In Situ Fabrication of CdS-TiO2 Heterojunction Self-Supporting Electrode for Photoelectrochemical Glutathione Sensing

Abstract Unlike conventional coated electrodes, self-supporting photoelectrodes inherently avoid interfacial resistance and material peeling, enabling superior charge separation and transport efficiency. In this study, a CdS-TiO2 heterojunction photoelectrode was fabricated via in situ growth of an anatase/rutile TiO2 film on FTO conductive glass, followed by CdS nanoparticle modification, and was employed to construct a photoelectrochemical (PEC) sensor for glutathione (GSH) detection. The morphology, structure, and composition of the electrode were analyzed in detail through systematic material characterization. Compared with the photoelectrode of the same composition loaded on a glassy carbon electrode, the self-supporting photoelectrode exhibits a stronger photocurrent. PEC evaluation results indicate that this self-supporting sensor exhibits relatively high sensing performance for GSH. Specifically, under visible light, the electrode exhibits a linear response to GSH in the range of 0–90 μM. The sensitivity is 0.348 nA cm–2 μM–1, and the limit of detection (LOD) is 8.3 μM (S/N = 3). Theoretical calculations and energy-level structure analysis reveal a staggered Type-II band structure at the CdS-TiO2 heterojunction. This heterojunction prolongs the lifetime of photogenerated electrons and enhances photoelectric conversion efficiency via spatially separated charge transfer pathways. Simultaneously, its abundant active interfaces provide sufficient active sites for the GSH oxidation reaction, thereby significantly enhancing the sensing signal. Obtained results provide material design strategies and experimental evidence for the development of highly efficient and reliable PEC sensors.