Cato A. R. Pappijn, Ruben Van de Vijver, Marie-Françoise Reyniers, Maarten K. Sabbe, Guy B. Marin, Kevin M. Van Geem
First-principles based kinetic modeling is essential to gain insight into the governing chemistry of nitrogen-containing compounds over a wide range of technologically important processes, e.g. pyrolysis, oxidation and combustion. It also enables the development of predictive, fundamental models key to improving understanding of the influence of nitrogen-containing compounds present as impurities or process additives, considering safety, operability and quality of the product streams. A prerequisite for the generation of detailed fundamental kinetic models is the availability of accurate thermodynamic properties. To address the scarcity of thermodynamic properties for nitrogen-containing compounds, a consistent set of 91 group additive values and three non-nearest-neighbor interactions has been determined from a dataset of CBS-QB3 calculations for 300 species, including 104 radicals. This dataset contains a wide range of nitrogen-containing functionalities, i.e. imine, nitrile, nitro, nitroso, nitrite, nitrate and azo functional groups. The group additivity model enables the approximation of the standard enthalpy of formation and standard entropy at 298 K as well as the standard heat capacities over a large temperature range, i.e. 300–1500 K. For a test set of 27 nitrogen-containing compounds, the group additivity model succeeds in approximating the ab initio calculated values for the standard enthalpy of formation with a MAD of 2.3 kJ mol−1. The MAD for the standard entropy and heat capacity is lower than 4 and 2 J mol−1 K−1, respectively. For a test set of 11 nitrogen-containing compounds, the MAD between experimental and group additivity approximated values for the standard enthalpy of formation amounts to 2.8 kJ mol−1.
{"title":"Modeling the thermochemistry of nitrogen-containing compounds via group additivity","authors":"Cato A. R. Pappijn, Ruben Van de Vijver, Marie-Françoise Reyniers, Maarten K. Sabbe, Guy B. Marin, Kevin M. Van Geem","doi":"10.1039/d4cp00727a","DOIUrl":"https://doi.org/10.1039/d4cp00727a","url":null,"abstract":"First-principles based kinetic modeling is essential to gain insight into the governing chemistry of nitrogen-containing compounds over a wide range of technologically important processes, <em>e.g.</em> pyrolysis, oxidation and combustion. It also enables the development of predictive, fundamental models key to improving understanding of the influence of nitrogen-containing compounds present as impurities or process additives, considering safety, operability and quality of the product streams. A prerequisite for the generation of detailed fundamental kinetic models is the availability of accurate thermodynamic properties. To address the scarcity of thermodynamic properties for nitrogen-containing compounds, a consistent set of 91 group additive values and three non-nearest-neighbor interactions has been determined from a dataset of CBS-QB3 calculations for 300 species, including 104 radicals. This dataset contains a wide range of nitrogen-containing functionalities, <em>i.e.</em> imine, nitrile, nitro, nitroso, nitrite, nitrate and azo functional groups. The group additivity model enables the approximation of the standard enthalpy of formation and standard entropy at 298 K as well as the standard heat capacities over a large temperature range, <em>i.e.</em> 300–1500 K. For a test set of 27 nitrogen-containing compounds, the group additivity model succeeds in approximating the <em>ab initio</em> calculated values for the standard enthalpy of formation with a MAD of 2.3 kJ mol<small><sup>−1</sup></small>. The MAD for the standard entropy and heat capacity is lower than 4 and 2 J mol<small><sup>−1</sup></small> K<small><sup>−1</sup></small>, respectively. For a test set of 11 nitrogen-containing compounds, the MAD between experimental and group additivity approximated values for the standard enthalpy of formation amounts to 2.8 kJ mol<small><sup>−1</sup></small>.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141489350","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Single-atom catalysts (SACs) play a vital role in the hydrogen evolution reaction (HER) owing to the highly desirable atom efficiency and the minimal amount of precious metals. Herein, we use TiO2 nanosheets to anchor stable atomically dispersed Iridium (Ir) to act as a catalyst (Ir@TiO2) for the HER. The atomic dispersion of Ir on TiO2 substrate is confirmed by Aberration-corrected scanning transmission electron microscopy and are anchored by numerous surface functional groups on abundant exposed basal planes in TiO2. In acidic media, the performance of the Ir@TiO2 catalyst (1.35 wt% Ir) in terms of a low overpotential (41 mV at 10 mA cm−2), a small Tafel slope of 42 mV/dec, and a decent durability for the 1000th cycles of HER polarization curve has only 1 mV shift, which are comparable with that of a commercial Pt/C catalyst with 20 wt% Pt. The work paves a way to design Ir atomically anchored catalysts with low cost and high activity.
