Gibbs Free Energy Of Reaction Research Articles

Coordination mechanism of aluminum with oxalate and fluoride in aluminum crystallization from vanadium extraction wastewater

Aluminum speciation is complex in a solution where organic and inorganic ligands coexist, and aluminum can form different complexes with various ligands. In this paper, the coordination mechanism of aluminum with oxalate and fluoride in aluminum recovery from vanadium extraction wastewater was investigated. By comparing the process of recovering aluminum with oxalate and fluoride precipitation, oxalate crystallization is found to perform better with vanadium extraction wastewater. Under optimum conditions, the crystallization percentage of aluminum was 87.10%. K3Al(C2O4)3·3H2O was obtained and characterized by XRD and FTIR, and the total recovery of aluminum was 80%. The coordination mechanism and migratory behavior of aluminum with oxalate and fluoride during crystallization were studied by thermodynamic simulation and quantum chemical calculation. Results showed that aluminum primarily exists as AlF2+, AlF2+, AlC2O4+, and Al(C2O4)2 in vanadium extraction wastewater. With the addition of K2C2O4 and an increase in solution pH, these complexes were coordinated by C2O42− and formed Al(C2O4)33– complex anions, which provided a saturated solution environment for K3Al(C2O4)3·3H2O crystallization. The DFT simulation showed that the Gibbs free energies of the coordination reactions for Al(C2O4)33– were negative, which indicates that these coordination reactions can proceed spontaneously. This study is important when enriching the coordination mechanism of aluminum and improving the comprehensive utilization rate of resources for vanadium-bearing shale.

Thermodynamics of germanium chemical vapor deposition via germane and digermane

Chemical vapor deposition is notoriously a challenging chemical process. Growth rates are stated either under mass-transfer control or under kinetic control at lower temperature. But a few drastic assumptions enable a radical simplification of the reaction mechanism. And both growth regimes are unified with Sedgwick’s simplified thermodynamic model. Linear functions of temperature akin to Gibbs free energy of reaction are mined out of germanium deposition experiments. Two growth mechanisms are identified, one with ΔHro = 83.4 kcal/mol (Ge–H bond) and a second one with ΔHro = 104.2 kcal/mol (H – H bond). The contribution of higher order germane is also discerned in germane thermal decomposition. The square root coupling of growth rates to input flows is neatly demonstrated with thermodynamics. Finally, chemical vapor deposition growth rate vs. precursor partial pressure plot fingerprints a hydrogen Langmuir adsorption isotherm. The adsorption isotherm reveals a thermodynamic contribution beneath a mass-transfer control.

Concentration Bias in Reference Potentials and the pH-Effect on the Electrocatalysis of Hydrogen and Oxygen Evolution for Water Electrolysis

The electrolysis of water at low temperatures involves the transition from the liquid to the gas phase. The reactant, liquid water, has a concentration of around 55 mol/L, whereas gases such as hydrogen and oxygen with a nearly ideal behavior correspond to a concentration of only 0.04 mol/L at standard conditions (room temperature, pressure equal to 1 bar). Moreover, the oxygen and hydrogen molecules produced during electrolysis are first formed in a dissolved state in the electrolyte before escaping to the gas phase. The saturation concentrations of these gases in liquid water are around 0.001 mol/L at standard conditions, even lower than the concentrations in the gas phase. Accordingly the water electrolysis reaction involves a concentration change from approx. 55 mol/L for the reactant down to approx. 0.001 mol/L for the products. This dramatic concentration drop strongly contributes to the entropic part of the Gibbs free energy of the water splitting reaction, and it therefore implicitly biases the equilibrium voltage.We discuss why this concentration bias can be obstructive for a clear perspective on the reaction kinetics when using the equilibrium voltage, or potentials, as a reference [1]. To provide an unbiased reference voltage, we propose a definition of reference conditions with balanced concentrations on the reactant and product side. The theoretical equilibrium voltage corresponding to such balanced reactive conditions is an unbiased intrinsic reference for kinetic analysis, for which reason we denote it the kinetic reference voltage Ukin. For the electrochemical water splitting reaction, it has a value of Ukin = 1.441 V, which is in remarkable agreement with commonly observed onset voltages for macroscopic electrolysis rates.Applying the same concept of balanced reactive conditions to half-cell reactions, we define the kinetic reference potential Ekin. For a simple electrochemical redox couple Red ↔ Ox + e− with a 1:1 stoichiometry, the kinetic reference potential Ekin is simply equal to the standard equilibrium potential, because the standard reference concentrations are already balanced (1 mol/L for dissolved species). In contrast, for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), the standard reference concentrations are very different for reactants and products, and the corresponding standard equilibrium potentials suffer from concentration bias. Accordingly, the unbiased kinetic reference potentials of HER and OER are shifted with respect to the standard equilibrium potentials. These shifts are different in acidic and alkaline conditions and reveal an intriguing correlation with the experimentally observed effect of the pH value on the kinetics of HER and OER.The concept of balanced reactive reference conditions thus sheds a new light on the activation overvoltage in water electrolysis and the pH-effect in the electrocatalysis of HER and OER.[1] T. Binninger, A. Heinritz, R. Mohamed, Kinetic Reference Potential, pH-Effect, and Energy Recovery in Electrolysis of Water, ChemRxiv (2020), preprint, DOI: 10.26434/chemrxiv.12739091.v1

