scholarly journals Non-Monotonic Trends of Hydrogen Adsorption on Single Atom Doped g-C3N4

Catalysts ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 84 ◽  
Author(s):  
Hao Li ◽  
Zhien Zhang ◽  
Zhijian Liu
Keyword(s):  
Dft Calculations ◽  
Hydrogen Evolution Reaction ◽  
Adsorption Energy ◽  
Hydrogen Adsorption ◽  
Function Theory ◽  
Density Function Theory ◽  
Single Atom ◽  
Free Energies ◽  
Adsorption Model ◽  
Adsorption Energies

To estimate the reaction free energies of the hydrogen evolution reaction (HER) on under-coordinated metallic sites, density function theory (DFT) calculations are usually employed to calculate the hydrogen adsorption energy with an “only-one-hydrogen-adsorption” model, assuming that adsorption with one hydrogen is the most thermodynamically favorable situation during catalysis. In this brief report, we show that on many single atom sites, adsorption of more than one hydrogen is sometimes even more thermodynamically favorable, with the presence of two or three hydrogens resulting in lower adsorption energies. These interesting non-monotonic trends indicate that modeling HER and other hydrogen-related reactions on under-coordinated sites should also consider the numbers of hydrogen being adsorbed at the same site, otherwise the results could deviate from real experimental situations.

Flower-like tungsten-doped Fe–Co phosphides as efficient electrocatalysts for hydrogen evolution reaction

CrystEngComm ◽  
2021 ◽  
Author(s):  
Qian Zhang ◽  
Shuihua Tang ◽  
Lieha Shen ◽  
Weixiang Yang ◽  
Zhen Tang ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Adsorption Energy ◽  
High Performance ◽  
Hydrogen Adsorption ◽  
Cost Effective

Developing cost-effective and high-performance electrocatalysts for hydrogen evolution reaction (HER) are imperative thanks to rapid increase of fuel-cell driven vehicles. Tungsten (W) possesses advantages of optimized hydrogen adsorption energy and...

scholarly journals When More Is Less: Nonmonotonic Trends in Adsorption on Clusters in Alloy Surfaces

2020 ◽  
Author(s):  
Abigale Monasterial ◽  
Calla Hinderks ◽  
Songkun Viriyavaree ◽  
Matthew Montemore
Keyword(s):  
Hydrogen Adsorption ◽  
Electronic States ◽  
Single Atom ◽  
Surface Site ◽  
Ensemble Size ◽  
Free Standing ◽  
Reactive Metal ◽  
Band Center ◽  
Adsorption Energies ◽  
Single Atom Alloys

<div> <div> <div> <p>Single-atom alloys can be effective catalysts and have been compared to supported single-atom catalysts. To rationally design single-atom alloys and other surfaces with localized ensembles, it is crucial to understand variations in reactivity when varying the dopant and the ensemble size. Here, we examined hydrogen adsorption on surfaces embedded with localized clusters and discovered general trends. Counterintuitively, increasing the amount of a more reactive metal sometimes makes a surface site less reactive. This behavior is due to the localized electronic states in many of these surfaces, making them similar to free-standing nanoclusters. Further, single-atom alloys have qualitatively different behavior than larger ensembles. Specifically, the adsorption energy is U-shaped when plotted against the dopant’s group for single atom alloys. Additionally, adsorption energies on single atom alloys correlate more strongly with the dopant’s p-band center than the d-band center. </p> </div> </div> </div>

First Principles Calculation on Adsorption of S on Impurity Fe (100)

2012 ◽  
Vol 472-475 ◽  
pp. 1538-1543
Author(s):  
Qiang Luo ◽  
Zhi Zhang ◽  
Qiang Zhang ◽  
Tai He Shi ◽  
Zeng Ling Ran
Keyword(s):  
Electronic Properties ◽  
Density Function ◽  
Molecular Orbital ◽  
Adsorption Energy ◽  
First Principles ◽  
Function Theory ◽  
Density Function Theory ◽  
First Principles Calculation ◽  
Generalized Gradient ◽  
Generalized Gradient Approximation

Using the first principles method, which is based on the density function theory (DFT), the structures and electronic properties of S atoms are adsorbed on the Fe (100) surface for X(X is Cr, Ni, Mo, C, Mn ,Si,P and S) impurities in Fe, and their molecular orbital and absorption energies were calculated with the generalized gradient approximation. The results show that S adsorbed on H site for Cr, Ni, Mn, C and Mo impurities in Fe is stable but for Si, S and P is B site. The adsorption energy for Ni in impurity Fe is almost nearby for the purity Fe and the effect for Ni in S absorption on Fe (100) surface is very small. In order to prevent S absorption on Fe surface，we can reduce the percentage of Ni.

