Strontium-Doped Tin Oxide Nanofibers for Enhanced Visible Light Photocatalysis

This study investigates the photocatalytic degradation of methylene blue (MB) using strontium-doped SnO2 nanofibers synthesized via electrospinning. The 1% Sr-doped SnO2 nanofibers exhibited remarkable photocatalytic activity, achieving 84.74% MB degradation under visible light irradiation, substantially outperforming both undoped SnO2 nanofibers (61%) and the same catalyst under UV light (69%) under identical experimental conditions. Comprehensive electrochemical investigations revealed that Sr doping fundamentally transformed interfacial charge transfer kinetics, with 1% Sr-doped nanofibers exhibiting a remarkable three-fold decrease in charge transfer resistance (404 Ω compared to 1350 Ω for undoped samples), a dramatic enhancement in charge carrier density (5.17 × 1022 versus 9.24 × 1019 for undoped samples), and an approximately eight-fold increase in diffusion coefficient (8.78 × 10⁻10 versus 1.13 × 10⁻10 cm2s⁻1). These electrochemical improvements were corroborated by comprehensive structural characterization, which demonstrated that strategic Sr incorporation induced beneficial oxygen vacancies, reduced crystallite size, increased microstrain, and enhanced dislocation density, collectively contributing to superior surface reactivity and accelerated photocatalytic mechanisms. This work establishes a quantitative correlation between electrochemical characteristics and photocatalytic activity in Sr-doped SnO2 nanofibers, revealing the fundamental mechanisms that transform the SnO2 nanostructure from UV-dependent to efficient visible light-driven catalysts for organic pollutant degradation.