Experimental and first-principles studies of BiVO4/BiV1-xMnxO4-y n-n+ homojunction for efficient charge carrier separation in sunlight induced water splitting. (16th August 2018)

• Record Type: Journal Article
• Authors: Srivastav, Anupam; Kumar, Pawan; Verma, Anuradha; Smith, York R.; Satsangi, Vibha Rani; Shrivastav, Rohit; Waghmare, Umesh V.; Dass, Sahab
• Is Part Of: International journal of hydrogen energy. Volume 43:Number 33(2018)
• Page Start: 15815
• Page End: 15822
• Publication Date: 2018-08-16
• Subjects: BiVO4 -- DFT -- Oxygen vacancy -- Photoelectrochemical -- Hydrogen; Hydrogen as fuel -- Periodicals; Hydrogène (Combustible) -- Périodiques; Hydrogen as fuel; Periodicals; 665.81
• DOI: 10.1016/j.ijhydene.2018.06.133
• Languages: English
• ISSNs: 0360-3199

Abstract

Abstract: Though bismuth vanadate (BiVO4 ) is extensively used as a photoactive material, its performance in harnessing solar energy is limited by ineffective separation of photo-excited charge carriers. We demonstrate here a concept of n-n + homojunction of BiVO4 /BiV1-x Mnx O4-y, which improves its charge separation efficiency. Using first-principles theoretical calculations, we determine the effect of Mn substitution on oxygen vacancy formation energies and associated changes in the electronic structure of BiVO4 . Showing that Mn substitution pushes the Fermi level of BiVO4 towards its conduction band, we predict that the associated enhanced bending of bands at the homojunction (BiVO4 /BiV1-x Mnx O4-y ) facilitates efficient separation of charge carriers. With Mott-Schottky experiments, we verify the increased band bending at the n-n + homojunction, and show that the maximum photocurrent density measured in a sample with n-n + homojunction is ten times higher than that obtained of the pristine sample. Secondly, Mn substitution in BiVO4 also reduces the oxygen vacancy formation energy, promoting higher concentration of O-vacancies, further enhancing the photoelectrochemical response. Graphical abstract: Highlights: First-principles study of shift in Fermi level with dopant and oxygen vacancy. Enhancement in efficiency with homojunction formation. Photocurrent density increased ten times in homojunction sample compared to pristine.