scholarly journals Regulating the Electron Localization of Metallic Bismuth for Boosting CO2 Electroreduction

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Dan Wu ◽  
Renfei Feng ◽  
Chenyu Xu ◽  
Peng-Fei Sui ◽  
Jiujun Zhang ◽  
...  
Keyword(s):  
Density Functional ◽  
Rational Design ◽  
Reaction Pathway ◽  
Highly Active ◽  
Mechanistic Pathway ◽  
The Density Functional Theory ◽  
Co2 Electroreduction ◽  
Metallic Bismuth ◽  
Local Electronic Structure ◽  
Positive Valence

AbstractElectrochemical reduction of CO2 to formate is economically attractive but improving the reaction selectivity and activity remains challenging. Herein, we introduce boron (B) atoms to modify the local electronic structure of bismuth with positive valence sites for boosting conversion of CO2 into formate with high activity and selectivity in a wide potential window. By combining experimental and computational investigations, our study indicates that B dopant differentiates the proton participations of rate-determining steps in CO2 reduction and in the competing hydrogen evolution. By comparing the experimental observations with the density functional theory, the dominant mechanistic pathway of B promoted formate generation and the B concentration modulated effects on the catalytic property of Bi are unravelled. This comprehensive study offers deep mechanistic insights into the reaction pathway at an atomic and molecular level and provides an effective strategy for the rational design of highly active and selective electrocatalysts for efficient CO2 conversion.

scholarly journals Comparative Experimental and Theoretical Study of Mg, Al and Zn Aryloxy Complexes in Copolymerization of Cyclic Esters: The Role of the Metal Coordination in Formation of Random Copolymers

Polymers ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2273
Author(s):  
Ilya Nifant’ev ◽  
Pavel Komarov ◽  
Valeriya Ovchinnikova ◽  
Artem Kiselev ◽  
Mikhail Minyaev ◽  
...  
Keyword(s):  
Density Functional ◽  
Rational Design ◽  
Qualitative Difference ◽  
Random Copolymers ◽  
Coordination Polymerization ◽  
Polymer Backbone ◽  
Catalytic Behavior ◽  
Cyclic Esters ◽  
Dft Modeling ◽  
The Density Functional Theory

Homogeneity of copolymers is a general problem of catalytic coordination polymerization. In ring-opening polymerization of cyclic esters, the rational design of the catalyst is generally applied to solve this problem by the equalization of the reactivities of comonomers—however, it often leads to a reduction of catalytic activity. In the present paper, we studied the catalytic behavior of BnOH-activated complexes (BHT)Mg(THF)2nBu (1), (BHT)2AlMe (2) and [(BHT)ZnEt]2 (3), based on 2,6-di-tert-butyl-4-methylphenol (BHT-H) in homo- and copolymerization of L-lactide (lLA) and ε-caprolactone (εCL). Even at 1:5 lLA/εCL ratio Mg complex 1 catalyzed homopolymerization of lLA without involving εCL to the formation of the polymer backbone. On the contrary, Zn complex 3 efficiently catalyzed random lLA/εCL copolymerization; the presence of mono-lactate subunits in the copolymer chain clearly pointed to the transesterification mechanism of copolymer formation. Both epimerization and transesterification side processes were analyzed using the density functional theory (DFT) modeling that confirmed the qualitative difference in catalytic behavior of 1 and 3: Mg and Zn complexes demonstrated different types of preferable coordination on the PLA chain (k2 and k3, respectively) with the result that complex 3 catalyzed controlled εCL ROP/PLA transesterification, providing the formation of lLA/εCL copolymers that contain mono-lactate fragments separated by short oligo(εCL) chains. The best results in the synthesis of random lLA/εCL copolymers were obtained during experiments on transesterification of commercially available PLLA, the applicability of 3/BnOH catalyst in the synthesis of random copolymers of εCL with methyl glycolide, ethyl ethylene phosphonate and ethyl ethylene phosphate was also demonstrated.

scholarly journals The effect of magnesium ions on triphosphate hydrolysis

2017 ◽  
Vol 89 (6) ◽  
pp. 715-727 ◽  
Author(s):  
Alexandre Barrozo ◽  
David Blaha-Nelson ◽  
Nicholas H. Williams ◽  
Shina C. L. Kamerlin
Keyword(s):  
Transition State ◽  
Metal Ions ◽  
Density Functional ◽  
Reaction Pathway ◽  
Enzymatic Reaction ◽  
Phosphate Ester ◽  
Mechanistic Pathway ◽  
Phosphate Hydrolysis ◽  
The Impact

AbstractThe role of metal ions in catalyzing phosphate ester hydrolysis has been the subject of much debate, both in terms of whether they change the transition state structure or mechanistic pathway. Understanding the impact of metal ions on these biologically critical reactions is central to improving our understanding of the role of metal ions in the numerous enzymes that facilitate them. In the present study, we have performed density functional theory studies of the mechanisms of methyl triphosphate and acetyl phosphate hydrolysis in aqueous solution to explore the competition between solvent- and substrate-assisted pathways, and examined the impact of Mg2+ on the energetics and transition state geometries. In both cases, we observe a clear preference for a more dissociative solvent-assisted transition state, which is not significantly changed by coordination of Mg2+. The effect of Mg2+ on the transition state geometries for the two pathways is minimal. While our calculations cannot rule out a substrate-assisted pathway as a possible solution for biological phosphate hydrolysis, they demonstrate that a significantly higher energy barrier needs to be overcome in the enzymatic reaction for this to be an energetically viable reaction pathway.