{"title":"Iridium single-atom anchored on TiO2 support as an efficient catalyst for the hydrogen evolution reaction","authors":"Wen xuan Li, Dashu Yin, Peng Li, Xinhua Zhao, shengcai hao","doi":"10.1039/d4cp01878h","DOIUrl":"https://doi.org/10.1039/d4cp01878h","url":null,"abstract":"Single-atom catalysts (SACs) play a vital role in the hydrogen evolution reaction (HER) owing to the highly desirable atom efficiency and the minimal amount of precious metals. Herein, we use TiO2 nanosheets to anchor stable atomically dispersed Iridium (Ir) to act as a catalyst (Ir@TiO2) for the HER. The atomic dispersion of Ir on TiO2 substrate is confirmed by Aberration-corrected scanning transmission electron microscopy and are anchored by numerous surface functional groups on abundant exposed basal planes in TiO2. In acidic media, the performance of the Ir@TiO2 catalyst (1.35 wt% Ir) in terms of a low overpotential (41 mV at 10 mA cm−2), a small Tafel slope of 42 mV/dec, and a decent durability for the 1000th cycles of HER polarization curve has only 1 mV shift, which are comparable with that of a commercial Pt/C catalyst with 20 wt% Pt. The work paves a way to design Ir atomically anchored catalysts with low cost and high activity.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141475258","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Nguyen Ca, Nguyen Thi Hien, Vu Xuan Quang, Nguyen Luyen, N. T. Kien, Nguyen Thi Khanh Van, Nguyen Thuy, Phan Van Do
NaGdF4:Dy3+ nanocrystals (NCs) have been synthesized by precipitation technique. The structural characteristics and morphology of the materials were analyzed via the measurements of X-ray diffractometer patterns and scanning electron microscope images, respectively. The photoluminescence excitation spectra, emission spectra and decay curves of all samples were recorded at room temperature. The color feature of the Dy3+ luminescence was estimated by CIE chromaticity coordinates and the correlated color temperature. The radiative properties of the Dy3+:4F9/2 level in material were analyzed within the framework of JO theory. In NaGdF4:Dy3+ NCs, the energy transfer from Gd3+ to Dy3+ causes the enhancement for the luminescence of the Dy3+ ions. The rate of the processes taking part in the depopulation of the Gd3+ was estimated. The energy transfer between Dy3+ ions leads to the luminescence quenching of NaGdF4:Dy3+. In this process, the dipole-dipole interaction, which is found by using the Inokuti-Hirayama model, is the dominant mechanism. The characteristic parameters of the energy transfer processes between Dy3+ ions have also been calculated in detail.
