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Sn/Be Sequentially co-doped Hematite Photoanodes for Enhanced Photoelectrochemical Water Oxidation: Effect of Be(2+) as co-dopant.


ABSTRACT: For ex-situ co-doping methods, sintering at high temperatures enables rapid diffusion of Sn(4+) and Be(2+) dopants into hematite (?-Fe2O3) lattices, without altering the nanorod morphology or damaging their crystallinity. Sn/Be co-doping results in a remarkable enhancement in photocurrent (1.7?mA/cm(2)) compared to pristine ?-Fe2O3 (0.7?mA/cm(2)), and Sn(4+) mono-doped ?-Fe2O3 photoanodes (1.0?mA/cm(2)). From first-principles calculations, we found that Sn(4+) doping induced a shallow donor level below the conduction band minimum, which does not contribute to increase electrical conductivity and photocurrent because of its localized nature. Additionally, Sn(4+)-doping induce local micro-strain and a decreased Fe-O bond ordering. When Be(2+) was co-doped with Sn(4+)-doped ?-Fe2O3 photoanodes, the conduction band recovered its original state, without localized impurities peaks, also a reduction in micro-strain and increased Fe-O bond ordering is observed. Also the sequence in which the ex-situ co-doping is carried out is very crucial, as Be/Sn co-doping sequence induces many under-coordinated O atoms resulting in a higher micro-strain and lower charge separation efficiency resulting undesired electron recombination. Here, we perform a detailed systematic characterization using XRD, FESEM, XPS and comprehensive electrochemical and photoelectrochemical studies, along with sophisticated synchrotron diffraction studies and extended X-ray absorption fine structure.

SUBMITTER: Annamalai A 

PROVIDER: S-EPMC4804299 | BioStudies | 2016-01-01

REPOSITORIES: biostudies

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