The conversion of energy from renewable and CO₂ free energy sources into chemical energy, has the potential to contribute significantly to cover our energy needs [1]. Photoelectrochemical (PEC) water splitting, with its simpler setup compared to combining a photovoltaic cell and an electrolyser, shows promise as a cost-effective method for producing green hydrogen in the future [2]. A PEC system consists of two separate electrodes connected by an ohmic contact, each providing a site for one of the two water-splitting half-reactions [2].

Research over the past decades has primarily focused on improving the photoanode efficiency, leading to a thorough understanding of the material properties required for high conversion efficiency [3-5]. However, for PEC systems to be viable on an industrial scale, the long-term stability of the photoelectrode materials is essential. These materials must withstand degradation  by the electrolyte and resist photo corrosion [2, 6] Investigating the degradation processes of photoelectrodes is therefore important from both scientific and practical perspectives, as it is crucial for developing photoelectrodes with longer lifespans [3, 7].  

In photoanodes, photogenerated holes  are known to participate either in the oxygen evolution reaction, to be lost to recombination, or to cause the oxidation of anions in the photocatalyst [6]. This oxidation process can lead to the dissolution of metal ions into the electrolyte, as the crystal lattice becomes destabilized due to changes in the local structure around the oxidized ions [8, 9].

Since oxynitrides are known for their good performance with respect to efficiency, LaTiO₂N based photoanodes were selected for this study on degradation. The LaTiO₂N was synthesized via solid state synthesis followed by thermal ammonolysis. The photoanodes were prepared by electrophoretic deposition followed by TiCl₄ necking and cocatalyst application via dip coating. 

The degradation of the LaTiO₂N based photoanodes was investigated as a function of the illumination conditions and the electrolyte temperature using chronoamperometry in combination with linear scan voltammetry. IPCMS was used to detect potential dissolution of cations into the electrolyte. The photoanodes were investigated postmortem with respect to compositional, morphological and optical changes using STEM-EDX, SEM and UV-Vis-Spectroscopy.