CO2 reduction mechanism on the Nb2CO2 MXene surface: Effect of nonmetal and metal modification

Electrochemical CO2 reduction to fuels offers a path to simultaneously address both CO2 emission and renewable energy storage challenges. Developing high efficient, selectivity and low overpotential nonprecious CO2 reduction reaction (CO2RR) catalysts is one of key factors for renewable energy. Herein, we explored the CO2RR as well as its side reaction (hydrogen evolution reaction (HER)) properties of pure Nb2CO2, nonmetal doping, and metal modification Nb2CO2 systems by using density functional theory calculations. Results indicated that the O terminal Nb2C (Nb2CO2) is more stable than that of the F and OH terminals. The reaction Gibbs free energy diagrams indicated that the pure Nb2CO2 is not suitable as catalyst for HER and CO2RR. Nonmetal doping can reduce potential limiting (UL) of CO2RR and will not change the reaction products. While surface metal modification not only reduced the UL of CO2RR, but also changed the reaction products. The V modified Nb2CO2 (VL) system is identified as the best CO2RR catalyst with against HER among modified systems with accounting HER side reaction. The charge transfers and electronic structure analysis indicates that the surface metal d have a strong interaction with Nb2CO2, leading the intermediates *COOH receive extra electrons from metal d bonding orbitals, which harm the ability of *COOH gaining electrons from proton, and therefore changed the reaction products.

Effect of ZnO-SiO2 Composite Abrasive on Sapphire Polishing Performance and Mechanism Analysis

Sapphire is widely used because of its excellent physical and chemical properties, and the requirements for its surface quality and processing efficiency are becoming more stringent. Chemical mechanical polishing (CMP) has been widely used to achieve non-damaged and atomically smooth surfaces on sapphire wafers. To promote the removal rate and surface quality, the effect of ZnO-SiO2 composite abrasive on sapphire CMP performance was studied. A higher material removal rate and lower Root mean squared surface roughness (Sq) (less than 0.3 nm) were obtained with the ZnO nano-particle slurry. HSC chemistry software was used to calculate the Gibbs free energy of possible chemical reactions between sapphire, SiO2, H2O, and ZnO to determine whether new reactions can occur. At the same time, the action and removal mechanism of sapphire using the ZnO-SiO2 composite slurry were investigated. X-ray photoelectron spectroscopy showed that the new reaction was produced and the product of the solid-state reaction was ZnAl2O4. In addition, only a hydration layer was observed on the surface of soaked sapphire in ZnO-based slurry, while the solid-state reaction products of Al2SiO5/Al2SiO5(OH)4 and ZnAl2O4 existed on the surface of polished sapphire. This indicates that mechanical processing provides energy or conditions which can promote chemical effects during CMP and lead to solid-phase reactions. Finally, a mechanochemical effect is introduced to explain the mechanism of solid state reaction in sapphire CMP process, which has a certain guiding significance to the mechanism analysis of CMP for different materials.

