Influence of Electron-Inducted effect of ligand on electrocatalytic reduction of CO2 by copper phthalocyanine

Molecular catalysts such as metallophthalocyanines have high chemical stability and a unique metal M-N4 unit as an electrochemical active site for carbon dioxide reduction (CO2RR). By regulating the electronic density of the M-N4 units in molecular catalysts, the performances of CO2RR can be controlled. In this study, the effects of electron induction of ligands on the electronic structure of copper phthalocyanine (CuPc) and the electrocatalytic performance of CO2RR were elucidated by electrochemical analysis, in-situ infrared and XPS characterizations combined with theoretical calculations. Compared with CuPc, CuPc-NH2 with electron-donating substituents significantly enhanced the electrocatalytic activity for CO2RR, achieving a 100 % Faradaic efficiency of CO. While CuPc-F8 with electron-withdrawing substituents predominantly facilitated hydrogen evolution reaction, significantly reducing the CO2RR activity, and the main reduction product of CO2 was HCOOH. It was proven that the electron-induced effect of the ligand not only changes the electrostatic potential distribution of the central metal Cu, but also changes the symmetry and spatial orientation of the highest occupied molecular orbital formed by the interaction between Cu and the ligand. This study revealed the mechanism of the central metal catalysis induced by electronic effects of phthalocyanine ligands, and provided a basis for the development of high performance CO2RR electrocatalysts.