Surface defects introduced by metal doping into layered double hydroxide for CO2 photoreduction: The effect of metal species in light absorption, charge transfer and CO2 reduction

The doping of transition metal into MgAl layered double hydroxide to create surface defects has been considered as an effective strategy to tailor band gap and promote electron transfer in CO2 photoreduction. Nevertheless, the report about comprehensive effect of doped elements in the whole reaction process, especially in CO2 surface reduction, is still lacking. Herein, the detailed mechanism of doped elements for activity improvement in light absorption, charge transport and surface reaction was revealed by the experiment and DFT calculation. The optimal doped element was screened from 5 kinds of metal elements (Co, Ni, Cu, Fe, and Cr) by the photocatalytic test with TEOA and [Ru(bpy)3]Cl2 as sacrificial agent and photosensitizer. Cr doped LDH was the optimal choice with the highest TOF value for CO production and the CO evolution rate of 3.91 μmol•g−1•h−1. The doping of Cr could reduce the band gap, introduce the intermediate band, generate more surface defects and obtain the lower energy of CO release, which accounted for the high activity comprehensively.