{"title":"NaGdF4:Dy3+ nanocrystals: new insights on optical properties and energy transfer processes","authors":"Nguyen Ca, Nguyen Thi Hien, Vu Xuan Quang, Nguyen Luyen, N. T. Kien, Nguyen Thi Khanh Van, Nguyen Thuy, Phan Van Do","doi":"10.1039/d4cp01334d","DOIUrl":"https://doi.org/10.1039/d4cp01334d","url":null,"abstract":"NaGdF4:Dy3+ nanocrystals (NCs) have been synthesized by precipitation technique. The structural characteristics and morphology of the materials were analyzed via the measurements of X-ray diffractometer patterns and scanning electron microscope images, respectively. The photoluminescence excitation spectra, emission spectra and decay curves of all samples were recorded at room temperature. The color feature of the Dy3+ luminescence was estimated by CIE chromaticity coordinates and the correlated color temperature. The radiative properties of the Dy3+:4F9/2 level in material were analyzed within the framework of JO theory. In NaGdF4:Dy3+ NCs, the energy transfer from Gd3+ to Dy3+ causes the enhancement for the luminescence of the Dy3+ ions. The rate of the processes taking part in the depopulation of the Gd3+ was estimated. The energy transfer between Dy3+ ions leads to the luminescence quenching of NaGdF4:Dy3+. In this process, the dipole-dipole interaction, which is found by using the Inokuti-Hirayama model, is the dominant mechanism. The characteristic parameters of the energy transfer processes between Dy3+ ions have also been calculated in detail.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141475125","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Paweł Andrzej Wieczorkiewicz, Tadeusz M Krygowski, Halina Szatylowicz
Five-membered N-heterocycles are principal constituents of many compounds of vital importance in various fields of chemistry, biochemistry or pharmaceutical chemistry. For this reason, unequivocal identification of structural factors determining electron donating/withdrawing properties of specific groups attached to the heterocyclic moiety becomes an utmost need together with elucidation of the substitution-induced changes in cyclic and noncyclic electron delocalization. Thus, quantum-chemical calculations were performed for pyrrole, imidazole, pyrazole, 1,2,3- and 1,2,4-triazole, and their C-substituted mono-derivatives (X = NO2, CN, Br, Cl, F, SH, OH, NH2). The obtained dataset contains information on substituent properties (cSAR – charge of the substituent active region method), delocalization (EDDB – electron density of delocalized bonds) and geometry. It follows that the positions of endocyclic N atoms relative to the substituent influence in the most profound manner its properties. N atoms in ortho positions significantly boost the electron-donation and weaken the electron-withdrawal by induction. Another factor is the resonance charge transfer from the substituents to N atoms, and then inductive interactions with further (non-ortho) N atoms. While substituent constants correctly describe the changes of their properties (including those attached to the heterocycles), a testimony to Hammett's genius, quantum chemical models must be used to quantify the exact properties. In most heterocycles, electron-donating substituents hinder the cyclic delocalization, except 4-pyrazole. The applied recent EDDB method allows to study this phenomenon in detail. It follows that changes in aromaticity originate from the π-electronic effects of substituents on the ring bonds, changing the localization and delocalization of particular bonds in a correlated manner.
