scholarly journals Decomposition of Formic Acid over Orthorhombic Molybdenum Carbide

2021 ◽  
Author(s):  
Kushagra Agrawal ◽  
Alberto Roldan ◽  
Nanda Kishore ◽  
Andrew J Logsdail
Keyword(s):  
Formic Acid ◽  
Density Functional ◽  
Molybdenum Carbide ◽  
Catalyst Surface ◽  
Energy Landscape ◽  
Functional Theory ◽  
Potential Energy Landscape ◽  
Temperature Programmed ◽  
Temperature Programmed Reaction ◽  
Dehydrogenation Mechanism

The decomposition of formic acid is investigated on the β-Mo<sub>2</sub>C (100) catalyst surface using density functional theory. The dehydration and dehydrogenation mechanism for the decomposition is simulated, and the thermochemistry and kinetics are discussed. The potential energy landscape of the reaction shows a thermodynamically favourable cleavage of H-COOH to form CO; however, the kinetics show that the dehydrogenation mechanism is faster and CO<sub>2</sub> is continuously formed. The effect of HCOOH adsorption on the surface is also analysed, in a temperature-programmed reaction, with the decomposition proceeding at under 350 K and desorption of CO<sub>2</sub> observed.

scholarly journals Decomposition of Formic Acid over Orthorhombic Molybdenum Carbide

2021 ◽  
Author(s):  
Kushagra Agrawal ◽  
Alberto Roldan ◽  
Nanda Kishore ◽  
Andrew J Logsdail
Keyword(s):  
Formic Acid ◽  
Density Functional ◽  
Molybdenum Carbide ◽  
Catalyst Surface ◽  
Energy Landscape ◽  
Functional Theory ◽  
Potential Energy Landscape ◽  
Temperature Programmed ◽  
Temperature Programmed Reaction ◽  
Dehydrogenation Mechanism

The decomposition of formic acid is investigated on the β-Mo<sub>2</sub>C (100) catalyst surface using density functional theory. The dehydration and dehydrogenation mechanism for the decomposition is simulated, and the thermochemistry and kinetics are discussed. The potential energy landscape of the reaction shows a thermodynamically favourable cleavage of H-COOH to form CO; however, the kinetics show that the dehydrogenation mechanism is faster and CO<sub>2</sub> is continuously formed. The effect of HCOOH adsorption on the surface is also analysed, in a temperature-programmed reaction, with the decomposition proceeding at under 350 K and desorption of CO<sub>2</sub> observed.

DFT STUDY OF THE FORMATION OF CH2=CF2 THROUGH BOTH METHYLENE INSERTION AND β-FLUORIDE ELIMINATION ON THE Ag(111) SURFACE

2004 ◽  
Vol 11 (02) ◽  
pp. 229-234 ◽  
Author(s):  
JYH SHING LIN ◽  
WEN-CHI CHOU
Keyword(s):  
Density Functional ◽  
Formation Rate ◽  
Bridge Site ◽  
Hollow Site ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Spin Polarized ◽  
Temperature Programmed ◽  
Temperature Programmed Reaction ◽  
Calculated Energy Barrier

Total energy calculations based on (1) density functional theory (DFT) in connection with ultrasoft pseudopotential and generalized gradient spin-polarized approximation (GGSA) and (2) the partial structural constraint path minimization (PSCPM) method have been used to investigate the energetically more favorable pathway for methylene ( CH 2) insertion into the Ag–CF 3 bond followed by β-fluoride elimination to generate an isolated CH 2= CF 2( g ) above the Ag(111) surface. The diffusion of the fcc-hollow site of CF 3( ads ) toward the bridge site of CH 2( ads ) is proposed as an energe*tically more favorable path for CH 2 insertion into the Ag–CF 3 bond to form the bridge site of CH 2 CF 3( ads ) on the Ag(111) surface. Then we proceed with β-fluoride elimination to form an isolated CH 2= CF 2( g ) and the bridge site of F (ads) on the Ag(111) surface. Our calculated energy barrier for β-fluoride elimination is 0.715 eV higher than that for CH 2 insertion on the Ag(111) surface. These calculated results imply that β-fluoride elimination rather than CH 2 insertion on the Ag(111) surface controls the CH 2= CF 2( g ) formation rate as observed from temperature-programmed reaction (TPR) experimental data. Finally, we attribute these different energy barriers to the different transition state structures — largely distorted seven-centered versus less distorted four-centered — involved in these two different processes.

