Optimizing Coordinated Active Sites of Transition Metal Complexes: Exploring Metal–Molecule Interactions for Governing CO2-to-CO Conversion

Syngas (H2/CO) is an essential chemical feedstock for industrial products. In these focal points, electrocatalytic CO2 reduction has emerged as a desirable strategy for realizing effective syngas production to satisfy energy and environmental requirements. In this work, a metal-molecule hybrid electrode with inherent H2 generation favorability has been crafted by loading molecular Co(Ni)-bpy (bpy = 2,2'-bipyridine) complexes on Ag foil. The efficient and stable CO2-to-CO conversion with adjustable faradic efficiency from 13 to 98% was realized by optimizing the Co(Ni)-bpy complexes. The regulation of molecular catalysts with the merits of high electron affinity can provide a coordination environment that allows for the localization of Co/Ni active sites at optimal positions with lower binding energies, maintaining their monodisperse properties, and being beneficial for strengthening the CO2 binding and inhibiting competitive reactions. An in-depth understanding of surface and coordination status has been realized by FIB-HRTEM and EXAFS, which confirm that the intimate metal-molecular interaction and well-dispersed mononuclear Co/Ni active sites play vital roles in enhancing catalytic performance. The strong electron residual between the Ag surface and metal-coordinated molecular catalysts may also contribute to the dramatic CO2-to-CO conversion. This study highlights the beneficial role of metal-molecule interactions in electrocatalytic reactions and contributes to ongoing efforts toward achieving controllable selectivity in electrocatalytic reduction of CO2 to syngas using molecular catalysts.