Conducting polymer nanofiber-supported Pt alloys: unprecedented materials for methanol oxidation with enhanced electrocatalytic performance and stability

Abstract

Conducting polymer nanostructures can be utilized as catalyst supports as alternatives to traditional carbon support materials, which is promising for fuel cell applications in the near future. We synthesized Pt nanoparticles (NPs) and Pt NPs-based multimetallic alloys on polypyrrole (Ppy) nanofibers by a facile and greener approach via radiolysis without using any reducing agents. Compared with the Pt NPs, the binary (Pt₆₆Pd₃₄/Ppy) and ternary (Pt₂₄Pd₂₆Au₅₀/Ppy) electrocatalysts demonstrate superior catalytic activities for methanol oxidation in alkaline medium as well as better tolerance to intermediate poisoning. Most importantly, the catalytic activity of Pt₂₄Pd₂₆Au₅₀/Ppy significantly improved up to 12.5 A per mg Pt, which is ∼15 times higher than that of commercial Pt/C (0.85 A per mg Pt). This can be attributed to the high number of intrinsic active sites, including Pt–Pd–Au heterojunctions, and cooperative action of the three metals in the alloy composition as well as close contact with the polymer nanofibers. Moreover, the chronoamperometric curves confirm the better stability of the ternary alloy catalysts compared to binary and commercial carbon-supported catalysts. The effective dispersion of the NPs within the polymer nanofibers can improve the catalytic activity. Long-term stability of the catalysts may be achieved via facilitating access of methanol molecules to the catalytic sites and preventing agglomeration of the Pt NPs. Hence, these polymer-supported Pt nanoalloys have promising applications as anode electrocatalysts in direct methanol fuel cells (DMFCs).