Pore size effect of graphyne supports on CO2 electrocatalytic activity of Cu single atoms

2020 ◽  
Vol 22 (3) ◽  
pp. 1181-1186 ◽  
Author(s):  
Youxuan Ni ◽  
Licheng Miao ◽  
Jiaqi Wang ◽  
Junxiang Liu ◽  
Mingjian Yuan ◽  
...  
Keyword(s):  
Size Effect ◽  
Pore Size ◽  
Coordination Number ◽  
Electrocatalytic Activity ◽  
Steric Effects ◽  
Single Atoms ◽  
Metal Atoms

Steric effects of graphyne supports on the intermediates and coordination number of metal atoms determine the CO2 electrocatalytic activity of SACs.

scholarly journals Atoms in Highly Symmetric Environments: H in Rhodium and Cobalt Cages, H in an Octahedral Hole in MgO, and Metal Atoms Ca-Zn in C20 Fullerenes

Symmetry ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1281
Author(s):  
Zikri Altun ◽  
Erdi Ata Bleda ◽  
Carl Trindle
Keyword(s):  
Density Functional Theory ◽  
Quantum Theory ◽  
Coordination Number ◽  
Electronic Structures ◽  
Density Functional ◽  
Functional Theory ◽  
Metal Atoms ◽  
Tetragonal Pyramidal ◽  
Non Covalent Interactions ◽  
Covalent Interactions

An atom trapped in a crystal vacancy, a metal cage, or a fullerene might have many immediate neighbors. Then, the familiar concept of valency or even coordination number seems inadequate to describe the environment of that atom. This difficulty in terminology is illustrated here by four systems: H atoms in tetragonal-pyramidal rhodium cages, H atom in an octahedral cobalt cage, H atom in a MgO octahedral hole, and metal atoms in C20 fullerenes. Density functional theory defines structure and energetics for the systems. Interactions of the atom with its container are characterized by the quantum theory of atoms in molecules (QTAIM) and the theory of non-covalent interactions (NCI). We establish that H atoms in H2Rh13(CO)243− trianion cannot be considered pentavalent, H atom in HCo6(CO)151− anion cannot be considered hexavalent, and H atom in MgO cannot be considered hexavalent. Instead, one should consider the H atom to be set in an environmental field defined by its 5, 6, and 6 neighbors; with interactions described by QTAIM. This point is further illustrated by the electronic structures and QTAIM parameters of M@C20, M=Ca to Zn. The analysis describes the systematic deformation and restoration of the symmetric fullerene in that series.

Thermostable carbon-supported subnanometer-sized (< 1 nm) Pt clusters for hydrogen evolution reaction

2021 ◽  
Author(s):  
Jing-Fang Huang ◽  
Ruo-Hua Zeng ◽  
Jeng-Lung Chen
Keyword(s):  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Electrocatalytic Activity ◽  
Atomic Scale ◽  
Single Atoms

The downsizing of catalysts to atomic-scale or subnanometer size can effectively maximize the atomic utilization and enhance the electrocatalytic activity. Carbon-supported Pt single atoms or sub-nanometer-sized Pt clusters (Ptc/C) are...

Foam Flow in Different Pore Systems—Part 1: The Roles of Pore Attributes and Their Variation on Trapping and Apparent Viscosity of Foam

SPE Journal ◽  
2021 ◽  
pp. 1-18 ◽  
Author(s):  
Abdulrauf Rasheed Adebayo
Keyword(s):  
Porous Medium ◽  
Aspect Ratio ◽  
Pore Size ◽  
Coordination Number ◽  
Apparent Viscosity ◽  
Absolute Permeability ◽  
Surface Relaxation ◽  
Foam Flow ◽  
Rock Samples ◽  
Lower Permeability

