Enthalpy Change Of Reaction Research Articles

Understanding the thermodynamic effects of chemically reactive working fluids in the Stirling heat pump

Within the realm of sustainable heating technologies, this study examines the performance of a Stirling heat pump employing chemically reactive working fluids in contrast to conventional inert counterparts. Reactive working fluids are energy vectors that enable the conversion of not only thermal but also chemical energy within the heat pump. The investigation spans a wide range of theoretical reactive gaseous mixtures, leveraging the ideal gas mixture thermodynamic model. Each fluid is characterized by an equilibrated chemical reaction, denoted as A2(g)⇄2A(g), and distinguished by a set of reaction coordinates: the standard entropy change of reaction and standard enthalpy change of reaction. The chemical reaction evolution and thermodynamic properties are observed in each transformation, and the overall coefficient of performance (COP) of the system is evaluated and benchmarked against that of comparable inert working fluids. It is observed that the exothermic reaction during isothermal compression significantly increases the thermal energy supplied to the heat sink, as well as the thermal energy density per unit maximum volume, by up to 269 %, compared to an inert gas system. However, for the majority of reactive fluids studied, chemical reactions introduce irreversibility in the internal regenerator due to heat transfer across a finite temperature difference, contrary to the case of inert working fluids, penalizing the COP. Consequently, a reduction of up to 28 % in the COP is observed. Nevertheless, there exists a range of reactive fluids, characterized by reversible heat exchange in the internal regenerator, offering increased thermal energy transfer to the heat sink without compromising the COP.

Reduction of the photogenerated electron transport path by modulating the conduction band region to achieve the highest lignin β–O–4 bond photocleavage efficiency under xenon excitation

Photocracking of lignin β–O–4 bonds is a green approach for the high-value modification of lignin. Graphitic carbon nitride (g-C3N4) that can photocleave the β–O–4 bond is presently the only stable, metal-free photocatalyst owing to the residual metal ions generated due to photocorrosion of metal sulfides. Herein, g-C3N4 with a N–C3 vacancy structure is prepared by etching site–engineering strategy based on the protection of C–N=C structure by chlorine atom. The N–C3 vacancy structure can reduce the transport path of the photogenerated electrons by tuning the conduction band (CB) region to the edge of the photocatalyst, which impedes the critical complexation of the photogenerated electron–hole pairs and enhances the photoelectric conversion efficiency five-fold. Combined with the unique chemisorption capacity (137.82 kJ/mol) of N–C3 vacancies for oxygen, the g-C3N4 photocatalysts with N–C3 vacancy structure can generate 9.6-fold higher superoxide radicals and 13-fold higher lignin β–O–4 bond photocleavage efficiency lignin compared with untreated g-C3N4. Based on the reaction enthalpy changes and free energies investigated through simulations, a route of lignin Cα–Cβ bonds being oxidized and dehydrogenated twice by photogenerated cavities is proposed for the first time. This work reveals the relation between the properties of g-C3N4 and the photocleavage efficiency of lignin β–O–4 bonds.

DMNP as an Effective Cage for Ln3+: A Spectroscopic and Thermodynamic Study.

Dimethoxynitrophenyl-EDTA (DMNP) is a popular calcium cage that is frequently used to investigate the role of Ca2+ in signaling processes in vivo. Lanthanides have been used in Ca2+ biomimetics due to similarities in coordination properties of Ln3+ and Ca2+ that may enable fluorescence and NMR studies of functional and structural properties of Ca2+ binding proteins. In this study, we show that Tb3+, Eu3+, and Nd3+ bind strongly to DMNP in a 1:1 ratio. Isothermal titration calorimetric measurements of Ca2+ displacement by Ln3+ in DMNP provide the equilibrium binding constants for Ln3+DMNP complexation with association constants, K11 = (1.2 ± 0.7) × 1012 M-1 for Eu3+, (2.5 ± 1.7) × 1012 M-1 for Nd3+, and (2.8 ± 0.8) × 1012 M-1 for Tb3+. The kinetics and thermodynamics of Ca2+, Mg2+, and Tb3+ release from DMNP were characterized using photothermal beam deflection (PBD). Ligand release from the DMNP cage was rapid and occurred within 10 μs upon cage photofragmentation and was associated with similar reaction volume and enthalpy changes that can be attributed to the photoreleased ion solvation. In the case of Ca2+DMNP photodissociation at subsaturating Ca2+ concentrations, we observed a slower phase with a lifetime of 300 μs that we attribute to Ca2+ rebinding to unphotolyzed DMNP. These results demonstrate that DMNP can serve as an effective photolabile cage for oxophilic Ln3+ that has similar coordination properties to Ca2+ and Mg2+.

