The Dependencies of Dissociation Energy of Binary Molecules and Formation Enthalpies of Single-Atom Gases on Initial Spatial-Energy Characteristics of Free Atoms

2016 ◽  
pp. 131-152
Keyword(s):  
Dissociation Energy ◽  
Single Atom ◽  
Energy Characteristics ◽  
Formation Enthalpies ◽  
Free Atoms

scholarly journals Tailoring Water Dissociation Energy by Platinum Single-Atom Catalyst Coupled with Transition Metal/metal Oxide Heterostructure for Accelerating Alkaline Hydrogen Evolution Reaction

2021 ◽  
Author(s):  
Changbao Han ◽  
Kailing Zhou ◽  
Qianqian Zhang ◽  
Jingbing Liu ◽  
Hui Yan ◽  
...  
Keyword(s):  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Dissociation Energy ◽  
Active Sites ◽  
Alkaline Media ◽  
Water Dissociation ◽  
High Mass ◽  
Single Atom ◽  
Adsorption Affinity ◽  
Metal Metal

Abstract High-activity catalysts in alkaline media are compelling for durable hydrogen evolution reaction (HER). Single-atom catalysts (SACs) provide an effective approach to reduce the amount of precious metals meanwhile maintain their catalytic activity. However, the sluggish activity of SACs for water dissociation in alkaline media has extremely hampered advances in highly efficient hydrogen production. Herein, we developed a platinum SAC immobilized NiO/Ni heterostructure (PtSA-NiO/Ni) as an alkaline HER catalyst. It was found that Pt SACs coupled with NiO/Ni heterostructure enable the tunable binding abilities of hydroxyl ions (OH*) and hydrogen (H*), which efficiently tailors the water dissociation energy for accelerating alkaline HER. In particular, the dual active sites consisting of metallic Ni sites and O vacancies modified NiO sites near the interfaces of NiO/Ni in PtSA-NiO/Ni have preferred adsorption affinity for H* and OH* groups, respectively, which efficiently lowers the energy barrier of water dissociation of Volmer step. Moreover, anchoring Pt single atoms at the interfaces of NiO/Ni heterostructure induces more free electrons on Pt sites due to the elevated occupation of the Pt 5d orbital at the Fermi level and reaches a near-zero H binding energy (ΔGH*, 0.07 eV), which further promotes the H* conversion and H2 evolution. Further enhancement of alkaline HER performance was achieved by constructing PtSA-NiO/Ni nanosheets on the Ag nanowires to form a hierarchical three-dimensional (3D) morphology that provides abundant active sites and accessible channels for charge transfer and mass transport. Consequently, the fabricated PtSA-NiO/Ni catalyst displays extremely high alkaline HER performances with a quite high mass activity of 20.6 A mg-1 for Pt at the overpotential of 100 mV, which is 41 times greater than that of the commercial Pt/C catalyst, significantly outperforming the reported catalysts.

Single Atom Image Contrast in Fixed Beam Dark Field Electron Microscopy

1974 ◽  
Vol 32 ◽  
pp. 366-367
Author(s):  
Wah Chi
Keyword(s):  
Scattering Amplitude ◽  
Present Report ◽  
Dark Field ◽  
Image Contrast ◽  
Single Atom ◽  
Optical Theorem ◽  
Hartree Fock ◽  
Heavy Atoms ◽  
Beam Stop ◽  
Fixed Beam

Resolution and contrast are the important factors to determine the feasibility of imaging single heavy atoms on a thin substrate in an electron microscope. The present report compares the atom image characteristics in different modes of fixed beam dark field microscopy including the ideal beam stop (IBS), a wire beam stop (WBS), tilted illumination (Tl) and a displaced aperture (DA). Image contrast between one Hg and a column of linearly aligned carbon atoms (representing the substrate), are also discussed. The assumptions in the present calculations are perfectly coherent illumination, atom object is represented by spherically symmetric potential derived from Relativistic Hartree Fock Slater wave functions, phase grating approximation is used to evaluate the complex scattering amplitude, inelastic scattering is ignored, phase distortion is solely due to defocus and spherical abberation, and total elastic scattering cross section is evaluated by the Optical Theorem. The atom image intensities are presented in a Z-modulation display, and the details of calculation are described elsewhere.

Atomic Spectroscopy in the FIM

1986 ◽  
Vol 44 ◽  
pp. 758-761
Author(s):  
J. J. Hren ◽  
S. D. Walck
Keyword(s):  
Electron Microscope ◽  
Electric Fields ◽  
Atom Probe ◽  
Atomic Spectroscopy ◽  
Single Atom ◽  
Statistical Sampling ◽  
Commercial Instrument ◽  
Available Technology ◽  
High Electric Fields ◽  
Field Ion Microscope

The field ion microscope (FIM) has had the ability to routinely image the surface atoms of metals since Mueller perfected it in 1956. Since 1967, the TOF Atom Probe has had single atom sensitivity in conjunction with the FIM. “Why then hasn't the FIM enjoyed the success of the electron microscope?” The answer is closely related to the evolution of FIM/Atom Probe techniques and the available technology. This paper will review this evolution from Mueller's early discoveries, to the development of a viable commercial instrument. It will touch upon some important contributions of individuals and groups, but will not attempt to be all inclusive. Variations in instrumentation that define the class of problems for which the FIM/AP is uniquely suited and those for which it is not will be described. The influence of high electric fields inherent to the technique on the specimens studied will also be discussed. The specimen geometry as it relates to preparation, statistical sampling and compatibility with the TEM will be examined.

