The photoconversion efficiency of CO 2 is hindered by severe charge recombination and sluggish multi-electron kinetics at the surface reaction. For strengthening CO 2 adsorption and activation process, abundant nitrogen vacancy (N v ) and –COOH groups are introduced into potassium doped carbon nitride (KCN) by mechanical ball milling and acid treatment for construting KCN treated by Mg-assisted (KCN-M2). Compared with pristine KCN (2.13 μmol·g –1 ·h –1 ), the photocatalytic CO evolution rates of KCN-M1, KCN-M2, and KCN-M3 materials increase to 6.79, 11.32, and 7.06 μmol·g –1 ·h –1 , respectively. KCN-M2 materials also show favorable photocatalytic CO evolution at low CO 2 concentrations (10% CO 2 (8.91 μmol·g –1 ·h –1 ) and air (0.04% CO 2 (6.16 μmol·g –1 ·h –1 )). The comprehensive analysis reveals that N v and –COOH groups can synergistically facilitate photogenerated electron transfer, CO 2 adsorption, and water affinity. Furthermore, density functional theory (DFT) computations for CO 2 conversion pathway reveal that KCN-M2 exhibits a lower energy change for the rate-determining step (*COOH → *CO) energy changes (0.82 eV) than pristine KCN (1.03 eV), confirming that N v and –COOH groups facilitate the transformation of *COOH to *CO intermediate. The results provide insights into photocatalyst design, contributing not only to the artificial carbon cycle but also to the realization of the critical dual-carbon goals.
Dong et al. (Fri,) studied this question.