skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Role of Short-Range Chemical Ordering in (GaN) 1–x (ZnO) x for Photodriven Oxygen Evolution

Abstract

(GaN)1–x(ZnO)x (GZNO) is capable of visible-light driven water splitting, but its bandgap at x ≤ 0.15 (>2.7 eV) results in poor visible-light absorption. Unfortunately, methods to narrow its bandgap by incorporating higher ZnO concentrations are accompanied by extensive Urbach tailing near the absorption-edge, which is indicative of structural disorder or chemical inhomogeneities. We evaluated whether this disorder is intrinsic to the bond-length distribution in GZNO or is a result of defects introduced from the loss of Zn during nitridation. Here, the synthesis of GZNO derived from layered double hydroxide (LDH) precursors is described which minimizes Zn loss and chemical inhomogeneities and enhances visible-light absorption. The average and local atomic structures of LDH-derived GZNO were investigated using X-ray and neutron scattering and are correlated with their oxygen evolution rates. An isotope-contrasted neutron-scattering experiment was conducted in conjunction with reverse Monte Carlo (RMC) simulations. We showed that a bond-valence bias in the RMC refinements reproduces the short-range ordering (SRO) observed in structure refinements using isotope-contrasted neutron data. The findings suggest that positional disorder of cation–anion pairs in GZNO partially arises from SRO and influences local bond relaxations. Furthermore, particle-based oxygen evolution reactions (OERs) in AgNO3 solution reveal that the crystallite size ofmore » GZNO correlates more than positional disorder with oxygen evolution rate. These findings illustrate the importance of examining the local structure of multinary photocatalysts to identify dominant factors in particulate-based photodriven oxygen evolution.« less

Authors:
 [1];  [2];  [1];  [3]; ORCiD logo [1]
  1. Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, United States
  2. Chemical and Engineering Materials Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
  3. Department of Geological Sciences, Indiana University, 1001 East 10th Street, Bloomington, Indiana 47405, United States
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
NSFUNIVERSITY
OSTI Identifier:
1376257
Resource Type:
Journal Article
Resource Relation:
Journal Name: Chemistry of Materials; Journal Volume: 29; Journal Issue: 15
Country of Publication:
United States
Language:
ENGLISH
Subject:
36 MATERIALS SCIENCE