An experimental study of sepiolite dissolution and growth rates as function of the aqueous solution saturation state at 60 °C

Clay mineral growth can directly affect the chemistry and permeability of many natural systems, including soils, marine sediments, Earth surface waters, geothermal powerplants and carbon dioxide storage sites. Notably, the sluggish precipitation of clay minerals has been hypothesised to hinder Earth surface weathering rates. To date, there are limited data on the rate of clay mineral growth and on the effect of the aqueous solution saturation states on these rates. In this study we quantify the growth and dissolution rates of sepiolite, a 2:1 layered Mg-phyllosilicate (Mg4Si6O15(OH)2 * 6H2O) as a function of aqueous solution saturation state in a series of mixed flow experiments. Results of the both the dissolution and growth experiments are consistent with r=-10-14.801-expΔGrσRT, where r refers to the surface area normalized growth rate of sepiolite in units of mol/cm2/s, ΔGr denotes Gibbs Free energy of the sepiolite dissolution reaction, which is <0 for undersaturated solutions, 0 at equilibrium and >0 for supersaturated solutions, σ refers to Temkin’s stoichiometric number, R stands for the gas constant and T symbolizes absolute temperature. This rate equation suggests that sepiolite dissolution and growth are consistent with transition state theory and the concept of micro-reversibility. The relative decrease in aqueous Mg2+ and Si concentrations in the outlet aqueous solutions of the experiments, and the X-Ray diffraction patterns of the precipitates collected from the experiments, confirm the growth of crystalline sepiolite. The results of longer-term experiments suggest that sepiolite growth rates decrease over time. Such a decrease in the growth rate has been associated with poisoning or destruction of the sepiolite reactive surface sites. Calculations of sepiolite growth coupled to either forsterite or enstatite dissolution, based on laboratory measured rates suggest that the dissolution of the primary mineral is the rate-limiting step during the weathering of most natural systems. These results, however, contradict the saturation states of natural fluids such as observed in Icelandic waters, where clays are strongly supersaturated, whilst primary phases are relatively close to equilibrium. This discrepancy may be due to the consumption of reactive sites over time such that clay mineral precipitation rates in most natural systems are controlled by the relative slow nucleation rates of new reactive sites on the clay mineral surface.

Adjusting the electronic structure of WS2 nanosheets by iron doping to promote hydrogen evolution reaction

Intraplanar heteroatom doping is an effective way to control the electronic structure and active sites of electrocatalysts by reducing the Gibbs free energy of the hydrogen evolution reaction (HER), as well as to improve the intrinsic electrical conductivity of the catalyst. Here, iron-doped tungsten disulfide (Fe-doped WS2) nanosheet arrays were synthesized on carbon cloth by solvothermal method. The experiment and first principle calculation results demonstrate that doping of iron can not only increase the charge transfer rate and reduce the interface transfer resistance, but also increase the active surface area and arouse the in-plane inert sites, thereby improving the HER activity of WS2. The optimal sample shows the overpotential of 166 mV (10 mA cm−2) and the Tafel slope of 82.2 mV dec−1 in 0.5 M H2SO4. This finding reveals that introducing dopant is a universal tool to regulate the electronic structure of WS2 and then to further improve its electrocatalytic activity.

Unveiling the Intramolecular Ionic Diels–Alder Reactions within Molecular Electron Density Theory

