Electrodeposition of Silver Metavanadate (AgVO3) As a Visible Light-Active P-Type Semiconductor

Abstract

The silver-based ternary oxides are promising candidates to use as a visible light active semiconductor because their band gaps are decreased due to the presence of the Ag 4d with O 2p orbitals in the valence band. Silver metavanadate (AgVO3), one of myriad silver-based ternary oxides, is a visible light active semiconductor because of its small band gap (2.5 eV).1 This paper describes the electrodeposition and characterization of electrodeposition of AgVO3. Electrodeposition is a fast and low temperature method which can be used to make thin films of a given semiconductor. In addition, the optical parameters (e.g., photocurrent, flat band potential) of the thin film semiconductors prepared by electrodeposition can be measured easily without any more processing steps. A two-step electrodeposition strategy was demonstrated for ternary oxides2 and was applied in this study, to prepare AgVO3 thin films on FTO substrate. In the first step, a silver thin film was deposited cathodically from silver nitrate solution. In the second step, the silver thin film was stripped anodically in ammonium metavanadate solution to generate Ag+ and subsequent in situ precipitation with VO3 - to yield AgVO3 thin film on the substrate. The electrochemical crystal micro balance (EQCM) analysis confirmed one electron transfer in both steps. The XRD pattern of the as-prepared sample confirmed that the as-prepared thin film was in α-AgVO3 form. Energy-dispersive X-ray analyses of the as-prepared sample gave the composition: Ag0.94±0.02V1.02±0.01O2.90±0.07 for the as-prepared thin film. β-AgVO3 was prepared by thermally annealing the as-prepared sample at 300 oC for 30 min. The energy band gaps of α-AgVO3 and β-AgVO3 thin films were measured by diffuse reflectance spectroscopy (DRS) and found to be 2.46 and 2.12 eV respectively. Atmospheric photoemission spectroscopy (APS) showed the valence band positions of α-AgVO3 and β-AgVO3 to be -5.65 and -5.41 eV respectively. By combining the DRS and APS results, the calculated conduction band edge positions of α-AgVO3 and β-AgVO3 were -3.19 and -3.29 eV respectively. These results will be discussed in the context of the application of these compounds for photoelectrochemical reduction processes such as hydrogen evolution or CO2 reduction. References R Konta, H. Kato, H. Kobayashib, and A.Kudo , Chem. Chem. Phys., 2003, 5, 3061–3065. H. Antonia, N. R. Tacconi, W. Chanmanee, H., N. Myung, and K. Rajeshwar, Electrochem. Solid-State Lett., 2010, 13, D29-D32.