Concentrated solar CO₂ reduction in H₂O vapour with >1% energy conversion efficiency

H₂O dissociation plays a crucial role in solar-driven catalytic CO₂ methanation, demanding high temperature even for solar-to-chemical conversion efficiencies <1% with modest product selectivity. Herein, we report an oxygen-vacancy (V₀) rich CeO₂ catalyst with single-atom Ni anchored around its surface V₀ sites by replacing Ce atoms to promote H₂O dissociation and achieve effective photothermal CO₂ reduction under concentrated light irradiation. The high photon flux reduces the apparent activation energy for CH₄ production and prevents V₀ from depletion. The defects coordinated with single-atom Ni significantly promote the capture of charges and local phonons at the Ni d-impurity orbitals, thereby inducing more effective H₂O activation. The catalyst presents a CH₄ yield of 192.75 µmol/cm²/h, with a solar-to-chemical efficiency of 1.14% and a selectivity ~100%. The mechanistic insights uncovered in this study should help further the development of H₂O-activating catalysts for CO₂ reduction and thereby expedite the practical utilization of solar-to-chemical technologies. Efficiency in this system reaches 1.14%. In-depth mechanism investigations using experimental and theoretical methods demonstrate that V₀ regenerated on the catalyst surface ensures a steady supply of active sites for CO₂ reduction. DFT and TDDFT calculations confirm the crucial roles of Ni and V₀ in enhancing carrier kinetics and reactant activation, and AIMD/TDDFT demonstrate H₂O dissociation proceeds via thermally assisted photocatalysis under concentrated irradiation.