Simultaneous Enhancement of Photocatalytic CH4 Conversion and H2O2 Production through Water Confinement in Nanoporous Core-Shell Catalysts

Aqueous photocatalytic CH ₄ oxidation offers a promising route for converting natural gas into liquid oxygenates, a process governed by multi-electron and proton transfer steps at the catalyst-water interface. Here, we demonstrate that spatially confining interfacial water within Au/TiO ₂ @pSiO ₂ core-shell catalysts – achieved by systematically reducing silica pore size to 1.7 nm – remarkably increases CH ₄ conversion threefold and H ₂ O ₂ production 22-fold compared to Au/TiO ₂ . This strategy is generalizable to other semiconductors and co-catalysts, with Pt/TiO ₂ @pSiO ₂ -1.7 exhibiting high oxygenate yields (32.7 mmol g ^− 1 h ^− 1 ) and a 14.1% apparent quantum yield at 365 nm. Kinetic isotope effect (KIE), FTIR and EPR studies reveal that the water confined within pores, with a weakened H-bonding network, alters proton-coupled electron transfer (PCET) pathways. Water oxidation transits to a concerted PCET pathway, favoring •OH production for CH ₄ conversion, while oxygen reduction shifts to a 2e ⁻ process, directly producing H ₂ O ₂ . This work highlights the potential of water confinement for designing efficient photocatalyst.