Formation and characterization of gray Ta2O5 and its enhanced photocatalytic hydrogen generation activity

• Published in: International journal of hydrogen energy Vol. 45; no. 33; pp. 16560 - 16568
• Main Authors: Liu, Wei-Szu, Liao, Ming-Wei, Huang, Sheng-Hsin, Reyes, Yves Ira A., Tiffany Chen, Hsin-Yi, Perng, Tsong-Pyng
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 24.06.2020
• Subjects: DFT calculations; Gray Ta2O5; IPCE; Oxygen vacancy; Photocatalytic hydrogen generation; Surface disorder; Photocatalytic hydrogen generation; IPCE; Gray Ta2O5; Surface disorder; DFT calculations; Oxygen vacancy
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2020.04.154

White and gray Ta2O5 powders were fabricated by sol-gel and then annealed at 850 °C in air and vacuum, respectively. Analyses by Raman spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, electron paramagnetic resonance spectroscopy, UV-visible reflectance spectroscopy, photoluminescence spectroscopy, and density functional theory calculations indicated that oxygen vacancies are formed on the surface of gray Ta2O5, resulting in a disordered shell and more absorption of visible light. Its surface concentration ratio of oxygen to tantalum was determined to be 2.31. It generated 48% higher photocatalytic hydrogen than that of the white one, and cycling test indicated that it remained stable during 12 h irradiation. It also exhibited higher incident photon-to-current conversion efficiency than that of white Ta2O5 in the wavelength range of 300–600 nm. EPR spectra and hydrogen generation rates of white and gray Ta2O5. [Display omitted] •Gray Ta2O5 was synthesized by sol-gel and then annealed in vacuum.•Oxygen vacancies and a disordered shell are formed on the surface of gray Ta2O5.•Gray Ta2O5 are characterized by Raman, XPS, PL, EPR, UV-vis spectroscopy, and HRTEM.•DFT calculations indicate that surface oxygen vacancies at cap sites are the most stable.•Gray Ta2O5 generates 48% higher photocatalytic hydrogen than that of the white Ta2O5.