Spin conversion of positronium in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mtext>NiO</mml:mtext><mml:mo>/</mml:mo><mml:msub><mml:mrow><mml:mtext>Al</mml:mtext></mml:mrow><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mtext>O</mml:mtext><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math>catalysts observed by coincidence Doppler broadening technique

Zhang, Hongjun; Chen, Z. Q.; Wang, S. J.; Kawasuso, A.; Morishita, Norio

doi:10.1103/physrevb.82.035439

Cited by 28 publications

(10 citation statements)

References 28 publications

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“…As seen in Figure 2I, the low momentum region (E < 511.68 eV) and high momentum zone (513.86 eV < E < 516.73 eV) are generally assigned to large nanovoids and small defects in the materials, respectively. [13] The electron momentum ratio curve of N-SnO 2 /SnO 2 exhibits a lower value in the low momentum and higher value in the high momentum region, indicating the elevated distribution of small vacancies in the N-SnO 2 , according well with the PAL results. Hence, the consideration of PAL and CDB reinforce that N-permeating behavior could tailor the mono-oxygen dislodgement and concurrently increase the small-vacancies concentrations over the whole available surface.…”

Section: Resultssupporting

confidence: 73%

Tailoring Unsymmetrical‐Coordinated Atomic Site in Oxide‐Supported Pt Catalysts for Enhanced Surface Activity and Stability

Xue

Yan

Wang

et al. 2021

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The catalytic properties of supported metal heterostructures critically depend on the design of metal sites. Although it is well-known that the supports can influence the catalytic activities of metals, precisely regulating the metal-support interactions to achieve highly active and durable catalysts still remain challenging. Here, the authors develop a support effect in the oxide-supported metal monomers (involving Pt, Cu, and Ni) catalysts by means of engineering nitrogen-assisted nanopocket sites. It is found that the nitrogen-permeating process can induce the reconstitution of vacancy interface, resulting in an unsymmetrical atomic arrangement around the vacancy center. The resultant vacancy framework is more beneficial to stabilize Pt monomers and prevent diffusion, which can be further verified by the density functional theory calculations. The final Pt-N/SnO 2 catalysts exhibit superior activity and stability for HCHO response (26.5 to 15 ppm). This higher activity allows the reaction to proceed at a lower operating temperature (100 °C). Incorporated with wireless intelligent-sensing system, the Pt-N/SnO 2 catalysts can further achieve continuous monitoring of HCHO levels and cloudbased terminal data storage.

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Section: Resultssupporting

confidence: 73%

Tailoring Unsymmetrical‐Coordinated Atomic Site in Oxide‐Supported Pt Catalysts for Enhanced Surface Activity and Stability

Xue

Yan

Wang

et al. 2021

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“…The two Ge detectors were set to record the two annihilation γ rays of positrons, and these two signals were then sent to a FAST Comtec multiparameter system. Details of the CDB setup can be found elsewhere [14] . The S parameter and W parameter were usually used to characterize the one-dimensional CDB spectrum, which were defined as the ratio of low-momentum(|P L | ∧ 0.68 keV) region and high-momentum (2.86 keV ∧ |P L | ∧ 5.73 keV) region to the total annihilation peak, respectively.…”

Section: Methodsmentioning

confidence: 99%

Chemical quenching and inhibition of positronium in Cr2O3/Al2O3 catalysts

Huang

Dai

Zhang

et al. 2011

Wuhan Univ. J. Nat. Sci.

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The pore structure of Cr 2 O 3 /Al 2 O 3 catalysts and the surface chemical properties of these pores were characterized by positron lifetime and coincidence Doppler broadening (CDB) measurements. Four lifetime components could be resolved from the positron lifetime spectrum, with two long lifetime components and two short lifetime components. The two long lifetimes τ 4 and τ 3 are attributed to ortho-positronium (o-Ps) annihilation in large pores and microvoids, respectively. With increasing Cr 2 O 3 content, both τ 4 and its intensity I 4 show sharp decrease, while τ 3 and its intensity I 3 keep nearly unchanged. The Doppler broadening S parameters also show sharp decrease with increasing Cr 2 O 3 content. Detailed analysis of the CDB spectrum reveals that the parapositronium (p-Ps) intensity also decreases with increasing Cr 2 O 3 content. This indicates that the change of o-Ps lifetime τ 4 is due to

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“…The XRD results for NiMo and Pt catalysts are shown in Figure 2A,B, respectively. In both plots, the diffraction peaks occurred at 2θ of 32.8 • , 37.1 • , 39.5 • , 45.6 • , 60.7 • , and 67 • and can be indexed with the γ-Al 2 O 3 phase having different planes such as ( 220), ( 311), ( 222), ( 400), (511), and (440) [32,33]. All XRD patterns of the different catalysts do not present notable sharp characteristic peaks for the Ni, Mo and Pt oxides or metal phases, which suggests either highly dispersed Ni, Mo or Pt dispersed on the supports or that the metal loadings were low.…”

Section: X-ray Diffraction (Xrd)mentioning

confidence: 99%

Hydrocracking of Octacosane and Cobalt Fischer–Tropsch Wax over Nonsulfided NiMo and Pt-Based Catalysts

Kang

Jacobs

et al. 2021

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The effect of activation environment (N2, H2 and H2S/H2) on the hydrocracking performance of a NiMo/Al catalyst was studied at 380 °C and 3.5 MPa using octacosane (C28). The catalyst physical structure and acidity were characterized by BET, XRD, SEM-EDX and FTIR techniques. The N2 activation generated more active nonsulfided NiMo/Al catalyst relative to the H2 or H2S activation (XC28, 70–80% versus 6–10%). For a comparison, a NiMo/Si-Al catalyst was also tested after normal H2 activation and showed higher activity at the same process conditions (XC28, 81–99%). The high activity of the NiMo/Al (N2 activation) and NiMo/Si-Al catalysts was mainly ascribed to a higher number of Brønsted acid sites (BAS) on the catalysts. The hydrocracking of cobalt wax using Pt/Si-Al and Pt/Al catalysts confirmed the superior activity of the Si-Al support. A double-peak product distribution occurred at C4–C6 and C10–C16 on all catalysts, which illustrates secondary hydrocracking and faster hydrocracking at the middle of the chain. The nonsulfided NiMo/Al and Pt/Al catalysts, and NiMo/Si-Al catalyst produced predominantly diesel (sel. 50–70%) and gasoline range (sel. > 50%) hydrocarbons, respectively, accompanied by some CH4 and light hydrocarbons C2–C4. On the other hand, the hydrocarbon distribution of the Pt/Si-Al varied with conditions (i.e., diesel sel. 87–90% below 290 °C or gasoline sel. 60–70% above 290 °C accompanied by little CH4) The dependence of the isomer/paraffin ratio on chain length was studied as well. The peak iso/paraffin value was observed at C10–C13 for the SiAl catalyst.

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Spin conversion of positronium inNiO/Al2O3catalysts observed by coincidence Doppler broadening technique

Cited by 28 publications

References 28 publications

Tailoring Unsymmetrical‐Coordinated Atomic Site in Oxide‐Supported Pt Catalysts for Enhanced Surface Activity and Stability

Tailoring Unsymmetrical‐Coordinated Atomic Site in Oxide‐Supported Pt Catalysts for Enhanced Surface Activity and Stability

Chemical quenching and inhibition of positronium in Cr2O3/Al2O3 catalysts

Hydrocracking of Octacosane and Cobalt Fischer–Tropsch Wax over Nonsulfided NiMo and Pt-Based Catalysts

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