Tan H.-YLin S.-CWang JChang C.-JHaw S.-CLin K.-HTsai L.DChen H.-CHAO MING CHEN2022-04-252022-04-25202119448244https://www.scopus.com/inward/record.uri?eid=2-s2.0-85111182382&doi=10.1021%2facsami.1c10059&partnerID=40&md5=8d410afef5349c6c7bd3c82998d45db6https://scholars.lib.ntu.edu.tw/handle/123456789/606873To reach a carbon-neutral future, electrochemical CO2 reduction reaction (eCO2RR) 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 CO2 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 eCO2RR. Herein, we synthesize sulfurized MOF-derived Mn SACs to study effects of the S dopant on the eCO2RR. Using complementary characterization techniques, the metal moiety of the sulfurized MOF-derived Mn SACs (MnSA/SNC) is identified as MnN3S1. Compared with its non-sulfur-modified counterpart (MnSA/NC), the MnSA/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 MnSA/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 eCO2RR. ? 2021 American Chemical Society.eCO2RRmetal-organic frameworkoperando spectroscopysingle-atom catalystssulfurizationXASAtomsCarbon dioxideCatalystsElectrolytic reductionManganeseMetal-Organic FrameworksOrganometallicsSulfurCentral metalsCharacterization techniquesElectroreduction of CO2Energy systemsFaradaic efficienciesMetalorganic frameworks (MOFs)Potential materialsSpectroscopic characterizationManganese compounds[SDGs]SDG7[SDGs]SDG13journal article10.1021/acsami.1c100592-s2.0-85111182382