Mechanistic insights of selective syngas conversion over Zn grafted on ZSM-5 zeolite

2020 ◽  
Vol 10 (24) ◽  
pp. 8173-8181
Author(s):  
Wei Chen ◽  
Dinesh Acharya ◽  
Zhiqiang Liu ◽  
Xianfeng Yi ◽  
Yao Xiao ◽  
...  
Keyword(s):  
Transition States ◽  
Reaction Pathways ◽  
Reaction Intermediates ◽  
Syngas Conversion ◽  
Zeolite P

On the basis of syngas conversion mechanism over Zn2+-ion exchanged ZSM-5 zeolite, the reaction pathways, reaction intermediates and transition states were determined clearly.

scholarly journals Finding Reaction Pathways and Transition States: r-ARTn and d-ARTn as an Efficient and Versatile Alternative to String Approaches

2020 ◽  
Vol 16 (10) ◽  
pp. 6726-6734 ◽  
Author(s):  
Antoine Jay ◽  
Christophe Huet ◽  
Nicolas Salles ◽  
Miha Gunde ◽  
Layla Martin-Samos ◽  
...  
Keyword(s):  
Transition States ◽  
Reaction Pathways

The Role of the Substituent Pattern in Determining Selectivity in the Preparation of Tricarbonyl(η5-cyclohexadienyl)iron(1+) Salts by Acid-Catalyzed Demethoxylation

1992 ◽  
Vol 45 (1) ◽  
pp. 121 ◽  
Author(s):  
GR Stephenson ◽  
DA Owen ◽  
H Finch ◽  
S Swanson
Keyword(s):  
Transition States ◽  
Kinetic Control ◽  
Reaction Intermediates ◽  
Acid Catalyzed

The factors that determine the selectivity of the acid-catalysed dealkoxylation of unsymmetrically substituted tricarbonyl(η4-alkoxycyclohexa-1,3-diene)iron(0) complexes have been investigated. Regioselective demethoxylation of complexes with a variety of substitution patterns has indicated that the selectivity arises from differences in the stabilization of the reaction intermediates and transition states by the diene substituents on the π-bound ligand. The observed regioisomers correspond to the product of the most stabilized intermediate pathway, rather than the product of minimum rearrangement. The reactions have been shown to proceed under kinetic control.

scholarly journals Identifying the Spectroelectrochemical Characteristics of Hematite Photoanodes for Water Oxidation

2021 ◽  
Author(s):  
Jifang Zhang ◽  
Qiyuan Lin ◽  
Zhenlei Wang ◽  
Haowen Liu ◽  
Yuegang Zhang
Keyword(s):  
Water Splitting ◽  
Water Oxidation ◽  
Surface States ◽  
Reaction Pathways ◽  
Reaction Intermediates ◽  
Fermi Level Pinning ◽  
Solar Water Splitting ◽  
Interfacial Processes ◽  
Active Reaction ◽  
Recombination Processes

Achieving efficient solar water splitting using hematite (α-Fe2O3), one of the most promising candidates for photoanodes, requires photogenerated holes to be efficiently used for water oxidation. However, this goal is obstructed by multiple undesirable recombination processes, as well as insufficient fundamental mechanistic understandings of water oxidation kinetics, particularly as to the nature of reaction pathways and possible reaction intermediates. Here we spectroelectro-chemically identify some of the most critical interfacial processes which determine the photoelectrocatalytic efficiencies of water oxidation, for hematite films with varied surface properties by tailoring the doping level of titanium. The spectroscopic signals of the processes inactive for water oxidation, including oxidation of intra-gap Fe2+ states and Fermi level pinning, are successfully distinguished from that of the active reaction intermediate, Fe(IV)=O. In addition, our kinetic analyses reveal two water oxidation pathways, of which the direct hole transfer mechanism becomes dominant over the surface states-mediated mechanism when the hematite surface is reconstructed by high levels of titanium dopants.

scholarly journals Role of Reaction Intermediate Diffusion on the Performance of Platinum Electrodes in Solid Acid Fuel Cells

Catalysts ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1065
Author(s):  
Oliver Lorenz ◽  
Alexander Kühne ◽  
Martin Rudolph ◽  
Wahyu Diyatmika ◽  
Andrea Prager ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Phase Boundary ◽  
Solid Acid ◽  
Diffusion Processes ◽  
Reaction Pathways ◽  
Reaction Intermediates ◽  
Boundary Area ◽  
Triple Phase Boundary ◽  
Boundary Length ◽  
Double Phase

Understanding the reaction pathways for the hydrogen oxidation reaction (HOR) and the oxygen reduction reaction (ORR) is the key to design electrodes for solid acid fuel cells (SAFCs). In general, electrochemical reactions of a fuel cell are considered to occur at the triple-phase boundary where an electrocatalyst, electrolyte and gas phase are in contact. In this concept, diffusion processes of reaction intermediates from the catalyst to the electrolyte remain unconsidered. Here, we unravel the reaction pathways for open-structured Pt electrodes with various electrode thicknesses from 15 to 240 nm. These electrodes are characterized by a triple-phase boundary length and a thickness-depending double-phase boundary area. We reveal that the double-phase boundary is the active catalytic interface for the HOR. For Pt layers ≤ 60 nm, the HOR rate is rate-limited by the processes at the gas/catalyst and/or the catalyst/electrolyte interface while the hydrogen surface diffusion step is fast. For thicker layers (>60 nm), the diffusion of reaction intermediates on the surface of Pt becomes the limiting process. For the ORR, the predominant reaction pathway is via the triple-phase boundary. The double-phase boundary contributes additionally with a diffusion length of a few nanometers. Based on our results, we propose that the molecular reaction mechanism at the electrode interfaces based upon the triple-phase boundary concept may need to be extended to an effective area near the triple-phase boundary length to include all catalytically relevant diffusion processes of the reaction intermediates.

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