Activity of Cu-Fe Mixed Oxide Catalysts in the Selective CO Oxidation (CO-PROX)

Veselovs’kyi, V. L.; Ischenko, Elena V.; Gayday, Snezhana V.; Byeda, Alexander; Tkach, Vasiliy V.; Lisnyak, Vladyslav V.

doi:10.2174/2211544711302010003

Cited by 5 publications

(4 citation statements)

References 18 publications

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“…Cuprous delafossite oxides have gained significant attention since the first demonstration of CuAlO 2 as a potential p-type transparent conducting oxide . While the conductivities and mobilities can actually be quite limited, the potential applications range from use as thermoelectric materials, electro/photocatalysts, − transparent p–n junctions, − and photovoltaic cathodes. − Their properties stem from a unique structure with alternating layers of linearly coordinated O–Cu I –O and M III O 6 edge-shared octahedra. The layers can adopt ABCABC or ABABAB stacking, to give the compounds either a rhombohedra (3R) or hexagonal (2H) symmetry .…”

Section: Introductionmentioning

confidence: 99%

2H-CuScO₂ Prepared by Low-Temperature Hydrothermal Methods and Post-Annealing Effects on Optical and Photoelectrochemical Properties

Draskovic

2015

Inorg. Chem.

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The delafossite structured CuScO2 is a p-type, wide band gap oxide that has been shown to support significant oxygen intercalation, leading to darkened color and increased conductivity. Control of this oxidation proves difficult by the conventional high-temperature solid-state syntheses. In addition, a pure hexagonal (2H) or rhombohedral (3R) polytype of CuScO2 requires careful control of synthetic parameters or intentional doping. Lower-temperature hydrothermal syntheses have thus far led to only a mixed 2H/3R product. Herein, control of hydrothermal conditions with the consideration of copper and scandium hydrolysis led to the synthesis of light beige, hierarchically structured particles of 2H-CuScO2. Absorption of the particles in the visible range was found to increase upon annealing of the sample in air, most likely due to the Cu(II) formation from oxygen interstitials. X-ray photoelectron spectroscopy confirmed purely Cu(I) in the as-synthesized 2H-CuScO2 and increased Cu(II) amounts upon annealing. Oxidation of the samples also led to shifts of the Fermi level toward the valence band as observed by increases in the measured flat band potentials versus normal hydrogen electrode, confirming increased hole carrier densities.

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Section: Introductionmentioning

confidence: 99%

2H-CuScO₂ Prepared by Low-Temperature Hydrothermal Methods and Post-Annealing Effects on Optical and Photoelectrochemical Properties

Draskovic

2015

Inorg. Chem.

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“…To date, numerous AMO 2 compounds (where A = Ag, Cu; and M = B, Al, Ga, In, Fe, Cr, Sc, Y, etc.) have been reported with high p -type conductivity (10 –2 –10 2 S cm –1 ) and high optical transparency (50%–85%), dependent on their chemical compositions and film deposition methods. − These delafossite oxides could play important roles in diverse photoelectronic and photoelectrochemical applications, such as field electron emitters, light-emitting diodes, solar cells, functional windows, photocatalysts, and so on. − …”

Section: Introductionmentioning

confidence: 99%

Synthesis and Characterization of CuAlO₂ and AgAlO₂ Delafossite Oxides through Low-Temperature Hydrothermal Methods

et al. 2014

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In this work, we present one-step low temperature hydrothermal synthesis of submicrometer particulate CuAlO2 and AgAlO2 delafossite oxides, which are two important p-type transparent conducting oxides. The synthesis parameters that affect the crystal formation processes and the product morphologies, including the selection of starting materials and their molar ratios, the pH value of precursors, the hydrothermal temperature, pressure, and reaction time, have been studied. CuAlO2 crystals have been synthesized from the starting materials of CuCl and NaAlO2 at 320-400 °C, and from Cu2O and Al2O3 at 340-400 °C, respectively. AgAlO2 crystals have been successfully synthesized at the low temperature of 190 °C, using AgNO3 and Al(NO3)3 as the starting materials and NaOH as the mineralizer. The detailed elemental compositions, thermal stability, optical properties, and synthesis mechanisms of CuAlO2 and AgAlO2 also have been studied. Noteworthy is the fact that both CuAlO2 and AgAlO2 can be stabilized up to 800 °C, and their optical transparency can reach 60%-85% in the visible range. Besides, it is believed the crystal formation mechanisms uncovered in the synthesis of CuAlO2 and AgAlO2 will prove insightful guildlines for the preparation of other delafossite oxides.