Citation Formats

Chen, Dennis P., Neuefeind, Joerg C., Koczkur, Kallum M., Bish, David L., and Skrabalak, Sara E.. Role of Short-Range Chemical Ordering in (GaN) 1–x (ZnO) x for Photodriven Oxygen Evolution. United States: N. p., 2017. Web. doi:10.1021/acs.chemmater.7b02255.
Chen, Dennis P., Neuefeind, Joerg C., Koczkur, Kallum M., Bish, David L., & Skrabalak, Sara E.. Role of Short-Range Chemical Ordering in (GaN) 1–x (ZnO) x for Photodriven Oxygen Evolution. United States. doi:10.1021/acs.chemmater.7b02255.
Chen, Dennis P., Neuefeind, Joerg C., Koczkur, Kallum M., Bish, David L., and Skrabalak, Sara E.. 2017. "Role of Short-Range Chemical Ordering in (GaN) 1–x (ZnO) x for Photodriven Oxygen Evolution". United States. doi:10.1021/acs.chemmater.7b02255.
@article{osti_1376257,
title = {Role of Short-Range Chemical Ordering in (GaN) 1–x (ZnO) x for Photodriven Oxygen Evolution},
author = {Chen, Dennis P. and Neuefeind, Joerg C. and Koczkur, Kallum M. and Bish, David L. and Skrabalak, Sara E.},
abstractNote = {(GaN)1–x(ZnO)x (GZNO) is capable of visible-light driven water splitting, but its bandgap at x ≤ 0.15 (>2.7 eV) results in poor visible-light absorption. Unfortunately, methods to narrow its bandgap by incorporating higher ZnO concentrations are accompanied by extensive Urbach tailing near the absorption-edge, which is indicative of structural disorder or chemical inhomogeneities. We evaluated whether this disorder is intrinsic to the bond-length distribution in GZNO or is a result of defects introduced from the loss of Zn during nitridation. Here, the synthesis of GZNO derived from layered double hydroxide (LDH) precursors is described which minimizes Zn loss and chemical inhomogeneities and enhances visible-light absorption. The average and local atomic structures of LDH-derived GZNO were investigated using X-ray and neutron scattering and are correlated with their oxygen evolution rates. An isotope-contrasted neutron-scattering experiment was conducted in conjunction with reverse Monte Carlo (RMC) simulations. We showed that a bond-valence bias in the RMC refinements reproduces the short-range ordering (SRO) observed in structure refinements using isotope-contrasted neutron data. The findings suggest that positional disorder of cation–anion pairs in GZNO partially arises from SRO and influences local bond relaxations. Furthermore, particle-based oxygen evolution reactions (OERs) in AgNO3 solution reveal that the crystallite size of GZNO correlates more than positional disorder with oxygen evolution rate. These findings illustrate the importance of examining the local structure of multinary photocatalysts to identify dominant factors in particulate-based photodriven oxygen evolution.},
doi = {10.1021/acs.chemmater.7b02255},
journal = {Chemistry of Materials},
number = 15,
volume = 29,
place = {United States},
year = 2017,
month = 7
}
  • The atomic positional correlations in superconducting Tl/sub 2/Ba/sub 2/CaCu/sub 2/O/sub 8/ were studied by pair distribution function analysis of the pulsed-neutron scattering data. The results show for the first time strongly correlated local displacements of both thallium and oxygen atoms in the Tl-O plane from the high-symmetry crystallographic sites. As a consequence of the displacements Tl atoms form chains or pairs accompanied by displacement of nearby oxygen atoms, resulting in locally orthorhombic order. The ordering, however, remains very much short range and does not alter the average symmetry. The implications of these results with regard to the superconductivity of thesemore » oxides are discussed.« less
  • We present an electron diffraction study of three sillenites, Bi{sub 12}SiO{sub 20}, Bi{sub 25}FeO{sub 39}, and Bi{sub 25}InO{sub 39} synthesized using the solid-state method. We explore a hypothesis, inspired by optical studies in the literature, that suggests that trivalent sillenites have additional disorder not present in the tetravalent compounds. Electron diffraction patterns of Bi{sub 25}FeO{sub 39} and Bi{sub 25}InO{sub 39} show streaks that confirm deviations from the ideal sillenite structure. Multi-slice simulations of electron-diffraction patterns are presented for different perturbations to the sillenite structure - partial substitution of the M site by Bi{sup 3+}, random and ordered oxygen-vacancies, and amore » frozen-phonon model. Although comparison of experimental data to simulations cannot be conclusive, we consider the streaks as evidence of short-range ordered oxygen-vacancies.« less
  • CuSb{sub 2}O{sub 6} crystallizes in a monoclinically distorted trirutile structure. Atomic positions were determined by profile refinement of neutron powder diffraction data, space group P2{sub 1}/n, a = 4.6349(1), b = 4.6370(1), c = 9.2931(1), {beta} = 91.124(2). Magnetic susceptibility data exhibit a broad maximum at about 60 K and an abrupt transition at 8.5 K. The high temperature data can be fitted to a Curie-Weiss Law giving {mu}{sub eff} = 1.758 and {theta} = {minus}48 K. Although the crystal structure indicates a nearly square planar Cu{sup 2+} lattice as in other trirutiles, a Cu-O-O-Cu superexchange pathway seems to bemore » dominant, giving rise to short range correlations which are approximately one dimensional. The high-temperature susceptibility is explained well by the 1-d Heisenberg model with J/k = {minus}43.1 K. Analysis by Oguchi's method give a ratio of interchain to intrachain coupling constants of about 2 {times} 10{sup {minus}3}.« less
  • Short-range and long-range-order parameters were measured by Moessbauer spectrometry and x-ray diffractometry during the disorder {r arrow}{ital B}2 order transformation in equiatomic FeCo. The change from a homogeneous mode of ordering at high temperatures to a heterogeneous mode of ordering at low temperatures was confirmed. By comparing parametric plots of the {sup 57}Fe hyperfine magnetic field versus long-range-order parameter for ordering in these two modes, an early independent relaxation of the short-range order was found in the kinetic path for homogeneous ordering. This relaxation was in reasonable agreement with estimates based on statistical kinetic theory.
  • Eu{sup +3} was incorporated into the lattice of a lead-free ferroelectric Na{sub 1/2}Bi{sub 1/2}TiO{sub 3} (NBT) as per the nominal formula Na{sub 0.5}Bi{sub 0.5−x}Eu{sub x}TiO{sub 3}. This system was investigated with regard to the Eu{sup +3} photoluminescence (PL) and structural behaviour as a function of composition and electric field. Electric field was found to irreversibly change the features in the PL spectra and also in the x-ray diffraction patterns below the critical composition x = 0.025. Detailed analysis revealed that below the critical composition, electric field irreversibly suppresses the structural heterogeneity inherent of the host matrix NBT and brings about a longmore » range ferroelectric state with rhombohedral (R3c) distortion. It is shown that the structural disorder on the nano-scale opens a new channel for radiative transition which manifests as a new emission line branching off from the main {sup 5}D{sub 0}→{sup 7}F{sub 0} line along with a concomitant change in the relative intensity of the other crystal field induced Stark lines with different J values. The study suggests that Eu{sup +3} luminescence can be used to probe the relative degree of field induced structural ordering in relaxor ferroelectrics and also in high performance piezoelectric alloys where electric field couples very strongly with the lattice and structural degrees of freedom.« less