Boosting CH ₄ Selectivity in CO ₂ Photoreduction over a CdS QDs/MXene‐Derived TiO ₂ S‐Scheme Heterojunction via Interlayer Confinement Engineering

ABSTRACT The selective photoreduction of CO 2 to CH 4 faces a significant challenge because of the inefficient charge separation and complex reaction pathways (eight‐electron hydrogenation reaction process). In this paper, we addressed the above challenge by constructing a novel MXene‐derived TiO 2 (MT)/CdS quantum dots (QDs) S‐scheme heterojunction (MC‐X) via the interlayer confinement engineering. The optimized MC‐2 catalyst achieved an exceptional CH 4 production efficiency of about 64.98 µmol·g −1 ·h −1 with a high selectivity of 82.6%, significantly higher than the pure CdS QDs. This outstanding enhancement can be attributed to the synergistic interplay between the interlayer confinement effect of MT and the S‐scheme charge transfer mechanism at the MT/CdS interface. The formation of MT/CdS S‐scheme heterojunction is confirmed by the ex situ/in situ XPS tests, which efficiently separated the photogenerated charge carriers while suppressing the photo‐corrosion phenomenon of CdS QDs. CO 2 photoreduction and in situ FTIR results proved that the unique interlayer confined spaces of MXene‐derived TiO 2 can efficiently enrich CO 2 molecules and stabilize the key intermediates (CHO/CH 3 O), thereby steering the reaction pathway toward CH 4 . This work provides a novel strategy for designing efficient photocatalysts by integrating interlayer confinement effects with S‐scheme heterojunction synergy.