posted on 2020-08-28, 12:34authored byJie Fu, Faze Wang, Yequan Xiao, Yisen Yao, Chao Feng, Le Chang, Chang-Ming Jiang, Viktoria F. Kunzelmann, Zhiming M. Wang, Alexander O. Govorov, Ian D. Sharp, Yanbo Li
Ta3N5 is a promising semiconductor for solar-driven
photocatalytic or photoelectrochemical (PEC) water splitting. However,
the lack of an in-depth understanding of its intrinsic defect properties
limits further improvement of its performance. In this study, comprehensive
spectroscopic characterizations are combined with theoretical calculations
to investigate the defect properties of Ta3N5. The obtained electronic structure of Ta3N5 reveals that oxygen impurities are shallow donors, while nitrogen
vacancies and reduced Ta centers (Ta3+) are deep traps.
The Ta3+ defects are identified to be most detrimental
to the water splitting performance because their energetic position
lies below the water reduction potential. Based on these findings,
a simple H2O2 pretreatment method is employed
to improve the PEC performance of the Ta3N5 photoanode
by reducing the concentration of Ta3+ defects, resulting
in a high solar-to-hydrogen conversion efficiency of 2.25%. The fundamental
knowledge about the defect properties of Ta3N5 could serve as a guideline for developing more efficient photoanodes
and photocatalysts.