A novel strategy to produce compact and adherent thin films of SnO2/TiO2 composites suitable for water splitting and pollutant degradation

Abstract

SnO2/TiO2 composites have been widely studied as efficient photoanodes by various research groups around the globe. However, in this work, we display a novel and low cost strategy to synthesize thin films of such composites. According to the synthesizing strategy, various amounts of Degussa TiO2 P25 nanopowder ranging from 0.25 to 1.0 g were mixed to a fixed volume of SnO2 sol–gel solution. Then, the mixtures were spin-coated on doped tin oxide glass substrates. After a slow annealing at 500 °C, we obtained nanostructured SnO2/TiO2 composite thin films (CTFs). As-prepared CTFs were characterized by the scotch tape test, scanning electron microscope, X-ray diffraction and photoluminescence spectra. Furthermore, photoelectrochemical properties, photocatalytic activities and stability of all SnO2/TiO2 composite based PAs were studied. Results showed that composites with medium TiO2 amount exhibits more compact and adherent films than bare TiO2 films. We recorded an optimum situation for films prepared with 0.75 g of TiO2. It was proved that the SnO2 sol–gel method enabled compactness and adhesion of the processed composites. We correlated the photoluminescence intensity to the photocurrent density Jsc. The optimum Jsc, almost equal to 0.9 mA, was obtained in the case of 0.75 g amount of TiO2. This electrical performance is nearly nine times higher than that recorded with bare TiO2 photo-anodes. Moreover, replacing bare TiO2 photocatalyst by SnO2/TiO2 CTFs brought remarkable improvements to the photocatalytic degradation of methyl orange. Finally both morphological and mechanical properties of the composites were correlated to the stability and reusability of the CTF PAs.