In situ study of visible light-activated photocatalytic conversion reaction enhancement of biomass using a magnetic heterostructure

Although cadmium sulfide (CdS) is a promising visible light-active photocatalyst, it is highly toxic. Therefore, in addition to improving the photocatalytic properties of CdS, enhancing its recoverability would allow for more environmentally friendly photocatalytic reactions. In this study, ferrimagnetic Fe₃O₄ nanoparticles (NPs) were added to CdS to form a heterostructure, and photocatalytic CdS NPs were efficiently recovered. The photocatalytic reaction efficiency of this heterostructure for biomass conversion was measured. Using the CdS/Fe₃O₄ heterostructure system, the photocatalytic conversion rates of 5-hydroxymethylfurfural to 5-formylfuran-2-carboxylic acid and toluene to benzaldehyde were approximately 30% and 63% higher, respectively, than those achieved using pristine CdS NPs. Furthermore, the magnetic properties were reduced by only ∼6.8% compared to those of Fe₃O₄ NPs, confirming their applicability. The CdS/Fe₃O₄ heterostructure had better photocatalytic properties than CdS, and the magnetic properties were on par with those of Fe₃O₄. Changes in the electronic structure of the heterostructure system were monitored using in situ X-ray photoelectron spectroscopy during visible light irradiation and characterized using electron energy-loss spectroscopy in scanning transmission electron microscopy to analyze the defect structure changes occurring at the interface of the heterostructure system.