五元 N-杂环是许多化合物的主要成分，在化学、生物化学或药物化学的各个领域都具有重要意义。因此，明确鉴定决定杂环分子上特定基团电子捐赠/抽取特性的结构因素，以及阐明取代引起的环状和非环状电子脱定位变化，已成为当务之急。因此，我们对吡咯、咪唑、吡唑、1,2,3- 和 1,2,4-三唑及其 C 取代单衍生物（X = NO2、CN、Br、Cl、F、SH、OH、NH2）进行了量子化学计算。所获得的数据集包含有关取代基性质（cSAR--取代基活性区电荷法）、脱局（EDB--脱局键电子密度）和几何形状的信息。由此可见，内环 N 原子相对于取代基的位置对其性质影响最大。位于正交位置的 N 原子通过诱导作用显著增强了电子捐赠作用，削弱了电子撤回作用。另一个因素是从取代基到 N 原子的共振电荷转移，然后与更多的（非正交）N 原子发生感应作用。虽然取代基常数能正确描述其性质（包括杂环上的取代基常数）的变化，证明了哈米特的天才，但量子化学模型必须用来量化确切的性质。在大多数杂环中，除 4-吡唑外，电子捐赠取代基都会阻碍环向脱钙化。最近应用的 EDDB 方法可以详细研究这一现象。由此可见，芳香性的变化源于取代基对环键的π电子效应，它以相关的方式改变了特定键的定位和脱定位。
{"title":"Substituent effects and electron delocalization in five-membered N-heterocycles","authors":"Paweł Andrzej Wieczorkiewicz, Tadeusz M Krygowski, Halina Szatylowicz","doi":"10.1039/d4cp01709a","DOIUrl":"https://doi.org/10.1039/d4cp01709a","url":null,"abstract":"Five-membered N-heterocycles are principal constituents of many compounds of vital importance in various fields of chemistry, biochemistry or pharmaceutical chemistry. For this reason, unequivocal identification of structural factors determining electron donating/withdrawing properties of specific groups attached to the heterocyclic moiety becomes an utmost need together with elucidation of the substitution-induced changes in cyclic and noncyclic electron delocalization. Thus, quantum-chemical calculations were performed for pyrrole, imidazole, pyrazole, 1,2,3- and 1,2,4-triazole, and their C-substituted mono-derivatives (X = NO<small><sub>2</sub></small>, CN, Br, Cl, F, SH, OH, NH<small><sub>2</sub></small>). The obtained dataset contains information on substituent properties (cSAR – charge of the substituent active region method), delocalization (EDDB – electron density of delocalized bonds) and geometry. It follows that the positions of endocyclic N atoms relative to the substituent influence in the most profound manner its properties. N atoms in ortho positions significantly boost the electron-donation and weaken the electron-withdrawal by induction. Another factor is the resonance charge transfer from the substituents to N atoms, and then inductive interactions with further (non-ortho) N atoms. While substituent constants correctly describe the changes of their properties (including those attached to the heterocycles), a testimony to Hammett's genius, quantum chemical models must be used to quantify the exact properties. In most heterocycles, electron-donating substituents hinder the cyclic delocalization, except 4-pyrazole. The applied recent EDDB method allows to study this phenomenon in detail. It follows that changes in aromaticity originate from the π-electronic effects of substituents on the ring bonds, changing the localization and delocalization of particular bonds in a correlated manner.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141475266","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Eleonora Ascrizzi, Jacek Goniakowski, Jijin Yang, Stefano Agnoli, Anna Maria Ferrari
Metal oxides are a class of material of particular interest for catalytic purposes. Among them the iron oxide as a monolayer supported on gold, FeO/Au, stands out for its capability to promote the CO oxidation and the dissociation of O2 and H2. In this work, we use density functional theory calculations to characterize interfacial properties of this heterostructure. We consider a FeO/Au realistic model system, managing to reproduce the moiré pattern experimentally found. Specific features of the high-symmetry domains of the moiré are identified, providing a robust ground for establishing a structure-activity relationship and guessing how the surface would behave in catalytic conditions. We also describe a strategy to model smaller systems representative of each high-symmetry domains of the moiré, which will be useful in the future to model catalytic reaction mechanisms.
