Kinetics of Hydride Transfer from Metal-Free Hydride Donors to CO2

Selective reduction of CO2 to formate represents an ongoing challenge in photoelectrocatalysis. To provide mechanistic insights, we investigate the kinetics of hydride transfer (HT) from a series of metal-free hydride donors to CO2. The observed dependence of experimental and calculated HT barriers on the thermodynamic driving force was modeled using the Marcus hydride transfer formalism to obtain the insights into the effect of reorganization energies on the reaction kinetics. Our results indicate that, even if the most ideal hydride donor were discovered, the HT to CO2 would exhibit sluggish kinetics (less than 100 turnovers at 0.1 eV driving force), indicating that the conventional HT may not be an appropriate mechanism for Solar conversion of CO2 to formate. We propose that the conventional HT mechanism should not be considered for CO2 reduction catalysis and argue that the orthogonal HT mechanism, previously proposed to address thermodynamic limitations of this reaction, may also lead to lower kinetic barriers for CO2 reduction to formate.

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Reaction Kinetics of Poly-Si Etching in TMAH Solution

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.314.60 ◽

2021 ◽

Vol 314 ◽

pp. 60-65

Author(s):

Taegun Park ◽

Sangwoo Lim

Keyword(s):

Reaction Kinetics ◽

Alkaline Solution ◽

Etching Rate ◽

Tetramethylammonium Hydroxide ◽

Dissolved Gas ◽

Metal Free ◽

Effect Of Water ◽

Detailed Kinetics ◽

Kinetics Of ◽

Tmah Solution

Tetramethylammonium hydroxide (TMAH) is a metal-free strong alkaline solution which can etch poly-Si. The concentration of dissolved gas as well as the concentration of TMAH affects etching rate of poly-Si. The detailed kinetics of poly-Si etching in TMAH solution is investigated in this study. The effect of water and TMAH concentration on the etching kinetics of poly-Si was investigated by using various concentrations of TMAH solution. It is found that H2O in TMAH solution plays an important role in etching poly-Si. Presence of dissolved CO2 and O2 in TMAH solution tends to inhibit etching of poly-Si. The concentration of dissolved CO2 and O2 in TMAH were reduced by Ar bubbling, thereby the poly-Si etching rate increased.

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Thermodynamic driving force effects in the oxygen reduction catalyzed by a metal-free porphyrin

Electrochimica Acta ◽

10.1016/j.electacta.2012.03.129 ◽

2012 ◽

Vol 82 ◽

pp. 457-462 ◽

Cited By ~ 19

Author(s):

Antonín Trojánek ◽

Jan Langmaier ◽

Zdeněk Samec

Keyword(s):

Oxygen Reduction ◽

Driving Force ◽

Metal Free ◽

Thermodynamic Driving Force

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Selective Metathesis Synthesis of MgCr2S4 by Control of Thermodynamic Driving Forces

10.26434/chemrxiv.11324504.v1 ◽

2019 ◽

Cited By ~ 1

Author(s):

akira miura ◽

Hiroaki Ito ◽

Christopher Bartel ◽

Wenhao Sun ◽

Nataly Carolina Rosero-Navarro ◽

...

Keyword(s):

Driving Force ◽

Driving Forces ◽

S Phase ◽

Inorganic Materials ◽

Synthesis Methods ◽

Metathesis Reaction ◽

Reaction Enthalpy ◽

Alternative Synthesis ◽

Thermodynamic Driving Force ◽

Kinetics Of

MgCr2S4 thiospinel is predicted to be a compelling Mg-cathode material, but its preparation via traditional solid-state synthesis methods has proven challenging. Wustrow et al. [Inorg. Chem. 57, 14 (2018)] found that the formation of MgCr2S4 from MgS + Cr2S3 binaries requires weeks of annealing at 800 ℃ with numerous intermediate regrinds. The slow reaction kinetics of MgS + Cr2S3 --> MgCr2S4 can be attributed to a miniscule thermodynamic driving force of ΔH = –2 kJ/mol. Here, we demonstrate that the double ion-exchange metathesis reaction, MgCl2 + 2 NaCrS2 --> MgCr2S4 + 2 NaCl, has a reaction enthalpy of ΔH = –47 kJ/mol, which is thermodynamically driven by the large exothermicity of NaCl formation. Using this metathesis reaction, we successfully synthesized MgCr2S4 nanoparticles (< 200 nm) from MgCl2 and NaCrS2 precursors in a KCl flux at 500 °C in only 30 minutes. NaCl and other metathesis byproducts are then easily washed away by water. We rationalize the selectivity of MgCr2S4 in the metathesis reaction from the topology of the DFT-calculated pseudo-ternary MgCl2-CrCl3-Na2S phase diagram. Our work helps to establish metathesis reactions as a powerful alternative synthesis route to inorganic materials that have otherwise small reaction energies from conventional precursors.

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Selective Metathesis Synthesis of MgCr2S4 by Control of Thermodynamic Driving Forces

10.26434/chemrxiv.11324504 ◽

2019 ◽

Author(s):

akira miura ◽

Hiroaki Ito ◽

Christopher Bartel ◽

Wenhao Sun ◽

Nataly Carolina Rosero-Navarro ◽

...

