Concentrated solar CO 2 reduction in H 2 O vapour with >1% energy conversion efficiency.

H 2 O dissociation plays a crucial role in solar-driven catalytic CO 2 methanation, demanding high temperature even for solar-to-chemical conversion efficiencies <1% with modest product selectivity. Herein, we report an oxygen-vacancy (V o ) rich CeO 2 catalyst with single-atom Ni anchored around its surface V o sites by replacing Ce atoms to promote H 2 O dissociation and achieve effective photothermal CO 2 reduction under concentrated light irradiation. The high photon flux reduces the apparent activation energy for CH 4 production and prevents V o 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 H 2 O activation. The catalyst presents a CH 4 yield of 192.75 µmol/cm 2 /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 H 2 O-activating catalysts for CO 2 reduction and thereby expedite the practical utilization of solar-to-chemical technologies.