Summary Lateral propagation of foam in heterogeneous reservoirs, where pore geometries vary laterally, depends on the roles of pore geometries on the foam properties. In this paper, the pore attributes of 12 different rock samples were characterized in terms of porosity, permeability, pore shape, pore size, throat size, aspect ratio, coordination number, and log mean of surface relaxation times (T2LM). These were measured from gas porosimeter and permeameter, X-ray microcomputed tomography (CT)-basedpore-network models, thin-section photomicrographs, and nuclear magnetic resonance (NMR) surface relaxometry. The samples have a wide range of porosity: 12 to 29%; permeability: 1 to 5,000 md; average pore size: 3.7 to 9 µm; average throat size: 2.4 to 8 µm; average aspect ratio: 1 to 1.7; average coordination number: 2.6 to 5.2; and T2LM: 9.4 to 740 ms. Nitrogen foam flow experiments (without oil) were then conducted on each rock sample using a specialized coreflood apparatus. A graphical analysis of the coreflood data was used to estimate the total saturation of trapped foam (10 to 66%), flowing foam (3 to 14%), and apparent viscosity of foam (3.2 to 73 cp). Trapped foam saturation and apparent viscosity values were then correlated with each of the measured pore attributes. The results revealed that all pore attributes, except aspect ratio, have positive correlations with foam trapping and apparent viscosity. The best correlation with trapped foam saturation was obtained when the most influential pore attributes (pore size, throat size, aspect ratio, and coordination number) were combined into a single mathematical function. Foam apparent viscosity also appears to be mostly influenced by trapped foam saturation, permeability, and coordination number of pore systems. Trapping is also likely enhanced by the presence of fenestral or channel pores. Furthermore, the shape and angularity of pores seem to facilitate snap-off and trapping of foam, because rock samples with angular pores trapped the highest foam saturation compared with other samples with rounded and subrounded pores. It was also shown that the correlation between trapped foam saturation (and foam apparent viscosity) and the absolute permeability of porous media may reverse at some high-permeability values (greater than several darcies), when one or both of the following conditions exist: (1) The aspect ratio of a lower-permeability porous medium is lower than that of a higher-permeability porous medium, and (2) the coordination number of a lower-permeability porous medium is higher than that of a higher-permeability porous medium. Finally, T2LM showed a good correlation with foam trapping, making NMR logging a prospective tool for pre-evaluating foam performance in targeted reservoir sections.

Glass Transition in Sub-nanometer Confinement

1998 ◽  
Vol 543 ◽  
Author(s):  
A. Huwe ◽  
F. Kremer ◽  
M. Arndt ◽  
P. Behrens ◽  
W. Schwieger ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Relaxation Rate ◽  
Pore Size ◽  
Coordination Number ◽  
Single Molecule ◽  
Bulk Liquid ◽  
Bond Forming ◽  
Broadband Dielectric Spectroscopy ◽  
Molecule Dynamics

AbstractBroadband dielectric spectroscopy (10−2 Hz - 109Hz) is employed to study the molecular dynamics of low-molecular-weight glassforming liquids being confined to nanopores. For the H-bond forming liquid propylene glycol being confined to (uncoated and silanized) nanopores (pore size: 2.5 nm, 5.0 nm and 7.5 nm) a molecular dynamics is observed which is comparable to that of the bulk liquid. Due to surface effects in uncoated nanopores the relaxation time distribution is broadened on the long term side and the mean relaxation rate is decreased by about half a decade. This effect can be counterbalanced by lubricating the inner surfaces of the pores resulting in a relaxation rate which is slightly faster compared to the bulk liquid. For the H-bonded liquid ethylene glycol (EG) embedded in zeolites of different pore size and topology one observes a sharp transition from a single-molecule dynamics to that of a liquid depending on the coordination number of the confined molecules. While EG in silicalite (showing a single molecule relaxation) has four neighboring molecules, EG in zeolite beta or AIPO4-5 has a coordination number of five and behaves like a bulk liquid.

Analysis and modeling of the pore size effect on the thermal conductivity of alumina foams for high temperature applications

2017 ◽  
Vol 43 (16) ◽  
pp. 13356-13363 ◽  
Author(s):  
Pedro I.B.G.B. Pelissari ◽  
Ricardo A. Angélico ◽  
Vânia R. Salvini ◽  
Diogo O. Vivaldini ◽  
Victor C. Pandolfelli
Keyword(s):  
Thermal Conductivity ◽  
High Temperature ◽  
Size Effect ◽  
Pore Size ◽  
Temperature Applications

Study of the pore size effect on the charge storage of hydrous RuO2 nanoparticles supported within the pores of activated carbon

2021 ◽  
Vol 111 ◽  
pp. 106472
Author(s):  
Hiroyuki Itoi ◽  
Miho Ito ◽  
Yuto Kasai ◽  
Yuichiro Tanabe ◽  
Ryutaro Suzuki ◽  
...  
Keyword(s):  
Activated Carbon ◽  
Size Effect ◽  
Pore Size ◽  
Charge Storage

PORE SIZE EFFECT IN THE FIREEZE DRYING PROCESS

1971 ◽  
Vol 36 (3) ◽  
pp. 388-391 ◽  
Author(s):  
EDWARD B. STUART ◽  
GERARD CLOSSET
Keyword(s):  
Size Effect ◽  
Pore Size ◽  
Drying Process

Pore size effect on diffusion coefficient of rhodamine B in PNIPA gel

1999 ◽  
Vol 258 (2-3) ◽  
pp. 171-176 ◽  
Author(s):  
Fumiaki Tsunomori ◽  
Hideharu Ushiki
Keyword(s):  
Diffusion Coefficient ◽  
Size Effect ◽  
Pore Size ◽  
Rhodamine B
Sign in / Sign up

Export Citation Format

Share Document