Stable CO2 Reduction under Natural Air on Ni-Sn Hydroxide Photocatalyst with Dynamic Renewable Oxygen Vacancies

Abstract Advanced photocatalysts are highly desired to activate the photocatalytic CO 2 reduction reaction (CO 2 RR) with low concentration. Herein, the NiSn(OH) 6 with rich surface lattice hydroxyls was synthesized to boost the activity directly under the natural air. Results showed that terminal Ni–OH could serve as donors to feed protons and generate oxygen vacancies (V O ), thus beneficial to convert the activated CO 2 (HCO 3 − ) mainly into CO (5.60 μ mol g −1 ) in the atmosphere. It was flexible and widely applicable for a stable CO 2 RR from high pure to air level free of additionally adding H 2 O reactant, and higher than the traditional gas–liquid–solid (1.58 μ mol g −1 ) and gas–solid (4.07 μ mol g −1 ) reaction system both using high pure CO 2 and plenty of H 2 O. The strong hydrophilia by the rich surface hydroxyls allowed robust H 2 O molecule adsorption and dissociation at V O sites to achieve the Ni–OH regeneration, leading to a stable CO yield (11.61 μ mol g −1 ) with the enriched renewable V O regardless of the poor CO 2 and H 2 O in air. This work opens up new possibilities for the practical application of natural photosynthesis.