Hydrogen isotope effect on thermodynamic and kinetic properties of Pd based ternary alloys: Pd–Ag-M (M = Au, Zr)

Owing to the importance of hydrogen and its isotopes in energy sector, the present study investigates thermodynamic and kinetic hydrogen isotope effects on desorption reaction of newly synthesized Pd-based ternary alloy-hydrides/deuterides viz., Pd0.89Ag0.05M0.06 (M = Au, Zr)–H/D. Alloys were prepared by arc melting method followed by characterization using PXRD, SEM, TXRF and EDX techniques. The effect of hydrogen isotopes on thermodynamics of H2/D2 desorption reaction was investigated by generating pressure-temperature isotherms (PCIs) at various temperatures using a Sieverts' type volumetric apparatus. The PCT diagram of alloys depicts a single plateau which confirms desorption to be a one-step process. Both alloy systems display a normal isotope effect as indicated by higher plateau pressure for deuterides as compared to hydrides. The enthalpy and entropy changes for the desorption reactions were calculated using Van't Hoff equation. The separation factor derived from PCT data indicates that Pd0.89Ag0.05Au0.06 alloy has a significantly high separation factor as compared to other Pd based alloys reported in the literature. To get more insight into this behavior, non-isothermal kinetic analysis of H2/D2 desorption based on Differential Scanning Calorimeter (DSC) data acquired at four different heating rates was conducted and activation energies of desorption were calculated by invoking Kissinger's equation. The activation energies of alloys were found to be lower than that of palladium which explains the high separation factor of alloys as compared to Pd. The desired combination of higher separation factor and lower activation energy makes Pd0.89Ag0.05Au0.06 alloy a promising material for practical application in the separation of hydrogen isotopes via self-displacement gas chromatography (SDGC).

Study on the Mechanism of Lipid Peroxidation Induced by Carbonate Radicals.

Based on the reported research, hydroxyl radicals can be rapidly transformed into carbonate radicals in the carbonate-bicarbonate buffering system in vivo. Many of the processes considered to be initiated by hydroxyl radicals may be caused by carbonate radicals, which indicates that lipid peroxidation initiated by hydroxyl radicals can also be caused by carbonate radicals. To date, theoretical research on reactions of hydrogen abstraction from and radical addition to polyunsaturated fatty acids (PUFAs) of carbonate radicals has not been carried out systematically. This paper employs (3Z,6Z)-nona-3,6-diene (NDE) as a model for polyunsaturated fatty acids (PUFAs). Density functional theory (DFT) with the CAM-B3LYP method at the 6-311+g(d,p) level was used to calculate the differences in reactivity of carbonate radicals abstracting hydrogen from different positions of NDE and their addition to the double bonds of NDE under lipid solvent conditions with a dielectric constant of 4.0 (CPCM model). Grimme's empirical dispersion correction was taken into account through the D3 scheme. The energy barrier, reaction rate constants, internal energy, enthalpy and Gibbs free energy changes in these reactions were calculated With zero-point vibrational energy (ZPVE) corrections. The results indicated that carbonate radicals initiate lipid peroxidation primarily through hydrogen abstraction from diallyl carbon atoms. The reaction of hydrogen abstraction from diallyl carbon atoms exhibits the highest reaction rate, with a reaction rate constant approximately 43-fold greater than the second-ranked hydrogen abstraction from allyl carbon atoms. This process has the lowest energy barrier, internal energy, enthalpy, and Gibbs free energy changes, indicating that it is also the most spontaneous process.

