Galvanic Replacement-Assisted Synthesis of Cu–Ag Composite Membrane Catalysts for Potassium Ferricyanide Reduction

This study investigates the catalytic properties of mono- and bimetallic composite track-etched membranes (CTeMs) fabricated using a galvanic replacement strategy. Two bimetallic architectures, Ag/Cu@PET and Cu/Ag@PET, were synthesized by sequentially depositing copper and silver onto poly(ethylene terephthalate) (PET) templates. X-ray diffraction analysis revealed that doping Cu@PET with silver nanoparticles formed a substitutional solid solution (Ag₉₇Cu₃), which increased crystallinity by >45 % compared to monometallic Cu@PET. In contrast, doping Ag@PET with copper produced a two-layer tubular structure with phase-separated copper co-deposited along silver microtubes. The catalytic performance was evaluated through the pseudo-first-order reduction of potassium ferricyanide (PFC) by sodium borohydride. The Cu/Ag@PET composite with separate phases demonstrated superior activity, achieving 94.3 % PFC reduction within 40 minutes, significantly exceeding the performance of monometallic Ag@PET and Cu@PET. Kinetic analysis indicated that the rate constant and activation energy strongly depended on membrane structure and silver doping time in case of formation of substitutional solid solution phase. A minimum doping duration of 20 minutes was required for performance enhancement, with 30-minute Ag/Cu@PET samples reducing activation energy from 62.35 kJ/mol to 32.67 kJ/mol. These findings highlight the critical role of metal deposition order and structural configuration in optimizing catalytic activity, demonstrating the efficacy of galvanic replacement for designing high-performance, multi-metallic membrane catalysts.