Modulating photothermal properties by integration of fined Fe-Co in confined carbon layer of SiO2 nanosphere for pollutant degradation and solar water evaporation

Abstract

Environmental governance by photothermal materials especially for the separation of organic pollutants and regeneration of freshwater afford growing attention owing to their special solar-to-heat properties. Here, we construct a special functional nanosphere composed of an internal silica core coated by a thin carbon layer encapsulated plasmonic bimetallic FeCo₂O₄ spinel (SiO₂@CoFe/C) by a facile self-assembled approach and tuned calcination. Through combining the advantage of bimetallic Fe-Co and carbon layer, this obtained nanosphere affords improved multiple environmental governing functions including peroxymonosulfate (PMS) activation to degrade pollutants and photothermal interfacial solar water evaporation. Impressively, fined bimetal (FeCo) species (20 nm) acted as main catalytic substance were distributed on the N-doping carbon thin layer, which favors electron transfer and reactive accessibility of active metals. The increasing treatment temperature of catalysts caused the optimization of the surface active metal species and tuning catalytic properties in the AOPs. Besides, the incorporation of Co in the SiO₂@CoFe/C-700 could enable the improved PMS activation efficiency compared to SiO₂@Fe/C-700 and the mixed SiO₂@Co/C-700 and SiO₂@Fe/C-700, hinting a synergetic promotion effect. The bimetal coupled catalyst SiO₂@CoFe/C-700 affords enhanced photothermal properties compared to SiO₂@Co/C-700. Furthermore, photothermal catalytic PMS activation using optimal SiO₂@CoFe/C-700 was further explored in addressing stubborn pollutants including oxytetracycline, sulfamethoxazole, 2, 4-dichlorophenol, and phenol. The free radical quenching control suggests that both the sulfate radical, hydroxyl radical, superoxide radical, and singlet oxygen species are involved in the degradation, while the hydroxyl radical and singlet oxygen play a dominant role. Furthermore, the implementation of a solar-driven interfacial water evaporation model using SiO₂@CoFe/C-700 was further studied to obtain freshwater regeneration (1.26 kg m^-2 h^-1, 76.81% efficiency), indicating the comprehensive ability of the constructed nanocomposites for treating complicated environmental pollution including organics removal and freshwater regeneration.

Keywords: Advanced oxidation process; Bimetal; Core-shell; Photothermal conversion; Solar water evaporation.