Electronic Integration and Thin Film Aspects of Au-Pd/rGO/TiO 2 for Improved Solar Hydrogen Generation

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/TiO and Au-Pd/rGO/TiO nanocomposites using an ecofriendly hydrothermal method. Here, a 1:1 (w/w) Au-Pd bimetallic composition was dispersed on (a) high-surface-area (3000 m g ) 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 TiO . 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/TiO exhibits 43 times higher hydrogen (H ) yield in the thin film form (21.50 mmol h g ) compared to the powder form (0.50 mmol h g ). On the other hand, Au-Pd/C/TiO shows 13 times higher hydrogen (H ) yield in the thin film form (6.42 mmol h g ) compared to the powder form (0.48 mmol h g ). While powder forms of both catalysts show comparable activity, the Au-Pd/rGO/TiO thin film shows 3.4 times higher activity than that of Au-Pd/C/TiO . This can be ascribed to (a) an effective separation of photogenerated electron-hole pairs at the interface of Au-Pd/rGO/TiO 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/TiO and Au-Pd/rGO/TiO ) reiterates that charge utilization should be better compared to that in powder catalysts.