Cover Story: In conventional solid-liquid-gas photocatalytic carbon dioxide reaction systems, inefficient diffusion of CO₂ to the catalyst surface often leads to dominant hydrogen evolution reaction (HER), limiting CO₂ conversion efficiency and product selectivity. Herein, we propose a catalyst encapsulation strategy using porous silicon dioxide (SiO₂) to spatially control molecular transport toward the active sites. As shown in the figure, a dry cavity forms around the porous material, indicating that the ingress of water molecules is restricted. Meanwhile, CO₂ molecules pass unimpeded through the green SiO₂ shell and are reduced to CO by photo-generated electrons on the pale red Ag nanoparticles. By encapsulating Ag-modified titanium dioxide within a porous SiO₂ layer, we effectively restrict water access to the catalytic interface while facilitating CO₂ permeation. As a result, the parasitic HER is significantly suppressed, enabling an exceptional 100% selectivity for CO production from photocatalytic CO₂ reduction in pure water, which is a dramatic improvement from the mere 5.9% CO selectivity of the unencapsulated Ag-TiO₂ catalyst. This design achieves near-complete suppression of HER and 100% selectivity toward CO production under photocatalytic conditions. Our work provides a versatile interfacial engineering approach to overcome mass transfer limitations in three-phase photocatalytic systems, opening avenues for efficient gas-involving photoreactions.

Lu, J.; Li, Y.; Wang, Y.; Guan, Q.; Ge, Z.; Ren, Y.; Zhao, Y.; Wang, Q.; Jin, M. Encapsulation in Porous SiO₂ for Selective Suppression of Hydrogen Evolution in Photocatalytic CO₂ Reduction. Materials and Interfaces 2026, 3 (1), 1–9. https://doi.org/10.53941/mi.2026.100001