SiO ₂ Nanomembrane Coating on Supported Metal Catalysts via Scalable Photodeposition Method

The performance of supported metal catalysts is governed not only by the spatial arrangement and electronic environment of the active surface states formed by metal nanoparticles and their supporting materials. Here, we introduce an additional diffusional constraint via an ultrathin porous nanomembrane that locally encapsulates the metal nanoparticles. Using a photo‐irradiated continuous‐flow synthesis platform, photocatalytically induced pH shifts trigger the selective deposition of SiO 2 onto Pd and PdFe nanoparticles dispersed on TiO 2 . The nanomembrane forms a local overlayer only a few nanometers thick on metal nanoparticles, preserving direct access of reactants to the metal surface. The resulting catalysts were evaluated through CO oxidation and simulated exhaust‐gas purification, revealing enhanced high‐temperature sintering tolerance and molecular‐sieving effects. Reactant and product molecules of appropriate size permeate the nanomembrane and undergo transformation at the metal surface, whereas detrimental processes, including inhibition caused by bulk‐phase diffusion and degradation associated with metal leaching, are effectively suppressed. By introducing the concept of a nanomembrane overlayer introduced by photochemical reaction, this study expands the design space for catalyst materials beyond conventional metal–support pairings and provides a scalable route to next‐generation supported metal catalysts.