Photo-Driven Charge Transfer Mechanism in TiO₂-SnO₂ Nanocomposites for Enhanced Dye Degradation

The development of photocatalysts that can efficiently remove organic pollutants is crucial for environmental clean-up. In this study, we present the synthesis of stable TiO₂-SnO₂ nanocomposites using the sol-gel method. Various characterization techniques were employed to analyze the structural, morphological, and optical properties of the samples. The photocatalytic efficiency of the nanocomposites was assessed by examining the degradation of Congo red (CR) dye under sunlight. All samples exhibited over 90% degradation within 2 h, with the optimized sample achieving 99.0% efficiency and a rate constant of 3.3 × 10^− 2 min^− 1. The stability of the photocatalyst was validated through reusability tests, which showed more than 90% efficiency even after five cycles. The photocatalytic mechanism is thoroughly explained using band edge positions and effective charge transfer processes due to the formation of a heterojunction. Additionally, BET analysis and zeta potential measurements were conducted to gain a deeper understanding of the catalytic process.