Solid-liquid interface studies of titania and nanocarbon materials

Modifying TiO2 has been of great interest for applications in photocatalytic degradation of organic pollutants, production of hydrogen from water and photovoltaic applications. The chemical composition of TiO2 can be altered by doping by which the titanium and/or oxygen component is replaced. Doping alters the material’s optical properties, but sometimes at the cost of undesirable consequences.
A novel 2-propanol/HNO3 based one pot sol-gel evaporation method was developed and optimized for rapid growth of highly N doped TiO2 nanoparticles. With the adaptation of CasaXPS software, a novel MB absorption spectrum peak deconvolution technic is proposed. Total absorption area yields better pseudo-first-order reaction linearity than using maximum absorption peak height (MB monomer) was found to be a better indicator of MB degradation. This is especially true for exotic absorption spectra change with uneven peak reduction rate.
Photocatalytic degradation of MB by N-doped TiO2 takes place via the sequential decomposition of methyl groups from MB to azure A/B/C and further mineralisation. N-doping enables photocatalytic response under visible spectrum. Samples prepared using 2 mL concentrated nitric acid in 25 mL 2-propanol solution (0.5 M Ti concentration) and annealed at 300 °C for 10 hrs yield best photocatalytic results under visible spectrum irradiation.
Using a dip-coating method Sn doped anatase TiO2 thin film grown on 5%Nb:SrTiO3 (001) substrate and Sn doped rutile TiO2 thin film grown on FTO substrate are achieved. Doping level of up 15% were achieved with anatase TiO2 thin film epitaxial growth while maintaining host anatase structure. Sn doped anatase and rutile thin film as a photoanode material were investigated using a three-electrode setup. 10% Sn doped anatase thin film showed better photocurrent performance under UV while 1% Sn doped rutile anatase thin film performed better under simulated one sun illumination and visible spectrum. The main contribution to PEC performance is still due to the UV spectrum. The overall increase in photocurrent should be due to an increase in photoactive sites caused by Sn doping.
The underlying principle of water oxidation and reduction using a semiconductor photoanode/cathode-based PEC device was explored, and the reason for RHE scale is explained with multiple examples of PEC designs. This serves as a standard model in interpreting electrochemical data of photoanode/photocathode in a three-electrode setup.
Rice husk waste material can be used as a potential biomass-derived carbon material for EDLC electrode. Two different-sized bimetallic Co/Mn MOFs were grown in the channels of cRHs for improved EDLC performance. A drop-coating method was devised for EDLC testing using smaller material quantity. cRHs fabricated under different carbonisation conditions were tested with 400 °C carbonised in nitrogen (#4) showing best specific capacitance of 11.54 F/g. Carbonized metal acetate precursor derived MOFs sample #4 ACT yields a consistent specific capacitance of around 30 F/g irrespective of scan rate.

Keywords: photodegradation
interface
EDLC
semicondutor-electrolyte interface
PEC
TiO2
water splitting
energy alignment
Advisor: Foord, J