DFT STUDY OF METHYL (CH3) AND HYDROXYL (OH) ADSORPTION ON A GOLD (001) SURFACE

2019 ◽  
Vol 26 (05) ◽  
pp. 1850198 ◽  
Author(s):  
G. B. BOUKA-PIVOTEAU ◽  
M. N’DOLLO ◽  
B. R. MALONDA-BOUNGOU ◽  
B. MALOUMBI ◽  
P. S. MOUSSOUNDA ◽  
...  
Keyword(s):  
Dipole Moment ◽  
Surface Energy ◽  
Dft Calculations ◽  
Adsorption Energy ◽  
Energy Surface ◽  
Geometrical Parameters ◽  
Oh Radical ◽  
Spin Polarized ◽  
Surface Dipole ◽  
Adsorption Energies

We used the DACAPO code with the GGA-PW91 approximation to study the adsorption of methyl (CH3) and hydroxyl (OH) for four- and five-layer gold (Au) (001) slabs. We have determined for each species the best binding site, adsorption energy, the change in the work function, surface energy, surface dipole moment, geometrical parameters and projected density of states (PDOS). We performed spin-unpolarized and spin-polarized DFT calculations for free and adsorbed CH3 and OH species. The most important point is that the spin polarization diminishes the adsorption energies but does not change the geometrical parameters. For the CH3 species, only the top site was found to be stable for different coverages. We found that during the optimization phase, the hollow and bridge sites were found to be unstable. In both cases the CH3 species moves toward the top site. We observe that the adsorption energy decreases when increasing the coverage. However, the OH species was stable in all investigated sites (top, bridge and hollow). We notice that the adsorption energy is dependent on the number of slab layers and the bridge is the best site in adsorption energy. The analysis of the calculated O PDOS of OH radical shows a mixing between the O orbitals and the Au bands.

scholarly journals Insights into Hydrogen Evolution Reaction on 2D Transition Metal Dichalcogenides

2021 ◽  
Author(s):  
Zhenbin Wang ◽  
Michael Tang ◽  
Ang Cao ◽  
Karen Chan ◽  
Jens Kehlet Nørskov
Keyword(s):  
Transition Metal ◽  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Adsorption Energy ◽  
Density Functional ◽  
Hydrogen Adsorption ◽  
Activation Barrier ◽  
Transition Metal Dichalcogenides ◽  
Adsorbed Hydrogen ◽  
Metal Dichalcogenides

<p>Understanding the hydrogen evolution reaction (HER) behaviors over 2D transition metal dichalcogenides (2D-TMDs) is critical for the development of non-precious HER electrocatalysts with better activity. In this work, by combining density functional theory calculations with microkinetic modelling, we thoroughly investigated the HER mechanism on 2D-TMDs. We find there is an important dependence of simulated cell size on the calculated hydrogen adsorption energy and the activation barrier for MoS<sub>2</sub>. Distinct from previous “H migration” mechanisms proposed for the Heyrovsky reaction − the rate-determining step for MoS<sub>2</sub>, we propose the Mo site only serves as the stabilized transition state rather than H adsorption. In comparison to transition metal electrocatalysts, we find that the activation barrier of the Heyrovsky reaction on 2D-TMDs scales with the hydrogen adsorption energy exactly as for transition metals except that all activation energies are displaced upwards by <i>ca.</i> 0.4 eV. This higher Heyrovsky activation barrier is responsible for the substantially lower activity of 2D-TMDs. We further show that this higher activation barrier stems from the more positively charged adsorbed hydrogen on the chalcogenides interacting repulsively with the incoming proton. Based on these insights, we discuss potential strategies for the design of non-precious HER catalysts with activity comparable to Pt.</p>

When More Is Less: Nonmonotonic Trends in Adsorption on Clusters in Alloy Surfaces

2020 ◽  
Author(s):  
Abigale Monasterial ◽  
Calla Hinderks ◽  
Songkun Viriyavaree ◽  
Matthew Montemore
Keyword(s):  
Fermi Energy ◽  
Hydrogen Adsorption ◽  
Single Atom ◽  
Free Standing ◽  
Reactive Metal ◽  
Electronic Density ◽  
Band Center ◽  
Adsorption Energies ◽  
Single Atom Alloy ◽  
Single Atom Alloys

Single-atom alloys can be effective catalysts and have been compared to supported single-atom catalysts. To rationally design single-atom alloys and other surfaces with localized ensembles, it is crucial to understand variations in reactivity when varying the dopant and the ensemble size. Here, we examined hydrogen adsorption on surfaces embedded with localized clusters and discovered general trends. Counterintuitively, increasing the amount of a more reactive metal sometimes makes a surface site less reactive. This behavior is due to the hybridization and splitting of narrow peaks in the electronic density of states of many of these surfaces, making them analogous to free-standing nanoclusters. When a single-atom alloy has a peak just below the Fermi energy, the corresponding two-dopant cluster often has weaker adsorption than the single-atom alloy due to splitting of this peak across the Fermi energy. Further, single-atom alloys have qualitatively different behavior than larger ensembles. Specifically, the adsorption energy is a U-shaped function of the dopant’s group for single atom alloys. Additionally, adsorption energies on single atom alloys correlate more strongly with the dopant’s p-band center than the d-band center.

