Novel TiO2 nanomaterials as sonocatalytic agents for water-splitting

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Sonochemistry is the use of ultrasound generated bubbles to enable chemical reactions. Sound waves will cause the formation of bubbles in liquids and the eventual collapse of bubbles is termed as acoustic cavitation; the collapse induces local changes to the physicochemical environment which could be further used in catalytic reactions. This effect is long-known and used in drug deliveries; however, limited work has been done to explore its potential application in sustainable catalysis. Recently, the introduction of heterogeneous catalysts (catalysis that is not in the same phase as the reactants) has opened up new reactions not previously achievable using conventional sonochemistry. Yet, the control of cavitation - the primary driving force for sonochemistry - has yet to be achieved.This research aims to develop approaches for controlling cavitation around catalytic sites, understanding the underlying physics and chemistry, and, for the first time, applying this sonochemical approach towards partial water splitting. Partial water splitting is the reaction to split the water into its constituents. Hydrogen, as one of the products, is a carbon-free fuel that could be used directly in devices, and an oxidative chemical reaction could happen simultaneously to produce a high market value product from cheap raw material. In other words, the sonochemistry investigated in this project presents a potential application for saving operation energy and cost to produce two valuable chemicals, and could contribute greatly to understanding cavitation and sonochemistry.Experimental studies will include synthesising heterojunction nanoparticle catalysts and be conducted using a novel bespoke sonochemical reactor that will enable cavitation monitoring in controlled acoustic fields. The reactor setup will also be used to evaluate the sonocatalytic performance of the material. Chemical analysis (i.e. characterisation) of product species will be conducted using spectroscopic and chromatographic methods such as gas chromatography, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Finally, computations will be performed to explore the chemical mechanism for further understanding and control of the sonochemical reactions. Additionally, results from both the cavitation noise and chemical species analysis will advance our understanding of catalytic sonochemistry and enable future designs of sonochemical reactors, catalytic cavitation agents, and the potential chemistries possible using the approaches developed in this work.This project falls within the EPSRC Engineering and Energy research area.