Facile one-step aqueous-phase synthesis of porous PtBi nanosponges for efficient electrochemical methanol oxidation with a high CO tolerance

Deliberate control in the composition and morphology of Pt-based catalysts is an efficient route for enhancing the methanol oxidation reaction (MOR). Herein we developed a facile method for rational one-step aqueous-phase synthesis of PtBi nanosponges with tunable composition, based on the prompt reduction of an aqueous solution of Pt and Bi precursors using NaBH₄. Mechanistically, the high-reduction power of NaBH₄ formed multiple small colloidal PtBi nanocrystals (NCs), which coalesce together to reduce their interfacial energy resulting in oriented attachment growth. The fabrication process is simple, quick (2 min), productive, and free of surfactants or organic solvents. PtBi nanosponges showed 3D network-like architectures with a rough surface and interconnected pores (mesopore and macropore). The MOR mass (specific) activity of Pt₆₇Bi₃₃, 1.8 A/mg_Pt (15.4 mA cm⁻²), outperformed Pt₇₈Bi₂₂, Pt, and Pt/C, by 2.3 (1.2), 4.8 (3.6), and 5.1 (24.7) times, respectively besides greater stability and CO tolerance. This method could be extended to synthesize other binary Pt-based catalysts for various electrocatalytic applications.