Solar‐Driven Photocatalytic Degradation of Ruthenium Red Over α‐Fe ₂ O ₃ Nanostructures: Kinetics and Mechanistic Insights

Solar‐driven semiconductor photocatalysis provides a sustainable and energy‐efficient approach for the treatment of persistent dye pollutants in wastewater. In this study, we report for the first time the degradation of an inorganic dye under natural sunlight using α‐Fe 2 O 3 nanoparticles. Nanostructured α‐Fe 2 O 3 was synthesized via a solar‐assisted photo‐redox complex formation route and evaluated as a visible‐light‐active photocatalyst for the degradation of ruthenium red, a representative inorganic coordination dye. Under direct natural sunlight irradiation (850 ± 50 W m −2 ), the α‐Fe 2 O 3 photocatalytic activity achieved a maximum degradation efficiency of 40.4% at an optimized catalyst loading of 60 mg per 200 mL, following pseudo‐first‐order kinetics ( k app = 2.93 × 10 −3 min −1 ). The activity observed without external oxidants demonstrates effective visible‐light utilization for a structurally stable coordination‐complex pollutant. Spectroscopic and kinetic analyses indicate that degradation proceeds through charge‐carrier‐mediated oxidative processes involving reactive oxygen species and progressive breakdown of the coordination framework. These findings establish α‐Fe 2 O 3 as a sustainable and earth‐abundant solar photocatalyst for inorganic dye treatment and provide a foundation for future material optimization strategies.