S-Scheme TiO2/CuNb2O6 Nanocomposite Photocatalyst with Enhanced H2 Evolution Activity from Aqueous Glycerol Solution

Abstract

Steering of photoexcitons via interface engineering of semiconductor photocatalysts is key to achieving a stable and efficient photocatalyst for continuous hydrogen production. Among them, the development of 1D nanostructures with several advantageous properties such as wide surface area, effective light harvesting, and increased electron moving kinetics has received special attention. In this work, 1D titania nanobars were successfully synthesized via the methanol-assisted solvothermal method, in which alcohol formed hydrogen bonds with nuclei, which consequently encouraged the growth of nanobars. Following this, the titania nanobars were integrated with solvothermally synthesized monoclinic CuNb2O6 nanoparticles. TEM analysis revealed the formation of TiO2 nanobars and their uniform interaction with CuNb2O6 nanoparticles. A S-scheme heterojunction is formed at the interface of TiO2 nanobars and CuNb2O6 nanoparticles. 1D morphology of titania and CuNb2O6 plays a key role in light absorption and boosts the photocatalytic activity by promoting the separation and transfer of photoexcited charge carriers. The electrons at the TiO2 conduction band and holes at the valance band of CuNb2O6 facilitated recombination at the heterojunction. The remaining electrons at the conduction band of CuNb2O6 and holes at the valance band of TiO2 tend to participate in redox reactions at their terminals. As the loading of CuNb2O6 increases, the rate of activity initially increases and then decreases, which is consistent with the trend for light penetration-dependent photocatalytic hydrogen evolution. The band edge potentials of TiO2 and CuNb2O6 were also revealed using VB-XPS and UPS analysis. In addition to catalytic stability, the effect of glycerol concentration, catalyst loading, time on stream, recyclability, and parametric analysis which aided in the discovery of ideal experimental conditions is revealed. Under optimal conditions, the photocatalyst showed an enhanced rate of H2 generation (146 mmol h–1 gcat–1) under simulated solar light irradiation. The solar to H2 conversion efficacy is also discussed with comparison.