Synergy of Various Defects in CoAl-Layered Double Hydroxides Photocatalyzed CO2 Reduction: A First-Principles Study

Defect engineering is accepted as an efficient strategy for tuning the electronic structure and enhancing photocatalytic performance of layered double hydroxides (LDHs), an emerging family of two-dimensional photocatalysts, in reducing CO2 to hydrocarbons. Herein, we systematically investigate how the different types of structural defects influence electronic behavior, band edge position and Gibbs free energy barrier of CoAl-LDHs by density functional theory plus U (DFT + U) method. Our calculations indicate that CoAl-LDHs with Al defects exhibits stronger CO2 absorption capacity and narrower band gap comparing perfect CoAl-LDHs, and CoAl-LDHs with hydroxyl (–OH) defects reduce band edge down to − 1.397 V by harvesting electrons around Co atom. Furthermore, CoAl-LDHs with mixed defects of –OH and Al presents a potential synergy in photocatalytic reduction of CO2, whose calculated Gibbs free energies imply the optimal pathway for reducing CO2 to CH4 to be \({\text{CO}}_{{2}} \, \to \,*{\text{COOH}}\, \to \,*{\text{CO}}\, \to \,*{\text{CHO}}\, \to \,*{\text{CH}}_{{2}} {\text{O}}\, \to \,*{\text{CH}}_{{3}} {\text{O}}\, \to \,*{\text{CH}}_{{3}} {\text{OH}}\, \to \,*{\text{CH}}_{{3}} \, \to \,{\text{CH}}_{{4}}\) through altering the potential-determining step and lowering the Gibbs free energy barrier from 0.452 to 0.203 eV. Our achievement valuably predicts catalytic performance of CoAl-LDHs with single and mixed defects in photocatalytic CO2 reduction.Graphical Abstract