High-index facet-rich quaternary PtCuFeCo octopods as anti-CO poisoning bifunctional electrocatalysts for direct methanol/ethylene glycol fuel cells

Abstract

High-index facets and doping strategies can generate unanticipated effects for Pt-based nanomaterials, but there is still a tremendous challenge to integrate the two advantages to construct advanced bifunctional electrocatalysts for direct proton/anion exchange membrane alcohol fuel cells. Herein, we successfully synthesized quaternary Pt_41.8Cu_51.6Fe_5.0Co_1.6 octopod nanocrystals (ODNs) with high-index facets through a double active auxiliary doping strategy. Electrochemical activity analysis reveals that Pt_41.8Cu_51.6Fe_5.0Co_1.6 ODNs/C could serve as an alluring bifunctional electrocatalyst for acidic methanol oxidation reaction (MOR) and alkaline ethylene glycol oxidation reaction (EGOR), displaying mass activities of 2.44 and 23.54 A mg_Pt⁻¹, respectively, which were 6.4 and 8.2 times higher than those of commercial Pt/C. Notably, Pt_41.8Cu_51.6Fe_5.0Co_1.6 ODNs/C demonstrated high power densities superior to those of Pt/C in practical direct proton exchange membrane methanol fuel cell (81.4 mW cm⁻²versus 41.8 mW cm⁻² of commercial Pt/C) and direct anion exchange membrane ethylene glycol fuel cell (217.5 mW cm⁻²versus 93.6 mW cm⁻² of commercial Pt/C) devices. Physical characterization studies indicated that the superior activity originated from the exposed surface of the high-index facets and the optimization of the Pt d-band center by alloying; in addition, the near-surface hydrophilic Fe and Co auxiliaries also facilitated the generation of active hydroxyl species, which further boosted the 6e⁻ MOR and 10e⁻ EGOR processes and anti-CO poisoning ability, as confirmed via in situ Fourier transform infrared spectroscopy. This work provides a feasible example for constructing efficient bifunctional low-Pt electrocatalysts for practical direct proton/anion exchange membrane alcohol fuel cell devices by integrating the merits of doping and high-index facets.