Repurposing Silver to Enable Ag–Pt Alloy Decoration on Silicon Nanowires for Efficient Hydrogen Evolution Reaction

In this study, we report a strategy to enhance the HER performance by exploiting the effective utilization of repurposed silver (Ag) to form bimetallic Pt–Ag alloy nanoparticles on silicon nanowires (SiNWs). Vertically aligned SiNWs were synthesized via metal-assisted chemical etching (MACE) on p-type silicon wafers during which Ag nanoparticles were intentionally retained at the nanowire base (rAg-SiNWs) to serve as nucleation sites for subsequent Pt photodeposition. Comprehensive characterizations using SEM, EDS, XRD, XPS, TEM, HRTEM, and HAADF-STEM confirmed the successful deposition of both Ag and Pt, as well as the formation of a uniform Pt–Ag alloy, as evidenced by distinct binding energy shifts in the deconvoluted Pt 4f spectra. Electrochemical measurements reveal that the Pt-decorated repurposed Ag-SiNWs (Pt-rAg-SiNWs) exhibit significantly enhanced HER performance compared with Pt-decorated SiNWs without repurposed Ag (Pt-SiNWs). Notably, the Pt-rAg-SiNWs contain a significantly lower Pt loading (0.18%) compared with Pt-SiNWs (0.75%). Despite this, they exhibit markedly higher current densities, lower overpotentials, and reduced Tafel slopes, highlighting the performance benefits associated with Pt–Ag alloy formation. The improved performance is attributed to the synergistic interaction between Pt and Ag, which enhances electron transfer, increases the electrochemically active surface area, and stabilizes the Pt active sites. These results provide valuable insights into the critical role of Ag positioning in facilitating effective Pt utilization via alloy formation and offer a cost-effective pathway for the design of advanced electrocatalysts for renewable energy applications.