The intramolecular ionic Diels–Alder (IIDA) reactions of two dieniminiums were studied within the Molecular Electron Density Theory (MEDT) at the ωB97XD/6-311G(d,p) computational level. Topological analysis of the electron localization function (ELF) of dieniminiums showed that their electronic structures can been seen as the sum of those of butadiene and ethaniminium. The superelectrophilic character of dieniminiums accounts for the high intramolecular global electron density transfer taking place from the diene framework to the iminium one at the transition state structures (TSs) of these IIDA reactions, which are classified as the forward electro density flux. The activation enthalpy associated with the IIDA reaction of the experimental dieniminium, 8.7 kcal·mol−1, was closer to that of the ionic Diels–Alder (I-DA) reaction between butadiene and ethaniminium, 9.3 kcal·mol−1. However, the activation Gibbs free energy of the IIDA reaction was 12.7 kcal·mol−1 lower than that of the intermolecular I-DA reaction. The strong exergonic character of the IIDA reaction, higher than 20.5 kcal·mol−1, makes the reaction irreversible. These IIDA reactions present a total re/exo and si/endo diastereoselectivity, which is controlled by the most favorable chair conformation of the tetramethylene chain. ELF topological analysis of the single bond formation indicated that these IIDA reactions take place through a non-concerted two-stage one-step mechanism. Finally, ELF and atoms-in-molecules (AIM) topological analyses of the TS associated with the inter and intramolecular processes showed the great similarity between them.

Mechanistic Insights into Interactions of Polysulfides at VS2 Interfaces in Na-S Batteries: A DFT Study.

Room temperature sodium-sulfur (Na-S) batteries, because of their high theoretical energy density and low cost, are considered as a promising candidate for next-generation energy storage devices. However, the practical utilization of the Na-S batteries is greatly hindered by various deleterious factors such as dissolution of sodium polysulfides (Na2Sn) into the electrolyte commonly termed as "shuttle effect," sluggish decomposition of solid Na2S, and poor electronic conductivity of sulfur. To overcome the challenges, we introduced single-layer vanadium disulfide (VS2) as an anchoring material (AM) to immobilize higher-order polysulfides from the dissolution and also to accelerate the otherwise sluggish kinetics of insoluble short-chain polysulfides. We employ density functional theory (DFT) calculations to elucidate the Na2Sn interactions at the VS2 interfaces. We show that the adsorption strengths of various Na2Sn species on the VS2 basal plane are adequate (1.21-4.3 eV) to suppress the shuttle effect, and the structure of Na2Sn are maintained without any decomposition, which is necessary to mitigate capacity fading. The calculated projected density of states (PDOS) reveals that the metallic character of the pristine VS2 is retained even after Na2Sn adsorption. The calculated Gibbs free energy of each elementary sulfur reduction reaction indicates a significant decrement in the free energy barrier due to the catalytic activity of the VS2 surface. Furthermore, VS2 is found to be an excellent catalyst to significantly reduce the oxidative decomposition barrier of Na2S, which facilitates accelerated electrode kinetics and higher utilization of sulfur. Overall, VS2 with strong adsorption behavior, enhanced electronic conductivity, and improved oxidative decomposition kinetics of polysulfides can be considered as an effective AM to prevent the shuttle effect and to improve the performance of Na-S batteries.

The InSe/g-CN van der Waals hybrid heterojunction as a photocatalyst for water splitting driven by visible light

Designing and developing the highly efficient photocatalysts is full of significance to achieve spontaneous photolysis water. In this work, using the first-principles calculations, we have performed a systematic theoretical study of water splitting photocatalytic activity of the InSe/g-CN heterojunction. It is concluded that the InSe/g-CN heterojunction is a typical type-II semiconductor, whose electrons and holes can be effectively separated. And the potential of the conduction band minimum (CBM) and valence band maximum (VBM) satisfy the requirements for photolysis water. Moreover, the changes of Gibbs free energy (ΔG) of the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) are calculated to investigate thermodynamic sustainability of photolysis water. The results show that when pH = 7, the potential driving force provided by the InSe/g-CN heterojunction can ensure the spontaneous progress of HER and OER. In addition, it is found that the solar conversion efficiency (ηS) of the InSe/g-CN heterojunction is up to 13.7%, which indicates it has broad commercial application prospects. Hence, the InSe/g-CN heterojunction is expected to be an excellent candidate for photolysis water.