First-principles insights into ammonia decomposition on MoN (0001) surface

2021 ◽  
Author(s):  
kun yuan ◽  
pengju hao ◽  
Xiaolin Li ◽  
Yang Zhou ◽  
jiangbo zhang ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Electronic Structure ◽  
Surface Energy ◽  
Geometric Structure ◽  
First Principles ◽  
Density Functional ◽  
Slab Model ◽  
Ammonia Adsorption ◽  
Functional Theory ◽  
Dehydrogenation Mechanism

Density functional theory (DFT) and periodic slab model were used to study the geometric structure, electronic structure and dehydrogenation mechanism of ammonia adsorption on MoN (0001) surface. The surface energy...

Fast-ion conduction and local environments in BIMEVOX

2021 ◽  
Vol 379 (2211) ◽  
Author(s):  
Harry J. Stroud ◽  
Chris E. Mohn ◽  
Jean-Alexis Hernandez ◽  
Neil L. Allan
Keyword(s):  
Density Functional ◽  
Energy Landscape ◽  
Diffusion Mechanism ◽  
Ion Conduction ◽  
Functional Theory ◽  
Ion Conductor ◽  
Local Environments ◽  
Fast Ion Conductor ◽  
Fast Ion ◽  
Oxide Ions

The energy landscape of the fast-ion conductor Bi 4 V 2 O 11 is studied using density functional theory. There are a large number of energy minima, dominated by low-lying thermally accessible configurations in which there are equal numbers of oxygen vacancies in each vanadium–oxygen layer, a range of vanadium coordinations and a large variation in Bi–O and V–O distances. By dividing local minima in the energy landscape into sets of configurations, we then examine diffusion in each different layer using ab initio molecular dynamics. These simulations show that the diffusion mechanism mainly takes place in the 〈110〉 directions in the vanadium layers, involving the cooperative motion of the oxide ions between the O(2) and O(3) sites in these layers, but not O(1) in the Bi–O layers, in agreement with experiment. O(1) vacancies in the Bi–O layers are readily filled by the migration of oxygens from the V–O layers. The calculated ionic conductivity is in reasonable agreement with the experiment. We compare ion conduction in δ-Bi 4 V 2 O 11 with that in δ-Bi 2 O 3 . This article is part of the Theo Murphy meeting issue ‘Understanding fast-ion conduction in solid electrolytes’.

scholarly journals Propane Fuel Cells: Selectivity for Partial or Complete Reaction

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Shadi Vafaeyan ◽  
Alain St-Amant ◽  
Marten Ternan
Keyword(s):  
Fuel Cells ◽  
Density Functional ◽  
Catalyst Surface ◽  
Polymer Electrolyte Membrane ◽  
Platinum Group Metal ◽  
Pem Fuel Cells ◽  
Metal Catalyst ◽  
Boltzmann Factor ◽  
Functional Theory ◽  
Electrolyte Membrane

The use of propane fuel in high temperature (120°C) polymer electrolyte membrane (PEM) fuel cells that do not require a platinum group metal catalyst is being investigated in our laboratory. Density functional theory (DFT) was used to determine propane adsorption energies, desorption energies, and transition state energies for both dehydrogenation and hydroxylation reactions on a Ni(100) anode catalyst surface. The Boltzmann factor for the hydroxylation of a propyl species to form propanol and its subsequent desorption was compared to that for the dehydrogenation of a propyl species. The large ratio of the respective Boltzmann factors indicated that the formation of a completely reacted product (carbon dioxide) is much more likely than the formation of partially reacted products (alcohols, aldehydes, carboxylic acids, and carbon monoxide). That finding is evidence for the major proportion of the chemical energy of the propane fuel being converted to either electrical or thermal energy in the fuel cell rather than remaining unused when partially reacted species are formed.

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