TiO2/SnO2 photocatalysts by electrospinning and atomic layer deposition for pharmaceutical contaminant removal

Advanced technologies, including photocatalysis, are required to address the increasing global need for clean water. Titanium dioxide (TiO₂) is often used as a photocatalyst for pollutant removal, but its performance is hampered by its large band gap and fast charge carrier recombination. This study describes the synthesis, characterization, and photocatalytic performance of TiO₂/tin oxide (SnO₂) core-shell nanofibers for the degradation of acetaminophen (ACT), a persistent pharmaceutical pollutant. TiO₂ nanofibers, fabricated by electrospinning, were coated with thin SnO₂ films by atomic layer deposition (ALD). After their structural, morphological, and chemical characterization, TiO₂ and TiO₂/SnO₂ composites were tested as photocatalysts to degrade ACT under UV light. Within 40 min, 99.8 % and 70 % of ACT was degraded in the presence of the optimal TiO₂/SnO₂ composite (SnO₂ layer thickness of 5 nm) and of TiO₂ nanofibers, respectively. Moreover, the optimal TiO₂/SnO₂ composite showed excellent recyclability and stability over five consecutive cycles. Hydroxyl radicals (^•OH), superoxide anions (^•O₂⁻), and holes (h⁺) were the main reactive species implicated in ACT removal. Density functional theory (DFT) modeling confirmed that the band alignment between TiO₂ and SnO₂ enhanced charge separation. This study demonstrates that TiO₂/SnO₂ is a promising photocatalyst for removing pharmaceutical contaminants from the environment.