XPS study of the SnO 2 films modified with Rh

Highly efficient mobility, separation and charge transfer in black SnO2-TiO2 structures with co-catalysts: the key step for the photocatalytic hydrogen evolution

Oxygen vacancies and co-catalysts enhance photocatalytic hydrogen production by improving the charge carrier separation. Herein, the black SnO2-TiO2 structure (BST) was synthesized for the first time by two consecutive methods. First, the sol-gel nucleation method allowed TiO2 to form on the SnO2 nanoparticles, creating a strong interaction and direct contact between them. Subsequently, this structure was reduced by NaBH4 during thermal treatment, generating (Ti3+/Sn2+) states to form the BST. Then, 2 wt% of Co, Cu or Pd was impregnated onto BST. The results showed that the activity raised with the presence of Ti3+/Sn2+ states, reaching a hydrogen generation rate of 147.50 μmol g-1 h-1 with BST in comparison with the rate of 99.50 μmol g-1 h-1 for white SnO2-TiO2. On the other hand, the interaction of the co-catalysts with the BST structure helped to increase the photocatalytic hydrogen production rates: 154.10 μmol g-1 h-1, 384.18 μmol g-1 h-1 and 480.20 μmol g-1 h-1 for cobalt-BST, copper-BST and palladium-BST, respectively. The results can be associated with the creation of Ti3+/Sn2+ at the BST interface that changes the lifetime of the charge carrier, improving the separation of photogenerated electrons and holes and the co-catalysts in the structures move the flat band position and increasing the photocurrent response to having electrons with greater reducing power.

Synthesis and characterization of SnO2/rGO nanocomposite for an efficient photocatalytic degradation of pharmaceutical pollutant: Kinetics, mechanism and recyclability

The SnO₂ and SnO₂/rGO nanostructures were successfully synthesized using the facile hydrothermal synthesis technique. The prepared nanostructures were well studied using different techniques such as XRD, XPS, UV-DRS, FT-IR, EDX, SEM and HR-TEM analysis. The crystalline nature of SnO₂ and SnO₂/rGO was confirmed by the XRD technique. The formation of highly pure SnO₂ and SnO₂/rGO nanostructures was confirmed by EDX analysis. The morphological results show the good agglomeration of several spherical nanoparticles. The optical properties were studied through the UV-DRS technique and the bandgap energies of SnO₂ and SnO₂/rGO are estimated to be 3.12 eV and 2.71 eV, respectively. The photocatalytic degradation percentage in presence of SnO₂ and SnO₂/rGO against RhB was found to be 96% and 98%, respectively. The degradation of TTC molecules was estimated as 90% and 88% with SnO₂/rGO and SnO₂, respectively. The degradation of both RhB and TTC molecules was well suited with the pseudo-first-order kinetics. The results of successive experiments clearly show the enhancement in the photocatalytic properties in the SnO₂/rGO nanostructures.