Electronic Integration and Thin Film Aspects of Au–Pd/rGO/TiO₂ for Improved Solar Hydrogen Generation

Abstract

In the present work, we have synthesized noble bimetallic nanoparticles (Au–Pd NPs) on a carbon-based support and integrated with titania to obtain Au–Pd/C/TiO2 and Au–Pd/rGO/TiO2 nanocomposites using an ecofriendly hydrothermal method. Here, a 1:1 (w/w) Au–Pd bimetallic composition was dispersed on (a) high-surface-area (3000 m2 g–1) activated carbon (Au–Pd/C), prepared from a locally available plant source (in Assam, India), and (b) reduced graphene oxide (rGO) (Au–Pd/rGO); subsequently, they were integrated with TiO2. The shift observed in Raman spectroscopy demonstrates the electronic integration of the bimetal with titania. The photocatalytic activity of the above materials for the hydrogen evolution reaction was studied under 1 sun conditions using methanol as a sacrificial agent in a powder form. The photocatalysts were also employed to prepare a thin film by the drop-casting method. Au–Pd/rGO/TiO2 exhibits 43 times higher hydrogen (H2) yield in the thin film form (21.50 mmol h–1 g–1) compared to the powder form (0.50 mmol h–1 g–1). On the other hand, Au–Pd/C/TiO2 shows 13 times higher hydrogen (H2) yield in the thin film form (6.42 mmol h–1 g–1) compared to the powder form (0.48 mmol h–1 g–1). While powder forms of both catalysts show comparable activity, the Au–Pd/rGO/TiO2 thin film shows 3.4 times higher activity than that of Au–Pd/C/TiO2. This can be ascribed to (a) an effective separation of photogenerated electron–hole pairs at the interface of Au–Pd/rGO/TiO2 and (b) the better field effect due to plasmon resonance of the bimetal in the thin film form. The catalytic influence of the carbon-based support is highly pronounced due to synergistic binding interaction of bimetallic nanoparticles. Further, a large amount of hydrogen evolution in the film form with both catalysts (Au–Pd/C/TiO2 and Au–Pd/rGO/TiO2) reiterates that charge utilization should be better compared to that in powder catalysts.

Electronically Integrated Mesoporous Ag–TiO2 Nanocomposite Thin films for Efficient Solar Hydrogen Production in Direct Sunlight

“…It is well-known that, 1) the light absorption is more with thin films, whereas the same material in suspension form scatters the light, rather than absorption. [48][49][50] Smaller amount of catalyst (1 mg) absorbs photons much higher than larger amount (25 mg). 2) Exposure of maximum surface-to-solar radiation in thin-film form is beneficial for enhancing light harvesting and light-induced electron excitation processes and increases hydrogen production and AQY; 3) maximum utilization of surface area and active sites is possible with thin-film form, which is good for diffusion of charges toward reaction sites; 4) better contact of catalyst nanoparticles is possible in the film form, which enhances charge separation and charge utilization, whereas charge recombination is severe in powder form; 5) thin-film form also helps for internal scattering of light within the depth of thin films and enhances charge carrier production.…”

CdS decorated MnWO4 nanorod nanoheterostructures: a new 0D–1D hybrid system for enhanced photocatalytic hydrogen production under natural sunlight

“…Nevertheless, the expected outcome in the activity of photocatalyst is unremarkable because of poor efficiency and mixed side products. 15,16 Therefore, the development of active semiconductor photocatalyst is still a great challenge for the scientific community. Recently, transition metal tungstate of the type (MWO4) (M = CO, Ni, Cu, and Zn, etc.)…”

Enhancement of photocatalytic by Mn3O4 spinel ferrite decorated graphene oxide nanocomposites

“…Because of the difference in the mobility's of the electrons and holes, charge separation will occur and when this happens, one encounters a suppression of the annihilation of electron/ hole pairs and therefore an increase in the photo-catalytic activity. This was the explanations given by Patra et al [80], for the enhanced solar generation by MoS 2 /GO and MoS 2 / MoS 3-x /GO multi-functional NC's, for solar water splitting by Au-Pd/rGO/TiO 2 hetero junctions by Tudu et al [81], and by Au-RGO/N-RGO-TiO 2 hetero junctions by Bharad et al [82].…”