Short-Range Mass Transfer in Core-Shell Catalysts Suppresses Radical Self-Quenching for Efficient Water Purification

Fenton-like reactions hold considerable promise for organic wastewater treatment. However, their practical application remains limited by the difficulty of synthesizing the catalyst's local structure in a controlled manner through a sustainable route. Herein, a coordination engineering strategy is developed to facilitate rapid Joule-heating synthesis of a core-shell material from Fenton sludge. The organic ligand skeleton promotes the formation of highly loaded Fe0 at the ultrahigh temperatures generated by the applied current. Meanwhile, rapid cooling drives the deposition of a highly graphitized carbon layer (the shell) onto the surface of small-sized Fe0 particles (the core). This core-shell structure enables short-range mass transfer of reactive oxygen species to pollutants, achieving excellent removal of organic pollutants at ultralow oxidant doses. By confining reactive oxygen species near the enriched pollutants, this short-range mass transfer suppresses radical self-quenching and improves oxidant utilization. Density functional theory calculations corroborate this picture, showing that the core-shell structure exhibits stronger pollutant adsorption and a lower energy barrier for oxidant activation than the surface-loaded structure. Notably, this strategy enables the synthesis of core-shell structures from five different types of sludge (availability rate up to 95.23%). Finally, we develop a continuous Joule-heating method for scalable synthesis, reducing greenhouse gas emissions by over 50% compared with pyrolysis. This study presents a strategy for converting sewage sludge into core-shell materials for sustainable industrial applications.