Book Description
This thesis covers synthetic investigations, characterization, and applications of transition metal doped titanium dioxide materials and transition metal phosphide/sulfide structures. Both areas are useful in heterogeneous catalysis, battery energy storage, and in semiconductor light to energy conversion. Two main synthesis routes have been investigated: 1) rapid solid state metathesis (SSM) of transition metal oxides, phosphides, sulfides, and thiophosphates, and 2) sealed ampoule routes of transition metal phosphides and thiophosphates. SSM reactions tend to yield kinetically controlled multiphase products while sealed ampoule routes gave more thermodynamically favorable single phase materials. Approximately 10 mol% of many first row transition metals (M = Cr, Mn, Fe, Co, Ni, Cu) were targeted for doping into TiO2, using MClx, and sodium peroxide in SSM reactions, targeting an ideal mixed phase of M0.1Ti0.9O2. X-ray diffraction showed rutile TiO2 forms and no separate dopant metal phases were seen until subsequent 1000 °C annealing in air. EDS, ICP, and XPS analysis showed slightly lower than the targeted M:Ti ratios however, the manganese sample had more than the ideal 10 mol % of dopant. DRS data showed estimated bandgap energies of the doped samples within 1.33-2.55 eV. Magnetic susceptibility showed small paramagnetic responses from all samples that increase upon annealing. SEM showed that the doped SSM-TiO2 samples were mixtures of aggregates and blocky particles. The synthesized doped titanias were tested for methylene blue and methyl orange photodegradation under UV and visible light and for H2 generation from water reduction under UV light. The doped titania samples absorb significant amounts of methylene blue dye in the dark with the manganese doped TiO2 sample being the most absorbent. Degradation of methylene blue under UV illumination was observed, however, only modest degradation under visible light was observed.