Tuning the Nanoarchitectonics of NaNbO3 for Overall Photocatalytic Nitrogen Fixation: Insights into Defect Engineering and Heteroatom Doping

Abstract

Over the past few years, defect engineering has emerged as a powerful tool to enhance the photocatalytic activities of semiconductor materials. This approach has been utilized to provide enhanced number of active sites on the catalyst surface. Vacancy engineering and heteroatom doping are the most common methods used to generate defects in semiconductors. However, these methods have never been compared in terms of their effect on photocatalytic activity of semiconductors. In this work, we have compared the nitrogen fixation activity of oxygen-vacancy-rich NaNbO3 and V-doped NaNbO3 photocatalysts. Both oxygen-vacancy-rich and V-doped NaNbO3 photocatalysts performed better than the pristine counterpart (bare NaNbO3). The overall highest activity was observed for V-doped NaNbO3 (NVNO0.25) having an ammonia generation rate of 36 µmol g-1 h-1 as compared to the best oxygen-vacancy-rich NaNbO3 sample (DNNO2), wherein the ammonia generation rate was 26 µmol g-1 h-1 under visible light irradiation. Furthermore, the light to chemical conversion efficiency and turnover frequency for NVNO0.25 were found to be 0.052% and 0.095 h-1, respectively under visible light irradiation. Besides, the nitrogen fixation activity of the photocatalysts was also explored under direct sunlight irradiation. In addition to ammonia, the formed nitrate and nitrite species were also quantified. Thus, this work provides a one-on-one comparison of the nitrogen fixation activity of two types of NaNbO3 photocatalysts. The insights provided by this work can help researchers to design and develop efficient materials for photocatalytic nitrogen fixation.