Numerical simulation study on microdischarge via a unified fluid model

Numerical simulation has become an indispensable tool in the study of gas discharge. However, it is typically used to reveal microscopic properties in a discharge under specific conditions. In this work, a unified fluid model for discharge simulation is introduced in detail. The model includes the continuity equation, the energy conservation equation of the species (electrons and heavy particles), and Poisson’s equation. The model takes into account some processes such as cathode electron emission (secondary electron emission and thermionic emission), reaction enthalpy change, gas heating, and cathode heat conduction. The full current-voltage characteristic (CVC) curve covers a range of discharge regimes, such as the Geiger-Müller discharge regime, Townsend discharge regime, subnormal glow discharge regime, normal glow discharge regime, abnormal glow discharge regime, and arc discharge regime. The obtained CVC curve is consistent with the results in the literature, confirming the validity of the unified fluid model. On this basis, the CVC curves are obtained in a wide pressure range of 50–3000 Torr. Simulation studies are carried out focusing on the discharge characteristics for microgap of 400 µm at pressures of 50 Torr and 500 Torr, respectively. The distributions of typical discharge parameters under different pressure conditions are analyzed by comparison. The results indicate that the electric field in the discharge gap is uniform, and that the space charge effect can be ignored in Townsend discharge regime. The cathode fall region and the quasi-neutral region both appear in glow discharge regime, and the space charge effect is significant. In particular, the electric field reversal occurs in abnormal discharge regime due to the heightened particle density gradient. The electron density reaches about 10<sup>22</sup> m<sup>–3</sup> in arc discharge regime dominated by thermionic emission and thermal ionization, with the current density increasing. The gas temperature peak is 11850 K when the pressure is 500 Torr, and the cathode surface is heated to nearly 4000 K due to heat conduction. The present model can be used to simulate gas discharge across a wide range of condition parameters, promoting and expanding fluid model applications, and assisting in a more comprehensive investigation of discharge parameter properties.

Aminoalkyl organosilicon with dual chemical sites for SO2 absorption and analysis of site-specific absorption entropy and enthalpy

Wet flue gas desulfurization is widely used for its high efficiency, however, the low absorption capacity, high viscosity and poor thermal stability of absorbents remains an open question. Herein, a low viscosity and high thermal stability SO2 absorbent with dual interacting sites was synthesized by introducing phenyl into organic silicon. The thermal stability of 1,5-bis (diethylamino)− 1,1,5,5-tetramethyl-3,3-diphenyltrisiloxane (BADPS) is comparable to ILs, while its viscosity is much lower than that of ILs. For the first time, we use a variant of the pseudo-first-order reaction rate equation obtained the reaction rate constant and the saturation absorption capacity. In addition, the optimal absorption and desorption temperatures were obtained based on an objective function. Mostly importantly, the absorption enthalpy change (ΔH) and entropy change (ΔS) of BADPS absorption reaction show the highest absolute values of SO2 absorbents reported so far. These results indicated that the prepared amine alkyl organosilicon could serve as a promising desulfurizing agent with low-energy consumption.

Preparation and Embedding Characterization of Hydroxypropyl-β-cyclodextrin/Menthyl Acetate Microcapsules with Enhanced Stability.

Hydroxypropyl-β-cyclodextrin (HP-β-CD)/menthyl acetate (MA) microcapsules were developed to overcome the volatile and unstable defects of MA and improve the ease of use and storage. MA microcapsules were prepared via spray drying using HP-β-CD as the wall material. The embedding rate of MA microcapsules was determined through gas chromatography. The embedding characteristics were studied using phase solubility and nuclear magnetic resonance (NMR). The stability was characterized via differential scanning calorimetry (DSC) and the release and retention rates of MA microcapsules at different temperatures. The embedding rate of HP-β-CD /MA microcapsules was 96.3%. The Gibbs free energy change, enthalpy change and entropy change of the embedding reaction between HP-β-CD and MA were all less than zero, indicating that the embedding process was a spontaneous exothermic reaction. NMR spectra showed that MA entered the cavity of HP-β-CD through the large opening end and interacted with the inner wall of the small opening end. DSC and the release and retention rates of MA microcapsules at different temperatures showed that the stability of MA was significantly enhanced after being embedded in HP-β-CD. The HP-β-CD/MA microcapsules are able to significantly improve the stability of MA and reduce the volatilization of MA.

