Durable and efficient photoelectrochemical water splitting using TiO2 and 3C–SiC single crystals in a tandem structure

Abstract

Hydrogen can be generated by the photolysis of water with semiconductors as photocatalysts. The most important characteristics of water splitting are its durability and efficiency. Furthermore, TiO 2 and 3C–SiC are durable photocatalysts. Because of their different band gaps and conductivity types, a tandem structure combined with these materials functions as an efficient and durable solar water splitting system. It was observed that the photocurrent from the tandem structure was higher at low pH, as noted by the pH dependence of the photocurrent at the TiO 2 photoanode. The photocurrent from the tandem structure had a light intensity dependence similar to the photocurrent from the TiO 2 photoanode. Therefore, the performance of the tandem structure appears to be limited by the photocurrents from the TiO 2 photoanode. We obtained a maximum applied bias photon-to-current conversion efficiency of approximately 0.74% from the tandem structure with no additional bias applied. We also confirmed the presence of a stable photocurrent from the tandem structure for over ~100 days. •The pH dependence and the irradiation light intensity dependence of TiO 2 , 3C–SiC single crystals and the tandem structure combined were characterized. •The lower the pH, the higher the irradiation light intensity, the better the performance of TiO 2 , 3C–SiC single crystals and the tandem structure. •The measured value of the hydrogen generation is 85% of the calculated value which means that hydrogen is almost completely generated in the actual hydrogen and oxygen generation experiment. •The tandem structure shows a 100 days' long-term durability which is pretty longer than most of the photoelectrodes and photocatalysts.