Phase Transformation Synthesis of Strontium Tantalum Oxynitride-Based Heterojunction for Improved Visible Light-Driven Hydrogen Evolution

Abstract

Tantalum oxynitride-based materials, which possess narrow band gaps and sufficient band energy potentials, have been of immense interest for water splitting. However, the efficiency of photocatalytic reactions is still low because of the fast electron-hole recombination. Here, a Sr₂Ta₂O_{7- x}N _x/SrTaO₂N heterostructured photocatalyst with a well-matched band structure was in situ constructed by the nitridation of hydrothermal-prepared Sr₂Ta₂O₇ nanosheets. Compared to Sr₂Ta₂O_{7- x}N _x and pure SrTaO₂N, the Sr₂Ta₂O_{7- x}N _x/SrTaO₂N heterostructured photocatalyst exhibited the highest rate of hydrogen evolution, which is ca. 2.0 and 76.4 times of Sr₂Ta₂O_{7- x}N _x and pure SrTaO₂N, respectively, under the similar reaction condition. The enhanced performance arises from the formation of suitable band-matched heterojunction-accelerated charge separation. This work provides a promising strategy for the construction of tantalum oxynitride-based heterojunction photocatalysts.