Hierarchical NiCo2O4 hollow nanocages for photoreduction of diluted CO2: Adsorption and active sites engineering

CO 2 adsorption is a critical step for CO 2 photoreduction, especially in diluted CO 2 , whereas an in-depth understanding of CO 2 adsorption effects is still lacking. Herein, isostructural NiCo 2 O 4 and MgCo 2 O 4 hierarchical hollow nanocages (NiCo 2 O 4 HCs and MgCo 2 O 4 HCs) have been ingeniously constructed for diluted CO 2 photoreduction. NiCo 2 O 4 HCs exerts an apparent quantum yield of 1.56% with CO selectivity of 89%, exceeding most previous inorganic catalysts in pure CO 2 . Nevertheless, MgCo 2 O 4 HCs is almost inert, even though it shows higher CO 2 uptake ability. DFT calculations results indicate that CO 2 molecule adsorbed on Ni sites can be readily reduced to CO, while the CO 2 on Mg sites cannot participate in this reaction. Therefore, only adsorbed CO 2 which can participate in reduction reactions, named active adsorption , can accelerate the whole reactions. This work unearths atomic-level insights into the relation between CO 2 adsorption and reduction, providing fundamental guidance to improve photocatalytic performance.