The promoted activity and enhanced selectivity of electrocatalysts is commonly ascribed to specific structural features such as surface facets, morphology, and atomic defects. However, unraveling the factors that really govern the direct electrochemical reduction of CO2 (CO2RR) is still very challenging since the surface state of electrocatalysts is dynamic and difficult to predict under working conditions. Moreover, theoretical predictions from the viewpoint of thermodynamics alone often fail to specify the actual configuration of a catalyst for the dynamic CO2RR process. Herein, we re‐survey recent studies with the emphasis on revealing the dynamic chemical state of Cu sites under CO2RR conditions extracted by in situ/operando characterizations, and further validate a critical link between the chemical state of Cu and the product profile of CO2RR. This point of view provides a generalizable concept of dynamic chemical‐state‐driven CO2RR selectivity that offers an inspiration in both fundamental understanding and efficient electrocatalysts design.

Unraveling the reaction mechanism behind CO2 reduction reaction (CO2RR) is a crucial step for advancing the development of efficient and selective electrocatalyst to yield valuable chemicals. To understand the mechanism...

To 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.

USA). He joined the Department of Chemistry as an assistant professor at NTU in 2013 and was promoted to associate professor in 2018. His current research interests include the development of in situ/operandom ethodology for studying liquid/solid interfaces and the synthesis of nanomaterials for energy conversion.

A molecular-level picture clearly describing the dynamic interfacial interactions with their correlation to CO2RR properties is established, which enables us to spatially and temporally understand electrochemical reactions at the solid–liquid interface.