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

Abstract

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.