Surface-State–Regulated Product Distribution in Photothermal CO2 Hydrogenation over MXene-based S-Scheme Catalyst

The rational design of heterostructured photocatalysts that simultaneously enable efficient carrier separation, photothermal synergy, and controllable reaction pathways is crucial for advancing CO2 conversion. Here, a Ni/Ti3 C2 Clx MXene heterojunction is synthesized via Lewis acid molten-salt etching, featuring ultrathin Ni platelets strongly anchored to the MXene substrate through interfacial TiNi3 bonding. This architecture establishes an S-scheme charge transfer pathway, as evidenced by in situ irradiated X-ray photoelectron and X-ray absorption spectroscopy, which confirm efficient carrier transfer and separation, while femtosecond transient absorption spectroscopy reveals ultrafast interfacial dynamics. Under photothermal conditions, the cooperative interplay of metallic Ni, surface NiOx , and the conductive MXene substrate couples directional charge migration with thermally assisted molecular activation and barrier lowering, thereby enabling regulated CO2 hydrogenation product distribution between CH4 and CH3 OH. Density functional theory demonstrates that surface-state evolution, rather than simple oxidation degree, modulates adsorption energetics and alters the relative barriers of CH4 and CH3 OH pathways, such that moderately oxidized Ni–NiOx interfacial ensembles favour methanol forming intermediates, whereas extensive oxidation suppresses CH3 OH formation. Collectively, these findings demonstrate a robust strategy for exploiting MXene-based heterojunction interfaces in photothermal catalysis and underscore the pivotal role of surface state regulated reaction pathways in steering product distribution during CO2 hydrogenation.