Photoelectrochemical, photocatalytic and electrocatalytic behavior of titania films modified by nitrogen and platinum species

Co-doping of titania by N and Pt species was employed to tune the electronic structure and enhance the electrocatalytic and photocatalytic activity of the films. Herein, the different approaches of synthesis procedure of Pt- and Pt,N–TiO₂ films were used to investigate their effect on the platinum oxidation states. The resulting different species of Pt led to the changes in the electronic structure of TiO₂, with consequent bandgap narrowing, anodic shift of the flat band potential, and cathodic shift of the valence band The quantum yield efficiency was correlated with Pt⁰ atomic content and the relative atomic content of Ptⁿ⁺–O–Ti fragments, whereas its decrease for some samples can be caused by the presence of N and Ptⁿ⁺. The highest response for N₂O photocatalytic decomposition was observed over Pt,N–TiO₂ films. The presence of metal and non-metal species in TiO₂ structure resulted in synergistic effect including (1) inhibition of recombination of the electrons and holes and (2) narrowing of the bandgap. Electrocatalytic properties in hydrogen and oxygen evolution reactions were improved by Pt doping. The formed Pt²⁺–O–Ti bonds rather than Pt nanoparticles are suggested to be responsible for the highest electrocatalytic activity. The additional UV exposure of the electrodes led to Pt NPs aggregation as a result of photodeposition of Pt ions. The mechanism of the Pt²⁺ photoreduction in TiO₂ structure is proposed.