Functioning of a Fluorescein pH-Probe in Aqueous Media: Impact of Temperature and Viscosity.

In this work, we considered the influence of viscogenic agents (glycerol, sucrose) as well as the temperature on the fluorescent characteristics of fluorescein at pH 6.5 in order to describe the acid-base status of local environment in terms of a spectrally detectable dianion-anion equilibrium. The protolytic equilibrium of fluorescein was found to depend on the solvent viscosity in a complex way. Whereas in the presence of sucrose the ratiometric signal of fluorescein (I488/I435) remains rather unchanged, the addition of glycerol (up to 40% w/w) results in the increase of the signal (up to 19%), that can be attributed to the different mechanisms of cosolvents effects on dye molecules in the ground state. Molecular dynamics of the dye in the presence of glycerol and sucrose revealed that the cosolvents preferentially interact with fluorescein monoanion and dianion, displacing water molecules from the local environment which in turn reduces the average number of the hydrogen bonds between xanthene ring of the dye and water molecules. The ratiometric signal demonstrates linear growth with the temperature in the range of 10-80 °C regardless of the presence of viscogenic agents. A linear correlation between the temperature sensitivity of the ratiometric signal and the change in the molar enthalpy of the proton dissociation reaction in buffer and viscous media was determined.

Thermodynamic properties of aqueous lanthanum sulfate solutions taking into account the association

Thermodynamic properties (the mean activity coefficients, γ±, and the relative apparent molar enthalpies, φL) of lanthanum sulfate aqueous solutions, strongly deviating from the Debye-Hückel limiting law even at lowest experimentally accessible concentrations, can easily and quantitatively be reproduced assuming the formation of two sulfate complexes, LaSO4+ and LaSO42-, whose existence was established in numerous complex formation studies. The analysis was carried out using a simple SIT model for the activity coefficients of ions with only the electrostatic Debye-Hückel terms. Excellent agreement between measured values of γ± and φL and the values of equilibrium constants was obtained by using the following values of equilibrium constants and enthalpy changes of reactions of formation of LaSO4+ (La3++SO42-⇄ LaSO4+) and La(SO4)2- (La3++2SO42-⇄ La(SO4)2-): log10K1o = 3.65 ± 0.05; log10K2o = 5.63 ± 0.2, ΔrH1o = 17.6 ± 1.0 kJ mol−1; ΔrH20 = 28.1 ± 4.0 kJ mol−1. The agreement with literature data is excellent for log10K1o and ΔrH1o and satisfactory for log10K2o and ΔrH2o. With these log10K1o, log10K2o, ΔrH1o and ΔrH2o results the experimental γ± and φL values are reproduced quantitatively.

Solvent Effect on the Chemical Equilibrium of Ammonium Carbamate for Chemical Heat Pump

Chemical heat pump based on ammonium carbamate (AC) is a promising low-grade heat utilization technology. It is essential to know the chemical equilibrium properties in the application of AC-based technologies. AC is usually mixed with solvents to realize circulation. However, the existing studies mainly focus on AC in the solid phase. Therefore, the influence of solvents on the chemical equilibrium of AC was experimentally investigated in this work. The results confirm the solvent effect on the equilibrium pressure of AC in the range of 10∼90 °C. For solvents capable of dissolving AC, the equilibrium pressure increases with both AC concentration and temperature. The solvent effect is mainly due to the influence on both the reaction enthalpy and entropy change terms. An equilibrium pressure–temperature–concentration relationship of AC solution is established. These results provide essential parameters for the design and operation of low-grade heat management and utilization systems based on AC.

