A review on TiO2/SnO2 heterostructures as a photocatalyst for the degradation of dyes and organic pollutants

Industrialization, civilization and human activities have all grown steadily in recent years. As a result, small and large industries discharge many organic pollutants into the environment and contribute to environmental pollution. These compounds are quite stable and challenging to break down over time, posing a long-term risk. The heterogeneous advanced oxidation processes technology has gained tremendous attention. It depends on the light-induced formation of e(-)/h(+/-) pairs, which combine with water and aqueous oxygen to generate highly reactive hydroxyl radicals that degrade the organic pollutants in a solution and convert them ultimately into nontoxic products. In this paper, the synergetic impact of TiO2-SnO2 coupling with other semiconductor materials and their photodegradation performance on toxic contaminants in an aqueous medium has been reviewed. In addition, multiple approaches for the synthesis of TiO2-SnO2 photocatalysts have been discussed. Among them, hydrothermal, sol-gel, electrospinning, precipitation and even their combination are extensively used to synthesize various forms of nanostructures. These techniques demonstrate better tunability for visible absorption, suppression of e(-)/h(+/-) pair recombination and enhanced e(-)/h(+/-) separation to improve photocatalytic performance. This paper also summarises the role of different operating factors such as catalyst loading, pH, pollutants variation concentration, various light sources and oxidizing agents on the photodegradation of organic pollutants.