金属氧化物是一类具有特殊催化作用的材料。其中，以金为支撑的单层氧化铁（FeO/Au）因其促进 CO 氧化以及 O2 和 H2 解离的能力而脱颖而出。在这项工作中，我们利用密度泛函理论计算来描述这种异质结构的界面特性。我们考虑了一个铁氧体/金的现实模型系统，成功地再现了实验中发现的摩尔纹。我们确定了摩尔纹高对称域的具体特征，为建立结构-活性关系和猜测表面在催化条件下的行为方式提供了坚实的基础。我们还介绍了模拟摩尔纹每个高对称性结构域的较小系统的策略，这将有助于将来模拟催化反应机制。
{"title":"DFT study of the Moiré Pattern of FeO monolayer on Au(111)","authors":"Eleonora Ascrizzi, Jacek Goniakowski, Jijin Yang, Stefano Agnoli, Anna Maria Ferrari","doi":"10.1039/d4cp01546k","DOIUrl":"https://doi.org/10.1039/d4cp01546k","url":null,"abstract":"Metal oxides are a class of material of particular interest for catalytic purposes. Among them the iron oxide as a monolayer supported on gold, FeO/Au, stands out for its capability to promote the CO oxidation and the dissociation of O2 and H2. In this work, we use density functional theory calculations to characterize interfacial properties of this heterostructure. We consider a FeO/Au realistic model system, managing to reproduce the moiré pattern experimentally found. Specific features of the high-symmetry domains of the moiré are identified, providing a robust ground for establishing a structure-activity relationship and guessing how the surface would behave in catalytic conditions. We also describe a strategy to model smaller systems representative of each high-symmetry domains of the moiré, which will be useful in the future to model catalytic reaction mechanisms.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141475213","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ye Mao, Hanghang Chen, Zijiang Yang, bayaer buren, Maodu Chen
Controlling the relative arrangement of colliding molecules is crucial to determine the dynamical outcomes of chemical processes and has emerged as a hot spot of experimental research. Here, the quantum scattering calculations are conducted to investigate the stereodynamic control in collisions between Be+(2P) and H2 (v = 0, j = 2), which undergo nonadiabatic transitions to the electronic ground state. The stereodynamic preparation is achieved by controlling the initial alignment of the H2 bond axis relative to the scattering frame. For product BeH+ in the reactive process, the differential cross sections (DCSs) are significantly enhanced in the forward and sideways hemispheres when the alignment angle β is 60°. For the product H2 in the quenching channel, the β = 0° preparation can result in a more than one-fold increase in the DCS at the polar scattering angle of 0°. Furthermore, varying alignment angle β also have noteworthy effects on the rotational-state distributions of BeH+ products. Specifically, β = 0° preparation can induce the disappearance of the bimodal distribution of rotational states at a collision energy of 0.05 eV.
{"title":"Stereodynamic control of nonadiabatic progresses in low-energy Be+(2P) + H2 (v = 0, j = 2) collisions","authors":"Ye Mao, Hanghang Chen, Zijiang Yang, bayaer buren, Maodu Chen","doi":"10.1039/d4cp01996b","DOIUrl":"https://doi.org/10.1039/d4cp01996b","url":null,"abstract":"Controlling the relative arrangement of colliding molecules is crucial to determine the dynamical outcomes of chemical processes and has emerged as a hot spot of experimental research. Here, the quantum scattering calculations are conducted to investigate the stereodynamic control in collisions between Be<small><sup>+</sup></small>(<small><sup>2</sup></small>P) and H<small><sub>2</sub></small> (<em>v</em> = 0, <em>j</em> = 2), which undergo nonadiabatic transitions to the electronic ground state. The stereodynamic preparation is achieved by controlling the initial alignment of the H<small><sub>2</sub></small> bond axis relative to the scattering frame. For product BeH<small><sup>+</sup></small> in the reactive process, the differential cross sections (DCSs) are significantly enhanced in the forward and sideways hemispheres when the alignment angle <em>β</em> is 60°. For the product H<small><sub>2</sub></small> in the quenching channel, the <em>β</em> = 0° preparation can result in a more than one-fold increase in the DCS at the polar scattering angle of 0°. Furthermore, varying alignment angle <em>β</em> also have noteworthy effects on the rotational-state distributions of BeH<small><sup>+</sup></small> products. Specifically, <em>β</em> = 0° preparation can induce the disappearance of the bimodal distribution of rotational states at a collision energy of 0.05 eV.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141475127","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Gabriela Horwitz, Vera Kunz, Sam Niblett, Clare P. Grey
