The synthesis of glutathione-coated Ag/Pt/Pd alloy nanoparticles (NPs) and their self-assembly into aerogels for the electro-oxidation of methanol and ethanol within fuel cells is discussed. Lower carbon dioxide emissions make the use of methanol and ethanol in fuel cells more attractive than traditional petroleum fuels from an environmental standpoint. While direct alcohol fuel cells (DAFC) have potential, the reactions are often slow, inefficient and require costly and rare earth metals. The use of NP structures provide materials with a high surface to volume ratio, large enough for practical use, while alloying the metals reduces the amount of precious metals needed. Additionally, oxidative removal of surface ligands induces direct interconnectivity of NPs. Direct connections and the nature of aerogel superstructures provide a rapid transport and enhanced diffusion of charge carriers and analytes to reactive surfaces, increasing both the DAFC activity and structural stability. Three distinct compositions of Ag/Pt/Pd alloy NPs were produced using stepwise galvanic replacement reactions starting with a glutathione (GSH)-coated Ag sacrificial NP template. The ternary alloy NPs were subject to oxidation using tetranitromethane, yielding hydrogels. Subsequent aerogel superstructures were produced by supercritical drying of the hydrogels. The as-synthesized self-supported aerogels showed direct NP connectivity, high surface area and porosity, and low densities. The catalytic activity of each Ag/Pt/Pd aerogel in methanol and ethanol was compared using cyclic voltammetry and chronoamperometry. Aerogels with higher amounts of Pt resulted in higher activity for methanol oxidation. All materials show high catalytic activity and stability for oxidation of alcohols under alkaline conditions.

Ag/Pt/Pd alloy nanoparticles and aerogels as high-efficiency alcohol oxidation electrocatalysts

ACS Spring 2022

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