MOF-Templated Sulfurization of Atomically Dispersed Manganese Catalysts Facilitating Electroreduction of CO2 to CO

To reach a carbon-neutral future, electrochemical CO2 reduction reaction (eCO(2)RR) has proven to be a strong candidate for the next-generation energy system. Among potential materials, single-atom catalysts (SACs) serve as a model to study the mechanism behind the reduction of CO(2)to CO, given their well-defined active metal centers and structural simplicity. Moreover, using metal-organic frameworks (MOFs) as supports to anchor and stabilize central metal atoms, the common concern, metal aggregation, for SACs can be addressed well. Furthermore, with their turnability and designability, MOF-derived SACs can also extend the scope of research on SACs for the eCO(2)RR. Herein, we synthesize sulfurized MOF-derived Mn SACs to study effects of the S dopant on the eCO(2)RR. Using complementary characterization techniques, the metal moiety of the sulfurized MOF-derived Mn SACs (Mn-SA/SNC) is identified as MnN3S1. Compared with its non-sulfur-modified counterpart (Mn-SA/NC), the Mn-SA/SNC provides uniformly superior activity to produce CO. Specifically, a nearly 30% enhancement of Faradaic efficiency (F.E.) in CO production is observed, and the highest F.E. of approximately 70% is identified at -0.45 V. Through operando spectroscopic characterization, the probing results reveal that the overall enhancement of CO production on the Mn-SA/SNC is possibly caused by the S atom in the local MnN3S1 moiety, as the sulfur atom may induce the formation of S-O bonding to stabilize the critical intermediate, *COOH, for CO2-to-CO. Our results provide novel design insights into the field of SACs for the eCO(2)RR.

Automated summary

This study investigates the impact of sulfur dopants on the electrochemical CO2 reduction reaction by synthesizing sulfurized MOF-derived Mn single-atom catalysts, revealing significantly enhanced activity in CO production. Through characterizations and spectroscopic analysis, it is found that the presence of sulfur atoms in the MnN3S1 moiety contributes to the stabilization of critical intermediates and leads to improved overall CO production efficiency.