A theoretical framework to explain how interactions between redox mediators (RMs) and electrolyte components impact electron transfer kinetics, thermodynamics, and catalytic efficiency is presented. Specifically focusing on ionic association, 2,5-di-tert-butyl-1,4-benzoquinone (DBBQ) is used as a case study to demonstrate these effects. Our analytical equations reveal how the observed redox couple potential and electron transfer rate constants evolve with Li+ concentration, resulting from different redox activity mechanisms. Experimental validation by cyclic voltammetry measurements shows that DBBQ binds to three Li+ ions in its reduced state and one Li+ ion in its neutral form, leading to a maximum in the electron transfer kinetic constant at around 0.25M. The framework is extended to account for other phenomena that can play an important role in the redox mechanism of RMs: the effect of Li+ ion solvation and its association with the supporting salt counteranion on the redox processes is considered, and the role of “free Li+” concentration in determining the electrochemical behaviour is emphasized. The impact of Li+ concentration on oxygen reduction reaction (ORR) catalysis was then explored, again using DBBQ and modelling the effects of the Li+ concentration on electron transfer and catalytic kinetics. We show that even though the observed catalytic rate constant increases with Li+ concentration, the overall catalysis can become more sluggish depending on the electron transfer pathway. Cyclic voltammograms are presented as illustrative examples. The strength of the proposed theoretical framework lies in its adaptability to a wider range of redox mediators and their interactions. By understanding these effects, we open up new avenues to tune electron transfer and catalytic kinetics and thus improve the energy efficiency and rate capability of Li-O2 batteries. Although exact results may not transfer to different solvents, the predictions of our model will provide a starting point for future studies of similar systems, and the model itself is easily extensible to new chemistries.
{"title":"The Effect of Ionic Association on the Electrochemistry of Redox Mediators for Li-O2 Batteries: Developing a Theoretical Framework","authors":"Gabriela Horwitz, Vera Kunz, Sam Niblett, Clare P. Grey","doi":"10.1039/d4cp01488j","DOIUrl":"https://doi.org/10.1039/d4cp01488j","url":null,"abstract":"A theoretical framework to explain how interactions between redox mediators (RMs) and electrolyte components impact electron transfer kinetics, thermodynamics, and catalytic efficiency is presented. Specifically focusing on ionic association, 2,5-di-tert-butyl-1,4-benzoquinone (DBBQ) is used as a case study to demonstrate these effects. Our analytical equations reveal how the observed redox couple potential and electron transfer rate constants evolve with Li<small><sup>+</sup></small> concentration, resulting from different redox activity mechanisms. Experimental validation by cyclic voltammetry measurements shows that DBBQ binds to three Li<small><sup>+</sup></small> ions in its reduced state and one Li<small><sup>+</sup></small> ion in its neutral form, leading to a maximum in the electron transfer kinetic constant at around 0.25M. The framework is extended to account for other phenomena that can play an important role in the redox mechanism of RMs: the effect of Li<small><sup>+</sup></small> ion solvation and its association with the supporting salt counteranion on the redox processes is considered, and the role of “free Li<small><sup>+</sup></small>” concentration in determining the electrochemical behaviour is emphasized. The impact of Li<small><sup>+</sup></small> concentration on oxygen reduction reaction (ORR) catalysis was then explored, again using DBBQ and modelling the effects of the Li<small><sup>+</sup></small> concentration on electron transfer and catalytic kinetics. We show that even though the observed catalytic rate constant increases with Li<small><sup>+</sup></small> concentration, the overall catalysis can become more sluggish depending on the electron transfer pathway. Cyclic voltammograms are presented as illustrative examples. The strength of the proposed theoretical framework lies in its adaptability to a wider range of redox mediators and their interactions. By understanding these effects, we open up new avenues to tune electron transfer and catalytic kinetics and thus improve the energy efficiency and rate capability of Li-O<small><sub>2</sub></small> batteries. Although exact results may not transfer to different solvents, the predictions of our model will provide a starting point for future studies of similar systems, and the model itself is easily extensible to new chemistries.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141475278","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The mechanism of the proton transfer in the reaction between CO2 and 3-amino-1-propanol with and without water molecules is investigated quantum-mechanically. The studies revealed that water molecules and the hydroxy group of 3-amino-1-propanol explicitly participate in the proton transfer, forming the carbamic acid. It is found that water has a high impact on the energetics of CO2 absorption by reducing the barrier for proton transfer. Apart from the water molecules, the hydroxy group of alkanolamine significantly affects the energetics of the reaction. Five cases involving two, three, and four protons are discussed, and it is found that the proton transfer occurs in a concerted manner that depends on the initial configuration of the reaction complex. The present study unequivocally confirms the role of water molecules in the CO2 capturing via amine-based solvents.
