Electronic regulation & improved conductivity of molecular catalysts as electrocatalysts

Abstract

Molecular catalysts with well-designed structures and abundant metal–nitrogen active sites have received a lot of attention for effective electroreduction of carbon dioxide (ERCD) due to the advantages of having clearly defined active sites for mechanism investigations. However, this metal–nitrogen combination with a fixed electronic structure severely restricts the catalytic efficiency and selectivity, resulting in low production efficiency of more valuable compounds. This work presents the synthesis of metal macrocyclic compounds MPc (M = Fe, Co, Ni, and Zn) through in situ anodic oxidation of N-doped Ti₃C₂T_x (N-MXene) nanosheets with anchored MPc nanoparticles (named MPc/o-N-MXene). The resulting catalysts exhibit high activity and moreover tailorable selectivity for ERCD on CoPc; CoPc/o-N-MXene shows a faradaic efficiency (FE) for methanol as high as 39.0% with a current density of 32.7 mA cm⁻² at −1.0 V (vs. RHE). The oxidation process creates a significant contact between the M–N₄ active sites and N-MXene, which regulates the selectivity of ERCD. DFT calculations suggest that only the electronic regulation of Co–N₄ by N-doped MXene supports the creation of intermediate *HCO in the generation of methanol in ERCD. Our study presents a new route for the synthesis of efficient catalysts and provides a comprehensive perspective on the mechanism of ERCD on MPc.