Unlocking ultrawide potential windows through S-engineering of M-N-C (M=Cu, Ni, Fe, Co) catalysts at industrial current densities in electrochemical CO2 reduction

The development of a stable and efficient electrochemical carbon dioxide reduction (ECR) catalyst with wide potential window and high current density is crucial for mitigating energy fuel issues and protecting the ecological environment. However, with the widening of the potential window, the increased competition from hydrogen evolution reaction (HER) leads to a significant decrease in product generation efficiency, thereby limiting the energy efficiency for large-scale industrial applications. Herein, a series of sulfur-doped transition metal atomic catalysts M-SN-C (M= Cu, Ni, Fe, Co) have been synthesized by S-engineering on the basis of M-N-C, which generally enhanced their performance. The CO Faraday efficiency (FE_CO) of Ni-SN-C at a ultrawide potential window of −0.2 to −1.4 V vs. reversible hydrogen electrode (RHE) exceeds 90 % and the maximum FE achieves 99.6 % at −0.8 V vs. RHE. Moreover, it demonstrates stable performance at industrial-level current density and holds promising potential for industrial-scale application. The mechanism of S atom affecting the ECR performance of materials is investigated using in-situ analysis and also supported by the density functional theory (DFT) calculations. The introduction of S atom changes the rate determining step and significantly reduces the free energy barrier of ECR, facilitating the formation of *COOH and the subsequent transformation of *COOH into *CO. This work provides a promising strategy for its practical industrial application and insights into the structure-performance relationship between heteroatom-doped transition metal catalysts and ECR.