P-024

Kamila Turuta

kamila.turuta@ftmc.lt

Irena Savickaja, Jelena Kovger-Jaroševič, Milda Petrulevičienė, Jurga Juodkazytė

Center for Physical Sciences and Technology (FTMC), Lithuania

The Effect of Electrolyte Composition on Photoelectrochemical Water Splitting

Photoelectrochemical (PEC) water splitting is considered a promising method for sustainable hydrogen production using solar energy. Compared to photocatalytic processes, PEC systems offer advantages such as better control, higher efficiency and easier product separation. The ability to adjust the applied voltage enhances charge carrier separation and reduces recombination losses, while the spatial separation of oxidation and reduction reactions at different electrodes, simplifies product isolation and improves purity. Electrolyte is a critical component in PEC systems. However, the effect of electrolyte composition on photoinduced charge transfer processes is often overlooked. The role of dissolved substances is commonly confined to that of maintaining electrical conductivity. In fact, dissolved species compete with water molecules in the processes of light-induced electron/hole scavenging, and this competition leads to the formation of products other than H2 and O2. In our studies we have demonstrated efficient visible light induced formation of strong oxidants (hypochlorite, chlorite, persulfate) in PEC systems with WO3 and BiVO4 photoanodes in simple chloride and sulfate electrolytes. Various photoelectrode optimization strategies, including metal doping, morphological engineering, and heterostructuring have been explored in order to enhance the efficiency of light-to-chemical energy conversion and fine-tune the selectivity of light-driven reactions. It was found that in the case of  WO3 the Faradaic efficiency (FE) of active chlorine species formation varied between 50 % and 100 %, and for persulphate it ranged between 30 % and 90 %. With BiVO4 photoanodes FEs were in the range of 35-80 % and 70-85 % in chloride and sulphate media, respectively. Applicability of studied PEC systems for degradation of organic pollutants and disinfection with simultaneous production of H2 has been demonstrated. Analysis of the mechanistic aspects of light induced reactions revealed the involvement of highly reactive radical species and the critical influence of electrolyte pH.