Template- and ligand-free synthesis of Pt nanowire arrays as methanol oxidation electrocatalyst

Pt-based nanowires are promising catalyst materials, yet synthesizing ultrathin and ultralong Pt-based nanowires remains quite challenging. Templates or ligands are often indispensable to the one-dimensional (1D) growth of metal nanowires. Herein, a template-less and ligand-less electrodeposition method was developed to grow Pt nanowires arrays (Pt NWAs) with tunable lengths and diameters on Si wafer, a bulk flat substrate. Comprehensively investigation revealed an unconventional active-surface-growth mechanism: instead of small organic molecule ligand, the surface-adsorbed H⁺ functionalize as "ligand" and passivate most of the Pt surface; and the 1D growth results from the continuous preferential deposition at the rest surface that bound to the wafer substrate and less passivated. The growth of the nanowires at various deposition potentials and pH was assessed to illustrate the versatility of the growth. Furthermore, the synthesis was extended to carbon paper substrate, and the as-prepared Pt NWA-supported carbon paper can be directly applied as catalytic electrode. Owing to the unique nanowire array morphology, the Pt NWAs with the length of 650 nm exhibited an unusual deferring of the turn-off potential at 1.76 V (vs. RHE), as well as a current density of 241.4 mA cm^-2 that is almost twice to that of the Pt/C, in methanol oxidation reaction.