Abstract:

The escalating pace of industrialization has significantly intensified water pollution challenges, for instance, the persistent organic pollutants like methyl orange（MO）. Conventional remediation techniques, such as adsorption and biological degradation, are often hampered by low efficiency and the risk of secondary pollution. Photocatalysis emerges as a promising sustainable alternative; however, the benchmark material titanium dioxide（TiO₂）suffers from its intrinsic limitations, notably its wide bandgap energy（≥3.4 eV）restricting its activity to the region of the ultraviolet light and its rapid recombination of photogenerated charge carriers. To overcome these constraints, this research focused on synthesizing novel TiO₂/Sn₃O₄ heterojunction composite photocatalysts via a solvothermal approach. Comprehensive characterization techniques confirmed the successful formation of the composite, which revealed that ultrathin Sn₃O₄ nanosheets uniformly coated TiO₂ nanospheres. This unique architecture effectively reduced the overall crystallinity and introduced the beneficial oxygen vacancies. Under visible-light irradiation（λ≥420 nm）, the optimized TiO₂/Sn₃O₄ composite exhibited the exceptional photocatalytic performance, which achieved 96% degradation of MO within just 60 minutes. The calculated apparent kinetic rate constant（0.103 min^-1）was remarkably（5.15 times）higher than that of pristine TiO₂. ESR experiments identified that hydroxyl radicals（·OH）was the predominant active species driving the degradation. Furthermore, cyclic degradation tests demonstrated its excellent material stability, with the composite retaining 85% of its initial efficiency after four consecutive reuse cycles. This work underscored the synergistic effects within the TiO₂/Sn₃O₄ heterojunction, which significantly enhanced the visible-light absorption, charge separation, and photocatalytic activity, which provided the valuable insights for designing efficient, stable catalysts for the advanced environmental remediation applications.

Key words: TiO₂/Sn₃O₄ composite, visible-light photocatalysis, methyl orange degradation, oxygen vacancies, hydroxyl radicals