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10. Dye-Mediated Growth of 2D Coppercarbodiimide (CuNCN) Nanostructures and their Metamorphosis into a 3D Cu@C xNy Hybrid.

Author

Ressnig, Debora, Clavel, Guylhaine, Scharnagl, Nico, and Antonietti, Markus

Subjects
*COPPER, *CARBODIIMIDES, *NANOSTRUCTURES, *ORGANIC dyes, *METAMORPHOSIS, *MORPHOLOGY, *NANOSTRUCTURED materials
Abstract

The concept to translate morphological and structural features from a crystalline precursor into a hybrid material is presented. Cationic organic dyes mediate the formation of loosely interconnected, highly anisotropic CuNCN crystals. Their thermal decomposition affords a macroporous CxNy polymer decorated with copper nanoislands. The hybrid is found to be highly active as hydrogenation catalysts. [ABSTRACT FROM AUTHOR]

Published
2014
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12. Morphology control of BiVO4 photocatalysts: pH optimization vs. self-organization

Author

Ressnig, Debora, Kontic, Roman, and Patzke, Greta R.

Subjects
*VANADATES, *BISMUTH compounds, *PHOTOCATALYSIS, *HYDROGEN-ion concentration, *MATHEMATICAL optimization, *SURFACE area, *DIMETHYL methylphosphonate
Abstract

Abstract: The influence of the pH value on the hydrothermal formation of BiVO4 photocatalysts from Bi(NO3)3·5H2O and NH4VO3 was investigated. Optimal nanostructuring and surface area values are obtained for BiVO4 nanoplatelets synthesized at pH 4. Screening of phosphorus-containing templates brought forward dimethyl methylphosphonate (DMMP) as the most efficient surfactant to fine-tune the synthesis of hierarchically structured BiVO4 architectures. Their growth processes were subsequently monitored with ex situ studies. The formation of different BiVO4 microsphere types proceeds via a gradual transformation of zircon-type BiVO4 precursors into self-organized hollow shells of monoclinic BiVO4 crystallites. A slight variation of the synthetic conditions induces the formation of dumbbell-shaped BiVO4 particles consisting of small BiVO4 building blocks arranged around a cylindrical core unit via a different pathway. Catalytic test series for organic dye degradation and water oxidation show that template-free BiVO4 nanoplatelets obtained at pH 4 exhibit optimal activity in both processes. Their MB degradation performance is further improved in alkaline media and the influence of synthetic parameter tuning on BiVO4 catalyst growth and reactivity is discussed. [Copyright &y& Elsevier]

Published
2012
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13. Photochemical and electrocatalytic water oxidation activity of cobalt carbodiimide

Author

Greta R. Patzke, Menny Shalom, Debora Ressnig, Fabio Evangelisti, Jörg Patscheider, Markus Antonietti, René Moré, University of Zurich, and Ressnig, Debora

Subjects
10120 Department of Chemistry, Materials science, Inorganic chemistry, Oxide, chemistry.chemical_element, 2105 Renewable Energy, Sustainability and the Environment, 1600 General Chemistry, 02 engineering and technology, 010402 general chemistry, Photochemistry, 7. Clean energy, 01 natural sciences, law.invention, Catalysis, chemistry.chemical_compound, law, 540 Chemistry, General Materials Science, Cobalt oxide, Carbodiimide, Electrolysis, Renewable Energy, Sustainability and the Environment, Oxygen evolution, General Chemistry, 021001 nanoscience & nanotechnology, 2500 General Materials Science, 0104 chemical sciences, chemistry, Catalytic oxidation, 0210 nano-technology, Cobalt
Abstract

Cobalt carbodiimide is introduced as a heterogeneous non-oxidic water oxidation catalyst prototype with dual photochemical and electrocatalytic activity in neutral and basic media. CoNCN exhibits higher initial turnover frequencies of (TOF/SBET: 2.1 × 10−1) for visible-light-driven oxygen evolution than cobalt oxide catalysts (TOF/SBET: 3.5 × 10−3) and a 18% higher oxygen yield (Ru-dye sensitized standard setup). Furthermore, CoNCN maintains stable current densities in electrolysis over 20 h, and structural tuning through cationic substitution revealed that mixed (Co, Ni)NCN catalysts with low Ni contents display higher current densities than pristine CoNCN. A wide range of bulk (XAFS/EXAFS, XRD, FTIR) and surface (XPS, EELS, HRTEM) analytical methods together with catalytic parameter variations and reference experiments were performed to confirm the stability of CoNCN under standard operational conditions. The carbodiimide matrix thus offers a straightforward structural alternative to oxide systems and a clear-cut starting point for optimization strategies and for mechanistic studies on the possible role of active carbon or nitrogen sites. This paves the way to metal carbodiimides as a novel catalyst design platform for heterogeneous energy conversion systems.

Published
2015

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