title: 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 (α-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 α-Fe2O3 (0.7 mA/cm(2)), and Sn(4+) mono-doped α-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 α-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.
authors.affiliation: Division of Biotechnology, Advanced Institute of Environmental and Bioscience, College of Environmental and Bioresource Sciences, Chonbuk National University, Iksan 570-752, Republic of Korea.|Department of Physics, Umeå University, Umeå, SE-901 87, Sweden.
authors.forename: Alagappan
authors.initials: A
authors.lastname: Annamalai
authors.affiliation: Pohang Accelerator Laboratory, POSTECH, Pohang 790-784, Republic of Korea.
authors.forename: Hyun Hwi
authors.initials: HH
authors.lastname: Lee
authors.affiliation: Pohang Accelerator Laboratory, POSTECH, Pohang 790-784, Republic of Korea.
authors.forename: Sun Hee
authors.initials: SH
authors.lastname: Choi
authors.affiliation: Pohang Accelerator Laboratory, POSTECH, Pohang 790-784, Republic of Korea.
authors.forename: Su Yong
authors.initials: SY
authors.lastname: Lee
authors.affiliation: Department of Physics, Umeå University, Umeå, SE-901 87, Sweden.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Gracia-Espino
authors.affiliation: Division of Biotechnology, Advanced Institute of Environmental and Bioscience, College of Environmental and Bioresource Sciences, Chonbuk National University, Iksan 570-752, Republic of Korea.
authors.forename: Arunprabaharan
authors.initials: A
authors.lastname: Subramanian
authors.affiliation: Center for Chemical Safety and Security, Korea Research Institute of Chemical Technology (KRICT) Daejeon, 305-343, Republic of Korea.
authors.forename: Jaedeuk
authors.initials: J
authors.lastname: Park
authors.affiliation: Center for Chemical Safety and Security, Korea Research Institute of Chemical Technology (KRICT) Daejeon, 305-343, Republic of Korea.
authors.forename: Ki-Jeong
authors.initials: KJ
authors.lastname: Kong
authors.affiliation: Division of Biotechnology, Advanced Institute of Environmental and Bioscience, College of Environmental and Bioresource Sciences, Chonbuk National University, Iksan 570-752, Republic of Korea.
authors.forename: Jum Suk
authors.initials: JS
authors.lastname: Jang