Carbon-supported CoS4-C single-atom nanozyme for dramatic improvement in CO2 electroreduction to HCOOH: A DFT study combined with hybrid solvation model

Single-atom nanozymes (SANs) have attracted extensive attention due to their characteristics of both single-atom catalysts (SACs) and enzymes. Using spin-polarized density functional theory (DFT) calculations combined with the hybrid solvation model, this work designed a series of carbon-supported Group VIII transition metals TMS4-C SANs, similar to the TMS4 active center of formate dehydrogenase (FADH), aiming to develop highly efficient SANs for CO2 electroreduction. DFT calculations show that compared with TMN4-C, TMS4-C have FADH-like feature, which can selectively reduce CO2 to formic acid. Particularly, CoS4-C is the most promising SAN for CO2 reduction, with a low limiting potential of -0.07 V, which exceeds most reported catalysts. Two descriptors of TMX4-C (X = N, S) based on intrinsic and electronic structure properties were proposed to shed light on the origin activity of candidates. The findings presented here will provide new insights into the design of novel enzyme-like catalysts for electrochemical CO2 reduction.