Effect of Microwave Irradiation to Kinetics of Carbothermic Reduction of NiO

The carbothermic reduction of NiO was carried out by microwave irradiation at 2.45 GHz under a constant rate of temperature rise. The state of reaction was analyzed by means of non-equilibrium thermodynamics. The rates of the dominant reaction was the Boudouard reaction followed by NiO + CO → Ni + CO2, differing from that by conventional radiant heating. The uncompensated heat of reactions and the enthalpy change of reactions were almost same amount. The activation energy was 141 kJ/mol for the carbothermic reduction of NiO, 115 kJ/mol for the NiO reduction by CO gas and 166 kJ/mol for the Boudouard reaction. The former two values were smaller than conventional radiant heating.

H2S absorption with deep eutectic solvents: Low partial pressure capture and thermodynamic analysis

AbstractIn the present work, a series of deep eutectic solvents (DESs) based on organic amine as hydrogen bond acceptors (HBAs), and ethylene glycol (EG) as hydrogen bond donor (HBD) were prepared for the H2S absorption. Thermal decomposition temperature, HBA mass ratios, alkalinity and structure effect on absorption behavior were systematically investigated. The reaction mechanism was demonstrated by FT‐IR and 1H NMR spectroscopy. The reaction equilibrium constants, Henry constant, enthalpy and entropy change were calculated based on the thermodynamic model to reveal the interactions between DESs and H2S. It was found that H2S absorption capacities of the most of DESs with HBA/HBD mass ratio of 1:4 was close to 1 mol/mol at 303.15 K and 0.2 bar. The absorption capacity of DESs depends on the alkalinity and structure of HBAs; Additionally, a good linear correlation between the alkalinity of HBA and the absorption equilibrium constant (lnK) of DESs to H2S was found.

Thermodynamic Study of H2-FeO Based on the Principle of Minimum Gibbs Free Energy

Studies have shown that the reduction of wustite is the limiting factor in the ironmaking process, whether in hydrogen-based shaft furnaces, hydrogen-rich blast furnaces or smelting reduction vessels. The study of the thermodynamic conditions for the reduction of molten wustite by hydrogen is of great significance for the optimization of the ironmaking process, energy saving and emission reduction. Previous studies have mostly focused on the thermodynamic study of the reduction at a lower temperature, but the data at high temperatures are different, which makes the calculation of thermodynamics difficult. Moreover, it is difficult to obtain experimental evidence for the data at high temperature, so calculation is needed to verify its feasibility. In this paper, a thermodynamic calculation model for the reduction of molten wustite by hydrogen based on the principle of minimum Gibbs free energy is developed. The enthalpy changes of the reaction at different temperatures and the partial pressure of hydrogen required for the reaction to occur are calculated, and the energy change during the reaction is analyzed. The results show that the partial pressure of hydrogen for the reduction of molten wustite by hydrogen at high temperatures decreases from 0.67 at 1650 K to about 0.65 at 2000 K. The enthalpy changes of reaction at 1873 K are only 1/4 to 1/3 of that at 1173 K compared with that at the corresponding temperature between hydrogen for the reduction of molten wustite (1873 K) and hydrogen-based shaft furnace reaction (1173 K). Interestingly, the thermodynamic calculations show that the effect of energy absorption in the gas–liquid reaction of hydrogen with wustite at high temperatures is much lower than in the gas–solid reaction zone at low temperatures. These results indicate that the energy change of the reduction of molten wustite by hydrogen at high temperatures is better than that of hydrogen reduction at low temperatures, and the thermodynamic conditions are more favorable, with slightly different results from different thermodynamic databases, but the general trend is the same. The results of this study will provide fundamental data to support new hydrogen metallurgy technologies in the future. If its correctness can be verified experimentally in the future, this result will be promoted to the development of a new alternative ironmaking technology, hydrogen-based smelting reduction.

Effect of Internal Ligand Strain on Coordination Behavior of PSP Pincer Ligands.

