A universal strategy for green synthesis of biomass-based transition metal single-atom catalysts by simple hydrothermal and compression treatment

Carbon-based single-atom catalysts (SACs) have attracted increasing extensive attention due to their excellent catalytic performance and high atomic utilization efficiency. Traditional porous carbon materials are not suitable supports for SACs synthesis owing to the inert surface and heteroatoms such as N and S are necessarily introduced as increased anchoring sites for single metal atoms. Herein, we reported a novel universal strategy to synthesize carbon-based transition metal (Fe, Co, Ni, Cu, and Zn) SACs by one-pot hydrothermal treatment combined with a mechanochemical method by virtue of abundant active oxygen naturally in biomass feedstock. The hydrothermal treatment resulted in relatively monodispersed metal ions within the carbonaceous matrix and compression process played a vital role in the formation and anchoring of the single atom, preventing self-aggregation during pyrolysis by confinement effect. The characterization results showed the metal atoms were atomically dispersed on carbon support in the form of M-O₃C coordination and had relatively high metal contents of up to 1.15 wt%. Due to the in-situ formation, unique coordination surroundings, and high content of metal atoms, the prepared catalyst exhibited excellent reactivity performance. This work demonstrated the sustainability and economic feasibility of carbon-based SACs synthesis simultaneously by co-using natural oxygen as anchoring sites and abundant carbon as the skeleton in biomass feedstock and offered a novel approach for high-value utilization of biomass.