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“…With regard to delafossites, the level of understanding of synthesis and property aspects could be significantly enhanced. These mixed oxides, particularly cuprous delafossites (having the general formula A + B 3+ O 2 ), have attracted substantial interest due to their exceptional (thermo)electric, magnetic, and optical properties, finding diverse technological applications, namely, in the fields of optoelectronic devices, field electron emitters, light emitting diodes, laser diodes, solar cells, functional windows, and thermoelectric materials. − In addition, cuprous delafossites have also been reported as catalysts for the conversion of synthesis gas to linear alcohols and aldehydes, , water splitting, the decomposition of toxic gases originating from internal combustion engines, the oxidation of unburnt combustion gases and CO, selective CO oxidation, , HCl oxidation, and as photocatalysts for the reduction of CO 2 …”

Section: Introductionmentioning

confidence: 99%

Solid-State Chemistry of Cuprous Delafossites: Synthesis and Stability Aspects

et al. 2013

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Cuprous delafossites exhibit exceptional electrical, magnetic, optical, and catalytic properties. Through the application of a battery of in situ and ex situ characterization methods complemented by density functional theory (DFT) calculations, we gathered an in-depth understanding of the synthesis of CuMO 2 (M = Al, Cr, Fe, Ga, Mn) by the solid-state reaction of Cu 2 O and M 2 O 3 and of their stability against oxidative disproportionation to CuM 2 O 4 and CuO. TGA-DTA and XRD studies of the synthesis revealed that the nature of the M 3+ cation strongly impacts (i) the formation temperature of the delafossite phase, which occurred at a much lower temperature for CuCrO 2 than for the other metals (1073 versus 1273− 1423 K), (ii) the mechanism of formation of the CuMO 2 in different atmospheres, which was found to comprise up to four steps in air and a single step in N 2 , and (iii) the kinetics of the process, which could be significantly accelerated upon mechanochemical activation of the precursors by ball milling. The identification of unstable intermediate phases and, thus, a proper description of the synthesis mechanism was only possible by the application of in situ XRD. Electron microscopy, nitrogen sorption, and mercury porosimetry analyses of the precursor oxide mixtures at different stages of the synthesis in air revealed that particle agglomeration took place prior to the solid-state reactions forming the intermediate spinel phase and the delafossite, respectively, and that these led to a substantial drop in porosity and specific surface area. On the basis of XRD and He pycnometry, the resulting CuMO 2 samples exhibit pure delafossite phase with rhombohedral structure (R3̅ m), except for CuMnO 2 which features a monoclinic structure (C2/m). Upon heating in air, CuCrO 2 retained its structure up to 1373 K, while all other delafossites decomposed, CuAlO 2 at 1073 K, CuGaO 2 at 873 K, CuFeO 2 at 773 K, and CuMnO 2 at 673 K. The DFT-calculated surface phase diagram of CuCrO 2 and CuAlO 2 indicated that, at elevated oxygen pressures, the terminations with 1/2 and 0 ML of Cu are the most stable for the (0001) facet. The formation enthalpy for interstitial oxygen species in the bulk is endothermic for both delafossites, while that for oxygen insertion in subsurface layers of these terminations is still endothermic for CuCrO 2 but slightly exothermic for CuAlO 2 . These results provide an improved understanding of the chemistry of these mixed oxides, enabling their optimization for specific applications.

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Activity of Cu-Fe Mixed Oxide Catalysts in the Selective CO Oxidation (CO-PROX)

Cited by 5 publications

References 18 publications

2H-CuScO₂ Prepared by Low-Temperature Hydrothermal Methods and Post-Annealing Effects on Optical and Photoelectrochemical Properties

2H-CuScO₂ Prepared by Low-Temperature Hydrothermal Methods and Post-Annealing Effects on Optical and Photoelectrochemical Properties

Synthesis and Characterization of CuAlO₂ and AgAlO₂ Delafossite Oxides through Low-Temperature Hydrothermal Methods

Solid-State Chemistry of Cuprous Delafossites: Synthesis and Stability Aspects

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Activity of Cu-Fe Mixed Oxide Catalysts in the Selective CO Oxidation (CO-PROX)

Cited by 5 publications

References 18 publications

2H-CuScO2 Prepared by Low-Temperature Hydrothermal Methods and Post-Annealing Effects on Optical and Photoelectrochemical Properties

2H-CuScO2 Prepared by Low-Temperature Hydrothermal Methods and Post-Annealing Effects on Optical and Photoelectrochemical Properties

Synthesis and Characterization of CuAlO2 and AgAlO2 Delafossite Oxides through Low-Temperature Hydrothermal Methods

Solid-State Chemistry of Cuprous Delafossites: Synthesis and Stability Aspects

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2H-CuScO₂ Prepared by Low-Temperature Hydrothermal Methods and Post-Annealing Effects on Optical and Photoelectrochemical Properties

2H-CuScO₂ Prepared by Low-Temperature Hydrothermal Methods and Post-Annealing Effects on Optical and Photoelectrochemical Properties

Synthesis and Characterization of CuAlO₂ and AgAlO₂ Delafossite Oxides through Low-Temperature Hydrothermal Methods