Methanol formation by catalytic hydrogenation of CO2 on a nitrogen doped zinc oxide surface: an evaluative study on the mechanistic pathway by density functional theory

RSC Advances ◽  
2015 ◽  
Vol 5 (74) ◽  
pp. 60524-60533 ◽  
Author(s):  
Ramasamy Shanmugam ◽  
Arunachalam Thamaraichelvan ◽  
Balasubramanian Viswanathan
Keyword(s):  
Density Functional ◽  
Reaction Pathway ◽  
Oxide Surface ◽  
Functional Theory ◽  
Nitrogen Doped ◽  
Evaluative Study ◽  
Mechanistic Pathway ◽  
Computational Evaluation ◽  
Methanol Formation ◽  
Simultaneous Activation

Computational evaluation of reaction pathway for simultaneous activation of CO2 and water on N doped ZnO surface revealed carbamate mediated methanol formation.

scholarly journals Substituição nucleofílica alifática: qual o mecanismo preferencial? Estudo computacional dos efeitos da estrutura do substrato e solvente

2020 ◽  
Author(s):  
Bárbara Pereira Peixoto ◽  
José Walkimar de M. Carneiro ◽  
Rodolfo Goetze Fiorot
Keyword(s):  
Density Functional ◽  
Reaction Pathway ◽  
Computational Method ◽  
Reaction Pathways ◽  
Substitution Reactions ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
High Dielectric ◽  
Energy Reaction ◽  
Bimolecular Mechanism

Nucleophilic aliphatic substitution reactions constitute important steps in the synthesis of substances with biological activity and industrial appeal, beyond to participating in steps in biosynthetic routes of natural products. Unimolecular (SN1) and bimolecular (SN2) pathways can be understood as limiting cases of a mechanistic continuum. In between them, borderline mechanisms are proposed. The preference for one path over another depends on several factors, such as the structure of the substrate, the nucleophile and the solvent used. This plurality is still a topic of discussion and needs further understanding. In this context, the present work aims to rationalize the preferential reaction pathway for nucleophilic aliphatic substitutions, whose substrates do not fit only in the uni- and bimolecular models, by identifying lower energy reaction pathways due to the structural and electronic characteristics. The evaluation was carried out by molecular modeling at the Density Functional Theory (DFT) level, simulating substrates with the nucleofuge (Cl and NH3 + ) connected to secondary carbon atoms, with the computational method M06-2X/aug-cc-pVTZ, previously validated according to geometrical and energetic parameters. Besides, we checked the effect of a polar solvent with high dielectric constant in the reaction pathways. The analyzed substrates demonstrated preference for the bimolecular mechanism and the influence of a solvent in these reactions was evident.

A density functional study on the oxygen reduction reaction mechanism on FeN2-doped graphene

2018 ◽  
Vol 42 (9) ◽  
pp. 6873-6879 ◽  
Author(s):  
Yuewen Yang ◽  
Kai Li ◽  
Yanan Meng ◽  
Ying Wang ◽  
Zhijian Wu
Keyword(s):  
Reaction Mechanism ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Density Functional ◽  
Rational Design ◽  
Reduction Reaction ◽  
Functional Study ◽  
Highly Active ◽  
Doped Graphene ◽  
Commercial Applications

The rational design of heteroatom doped graphene as a highly active and non-noble oxygen reduction reaction (ORR) electrocatalyst is significant for the commercial applications of fuel cells.

scholarly journals Regulating the absorption spectrum of polydopamine

2020 ◽  
Vol 6 (36) ◽  
pp. eabb4696 ◽  
Author(s):  
Yuan Zou ◽  
Xiaofeng Chen ◽  
Peng Yang ◽  
Guijie Liang ◽  
Ye Yang ◽  
...  
Keyword(s):  
Light Absorption ◽  
Density Functional ◽  
Rational Design ◽  
Complex Structure ◽  
Photothermal Effect ◽  
Absorption Property ◽  
Functional Theory ◽  
Solar Desalination ◽  
The Density Functional Theory ◽  
Donor Acceptor

Polydopamine (PDA) has been increasingly exploited as an advanced functional material, and its emergent light absorption property plays a crucial role in determining various utilizations. However, the rational design and efficient regulation of PDA absorption property remain a challenge due to the complex structure within PDA. In this work, we propose a facile method to regulate the light absorption behaviors of PDA by constructing donor-acceptor pairs within the microstructures through the chemical connections between indoledihydroxy/indolequinone and their oligomers with 2,2,6,6-tetramethylpiperidine-1-oxyl moiety. The detailed structural and spectral analysis, as well as the density functional theory simulation, further confirms the existence of donor-acceptor molecular pair structures, which could decrease the energy bandgap and increase the electron delocalization for enhancing light absorption across a broad spectrum. These rationally designed PDA nanoparticles with tunable absorption properties also show improved total photothermal effect and demonstrate excellent performances in solar desalination.