{"title":"Water-assisted absorption of CO2 by 3-Amino-1-propanol: A mechanistic insight","authors":"Shivam Rawat, C. N. Ramachandran","doi":"10.1039/d4cp02207f","DOIUrl":"https://doi.org/10.1039/d4cp02207f","url":null,"abstract":"The mechanism of the proton transfer in the reaction between CO2 and 3-amino-1-propanol with and without water molecules is investigated quantum-mechanically. The studies revealed that water molecules and the hydroxy group of 3-amino-1-propanol explicitly participate in the proton transfer, forming the carbamic acid. It is found that water has a high impact on the energetics of CO2 absorption by reducing the barrier for proton transfer. Apart from the water molecules, the hydroxy group of alkanolamine significantly affects the energetics of the reaction. Five cases involving two, three, and four protons are discussed, and it is found that the proton transfer occurs in a concerted manner that depends on the initial configuration of the reaction complex. The present study unequivocally confirms the role of water molecules in the CO2 capturing via amine-based solvents.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141475161","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
YUCHI KAO, Yi-Ming Wang, Jyun-Yi Yeh, Shih-Cheng Li, Kevin C. W. Wu, Li-Chiang Lin, Yi-Pei Li
Quantum mechanics/molecular mechanics (QM/MM) simulations offer an efficient way to model reactions occurring in complex environments. This study introduces a specialized set of charge and Lennard-Jones parameters tailored for electrostatically embedded QM/MM calculations, aiming to accurately model both adsorption processes and catalytic reactions in zirconium-based metal-organic frameworks (Zr-MOFs). To validate our approach, we compare adsorption energies derived from QM/MM simulations against experimental results and Monte Carlo simulation outcomes. The developed parameters showcase the ability of QM/MM simulations to represent long-range electrostatic and van der Waals interactions faithfully. This capability is evidenced by the prediction of adsorption energies with a low root mean square error of 1.1 kcal/mol across a wide range of adsorbates. The practical applicability of our QM/MM model is further illustrated through the study of glucose isomerization and epimerization reactions catalyzed by two structurally distinct Zr-MOF catalysts, UiO-66 and MOF-808. Our QM/MM calculations closely align with experimental activation energies. Importantly, the parameter set introduced here is shown to be compatible with the widely used universal force field (UFF). Moreover, we thoroughly explore how the size of the cluster model and the choice of density functional theory (DFT) methodologies influence the simulation outcomes. This work provides an accurate and computationally efficient framework for modeling complex catalytic reactions within Zr-MOFs, contributing valuable insights into their mechanistic behaviors and facilitating further advancements in this dynamic area of research.
