Carbon-Supported and Shape-Controlled PtPd Nanocrystal Synthesis in Flowing Deep Eutectic Solvents for the Methanol Oxidation Reaction

Practical applications of advanced nanocrystals are limited by the lack of low-cost, scalable, and environmentally friendly manufacturing methods with consistent shape and size control. To address this challenge, we demonstrate here the use of continuous-flow reactors and environmentally benign deep eutectic solvents for the shape-controlled synthesis of intermetallic PtPd nanocrystals with almost exclusive octahedral shape and an average size of 12.8 nm within only 6 min of reaction time, much faster than conventional methods. The critical roles of solvent species were elucidated using a family of deep eutectic solvent combinations. We further demonstrate the direct growth of these shaped nanocrystals on carbon using a one-step process by harnessing their strong interactions with a Co- and N-codoped carbon surface, thus avoiding the mandatory additional catalyst separation and loading steps with conventional methods. The produced PtPd nanocrystals exhibited outstanding performance toward the electrooxidation of methanol and reached an activity of 201 mA mg^-1 along with improved stability, confirming the promise of our method for scalable and low-cost manufacturing of shape-controlled electrocatalyst materials.