Chelating ligands and most specifically pincer ligands, with their characteristic co-planar binding, usually undergo deformations upon coordination, resulting in a significant ligand strain. Such an effect on the properties of the so formed complex has rarely been explored. This study is an attempt to analyze this strain and its contribution to the overall binding energy and coordination behavior of PSP pincer ligands. Hence, we designed a rigid thioxanthone-based PSP pincer ligand (I) and studied the difference in the coordination properties with the more flexible thioxanthene and thioether-based PSP pincer ligands (II and III). Although with one equivalent of Pd(II) precursor, the three ligands exhibited a similar coordination behavior leading to similar κ3-P,S,P pincer complexes, an in-depth computational analysis pointed out the different contributions of the internal strain energy in lowering the binding energy of these complexes. This effect was clearly reflected when we calculated the enthalpy change of these ligand-exchange reactions. As these exchange reactions are enthalpy-driven, these results could also be confirmed experimentally. With two equivalents of Pd(II), the three ligands diverged in their coordination behavior. Specifically, ligands I and III gave each a binuclear complex, with different coordination modes, whereas the pincer complex of ligand II remained unaffected by excess of Pd(II). Our calculations suggest that the driving force for the formation of binuclear Pd(II) complexes is the relief of the internal ligand strain. With Pt(II), only the mononuclear κ3-P,S,P pincer complexes were obtained irrespectively of the amount of the Pt(II) precursor. In these cases, we assume that kinetic inertness of the formed mononuclear pincer Pt(II) complexes prevents binding of an additional Pt(II) nucleus. This study points out the important role of the internal ligand strain in PSP pincer ligand coordination behavior. We believe that our findings can be extended to other pincer ligands systems as well.

Thermodynamic Study of Am(III)-Isosaccharinate Complexation at Various Temperatures Implicating a Stepwise Reduction in Binding Denticity.

Isosaccharinic acid, a major final product of cellulose degradation under highly alkaline cement porewater conditions, is known to increase the mobility of actinides via strong complex formation. In this study, the formation of Am(III) complexes with α-d-isosaccharinate (ISA) was studied in terms of thermodynamics and coordination structures by combining spectrophotometry, time-resolved laser fluorescence spectroscopy (TRLFS), and density functional theory (DFT) calculations. The formation constants of the Am(III)-ISA complexes were determined by absorption spectroscopy at temperatures in the range of 15-70 °C. The measured reaction enthalpy and entropy changes indicate that the formation of a 1:1 Am(III)-ISA complex is driven by an increase in entropy. By contrast, the 1:2 complex formation is exothermic with a much less increase in entropy. DFT calculations predict that C2- and C4-hydroxyl groups, along with the carboxyl group, participate in the tridentate chelate binding of the primary ISA. The thermodynamic, TRLFS, and DFT results collectively suggest the tridentate binding of the primary ISA to Am(III) via a carboxylate and C2- and C4-hydroxyl groups in the protonated state and reduced dentate binding of the secondary ISA, such as bidentate binding, forming a four-membered ring structure via the carboxylate group.

Entropy enthalpy compensation in the SO2 absorption reaction and the optimal capture temperature range with amine alkyl siloxane as absorbent

In the present work, a kind of amine alkyl siloxane N-butyl-N-((1,1,3-trimethyl-3,3-diphenyldisiloxaneyl)methyl)butan-1-amine (BTDMBA) was synthesized and used to capture SO2. Its thermal decomposition temperature is 160℃, which is comparable with that of Ionic liquids (ILs), but its viscosity is only 125 mPa∙s at 25℃ after the absorption of SO2, which is much lower than that of ILs. The reaction mechanism is that BTDMBA reacted with SO2 to form charge transfer complex BTDMBA∙SO2. The reaction enthalpy and entropy change are −83.95 kJ/mol and −240.48 J·mol−1·K−1, respectively, which are more negative than that of ILs. By comparing the enthalpy and entropy change of amine alkyl siloxane and absorbents reported in literatures, an unexpected entropy enthalpy compensation phenomenon was discovered and the isokinetic temperature was found to be 371 K. Based on this phenomenon and the optimization objective function, it was also found that with the decrease of entropy change, the optimal absorption and desorption temperature difference increased initially and decreased afterwards. The maximum of entropy changes is −201 J·mol−1·K−1 for absorbent to achieve recycle absorption capacity 0.79 mol/mol under the condition of absorption pressure 0.002 bar and desorption pressure 1 bar.

