Probing the Behavior of Composition‐Tunable Ultrathin PtNi Nanowires for CO Oxidation and Small‐Molecule Electrocatalytic Reactions

Abstract We have successfully synthesized ultrathin nanowires of pure Pt, Pt₉₉Ni₁, Pt₉Ni₁, and Pt₇Ni₃ using a modified room‐temperature soft‐template method. Analysis of both methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR) results found that the Pt₇Ni₃ samples yielded the best performance with specific activities of 0.36 and 0.34 mA/cm² respectively. Additionally, formic acid oxidation reaction (FAOR) tests noted that both Pt and PtNi nanowires oxidize small organic molecules (SOMs) via an indirect pathway. CO oxidation data suggests little measurable performance without any pre‐reduction treatment; however, after annealing in H₂, we detected significantly improved CO₂ formation for both Pt₉Ni₁ and Pt₇Ni₃ motifs. These observations highlight the importance of pre‐treating these nanowires under a reducing atmosphere to enhance their performance for CO oxidation. To explain these findings, we collected extended x‐ray adsorption fine structure (EXAFS) spectroscopy data, consistent with the presence of partial alloying with a tendency for Pt and Ni to segregate, thereby implying the formation of a Pt‐rich shell coupled with a Ni‐rich core. We also observed that the degree of alloying within the nanowires increased after annealing in a reducing atmosphere, a finding deduced through analysis of the coordination numbers and calculations of Cowley's short range order parameters.