Integrated knowledge mining, genome-scale modeling, and machine learning for predicting Yarrowia lipolytica bioproduction

Predicting bioproduction titers from microbial hosts has been challenging due to complex interactions between microbial regulatory networks, stress responses, and suboptimal cultivation conditions. This study integrated knowledge mining, feature extraction, genome-scale modeling (GSM), and machine learning (ML) to develop a model for predicting Yarrowia lipolytica chemical titers (i.e., organic acids, terpenoids, etc.). First, Y. lipolytica production data, including cultivation conditions, genetic engineering strategies, and product information, was manually collected from literature (~100 papers) and stored as either numerical (e.g., substrate concentrations) or categorical (e.g., bioreactor modes) variables. For each case recorded, central pathway fluxes were estimated using GSMs and flux balance analysis (FBA) to provide metabolic features. Second, a ML ensemble learner was trained to predict strain production titers. Accurate predictions on the test data were obtained for instances with production titers >1 g/L (R2 = 0.87). However, the model had reduced predictability for low performance strains (0.01–1 g/L, R2 = 0.29) potentially due to biosynthesis bottlenecks not captured in the features. Feature ranking indicated that the FBA fluxes, the number of enzyme steps, the substrate inputs, and thermodynamic barriers (i.e., Gibbs free energy of reaction) were the most influential factors. Third, the model was evaluated on other oleaginous yeasts and indicated there were conserved features for some hosts that can be potentially exploited by transfer learning. The platform was also designed to assist computational strain design tools (such as OptKnock) to screen genetic targets for improved microbial production in light of experimental conditions.

Gibbs free energy change using Ru/Al2O3 catalyst – An application in supercritical water gasification process

In this communication, the supercritical water gasification process of ethanol and glycerol is simulated by considering the effect of the Ru/Al2O3 catalyst concentration in thermodynamic modeling. For this purpose, the changes in Gibbs free energy of gasification and methanation reactions are correlated using the experimental points and subsequently the results are used to find the optimum condition of the processes. Findings suggest that the H2 and CH4 curves have their maximum and minimum values against the catalyst concentration, respectively. Additionally, the extremum positions of the H2 and CH4 curves are not located in same catalyst concentration. Furthermore, to study the influence of temperature, feedstock concentration as well as catalyst concentration on water-gas-shift and CO methanation, a graphical approach is proposed to interpret the model outcome. The results show that the concentration of catalyst has a substantial impact on the modeling, and it is reasonable to be considered in the calculations.

Additivity of Diene Substituent Gibbs Free Energy Contributions for Diels-Alder Reactions between (F3C)2B = NMe2 and Substituted Cyclopentadienes.

Systematic computational studies of pericyclic Diels-Alder-type reactions between aminoborane (F3C)2B = N(CH3)2, 1, and all permutations of substituted cyclopentadienes c-C5R1R2R3R4R5aR5b (R = H, CH3, CF3, F) allow isolation of substitutional effects on Gibbs free energy barrier heights and reaction Gibbs free energies. The effects appear to be additive in all cases. Substitution at positions 5a and 5b always increases barriers and reaction energies, an effect explained by steric interactions between substituents and the aminoborane moiety. For cases R = CH3, regioselectivities differ from those expected from canonical organic chemistry predictions. Frontier molecular orbital calculations suggest this arises from the extreme polarization of the π interaction in 1. For cases R = CF3, the 2/3-substitution comparison accords with canon, but the 1/4-substitution comparison does not. This appears to arise from a combination of electronic and steric issues. For cases R = F, many of the reactions are exergonic, in contrast to the cases R = CH3, CF3. Additionally, fluorine substitution at positions 2 and 4 has a barrier-lowering effect. Frontier molecular orbital calculations support an orbital-based preference for formation of 2- and 4-substituted "meta" products rather than "ortho/para" products.

