Aqueous Synthesis of Highly Dispersed Pt₂Bi Alloy Nanoplatelets for Dimethyl Ether Electro-Oxidation

The high mass and volume-specific energy of dimethyl ether (DME) relative to hydrogen make it an attractive alternative electrochemical fuel source for portable applications such as powering drones and eVTOLs. A key stumbling block to the development of direct DME fuel cells (DDMEFCs) is the poisoning of the electrocatalyst surface by oxidation intermediates such as COads. In this study, an all-queous colloidal synthesis method for producing highly dispersed Pt2Bi alloy nanoplatelets (NPT) to mitigate such poisoning is presented. NPT synthesis entails the use of stannous chloride as an autocatalytic reducing and stabilizing agent for both Pt and Bi salts in aqueous solution. Sn and Bi stripping from the surface of these NPT is found to maximize activity for DME electrooxidation (DMEOR) relative to commercial Pt-C. A stable chronoamperometric current of 3.3 A gPt–1 (15.8 μA cmPt–2) is observed at the peak COads-stripping potential of 0.7 V vs RHE at 50 °C over a time interval where Pt-C activity becomes negligible. The response of anodic peak positions to potential sweep rates is used to reveal the impact of alloying (electronic structure) on the electro-oxidation rates of various intermediate species on Pt2Bi NPT. Resistance to poisoning coincides both with a reduction in the Cads specific activity onset potential by 25 mV relative to Pt-C and faster DME electro-oxidation kinetics. DDMEFC testing of the unsupported Pt2Bi NPT utilizing a phosphoric acid-doped polybenzimidazole (PBI) membrane operating at 240 °C yields a peak power of 56 W gPGM,anode–1. This represents a 30% increase relative to a commercial PtRu catalyst.