The synergistic effect of Co atomic clusters and single atoms facilitates the Fenton-like reaction on A- and R-TiO2

The regulation of single atom (SA) sites is crucial for the promotion of advanced oxidation processes (AOPs). Here A- and R-TiO₂ with Co mixed sites (clusters and single atoms, CS) were prepared to degrade sulfamethoxazole (SMX) by activating peroxymonosulfate (PMS). Co CS/A-TiO₂+PMS system can completely remove SMX within 14 min under secondary effluent and dark conditions, and its rate constant (0.4926 min⁻¹) was 4.4, 3.2 and 2.5 times higher than that of Co SA/R-TiO₂, Co SA/A-TiO₂ and Co CS/R-TiO₂ systems, respectively. Experiments and calculations verified that the electron configuration of Co SA was optimized by Co clusters, facilitating the adsorption, conversion and desorption of PMS by Co SA, leading to the enhancement of Fenton-like activity. Co CS/A-TiO₂ catalytic sponges exhibited exceptional degradation performance in microreactor treatment experiment. This work reveals the synergistic effect between SA and clusters at atomic level and provides an all-purpose strategy (catalytic sponge) for the recovery of non-magnetic catalysts in wastewater treatment.