Partial photoelectrocatalytic oxidation of 3-pyridinemethanol by Pt, Au and Pd loaded TiO2 nanotubes on Ti plate

Abstract

The photoelectrocatalytic (PEC) oxidation of 3-pyridinemethanol to 3-pyridinemethanal and vitamin B3 was investigated by using Pt, Au and Pd loaded (as single or bimetallic) nanotube structured TiO2 on Ti plate in water under UVA irradiation. Nanotube structured TiO2 on Ti plate samples were prepared as anode by anodic oxidation method in ethylene glycol solution in different times, and then they were calcined at 500 °C to be obtained in crystalline form. The anodes were loaded with noble metals by electrochemical reduction method and characterized by XRD, XPS, SEM, and photocurrent techniques. The TiO2 on the plates was in the anatase phase. The loaded metals were in metallic form and heterogeneously dispersed on the TiO2 surface in different sizes. The results indicate that a high amount of metal loading negatively affected the PEC activity of the metal loaded samples because UVA irradiation inside the nanotubes was inhibited by the presence of the metal. On the contrary, low amount of Pd showed high PEC activity and high product selectivity values with respect to the pristine sample. PEC experiments were also more selective than the photocatalytic ones for vitamin B3 production. Electrocatalytic (EC) and photocatalytic (PC) experiments were also conducted, however no or low activity was obtained, respectively. PEC experiments showed to be more selective than the PC ones for vitamin B3 production.