Single-atom catalysts for (photo)electrocatalytic biomass valorization to high-value-added chemicals

As a crucial renewable energy resource, biomass can be converted into high-value-added chemicals via unique catalytic routes, which facilitate the reduction of excessive dependency on fossil resources. However, the complex functional groups inherent in biomass and biomass-derived compounds enable considerable difficulties for their selective functionalization. The precise cleavage of special chemical bonds in biomass highly depended on the structure design of catalysts. Single-atom catalysts (SACs) have garnered significant attention in biomass valorization through the electrocatalytic and photoelectrocatalytic processes due to their maximal atom utilization efficiency, unique electronic structure, and tunable coordination environments. The present review outlines the latest research progress in this emerging field, focusing on the (photo)electrocatalytic application of SACs in biomass valorization, including cellulose-derived and hemicellulose-derived compounds and lignin. We also emphasize the innovative design and precise modulation of atomically dispersed metal active sites at the atomic level. Through state-of-the-art catalytic systems, we elaborately discuss the structure-activity relationship and elucidate the mechanisms of the (photo)electrocatalytic processes over SACs. Finally, we provide the prospects of SACs in (photo)electrocatalytic biomass valorization.