Role of Short-Range Chemical Ordering in (GaN) _1–x (ZnO) _x for Photodriven Oxygen Evolution

Journal Article · Fri Jul 21 04:00:00 EDT 2017 · Chemistry of Materials

DOI:https://doi.org/10.1021/acs.chemmater.7b02255· OSTI ID:1376257

Chen, Dennis P. ^[1]; Neuefeind, Joerg C. ^[2]; Koczkur, Kallum M. ^[1]; Bish, David L. ^[3]; Skrabalak, Sara E. ^[1]

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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

(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.

• Research Organization: Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
• Sponsoring Organization: NSFUNIVERSITY
• OSTI ID: 1376257
• Journal Information: Chemistry of Materials, Journal Name: Chemistry of Materials Journal Issue: 15 Vol. 29; ISSN 0897-4756
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: ENGLISH

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36 MATERIALS SCIENCE