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Project

Plasmonics-based Energy Harvesting fo Catalyisis (PLASMHACAT).

Many critical photochemical and photophysical processes, from photosynthesis in plants, to photo-catalytic reactions, and to generation of electricity in solar cells, depend on an efficient interaction between light and matter. In order to increase, for example, the efficiency of photo-catalysis, the interaction of the photo-catalyst with light has to be increased. This project has pursued two lines of investigation in order to achieve this. Firstly, the concept of light-harvesting has been exploited. Light energy can be harvested by collecting, directing and concentrating it at a reaction center, in a fashion that mimics that used by plants. Secondly, light enhancement at the metal nanoparticles (so-called plasmonic enhancement) was used to enable a more efficient light-matter interaction. The project combined both approaches, that is to create a plasmonic antenna to funnel light to a reaction center, whilst at the same time using the plasmons generated as an efficient reaction field in catalysis. The outcome of this timely and challenging proposal can make it possible to drastically increase activities of (photo)catalysts, enabling their efficient operation in the visible/IR region of the spectrum of sunlight or even in weak room light conditions. In this project, we mainly used titanium oxide (TiO2) as a model photo-catalyst because TiO2 is one of the most used materials in our life and exhibits excellent photo-catalytic materials for environmental purification as well as for sustainable light-energy conversion such as electrochemical solar cell and hydrogen generation through water-splitting. Although widely used, photo-catalytic efficiency of TiO2 is rather low because its activity lies in the UV region (only a few % of sunlight at the earth's surface). In order to extend the sensitivity to visible light, deposition of noble metal (gold or platinum) nanoparticles on TiO2 surface has been often used in the corresponding research field. However, the efficiency of deposition is not high enough, often resulted in low enhancement. This project developed an effective method to deposit metal nanoparticles on TiO2 surface using a simple wet-chemical approach. We used ethylene glycol as a solvent for the reaction. We found that ethylene glycol modify optical property of TiO2 upon molecular adsorption on the surface, which enhance the catalytic efficiency and lead to well-controlled metal nanoparticle deposition. Photo-catalytic efficiency of our metal-deposited TiO2 was tested with photo-decomposition of 4-chlorophenol (4-CP) in aqueous solution. 4-CP serves as the model molecule for halogenated pollutant, which are often used for pesticides and solvents or reagents from industrial processes. Not only are these compounds toxic, but they also cannot be mineralized with traditional wastewater processes. We found that our metal-deposited TiO2 shows higher catalytic efficiency compared to reported metal/TiO2 systems. In addition to photo-decomposition of toxic materials, we found that simple surface modification of TiO2 can induce visible sensitivity, which will be used for visible light water-splitting system by this project in near future.

Date:1 Oct 2011 →  30 Sep 2016
Keywords:Plasmonics, Harvesting, Catalysis
Disciplines:Atomic and molecular physics