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

Abstract

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