and improved CO tolerance for DMFCs. With fixing the atomic ratio of Pt:Ru = 1:1 and carbon Vulcan–multi-walled carbon nanotubes (C-MWCNTs) composite support with mass ratio C:MWCNTs = 7:3, the designed catalysts changed the third metal M (Fe, Co, Ni) and the Co atomic composition. The electrochemical study showed that all the Pt 1 Ru 1 M x (M = Fe, Co, Ni; x = 1, 3)/C-MWCNTs ternary catalysts presented significantly higher methanol oxidation activity over the corresponding Pt 1 Ru 1 /C-MWCNTs binary alloy. Remarkably, the catalytic performance of ternary metal nanoparticles on the C-MWCNTs support was PtRuCo/C-MWCNTs > PtRuNi/C-MWCNTs > PtRuFe/C-MWCNTs, the electron transfer resistance of those was PtRuCo/C-MWCNTs < PtRuNi/C-MWCNTs < PtRuFe/C-MWCNTs, but the resistance to CO poisoning was PtRuFe/C-MWCNTs > PtRuCo/C-MWCNTs > PtRuNi/C-MWCNTs. Since Co exhibited as the best additional metal over Fe and Ni for both x = 1 and 3, the Pt 1 Ru 1 Co y (y = 0, 0.5, 1, 2, 3, 4)/C-MWCNTs were studied in detail. As a result, the Co content greatly affected the methanol oxidation efficiency, in which Pt 1 Ru 1 Co 2 /C-MWCNTs revealed the highest value of current density (j f = 227.4 mA/mg PtRu ) and the smallest electron transfer resistance (R et = 2.76 Ω cm 2 ). Moreover, all the catalyst systems displayed strong tolerance for CO poisoning because of the small reverse anodic current density. Particularly, Pt 1 Ru 1 Co 2 /C-MWCNTs catalyst exhibited not only the highest methanol oxidation ability but also the lowest electron transfer resistance, which is suitable for use in DMFCs anode electrodes.