Simultaneous promotion of photocatalytic CH4 conversion and H2O2 production via nanopore water confinement

Aqueous photocatalytic CH 4 oxidation offers a promising route for converting natural gas into oxygenates, a process governed by multi-electron and proton transfer at the catalyst-water interface. Here, we demonstrate that spatially confining water within Au/TiO 2 @pSiO 2 core-shell catalysts—by reducing silica pore size to 1.7 nm—increases CH 4 conversion three-fold and H 2 O 2 production 22-fold compared to Au/TiO 2 . This strategy is generalizable to other semiconductors and cocatalysts, with Pt/TiO 2 @pSiO 2 -1.7 exhibiting oxygenate yields of 32.7 mmol g -1 h -1 and a 14.1% apparent quantum yield at 365 nm. Spectroscopic studies and molecular dynamics simulations reveal that water confined within pores, with a weakened hydrogen-bonding network, alters proton-coupled electron transfer pathways. Water oxidation transits to a concerted pathway, favoring •OH production for CH 4 conversion, while oxygen reduction shifts to a two-electron process, directly producing H 2 O 2 . This work highlights the potential of water confinement for designing efficient photocatalysts for CH 4 conversion.