What process causes the slowdown of pressure solution creep

The slowdown of pressure solution creep has been thought to be caused by stress redistribution. This study presents a fresh view towards this creep behaviour. Basically, two rate-limiting mechanisms come into play amid pressure solution creep: (1) stress redistribution across expanding inter-granular contacts and (2) solute accumulation in the water film. Because non-hydrostatic dissolution occurs under open system conditions, solute accumulation in the water film is constrained by the ensuing solute transport process. Relying on the matter exchange across the contact surface boundary, the active processes in the voids, e.g., solute migration and deposition, affect pressure solution creep. Based upon the above, we sum up two requirements that have to be met for achieving chemical compaction equilibrium: (1) the Gibbs free energy of reaction, i.e., the driving force of non-hydrostatic dissolution process, gets depleted and (2) the concentration gradient between the water film and surrounding pore water vanishes.HighlightsThe slowdown of pressure solution creep is a combined result of stress migration across contacts and solute accumulation in the water film.Matter exchange with the surroundings inhibits solute accumulation in the water film.This article identifies two prerequisites that need to be fulfilled for achieving chemical compaction equilibrium.

Extraction kinetics of lanthanum(III) by bis(2-ethylhexyl) phosphate and dimethylheptyl methyl phosphate in the presence of sulfonated kerosene using a Lewis cell

The extraction kinetics of lanthanum (III) from a chloride medium by bis(2-ethylhexyl) phosphate(HDEHP) and dimethylheptyl methyl phosphate(P350) in the presence of sulfonated kerosene are investigated using a Lewis cell. The effects of the stirring rate, temperature, and specific interfacial area on the extraction rate are investigated. The results show that the extraction process is controlled by diffusion and chemical reactions in the interfacial area rather than in the bulk phase. The apparent activation energy and the changes in the enthalpy, entropy, and Gibbs free energy of the extraction reaction are calculated using the Arrhenius equation and transition state theory. The rate equation derived from the experimental results is similar to that of the interface reaction model. A mass transfer model with a rate-control step is proposed. This study provides guidance and data support for an HDEHP-P350 system in industrial production applications.

Atomic-level insights into the activation of nitrogen via hydrogen-bond interaction toward nitrogen photofixation

Summary As the activation of N2 molecules is generally regarded as the bottleneck in N2 reduction, it is of significant importance to develop promising strategies to efficiently activate N2 molecules. Herein, we discovered an innovative approach to activate N2 molecules via hydrogen-bond interaction in N2 photofixation. Porous Cu with surface modification of S atoms (3%-S/Cu) exhibited remarkable catalytic activity and stability in N2 photofixation. Further mechanistic studies revealed that surface S atoms directly participated in the catalytic process by accepting and donating H atoms. In addition, the forming S–H bond significantly promoted the activation of N2 molecules via hydrogen-bond interaction, contributing to the enhanced catalytic activity.

Testing hypotheses of albite dissolution mechanisms at near-equilibrium using Si isotope tracers

Here, we demonstrate the potential advantages of using isotope tracers to test hypotheses of reaction mechanisms near-equilibrium. Using non-traditional stable Si isotopes as tracers, we measured albite unidirectional dissolution rates (r+) across a range of Gibbs free energy of reaction (ΔrG) close to equilibrium (−26 to −2 kJ/mol). Thirteen batch experiment series were conducted at 50 °C and pH ∼ 8 ± 0.25. Different distances from equilibrium were achieved by a stepwise increase of concentrations of Si (0–600 μM), Al (0–10 μM), and Na (0–1000 μM). The temperature, pH, sample preparation, and reaction duration were kept identical to isolate the ΔrG effect. Secondary phase precipitation, which is difficult to avoid in near-equilibrium, near-neutral pH experiments renders the rate measurement method based on changes in Si and Al concentration unworkable, but it should not impact the Si isotope ratios-based rates.The resulting r+ values were nearly constant in the experimental ΔrG range, signaling no major ΔrG-related switch of reaction mechanisms. Our results suggest that the switch from etch pit opening at far-from-equilibrium to step retreat at near-equilibrium does not operate under circum-neutral pH in low-temperature systems; this mechanism switch was proposed based on experimental data in alkaline solutions at hydrothermal temperatures. The nearly constant r+ values at pH 5–8 also suggest that an H2O-catalyzed reaction mechanism dominant at circumneutral pH, in addition to the H+- and OH–-catalyzed reaction mechanisms dominant at acidic and alkaline pH, respectively.The experimental results have implications for geochemical modeling of low-temperature geological and environmental processes. The results suggest that a term of H2O-catalyzed reaction mechanism should be included in rate laws and that the parallel rate law with a mechanism-switch is not applicable in the pH range of 5–8.