DFT Study of the Possible Reaction Path for Radical Promoted Esterification Mechanism of Free Fatty Acids of Soapnut Oil for the Production of Biodiesel

Abstract:Esterification of higher free fatty acids content by using a photo-catalyst has recently been proved as the most efficient method for the pretreatment of non-edible oil to synthesize biodiesel.Methods:In the current study, mechanistic details of photo-catalyzed esterification reaction for four different fatty acids through density functional theory (DFT) calculations are explored and compared with un-catalyzed esterification reaction.Results:Revealed that the presence of photo-catalyst lowers the activation barrier and the structure of fatty acid has no significant effect on its reactivity. Thermodynamic data also revealed that the presence of photo-catalyst lowered the activation energy from 51.67 kcal/mol to 0.7495 kcal/mol. Furthermore, Gibbs free energy changes (ΔrGm Ø) and molar enthalpy changes (ΔrHm Ø) of the photo-catalyzed esterification reaction are negative, indicating that it is a spontaneous exothermic reaction. On the other hand, free fatty acids esterification in the absence of a catalyst is a kinetically unfavorable process with positive values of ΔrGm Ø and ΔrHm Ø.Conclusion:Our findings theoretically clarify the mechanism of the photo-catalyzed esterification reaction of FFA present in non-edible oil, which facilitates the process of biodiesel production.

An investigation into the multi-parameter identification and model optimization strategy of the PCT curves of hydrogen storage alloys by multiple intelligent algorithms

A multi-parameter sensitivity analysis method was proposed based on Latin hypercube sampling and the rank correlation method. The general genetic algorithm was improved by incorporating a niche parallel algorithm, suspicious peak point judgment, and a local search strategy, and both the improved genetic algorithm and multi-parameter sensitivity analysis method were implemented through C++ programming. The hydrogen pressure-composition isotherm (PCT curve) was found to play an important role in the study of hydrogen storage properties of metallic materials, and its reaction enthalpy change term was widely replaced by a power series form of smoothing. Based on the improved multi-parameter sensitivity analysis method, the effects of the range of parameter values and the number of samples on sensitivity were investigated, where the sensitivity ranking of the 10 parameters in the classical model was obtained. In addition, the equilibrium hydrogen pressure expression models of the highest order i of the power series from 3 to 9 were developed. The influence of the highest order on the optimization of multi-parameter identification was compared using an improved genetic algorithm, and we concluded that the eighth order polynomial model had the optimal convergence and fitting effect. Based on the inspiration of the function trend shape, two innovative forms of the PCT model power series were proposed in this work. Combined with typical examples, three high-order models were fully evolved, and a better power series form was obtained compared to the traditional model.

(Invited) Ligand Exchange at Chalcogenide and Perovskite Nanocrystal Surfaces Examined Via Isothermal Titration Calorimetry

I will describe our group’s efforts to quantify ligand association and exchange reactions on semiconductor nanocrystal (NC) surfaces via isothermal titration calorimetry (ITC). ITC provides a direct thermal measurement of reaction progress. As shown in earlier work by our group and others examining ligand exchange on chalcogenide and pnictide quantum dots, ITC is able to access the enthalpy change of reaction, equivalency, and effective equilibrium constants, including in cases that are challenging to resolve by NMR alone. Here, we will describe the extension of this approach to ligand exchange reactions on halide perovskite NCs, and to ligand exchange on chalcogenide NCs in aqueous solution. Such advances are needed to contribute a quantitative description of NC surface chemistry toward applications such as advanced optoelectronic devices, bioimaging probes, and photocatalysis.