Synergistic physical confinement and chemical adsorption in yolk-Shell Ni@NC nanoreactors for enhanced photothermal CO2 methanation.

Solar-driven photothermal conversion of dilute CO2 into CH4 offers a promising route toward carbon-neutral energy cycles, yet designing efficient catalysts for realistic low-concentration streams remains challenging. Herein, a yolk-shell structured nanoreactor composed of homogeneous Ni@NC units (denoted as Ni@NC-9 h) was fabricated via a time-controlled solvothermal and pyrolysis method. This unique architecture acts as a confined nanoreactor that integrates physical and chemical enrichment mechanisms: the internal cavity simultaneously enhances light harvesting and thermal localization via multiple scattering and increases local CO2 coverage, while the homogeneously distributed nitrogen sites ensure efficient chemical trapping of dilute CO2. Under mild conditions (420 nm LED, 180 °C, 12.5% CO2, 86.9 mW·cm-2), the Ni@NC-9 h catalyst achieves a remarkable CH4 production rate of 4.33 mmol·g-1·h-1 with 94.7% selectivity. Kinetic and in-situ DRIFTS insights uncover a photothermally reduced activation barrier that drives efficient stepwise hydrogenation through *COOH and *CO intermediates. This work provides insights into confinement-enhanced nanoreactor design and establishes a new structural paradigm for the efficient solar-driven upgrading of dilute CO2.