Field ion microscope investigations of atomic processes at surfaces

1989 ◽  
Vol 47 ◽  
pp. 228-229
Author(s):  
G. L. Kellogg ◽  
P. R. Schwoebel
Keyword(s):  
Single Crystal ◽  
Crystal Surface ◽  
Linear Chain ◽  
Atom Probe ◽  
Nucleation And Growth ◽  
Single Atom ◽  
Initial Structure ◽  
Atomic Processes ◽  
Single Crystal Surfaces ◽  
Field Ion Microscope

Although no longer unique in its ability to resolve individual single atoms on surfaces, the field ion microscope remains a powerful tool for the quantitative characterization of atomic processes on single-crystal surfaces. Investigations of single-atom surface diffusion, adatom-adatom interactions, surface reconstructions, cluster nucleation and growth, and a variety of surface chemical reactions have provided new insights to the atomic nature of surfaces. Moreover, the ability to determine the chemical identity of selected atoms seen in the field ion microscope image by atom-probe mass spectroscopy has increased or even changed our understanding of solid-state-reaction processes such as ordering, clustering, precipitation and segregation in alloys. This presentation focuses on the operational principles of the field-ion microscope and atom-probe mass spectrometer and some very recent applications of the field ion microscope to the nucleation and growth of metal clusters on metal surfaces.The structure assumed by clusters of atoms on a single-crystal surface yields fundamental information on the adatom-adatom interactions important in crystal growth. It was discovered in previous investigations with the field ion microscope that, contrary to intuition, the initial structure of clusters of Pt, Pd, Ir and Ni atoms on W(110) is a linear chain oriented in the <111> direction of the substrate.

Recent advancement in the electrocatalytic synthesis of ammonia

Nanoscale ◽  
2020 ◽  
Vol 12 (15) ◽  
pp. 8065-8094 ◽  
Author(s):  
Xudong Wen ◽  
Jingqi Guan
Keyword(s):  
Metal Oxide ◽  
Oxide Catalysts ◽  
Single Atom ◽  
Metal Oxide Catalysts ◽  
Metal Free ◽  
Recent Advancement ◽  
Nanocomposite Catalysts

Different kinds of electrocatalysts used in NRR electrocatalysis (including single atom catalysts, metal oxide catalysts, nanocomposite catalysts, and metal free catalysts) are introduced.

Rational prediction of multifunctional bilayer single atom catalysts for the hydrogen evolution, oxygen evolution and oxygen reduction reactions

Nanoscale ◽  
2020 ◽  
Vol 12 (39) ◽  
pp. 20413-20424
Author(s):  
Riming Hu ◽  
Yongcheng Li ◽  
Fuhe Wang ◽  
Jiaxiang Shang
Keyword(s):  
Oxygen Reduction ◽  
Hydrogen Evolution ◽  
Oxygen Evolution ◽  
Single Atom ◽  
Reduction Reactions ◽  
Oxygen Reduction Reactions

Bilayer single atom catalysts can serve as promising multifunctional electrocatalysts for the HER, ORR, and OER.

SINGLE ATOM DETECTABILITY OF A ToF ATOM-PROBE

1984 ◽  
Vol 45 (C9) ◽  
pp. C9-343-C9-347 ◽  
Author(s):  
T. Sakurai ◽  
T. Hashizume ◽  
A. Jimbo
Keyword(s):  
Atom Probe ◽  
Single Atom

Helicopter main reduction planetary gear fault diagnosis method based on SVDD

2020 ◽  
Vol 64 (1-4) ◽  
pp. 137-145
Author(s):  
Yubin Xia ◽  
Dakai Liang ◽  
Guo Zheng ◽  
Jingling Wang ◽  
Jie Zeng
Keyword(s):  
Fault Diagnosis ◽  
Planetary Gear ◽  
Gaussian Kernel ◽  
Support Vector ◽  
Support Vector Data Description ◽  
Vector Data ◽  
Energy Characteristics ◽  
Gear Fault ◽  
Channel Information ◽  
Diagnosis Method

Aiming at the irregularity of the fault characteristics of the helicopter main reducer planetary gear, a fault diagnosis method based on support vector data description (SVDD) is proposed. The working condition of the helicopter is complex and changeable, and the fault characteristics of the planetary gear also show irregularity with the change of working conditions. It is impossible to diagnose the fault by the regularity of a single fault feature; so a method of SVDD based on Gaussian kernel function is used. By connecting the energy characteristics and fault characteristics of the helicopter main reducer running state signal and performing vector quantization, the planetary gear of the helicopter main reducer is characterized, and simultaneously couple the multi-channel information, which can accurately characterize the operational state of the planetary gear’s state.

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