Block Copolymer Templated Synthesis of Core–Shell PtAu Bimetallic Nanocatalysts for the Methanol Oxidation Reaction

Direct methanol fuel cells (DMFCs) are an attractive portable energy technology due to their low operating temperatures, high-energy conversion efficiency, and lower pollutant production. For over a half-century, the default electrocatalyst for DMFCs has been platinum (Pt). The barriers to widespread deployment of DMFCs, however, are largely linked to the cost of this precious metal and its propensity to become poisoned in its role as the anode catalyst for the oxidation of methanol. Bimetallic platinum–gold (PtAu) catalysts, however, offer superior activity for the oxidation of methanol and can operate with increased electrocatalytic stability and resistance to poisoning. Here, we demonstrate a block copolymer template strategy for the preparation of arrays of clusters of PtAu nanocatalysts with tailored composition, particle density, and electrochemical activity. A detailed characterization by XPS, TEM, EDX, and electrochemistry was used to assign a core–shell nanostructure to the 3 nm PtAu nanocatalysts that constitute the clusters. The activity Pt-rich core–shell PtAu nanocatalysts for the electrocatalytic oxidation of methanol was approximately 2–4-fold that of a current Pt benchmark catalyst (ETEK), only 28% less than that of the PtRu bimetallic benchmark catalyst (XC-72R), and, in comparison to these same catalysts, exhibited a 2- to 3-fold increase in its metric for tolerance to carbonaceous poisoning (I_f/I_b ratio).