Durability of SrTiO3-TiO2 eutectic composite as a photoanode for photoelectrochemical water splitting.

ABSTRACT

The idea of employing sunlight - a virtually inexhaustible source of energy - to catalyze various chemical reactions or generate electrical current is intensively studied nowadays. Here, we describe a method for testing photoelectrochemical (PEC) stability developed using the example of photoanodes from an SrTiO3-TiO2 eutectic composite. Eutectic composite stability measurements were carried out in long-term cycles 0.5, 1, 2, 5, 10, 20 and 50 h of constant electrode operation (total of 88.5 h). After each cycle, cyclic voltammetry, electrochemical impedance spectroscopy, reflectance, roughness, SEM/EDS microstructure analysis and the content of Sr and Ti ions in the applied electrolyte solution were examined. The initial value of the photocurrent density was 1.95 mA cm-2 at a potential of 1.5 V vs. Ag/AgCl in a pH 2 electrolyte environment and under 6 suns of illumination it increased almost four times, reaching 7.22 mA cm-2 after a total of 88.5 h of PEC stability cycles. Due to the better catalytic properties of TiO2, this phase degrades faster, causing an increase in the roughness of the electrode surface. At the same time, reflectance of the photoanode active layer dropped from around 35% to 15%. The investigated method of PEC material testing can be applied in areas beyond photoelectrochemical water splitting, such as chemistry, photovoltaics, sensing and others.