Silicon-modified black TiO2 photocatalysts as a sustainable platform for micropollutant degradation under full-spectrum solar irradiation

Conventional wastewater treatment technologies are often ineffective in eliminating persistent micropollutants, such as neonicotinoid pesticides, which pose significant risks to ecosystems and human health. To address this challenge, silicon-modified black titanium dioxide (Si-b-TiO 2 ) photocatalysts were synthesised via a sol–gel route followed by chemical reduction, targeting sustainable environmental remediation under full-spectrum solar irradiation. Controlled Si incorporation (1–15 wt%) tuned the structural, optical, and electronic properties of black TiO 2 , as confirmed by XRD, TEM, and XPS and FT-IR analyses. Silicon modification suppressed electron–hole recombination and enhanced visible-light absorption, accompanied by increased generation of reactive oxygen species, as evidenced by hydroxyl radical ( HO ∙ ) probing using terephthalic acid fluorescence. The optimised Si1-b-TiO 2 photocatalyst achieved an imidacloprid degradation efficiency of approximately 70% within 180 min under full-spectrum irradiation, compared to ∼34% for pristine black TiO 2 , corresponding to an apparent rate constant of k = 6.84 ⋅ 10 −3 min −1 . In addition, the catalyst retained more than 90% of its initial activity after five consecutive degradation cycles, demonstrating good operational stability. At higher Si loadings (≥5 wt%), performance decreased due to pore blockage and recombination, underlining the importance of controlled doping. This work demonstrates that Si-modified black TiO 2 provides a cost-effective and scalable material platform for solar-driven water purification, contributing to the development of sustainable technologies for mitigating micropollutants. • Si-modified black TiO 2 synthesised via sol-gel and NaBH 4 reduction methods. • 1% Si-modified black TiO 2 showed 70% imidacloprid degradation in 3 h under full-spectrum light. • Si incorporation introduced mid-gap states and enhanced visible light absorption. • PL analysis showed reduced charge recombination with increasing Si content. • Surface Si incorporation improved charge separation and photocatalytic efficiency.