Selective photoelectrocatalytic oxidation of 3-pyridynemethanol by nanotube structured Ti/TiO2 photoanodes

In this thesis, photoelectrocatalytic (PEC) 3-pyridinemethanol oxidation to 3-pyridinemethanal and vitamin B3 was investigated. For this aim efficient nanotube structured TiO2 on Ti plate as photoanode were prepared by anodic oxidation method in ethylene glycol and characterized by XRD, SEM and photocurrent techniques. The effect of nanotube morphology, applied potential, Na2SO4 concentration, stirring speed of solution, and pH on the reaction activity and product selectivities were investigated. TiO2 phase of all of the anodes was mainly the anatase one. The PEC activity, the intensity of XRD peak and photocurrent increased by increasing the nanotube length. The activity decreased by decreasing both the Na2SO4 concentration and the applied potential, whereas 3-pyridinemethanal selectivity increased. By increasing the stirring speed of the solution, both the activity and the 3-pyridinemethanal selectivity increased. A low or no activity was observed for photocatalytic (PC) and electrocatalytic runs, respectively, which were carried out for the sake of comparison. No PC activity was obtained in the presence of N2, but PEC reactions in the presence of N2 were faster than in the presence of O2. The produced 3-pyridinemethanal in both N2 and O2 atmosphere was reduced at the cathode in PEC reaction, but its oxidation appeared to be much more favourable. The PC reactions could not be carried out under acidic conditions, whilst the PEC ones could be performed in the pH range 2-12.