{"title":"Tailoring Parameters for QM/MM Simulations: Accurate Modeling of Adsorption and Catalysis in Zirconium-Based Metal-Organic Frameworks","authors":"YUCHI KAO, Yi-Ming Wang, Jyun-Yi Yeh, Shih-Cheng Li, Kevin C. W. Wu, Li-Chiang Lin, Yi-Pei Li","doi":"10.1039/d4cp00681j","DOIUrl":"https://doi.org/10.1039/d4cp00681j","url":null,"abstract":"Quantum mechanics/molecular mechanics (QM/MM) simulations offer an efficient way to model reactions occurring in complex environments. This study introduces a specialized set of charge and Lennard-Jones parameters tailored for electrostatically embedded QM/MM calculations, aiming to accurately model both adsorption processes and catalytic reactions in zirconium-based metal-organic frameworks (Zr-MOFs). To validate our approach, we compare adsorption energies derived from QM/MM simulations against experimental results and Monte Carlo simulation outcomes. The developed parameters showcase the ability of QM/MM simulations to represent long-range electrostatic and van der Waals interactions faithfully. This capability is evidenced by the prediction of adsorption energies with a low root mean square error of 1.1 kcal/mol across a wide range of adsorbates. The practical applicability of our QM/MM model is further illustrated through the study of glucose isomerization and epimerization reactions catalyzed by two structurally distinct Zr-MOF catalysts, UiO-66 and MOF-808. Our QM/MM calculations closely align with experimental activation energies. Importantly, the parameter set introduced here is shown to be compatible with the widely used universal force field (UFF). Moreover, we thoroughly explore how the size of the cluster model and the choice of density functional theory (DFT) methodologies influence the simulation outcomes. This work provides an accurate and computationally efficient framework for modeling complex catalytic reactions within Zr-MOFs, contributing valuable insights into their mechanistic behaviors and facilitating further advancements in this dynamic area of research.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141475259","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jan RR Verlet, Connor Jack Clarke, Eleanor Michi Burrow
The unoccupied π* orbitals of the nucleobases are considered to play important roles in low-energy electron attachment to DNA, inducing damage. While the lowest anionic state is unbound in all neutral nucleobases, it remains unclear even for the simplest nucleobase, uracil (U), whether its valence anion (U–) is adiabatically bound, which has important implications on the efficacy of damage processes. Using anion photoelectron spectroscopy, we demonstrate that the valence electron affinity (EAV) of U can be accurately measured within weakly solvating clusters, U–(Ar)n and U–(N2)n. Through extrapolation to the isolated U limit, we show that EAV = −2 ± 18 meV. We discuss these findings in the context of electron attachment to U and its reorganization energy, and more generally establish guidance for the determination of molecular electron affinities from photoelectron spectroscopy of anion clusters.
核碱基未占据的π*轨道被认为在低能电子附着到DNA上并导致损伤方面发挥着重要作用。虽然所有中性核碱基的最低阴离子态都是非结合态，但即使是最简单的核碱基尿嘧啶（U），其价阴离子（U-）是否是绝热结合态仍不清楚，而这对损伤过程的有效性具有重要影响。利用阴离子光电子能谱，我们证明了 U 的价电子亲和力（EAV）可以在弱溶解簇 U-(Ar)n 和 U-(N2)n 中精确测量。通过外推至孤立的 U 极限，我们发现 EAV = -2 ± 18 meV。我们从电子附着到 U 及其重组能的角度讨论了这些发现，并为从阴离子团簇的光电子能谱测定分子电子亲和力提供了更广泛的指导。
{"title":"The valence electron affinity of uracil determined by anion cluster photoelectron spectroscopy","authors":"Jan RR Verlet, Connor Jack Clarke, Eleanor Michi Burrow","doi":"10.1039/d4cp02146k","DOIUrl":"https://doi.org/10.1039/d4cp02146k","url":null,"abstract":"The unoccupied π* orbitals of the nucleobases are considered to play important roles in low-energy electron attachment to DNA, inducing damage. While the lowest anionic state is unbound in all neutral nucleobases, it remains unclear even for the simplest nucleobase, uracil (U), whether its valence anion (U<small><sup>–</sup></small>) is adiabatically bound, which has important implications on the efficacy of damage processes. Using anion photoelectron spectroscopy, we demonstrate that the valence electron affinity (EAV) of U can be accurately measured within weakly solvating clusters, U<small><sup>–</sup></small>(Ar)<small><sub><em>n</em></sub></small> and U<small><sup>–</sup></small>(N<small><sub>2</sub></small>)<small><sub><em>n</em></sub></small>. Through extrapolation to the isolated U limit, we show that <em>EA</em><small><sub>V</sub></small> = −2 ± 18 meV. We discuss these findings in the context of electron attachment to U and its reorganization energy, and more generally establish guidance for the determination of molecular electron affinities from photoelectron spectroscopy of anion clusters.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141489166","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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