Surface‐State–Regulated Product Distribution in Photothermal CO ₂ Hydrogenation Over MXene‐Based S‐Scheme Catalyst

Abstract

ABSTRACT The rational design of heterostructured photocatalysts that simultaneously enable efficient carrier separation, photothermal synergy, and controllable reaction pathways is crucial for advancing CO 2 conversion. Here, a Ni/Ti 3 C 2 Cl x MXene heterojunction is synthesized via Lewis acid molten‐salt etching, featuring ultrathin Ni platelets strongly anchored to the MXene substrate through interfacial TiNi 3 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 NiO x , and the conductive MXene substrate couples directional charge migration with thermally assisted molecular activation and barrier lowering, thereby enabling regulated CO 2 hydrogenation product distribution between CH 4 and CH 3 OH. Density functional theory demonstrates that surface‐state evolution, rather than simple oxidation degree, modulates adsorption energetics and alters the relative barriers of CH 4 and CH 3 OH pathways, such that moderately oxidized Ni–NiO x interfacial ensembles favour methanol forming intermediates, whereas extensive oxidation suppresses CH 3 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 CO 2 hydrogenation.