Demonstration and investigation of hydrogen production by water splitting through plasmon assisted photocatalysis involving a cobalt catalyst.

Plasmonic heterostructures are of great interest within the industry and in the academia owing to theirapplications in photovoltaics and photocatalysis. The Localised surface plasmon resonance (LSPR) leading to an intensification of the electromagnetic (EM) field on the surface of the plasmonic nanoparticles results in an efficient absorption of light over miniscule thickness of the material. The non-radiative decay and subsequent formation of hot carriers makes it possible to them being harvested over a Schottky barrier formed with a semiconducting material thus extending their lifetimes to that required for photovoltaic and photocatalytic applications. This project makes use of a Schottky barrier free plasmonic heterostructure consisting of a plasmonic Au nanoparticles, a semiconductor and a newly synthesised catalyst capable of catalysing hydrogen production reactions. The project also intends to demonstrate and spectroscopically isolate the mechanism of hydrogen production.

Photophysical Study of Electron and Hole Trapping in TiO₂ and TiO₂/Au Nanoparticles through a Selective Electron Injection

The photophysics surrounding the electron and hole trapping in TiO2 do not have a scientific consensus. Herein, we studied the steady-state photoluminescence and time-resolved spectroscopy features from TiO2 and TiO2/Au nanoparticles (NPs). In TiO2/Au NPs, time-resolved photoluminescence indicates that the electrons from bandgap excitation decay slower (∼30 ps) than in TiO2 (<24 ps). We conclude this as a result of the band bending passivation effect on the surface electron traps. Meanwhile, electron trapping is proved as the dominant surface depopulation process because of the easy-fill characteristics of surface hole traps even under low excitation density, which also interprets the slow surface hole trapping (∼2 ns) in TiO2. Through plasmon-assisted electron injection, we distinguished the electron and hole behaviors at varied photon fluences and then obtained the intrinsic bulk trapping of electrons and holes in the ∼50 and ∼400 ps time range, respectively

Hydrogen evolution with hot electrons on a plasmonic-molecular catalyst hybrid system

Plasmonic systems convert light into electrical charges and heat, mediating catalytic transformations. However, there is ongoing controversy regarding the involvement of hot carriers in the catalytic process. In this study, we demonstrate the direct utilisation of plasmon hot electrons in the hydrogen evolution reaction with visible light. We intentionally assemble a plasmonic nanohybrid system comprising NiO/Au/[Co(1,10-Phenanthrolin-5-amine)2(H2O)2], which is unstable at water thermolysis temperatures. This assembly limits the plasmon thermal contribution while ensuring that hot carriers are the primary contributors to the catalytic process. By combining photoelectrocatalysis with advanced in situ spectroscopies, we can substantiate a reaction mechanism in which plasmon-induced hot electrons play a crucial role. These plasmonic hot electrons are directed into phenanthroline ligands, facilitating the rapid, concerted proton-electron transfer steps essential for hydrogen generation. The catalytic response to light modulation aligns with the distinctive profile of a hot carrier-mediated process, featuring a positive, though non-essential, heat contribution. Direct participation of plasmon-induced hot electrons in the photoelectrocatalytic synthesis of hydrogen. This report solves a long-lasting contentious issue surrounding plasmonic materials on catalytic applications