Built-in Axial Electric Field-Driven Electron-Rich Monomolecular Co Sites for Promoting CO2 Electroreduction to CO Over Ultrawide Potential Window.

Abstract

Using renewable electricity to convert CO2 into CO offers a sustainable route to producing a versatile intermediate to synthesize various chemicals and fuels. However, the conversion at scale is largely constrained owing to the lack of potential-universal feasibility. Here, we developed an electrocatalyst featuring CoPc anchored ZnO with rich oxygen vacancies (CoPc@ZnOv), thus improving the activity and selectivity of CO2-to-CO conversion. Notably, the FEco of CoPc@ZnOv remains above 90% over an ultrawide potential window of 1.3 V (-0.7 to -2.0 V versus RHE) in H-type cell, 1.40 V (-0.4 to -1.8 V versus RHE) in flow cell and 1.0 V (low cell voltages of 2.0-3.0 V) in the MEA device, surpassing those of previously reported molecular CoPc-based electrocatalysts and even most single metal site materials. Density functional theory calculations combined with in-situ spectroscopies reveal that the built-in axial electric field arising from the p-n junction rectification effect could drive electron-rich single Co-N4 sites with asymmetric charge distribution and geometric curvature, which promotes *COOH formation (i.e., strong CO2 adsorption, rapid H2O dissociation and proton supply), *CO desorption and as well suppresses the hydrogen evolution reaction, thus favoring the production of CO via CO2RR over ultrawide potential windows. This work presents a novel catalyst design strategy of asymmetrical monomolecular Co-N4 sites based on the built-in axial electric field theory, as well as a new way to tune the out-of-plane polarization for improved catalytic performance.