Keyword(s):

Driving Force ◽

Driving Forces ◽

S Phase ◽

Inorganic Materials ◽

Synthesis Methods ◽

Metathesis Reaction ◽

Reaction Enthalpy ◽

Alternative Synthesis ◽

Thermodynamic Driving Force ◽

Kinetics Of

MgCr2S4 thiospinel is predicted to be a compelling Mg-cathode material, but its preparation via traditional solid-state synthesis methods has proven challenging. Wustrow et al. [Inorg. Chem. 57, 14 (2018)] found that the formation of MgCr2S4 from MgS + Cr2S3 binaries requires weeks of annealing at 800 ℃ with numerous intermediate regrinds. The slow reaction kinetics of MgS + Cr2S3 --> MgCr2S4 can be attributed to a miniscule thermodynamic driving force of ΔH = –2 kJ/mol. Here, we demonstrate that the double ion-exchange metathesis reaction, MgCl2 + 2 NaCrS2 --> MgCr2S4 + 2 NaCl, has a reaction enthalpy of ΔH = –47 kJ/mol, which is thermodynamically driven by the large exothermicity of NaCl formation. Using this metathesis reaction, we successfully synthesized MgCr2S4 nanoparticles (< 200 nm) from MgCl2 and NaCrS2 precursors in a KCl flux at 500 °C in only 30 minutes. NaCl and other metathesis byproducts are then easily washed away by water. We rationalize the selectivity of MgCr2S4 in the metathesis reaction from the topology of the DFT-calculated pseudo-ternary MgCl2-CrCl3-Na2S phase diagram. Our work helps to establish metathesis reactions as a powerful alternative synthesis route to inorganic materials that have otherwise small reaction energies from conventional precursors.

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Kinetics of Hydride Transfer from Catalytic Metal-Free Hydride Donors to CO2

The Journal of Physical Chemistry Letters ◽

10.1021/acs.jpclett.0c03662 ◽

2021 ◽

Vol 12 (9) ◽

pp. 2306-2311

Author(s):

Ravindra B. Weerasooriya ◽

Jonathan L. Gesiorski ◽

Abdulaziz Alherz ◽

Stefan Ilic ◽

George N. Hargenrader ◽

...

Keyword(s):

Hydride Transfer ◽

Metal Free ◽

Catalytic Metal ◽

Kinetics Of

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Impact Of Synthesis Route on the Water Oxidation Kinetics of Hematite Photoanodes

10.26434/chemrxiv.12505742.v1 ◽

2020 ◽

Author(s):

Camilo A. Mesa ◽

Ludmilla Steier ◽

Benjamin Moss ◽

Laia Francàs ◽

James E. Thorne ◽

...

Keyword(s):

Oxygen Vacancy ◽

Reaction Kinetics ◽

Water Oxidation ◽

Oxidation Kinetics ◽

Oxidation Reaction ◽

Charge Accumulation ◽

Optical Signals ◽

Current Voltage ◽

Voltage Performance ◽

Kinetics Of

Operando spectroelectrochemical analysis is used to determine the water oxidation reaction kinetics for hematite photoanodes prepared using four different synthetic procedures. Whilst these photoanodes exhibit very different current / voltage performance, their underlying water oxidation kinetics are found to be almost invariant. Lower photoanode performance was found to correlate with the observation of optical signals indicative of charge accumulation in mid-gap oxygen vacancy states, indicating these states do not contribute directly to water oxidation.

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Metal-Free Photoredox-Catalyzed C–H/C–H Coupling of Arenes Enabled by Interrupted Pummerer Activation

10.26434/chemrxiv.9158564 ◽

2019 ◽

Author(s):

Miles Aukland ◽

Mindaugas Šiaučiulis ◽

Adam West ◽

Gregory Perry ◽

David Procter

Keyword(s):

Natural Product ◽

Selective Reduction ◽

Cross Coupling ◽

One Pot ◽

Complex Molecules ◽

Pummerer Reaction ◽

Metal Free ◽

Bond Forming ◽

Coupling Partner ◽

Bioactive Natural Product

Aryl–aryl cross-coupling constitutes one of the most widely used procedures for the synthesis of high-value materials, ranging from pharmaceuticals to organic electronics and conducting polymers. The assembly of (hetero)biaryl scaffolds generally requires multiple steps; coupling partners must be functionalized before the key bond-forming event is considered. Thus, the development of selective C–H arylation processes in arenes, that side-step the need for prefunctionalized partners, is crucial for streamlining the construction of these key architectures. Here we report an expedient, one-pot assembly of (hetero)biaryl motifs using photocatalysis and two non-prefunctionalized arene partners. The approach is underpinned by the activation of a C–H bond in an arene coupling partner using the interrupted Pummerer reaction. A unique pairing of the organic photoredox catalyst and the intermediate dibenzothiophenium salts enables highly selective reduction in the presence of sensitive functionalities. The utility of the metal-free, one-pot strategy is exemplified by the synthesis of a bioactive natural product and the modification of complex molecules of societal importance.

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