scholarly journals Photoinduced Change of UV-Absorption and Redox Potential of Alkyne-Bridged Diferrocenyl Azobenzene Derivative

2008 ◽  
Vol 2008 ◽  
pp. 1-4
Author(s):  
Limin Han ◽  
Jianchen Bai ◽  
Quanling Suo ◽  
Meihua Luo ◽  
Lifeng Zhang
Keyword(s):  
Dft Calculations ◽  
Redox Potential ◽  
Function Theory ◽  
Density Function Theory ◽  
Time Dependent ◽  
Photoinduced Change ◽  
Uv Absorbance ◽  
Td Dft ◽  
And Shifts ◽  
Dependent Density

An alkynyl-coupled diferrocenylpropane and azobenzene derivative has been synthesized. Photoinduced change of UV-absorbance and shifts of redox potential of synthesized compound were elucidated by time-dependent density function theory (TD-DFT) calculations, indicating that isomerization of trans to cis configuration occurs by UV irradiation.

P-block tin single atom catalyst for improved electrochemistry in lithium-sulfur battery: a theoretical and experimental study

2022 ◽  
Author(s):  
Caixia Xiao ◽  
Wanqing Song ◽  
Jingzhe Liang ◽  
Jiangwei Zhang ◽  
Zechuan Huang ◽  
...  
Keyword(s):  
Experimental Study ◽  
Density Function ◽  
Function Theory ◽  
Density Function Theory ◽  
Main Group ◽  
Single Atom ◽  
Nitrogen Doped ◽  
Main Group Metals ◽  
Sulfur Battery ◽  
Lithium Sulfur

Main group metals are routinely considered as catalytically inactive hence never employed for optimizing the lithium-sulfur electrochemistry. Herein, density function theory calculations reveal that atomically dispersed tin on nitrogen doped...

scholarly journals ADSORPTION MODEL OF Mn2+, Cd2+ and Hg2+ IN THE WATER - SEDIMENT SYSTEMS ALONG CODE RIVER, YOGYAKARTA

2010 ◽  
Vol 8 (3) ◽  
pp. 314-319 ◽  
Author(s):  
Muzakky Muzakky
Keyword(s):  
Metal Ions ◽  
Adsorption Energy ◽  
Initial Condition ◽  
Adsorption Model ◽  
River Dynamics ◽  
Binding Strength ◽  
Langmuir Adsorption ◽  
Langmuir Adsorption Model ◽  
Isotherm Adsorption ◽  
Adsorption Energies

Prediction of adsorption model of Mn2+, Cd2+ and Hg2+ in water-sediment systems along Code River, Yogyakarta has been experimentally investigated. The aim of this investigation is to predict the transfer models based on isotherm adsorption of Mn2+, Cd2+ and Hg2+ metal ions from water into sediment. In addition, this investigation is expected to be able to inform the initial condition of Code River, dynamics, and the fate of Mn2+, Cd2+ and Hg2+ ions from upstream to downstream. Based on the investigation the transfer of Mn2+, and Cd2+ ions into sediment follows Langmuir adsorption model, with the coefficient determination (R2) of 0,9916 and 0,9799, while the value of the adsorption energy are 20,95 kJ/mol and 16,85 kJ/mol. The transfer of Hg2+ ion tend to follow Freundlich adsorption model. From the adsorption energies, it is proven  that Mn2+ ion was chemically sorpted into the sediment, while Cd2+ ion will tend to be physically sorpted into the sediment. The binding strength of which ise in the order of Mn2+ > Cd2+ and the adsorption energy of Hg2+ ion could not be determined.   Keywords: adsorption model, chemically sorpted, physically sorpted

scholarly journals Design Pollution Gas Sensor Using Graphene Ribbon: Density Function Theory (DFT)

2021 ◽  
Author(s):  
Ruaa.S. Al-Hasnawy ◽  
Ali S. Shaker ◽  
Muntather H Albosaabar ◽  
Zahraa A. Al-Maamouri ◽  
Hamed A. Al-taee
Keyword(s):  
Density Function ◽  
Adsorption Energy ◽  
Function Theory ◽  
Energy Gap ◽  
Physical Adsorption ◽  
Wave Length ◽  
Density Function Theory ◽  
Chemical Adsorption ◽  
Graphene Ribbon ◽  
Gas Molecule

Abstract Density Function theory (DFT) calculation used to employed ground and excitation states for graphene ribbons, types of adsorption, energy gap, maximum wave length and optical band gap. Adsorption energy showed that CO2 gas molecule have chemical adsorption in distance 1 and 1.5 Angstrom, distance 2 and 2.5 Angstrom appear physical adsorption, adsorption energy decreased when distance between surface and gas molecule increasing. Resulting from chemical adsorption energy gap change with distance 1 and 1.5 Angstrom because attract gas molecule with surface. Excitation energy for nano system in sample 1 and 4 shifted to low wavelength (blue shift) change from 1018 nm to 993 nm and 718 nm on series. Other sample have red shift and energy gap becoming open. Result showed that graphene ribbon sense carbon dioxide gas (CO2).

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