Electronic potential-well driven CO-hydrogenation boxes enable 100% selective CO2-to-CH4 photoreduction

A strained Pd-O-Ti interface with abundant oxygen vacancies forms an electronic potential-well CO-hydrogenation box. • Spatial coupling of CO confinement and hydrogen activation enables exclusive CO 2 -to-CH 4 photoreduction. • This interfacial design provides a general strategy for deep CO 2 hydrogenation products. Solar-driven conversion of CO 2 to methane offers a route to carbon-neutral fuels, but directing the multielectron pathway beyond the CO intermediate remains a central challenge. Here, by growing Pd nanoparticles in situ on oxygen-deficient TiO 2 (Pd/TiO 2-x ), we construct an oxygen-vacancy-rich Pd-O-Ti interface that functions as a CO-hydrogenation box. Interfacial oxygen vacancies enrich and retain CO 2 -derived carbon intermediates, whereas adjacent Pd sites promote H 2 O activation and provide reactive surface hydrogen species in the same nanoscale region. This spatial coupling of CO confinement and hydrogen delivery favors sequential C-H bond formation and suppresses premature CO desorption, thereby redirecting CO 2 photoreduction toward CH 4 . As a result, Pd/TiO 2-x achieves 100% CH 4 selectivity with a CH 4 production rate 40 times higher than that of TiO 2 under AM 1.5 G irradiation. Under natural sunlight, the catalyst delivers a CH 4 production rate of 1.1 mmol h −1 g −1 and sustained activity over repeated daytime cycles. These results identify an interfacial design principle for steering multielectron CO 2 photoreduction toward deeply reduced hydrocarbon products. Download: Download high-res image (199KB) Download: Download full-size image