Tailoring plasmonic coupling in black gold-decorated porous polymer membranes via all-in-one synthesis for enhanced photocatalytic peroxymonosulfate activation
Abstract
Advanced oxidation processes (AOPs) employing heterogeneous metal catalysts offer promise for degrading persistent organic pollutants in water, but often suffer from low process efficiency, catalyst instability, and recovery challenges. Here, we report an “all-in-one” strategy combining in situ synthesis of gold nanoparticles (AuNPs) in a polyethersulfone (PES) casting solution with their simultaneous immobilization within porous PES membranes via film casting cum phase separation. Crucially, all used KAuCl4 precursor was fully converted and subsequently incorporated into the membrane matrix as AuNPs, yielding near-perfect material effciency. By copper doping, varying reductant (NaBH4) concentration, and polyvinylpyrrolidone (PVP) capping, we could precisely control effective size (5, 12, 26 or 51 nm) and spatial arrangement of AuNPs within the membranes. Notably, PVP capping promoted immobilization of AuNPs as well-dispersed nanoclusters with tailored plasmonic coupling, resulting in broadband black plasmonic visible-light absorption (7.5–3.0% reflectance, 400–800 nm). The gold-decorated membranes were evaluated for photocatalytic activation of peroxymonosulfate (PMS) in the flow-through oxidation of ofloxacin (OFL) in water. The black gold membrane exhibited significant visible-light enhancement (70% rate increase), achieving the highest OFL degradation rate (194 μg OFL per mg catalyst per h). Mechanistic studies suggested a dual gold catalysis pathway: surface-mediated non-radical PMS activation in the dark and plasmonic photocatalytic generation of superoxide radicals (˙O2−) under illumination. In continuous flow-through operation, the black gold membrane achieved >99% OFL (0.75 mg L−1) removal at short residence times (∼3.5 s), even in a complex wastewater ion matrix. It further mantained high stability over 12 h of operation without performance loss or gold leaching.