High-pressure phase and dual sulfur-oxygen vacancy induction in CdS-TiO2 heterojunctions for multifunctional photocatalytic applications

Abstract

The discovery of visible-light-active photocatalysts that operate without noble-metal co-catalysts remains a major bottleneck for environmental remediation and sustainable energy conversion. In the current investigation, a CdS-TiO₂ heterojunction is synthesized via a high-pressure torsion process at ambient temperature, integrating multiple beneficial features for photocatalysis: a high-pressure TiO₂ columbite phase with enhanced surface activity, dual sulfur and oxygen vacancies that increase light absorption and provide catalytic sites, and multiphase heterojunctions that promote charge separation and suppress recombination. These structural advantages lead to outstanding photocatalytic performance across different key applications: (i) efficient tetracycline antibiotic degradation under visible light without a co-catalyst, (ii) hydrogen production without a co-catalyst, (iii) hydrogen generation at a rate five times higher than TiO₂ with platinum co-catalyst addition, and (iv) CO₂ photoreduction with an activity 38 times greater than TiO₂ without co-catalyst. These results highlight dual-vacancy formation and high-pressure phase incorporation in heterostructured catalysts as an effective strategy for designing multifunctional, stable and low-band-gap photocatalysts for environmental and energy-related applications.