Reduction of Metal Oxides by Hydrogen

Taylor, Guy B.; Starkweather, Howard W.

doi:10.1021/ja01369a019

Cited by 27 publications

(14 citation statements)

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“…This pioneering research of early investigators established that NiO conversion versus time curves are sigmoidal in shape, suggesting an induction period followed by autocatalytic reduction [6,7]. Koga and Harrison, in reviewing general reactions between solids and H 2 , describe the induction process as generation of nickel atoms on the outer surface of NiO grains, followed by nucleation into nickel clusters [8].…”

Section: Introductionmentioning

confidence: 99%

X-ray diffraction study of the hydrogen reduction of NiO/α-Al2O3 steam reforming catalysts

Richardson

Scates

Twigg

2004

Applied Catalysis A: General

114

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Section: Introductionmentioning

confidence: 99%

X-ray diffraction study of the hydrogen reduction of NiO/α-Al2O3 steam reforming catalysts

Richardson

Scates

Twigg

2004

Applied Catalysis A: General

114

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“…41 The different rates of reduction and particle collapse observed in this study are in-line with previous studies that show an induction period before reduction begins, and then an autocatalytic reaction occurs where the reduction rate increases as the size of the nickel cluster increases. [41][42][43] The induction period has also been postulated to occur due to the slow initial generation of O vacancies in the NiO structure, creating a more reactive surface for hydrogen splitting. 44 This could explain the different reduction speeds as the different NiO particles would have different densities of defects in their structure, leading to a different number of oxygen vacancies.…”

Section: Resultsmentioning

confidence: 99%

In Situ Scanning Transmission Electron Microscopy of Ni Nanoparticle Redispersion via the Reduction of Hollow NiO

et al. 2017

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Oxidation and reduction cycles are used in the regeneration of nanoparticle catalysts that have deactivated due to sintering and poisoning. We examine the case of nickel oxidation and reduction on the regeneration of the smallest end of the particle size distribution via in-situ high angle annular dark field environmental scanning transmission electron microscopy (HAADF-ESTEM). Cycling the Ni/NiO system through successive redox cycles shows that the particles retain the same general size distributions even though Ostwald ripening and particle migration and coalescence is occurring. The regeneration of the smallest nanoparticle sizes which disappear due to sintering processes occurs by the ejection of small (2-3 nm) nickel particles during the reduction of the hollow nickel oxide nanostructures. The nickel nanoparticles above ~3.5 nm in size, form hollow polycrystalline nickel oxide upon oxidation. Upon reduction, the grains making up the shell of the hollow nickel oxide reduce separately at the grains surface and at the grain boundaries between the polycrystalline grains. The contraction in particle size upon reduction destabilizes the hollow nanostructure and causes the particle to rearrange and collapse. As this process occurs, some parts of the particle are ejected from the reducing particle and form small particles of nickel, which regenerate the smallest parts of the size distribution. Once the particle collapses, the nickel rearranges reforming solid nickel nanoparticles enclosed by their low index facets.

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“…The H 2 postreduction treatment has known that it would be an efficient way to generate oxygen vacancies with the mechanism shown below [17,29,34] The H 2 postreduction treatment has known that it would be an efficient way to generate oxygen vacancies with the mechanism shown below [17,29,34] …”

Section: Resultsmentioning

confidence: 99%

“…Interestingly, the relative ratio trend across H 2 reduction temperature was well consistent with the carrier concentration change. The H 2 postreduction treatment has known that it would be an efficient way to generate oxygen vacancies with the mechanism shown below

{normalO}_{normalo}^{x} + {normalH}_{2} (g) \to V_{normalo} + 2 {normale}^{-} + {normalH}_{2} O (g) ↑

…”

Section: Resultsmentioning

confidence: 99%

Optimized Activation of Solution‐Processed Amorphous Oxide Semiconductors for Flexible Transparent Conductive Electrodes

Choi

Park

Baeg

et al. 2017

Adv Elect Materials

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Here, the preparation of transparent amorphous oxide semiconductor (AOS) films with unprecedented conductivity via an optimized activation process under hydrogen atmosphere for applications in solution‐processed large‐area optoelectronics is reported. Owing to their high cost and mechanical vulnerability, conventional vacuum‐processed indium–tin oxide (ITO) electrodes are inappropriate for use in next‐generation flexible and wearable electronic devices and systems. As an alternative to the ITO electrodes, solution‐processed AOS films, such as a‐IZO and a‐ZITO, with an optimized composition and postreduction treatment under hydrogen show the highest electrical conductivity of ≈300 S cm−1 and a high optical transmittance of over 90% at 550 nm. The microstructures and electrical properties of these AOS films are also studied in order to determine the optimized chemical composition and postreduction conditions. It is found that a controlled hydrogen reduction treatment of AOS films is critical for achieving high electrical conductivity by suppressing the surface morphology degradation and grain boundary disconnection. Furthermore, the a‐IZO transparent conductive electrodes are successfully implemented for high efficiency organic photovoltaic cells based on the PTB7/PC71BM active layers. This technique promises the low‐cost fabrication of high mobility and/or conductive AOSs for their applications in large‐area transparent and flexible optoelectronics.

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Reduction of Metal Oxides by Hydrogen

Cited by 27 publications

References 0 publications

X-ray diffraction study of the hydrogen reduction of NiO/α-Al2O3 steam reforming catalysts

X-ray diffraction study of the hydrogen reduction of NiO/α-Al2O3 steam reforming catalysts

In Situ Scanning Transmission Electron Microscopy of Ni Nanoparticle Redispersion via the Reduction of Hollow NiO

Optimized Activation of Solution‐Processed Amorphous Oxide Semiconductors for Flexible Transparent Conductive Electrodes

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