Activation of CO2 on graphitic carbon nitride supported single-atom cobalt sites

• 1. Single-atom Co modified g-C 3 N 4 prepared by one-step thermal-polymerization of cobalt phthalocyanine (CoPc) and urea. • 2. Strong interaction between Co 3d electrons and C 2p electrons of CO 2 activate C = O bonds in CO 2 molecule. • 3. Optimal 1%Co-CN sample exhibits higher CO yield of 94.9 umol/g/h than pure g-C 3 N 4 0.25 umol/g/h. Using solar energy to realize photoreduction of CO 2 into valuable chemicals is a potential way to solve energy crisis and carbon cycle. Due to the extremely stable molecular configuration of CO 2 , activating CO 2 molecule is the key and difficult step in the whole CO 2 conversation process. In this work, we used density functional theory (DFT) to calculate the reaction pathways of CO 2 to CO on pure g-C 3 N 4 and single-atom cobalt (Co) modified g-C 3 N 4 . Theoretical calculation predicts that single-atom Co sites modified g-C 3 N 4 (Co-CN) possess stronger CO 2 adsorption ability and lower barrier of CO 2 hydrogenation activation than pure g-C 3 N 4 . The strong interaction between Co 3d electrons and C 2p electrons of CO 2 is the crucial factor to activate C = O bonds of CO 2 molecule. Better CO 2 adsorption and activation abilities also are proved in Co-CN by CO 2 adsorption, temperature programmed desorption (TPD), and sensor tests. As a result, the optimal 1%Co-CN exhibits higher CO yield of 94.9 umol/g/h than pure g-C 3 N 4 (0.25 umol/g/h). This work provides a new insight of the role of single-atom sites in CO 2 reduction reactions.