Materials development for solar energy conversion for water splitting by photoelectrochemical cells (PEC) is an important problem. Although TiO2 is the most promising material because of its oxidative stability, energy band position, and abundance, it is a wide band gap material that absorbs ~3% of sunlight from ultraviolet region. To enhance the light absorption, one should increase the thickness of TiO2, which is problematic because recombination rate of excitons is very high. Consequently, diffusion length of the excitons and charge carriers are very low as it reduces the charge transfer. In the AURORA project we study yttrium oxyhydride (YHO) for applications in PEC. YHO belongs to emerging family of materials called mixed anion systems. It has been first synthesized in the Institute for Energy Technology (IFE) group. Since then materials properties have been studied systematically. Before illumination, the average transparency and absorbance of the material is >85% and ~5%, respectively. However, after illumination with sunlight within ~10-15 minutes, transparency reduces and light absorbance increases to ~50%. By adjusting the film composition, work function of YHO can be varied between 3.1-3.6 eV. Furthermore, illumination of the material by UV light has enhanced antibacterial properties of thin layers of Ag. These findings have motivated us to study potential of YHO in PEC, which is an innovative idea.
The expected outcomes are: Clarifying the grain size and porosity, and electrochemical stability of YHO, fabrication of PEC with YHO- and oxides/YHO-based photoanodes, establishing performance of PEC, evaluation of potential of YHO for applications in PEC, submission of two joint journal articles, one conference proceeding, and a joint proposal to H2020 about PEC with the oxyhydride-based photoanode. Exchange visits of senior researchers, PhD students and young researchers between DEPSOL, KeraNor AS, and UP will be implemented.