Transformation from a high-temperature superconductor yttrium-barium-copper oxide to a photocatalytic material yttrium-barium oxide, a DFT-based investigation

Novel semiconductor photocatalysts are currently a hot research topic. We are inspired by the phenomenon that high-temperature superconductors can achieve superconductivity only under certain conditions (e.g., liquid nitrogen temperature). Here, based on the analysis of the energy band structure of the high-temperature superconductor YBCO (YBa2Cu3O7-x, YBCO), two new yttrium barium oxide (YBO) semiconductor materials, Y2Ba3O6 (YB3O) and Y2Ba4O7 (YB4O), are reported in this study. According to first-principles calculations, we find that YB4O and YB3O have stable formation energies, as well as forbidden band gaps, which are suitable for the visible light response. In addition, YB4O possesses a larger effective mass difference of carrier and stronger electron delocalization in various directions than that of YB3O, while YB3O possesses a larger light absorption threshold than that of YB4O. These two innovative yttrium-barium oxide materials show strong semiconducting properties and have great potential as photocatalysts.