There are currently two main lines of research in the field of photocatalysis: photocatalytic material and photocatalytic activity research.
Photocatalytic material research
This topic focuses on the development of photocatalytic materials and the characterisation of such materials.
Inadequate immobilisation, fast electron-hole recombination and insufficient activity under visible light are three of the main issues of the present generation of photocatalysts. In this topic, we try to immobilise the catalyst onto macroscopic surfaces such as glass beads, silicon wafers or metal plates by means of different coating techniques. We also concentrate on immobilisation by fabricating self-supporting photocatalytic foams or by metabolically incorporating the catalyst in the silica skeleton of diatoms. Additionally, we try to improve the photocatalytic activity by adding dopants or depositing noble metal nanoparticles displaying surface plasmon resonance effects allowing to capture light of lower energy (thus in the visible light region).
The specific surface area, pore size and pore volume of these materials are measured/calculated by N2-adsorption isotherms. The photocatalyst can further be characterised by measuring the band gap by UV VIS diffuse reflectance spectroscopy. The functionality of the surface is studied with Fourier transform infrared spectroscopy. Finally, qualitative and comparative information about the extent of electron-hole separation (and recombination) can be obtained through surface photovoltage (SPV) measurements.
Photocatalytic activity research
For this research, we have developed a modular and fully automated test set-up that enables us to mix the pollutant of interest with clean air, with the possibility to control the relative humidity in the system. The pollutants currently under study are: acetaldehyde, ethylene, nitric oxides and soot (particulate matter).
Due to the modularity of the set-up, we can choose between different reactor types (flat-bed, concentric, ...), or alter the irradiation source (UV-C, UV-A, blue visible light or Full Spectrum) resulting in a wide range of possible test conditions.
For detection, we rely on FTIR spectroscopy, sensors, chemiluminescence (CLD) and photoionisation (PID) detectors. The combination of these methods allows for a real-time and high quality image of pollutant, by-products and end-products in the gas phase. Additionally, we have developed an FTIR in situ reaction cell to perform real-time monitoring of the events occurring on the catalyst surface during reaction. The information on surface adsorbed species acquired from this study gives important insights regarding the reaction pathways.