Electrocatalytic Properties of Pulsed Laser-Deposited Titanium Dioxide and Titanium Oxynitride Thin Films Grown on Photo-Adsorbing Single Crystal Substrates with Different Orientations

The research focuses on the growth of (photo)electrocatalytic titanium dioxide (TiO₂) and Titanium oxynitride (TiON) thin films epitaxially grown on single crystal substrates at different orientations. The films are used as catalysts to examine the eclectrochemical reactions during water-splitting with the aim of producing hydrogen.The films were grown using pulsed laser deposition (PLD), which has many advantages, including fast response time, energetic evaporants, and congruent evaporation. These advantages were used to determine the optimal growth conditions, which, when combined with careful substrate selection, led to oxide and oxynitride films with well-defined strain and well-controlled vacancies. Furthermore, since PLD can transfer the composition of the target having elements with vapor pressures as different as 10⁶ from each other, it can enable the incorporation of non-Ti cations into TiO₂ and TiON (photo)electrocatalytic films. Soft X-ray absorption spectroscopy at the Ti L-edge, O K-edge, and N K-edge was collected on the TiON samples to obtain information regarding the electronic structure. This controls afforded by pulsed laser deposition (PLD) allows us to tailor the band edges of semiconductors and to evaluate the creation and evolution of water-splitting intermediates as a function of potential and/or photo triggers. This capability is then used to examine the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) mechanisms on oxide and oxynitride catalysts.