Visible-light activity of N-LiInO2: Band structure modifications through interstitial nitrogen doping

Abstract

Element doping is a promising strategy to improve the photo-response and photocatalytic activity of semiconductor photocatalyst with a wide band gap. To reduce the band gap of LiInO2 that is considered as a novel photocatalyst, nitrogen-doped LiInO2 (N-LiInO2) is successfully fabricated by treating LiInO2 and urea at 200°C. It is found that interstitial instead of substitutional configurations are formed in the crystal structure of N-LiInO2 due to the low-treating temperature and rich-oxygen conditions. The interstitial N-doping forms a doping state with 0.6eV above the valence band maximum and a defect state with 0.1eV below the conduction band minimum, reducing the band gap of LiInO2 from 3.5 to 2.8eV. N-LiInO2 exhibits higher photocatalytic activity towards methylene blue (MB) degradation under 380nm light irradiation, which is 1.4 times that of pure LiInO2. The enhanced photocatalytic activity of N-LiInO2 is attributed to the extended light absorption and the improved charge carrier separation, which result in more reactive species participating in the photcatalytic process. This work provides a further understanding on tuning the band structure of semiconductor photocatalyst by N-doping strategies.