THEORETICAL STUDY OF OH-INITIATED ATMOSPHERIC OXIDATION FOR PROPYL VINYL ETHER

2009 ◽  
Vol 08 (02) ◽  
pp. 261-277 ◽  
Author(s):  
MAOXIA HE ◽  
HUI WANG ◽  
XIAOYAN SUN ◽  
QINGZHU ZHANG ◽  
WENXING WANG
Keyword(s):  
Vinyl Ether ◽  
Density Functional ◽  
Energy Surface ◽  
Theoretical Study ◽  
Reaction Pathway ◽  
Oh Radicals ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Degradation Reaction ◽  
Total Energies

This paper reports a theoretical study on the reaction of propyl vinyl ether (PVE, CH3CH2CH2OCH=CH2) with OH radicals in the presence of O 2 and NO x. The reaction pathway has been studied with the density functional theory (DFT/B3LYP) at the 6-31G* level. The total energies of all geometries are corrected at the MP2/6-311+G** level. The profile of the potential energy surface was constructed. The possible channels involved in the reaction were discussed. The results show that six product pathways are energetically feasible for the degradation of PVE initiated by OH radicals in the atmosphere. The main products for this degradation reaction are propyl formate, formaldehyde, and glycolic acid propyl ester in which propyl formate and formaldehyde are mainly from the OH addition to C5 atom.

scholarly journals Insight into Composition and Intermediate Evolutions of Copper-Based Catalysts during Gas-Phase CO2 Electroreduction to Multicarbon Oxygenates

Catalysts ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1502
Author(s):  
Guihua Li ◽  
Yonghui Zhao ◽  
Jerry Pui Ho Li ◽  
Wei Chen ◽  
Shoujie Li ◽  
...  
Keyword(s):  
Gas Phase ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Superior Performance ◽  
Coupling Mechanism ◽  
Faradaic Efficiency ◽  
Carbon Neutrality ◽  
The Density Functional Theory ◽  
Co2 Electroreduction ◽  
Diffuse Reflectance Infrared

Conversion of CO2 to valuable chemicals driven by renewable electricity via electrocatalytic reduction processes is of great significance for achieving carbon neutrality. Copper-based materials distinguish themselves from other electrocatalysts for their unique capability to produce multicarbon compounds in CO2 electroreduction. However, the intrinsic active composition and C–C coupling mechanism of copper-based catalysts are still ambiguous. This is largely due to the absence of appropriate in situ approaches to monitor the complicated processes of CO2 electroreduction. Here, we adopted operando spectroscopy techniques, including Raman and infrared, to investigate the evolution of compositions and intermediates during gas-phase CO2 electroreduction on Cu foam, Cu2O nanowire and CuO nanowire catalysts. Although all the three copper-based catalysts possessed the activity of electroreducing gas-phase CO2 to multicarbon oxygenates, Cu2O nanowires showed the much superior performance with a 71.9% Faradaic efficiency of acetaldehyde. Operando Raman spectra manifested that the cuprous oxide remained stable during the whole gas-phase CO2 electroreduction, and operando diffuse reflectance infrared Fourier transform spectroscopy (DRFITS) results provide direct evidences of key intermediates and their evolutions for producing multicarbon oxygenates, in consistence with the density functional theory calculations.

scholarly journals Boosting oxygen reduction activity and enhancing stability through structural transformation of layered lithium manganese oxide

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Xuepeng Zhong ◽  
M’hamed Oubla ◽  
Xiao Wang ◽  
Yangyang Huang ◽  
Huiyan Zeng ◽  
...  
Keyword(s):  
Oxygen Reduction ◽  
Density Functional ◽  
Manganese Oxides ◽  
Rational Design ◽  
Reaction Pathway ◽  
Density Functional Theory Calculations ◽  
Cost Effective ◽  
Reduction Reaction ◽  
Proton Exchange ◽  
Type Structure

AbstractStructural degradation in manganese oxides leads to unstable electrocatalytic activity during long-term cycles. Herein, we overcome this obstacle by using proton exchange on well-defined layered Li2MnO3 with an O3-type structure to construct protonated Li2-xHxMnO3-n with a P3-type structure. The protonated catalyst exhibits high oxygen reduction reaction activity and excellent stability compared to previously reported cost-effective Mn-based oxides. Configuration interaction and density functional theory calculations indicate that Li2-xHxMnO3-n has fewer unstable O 2p holes with a Mn3.7+ valence state and a reduced interlayer distance, originating from the replacement of Li by H. The former is responsible for the structural stability, while the latter is responsible for the high transport property favorable for boosting activity. The optimization of both charge states to reduce unstable O 2p holes and crystalline structure to reduce the reaction pathway is an effective strategy for the rational design of electrocatalysts, with a likely extension to a broad variety of layered alkali-containing metal oxides.

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