Sponge‐Like Nickel Carbonate of High Porosity and Carbonate Vacancy for High‐Performance CO2 Photoreduction

Abstract As most of the fossil carbon on earth is stored in an oxidized state as carbonate minerals, exploration of metal carbonate catalyst for selective CO 2 reduction can open appealing access to boost the CO 2 capture and storage. However, carbonate is commonly regarded as a poor matrix to host photocatalytic active species, and current literature has few reports of carbonate‐based photocatalytic material. Herein, a hierarchically porous catalyst that features ≈5 nm deficient NiCO 3 nanoparticles embedded in sponge‐like high‐magnesium calcite is disclosed. In the photocatalytic CO 2 reduction reaction, the as‐prepared catalyst of low Ni content attains a high CO production rate of 10 565 µmol g −1 h −1 and a high selectivity of 94% relative to H 2 evolution, a performance that surpasses many other state‐of‐the‐art nickel‐based catalysts. Experiments and theoretical calculations reveal that the carbonate vacancy of NiCO 3 strengthens the adsorption and activation of CO 2 more significantly than the corresponding oxygen vacancy of NiO. The inert CO 2 molecule becomes highly deformed on the surface of NiCO 3 which can be readily activated to the key intermediate CO 2 ·− for the photoreduction reaction. The present findings add to the existing knowledge of advanced catalysis using defect materials and demonstrate an intriguing and rare case of highly performing carbonate‐based catalyst.