Optimal conditions determination for hydrodeoxygenation of free fatty acids to obtain green diesel

AbstractIn this work, the production of green diesel involving the hydrodeoxygenation reaction of vegetable oil, such as oleic acid, producing CO or CO2 as byproducts, was studied. This reaction takes place under hydrogen saturation to produce stearic acid; subsequently, heptadecane is produced by the decarbonylation and decarboxylation pathways, while octadecane is obtained by the subsequent hydrodeoxygenation of octadecanal. In the formation of octadecane, water is obtained as a byproduct, while the production of heptadecane leads to CO and CO2 as byproducts of the decarbonylation and decarboxylation reactions. When considering the products and reaction routes in the hydrotreatment of triglycerides and free acids, a mathematical model was found to be reliable in determining the minimization of the Gibbs free energy of reaction over a range of reaction temperatures and pressures. This model followed the methods of Marrero‐Gani, Joback‐Reid, and Chen‐Dinivahi‐Jeng for the estimation of thermodynamic properties of the pure components. The fugacity was calculated by considering the partial fugacity coefficients, and the Peng‐Robinson equation of state and the van der Waals mixing rule were used. The mole fractions at equilibrium were estimated by least squares analysis, using MATLAB, in order to account for non‐idealities in reaction thermodynamic properties and to find the equilibrium composition that minimized the total Gibbs free energy. Likewise, the reaction coordinates of the equilibrium reaction were estimated together with the known values of the composition in order to know the effect of pressure and temperature on the aforementioned reactions.

Thermodynamic Theory of Silicon Chemical Vapor Deposition

Silicon chemical vapor deposition via silane is determined with classical thermodynamics. Drastic assumptions are used, such as the hydrogen carrier gas does not interact with the silicon thin film growth and the energy of reaction is adjusted to experiments. As a result, a linear function of temperature akin to a Gibbs free energy of reaction is shown to control silicon growth rates, and the characteristic Arrhenius plot is fully determined. The surface response of the growth rate activation energy is neatly mapped, bringing clarity to the parameter space for which a single value is a valid metric. A meta-analysis of growth rates is carried out for a demonstration of the portability of the linear function of temperature across reactors and to mine out reactor scaling factors. A silane heterogeneous decomposition reaction is also a great model chemistry for chlorosilanes. Silicon deposition is notoriously a complex chemical process, but with thermodynamics, the reaction mechanism is successfully reduced to the essentials.

Facile fabrication of molybdenum compounds (Mo2C, MoP and MoS2) nanoclusters supported on N-doped reduced graphene oxide for highly efficient hydrogen evolution reaction over broad pH range

• Develop new molybdenum compounds (Mo 2 C, MoP and MoS 2 ) nanoclusters supported on N-doped reduced graphene oxide. • Prepared catalysts exhibit excellent and durable electrocatalytic performance over a broad pH range. • Potential applications of ordered self-assembled composites for water splitting to produce hydrogen. Electrocatalytic water splitting for hydrogen production is highly desirable to replace oil energy. The catalytic performance is closely related to the conductivity, active sites and reaction Gibbs free energy of the catalyst. A general guideline for improving catalytic performance is to obtain porous carbon-based materials with a high surface area, plentiful defects and metal compound loading. Here, defect-rich nitrogen-doped reduced graphene oxide (RGO) with molybdenum (Mo)-based compound loading was designed through a two-step method. The peroxide-assisted step under low-temperature carbonization with an air atmosphere promotes the formation of defects, and the hydrothermal process improves the crosslinking degree to form a porous structure at a high carbonization temperature. The obtained catalysts exhibit excellent and durable electrocatalytic performance over a broad pH range. In addition, the transmission electron microscopy (TEM) and electron paramagnetic resonance (EPR) results clearly reveal the presence of defects. The theoretical analysis demonstrates that the RGO and Mo-based compounds have an efficient synergetic effect on the catalytic activity. This work provides clues for the development of new catalysts for water splitting to produce hydrogen.