Thermodynamic properties of potassium metasilicate (K2SiO3)

The standard enthalpy of formation of potassium metasilicate (K₂SiO₃), determined by hydrofluoric acid solution calorimetry, was found to be ΔH^o_f,298 = −363.866±0.421 kcal mol⁻¹ (−1522.415±1.762 kj mol⁻¹). The standard enthalpy of formation from the oxides was found to beΔH^o₂₉₈ = −64.786±0.559 kcal mol⁻¹ (−271.065±2.339 kJ mol⁻¹).These experimentally determined data were combined with data from the literature to calculate the Gibbs energies of formation and equilibrium constants of formation over the temperature range of the literature data. The standard enthalpies of formation and Gibbs energies of formation are given as functions of temperature. The standard Gibbs energy of formation is ΔG_f,298.15⁰ = −341.705 kcal mol⁻¹ (−1429.694 kJ mol⁻¹).     

In Situ Reconstruction of a Hierarchical Sn-Cu/SnOx Core/Shell Catalyst for High-Performance CO2 Electroreduction

The electrochemical CO₂ reduction reaction (CO₂RR) to give C₁ (formate and CO) products is one of the most techno-economically achievable strategies for alleviating CO₂ emissions. Now, it is demonstrated that the SnO_x shell in Sn_2.7Cu catalyst with a hierarchical Sn-Cu core can be reconstructed in situ under cathodic potentials of CO₂RR. The resulting Sn_2.7Cu catalyst achieves a high current density of 406.7±14.4 mA cm⁻² with C₁ Faradaic efficiency of 98.0±0.9 % at −0.70 V vs. RHE, and remains stable at 243.1±19.2 mA cm⁻² with a C₁ Faradaic efficiency of 99.0±0.5 % for 40 h at −0.55 V vs. RHE. DFT calculations indicate that the reconstructed Sn/SnO_x interface facilitates formic acid production by optimizing binding of the reaction intermediate HCOO* while promotes Faradaic efficiency of C₁ products by suppressing the competitive hydrogen evolution reaction, resulting in high Faradaic efficiency, current density, and stability of CO₂RR at low overpotentials.     

Surface Adsorbed Hydroxyl: A Double-Edged Sword in Electrochemical CO2 Reduction over Oxide-Derived Copper

Oxide-derived Cu (OD−Cu) featured with surface located sub-20 nm nanoparticles (NPs) created via surface structure reconstruction was developed for electrochemical CO₂ reduction (ECO₂RR). With surface adsorbed hydroxyls (OH_ad) identified during ECO₂RR, it is realized that OH_ad, sterically confined and adsorbed at OD−Cu by surface located sub-20 nm NPs, should be determinative to the multi-carbon (C₂) product selectivity. In situ spectral investigations and theoretical calculations reveal that OH_ad favors the adsorption of low-frequency *CO with weak C≡O bonds and strengthens the *CO binding at OD−Cu surface, promoting *CO dimerization and then selective C₂ production. However, excessive OH_ad would inhibit selective C₂ production by occupying active sites and facilitating competitive H₂ evolution. In a flow cell, stable C₂ production with high selectivity of ∼60 % at −200 mA cm⁻² could be achieved over OD−Cu, with adsorption of OH_ad well steered in the fast flowing electrolyte.     

The kinetics and thermodynamics of a novel efficient mixed water–1,4-dioxan solvent for the effective complexation of a neutral ruthenium complex with carbon monoxide at atmospheric pressure

Kinetic and thermodynamic investigations were performed for a mixed aqueous-organic, 1:1 (v/v) water–1,4-dioxane medium, which was found to be an efficient solvent for the interaction of a neutral dichlorotris(triphenylphosphine) ruthenium(II), RuCl₂(PPh₃)₃ complex with carbon monoxide at atmospheric pressure. During the interaction, RuCl₂(PPh₃)₃ dissociates to a neutral complex dichlorobis(triphenylphosphine) ruthenium(II), RuCl₂(PPh₃)₂, by losing a coordinated PPh₃ ligand and RuCl₂(PPh₃)₂ coordinates with CO to form an in situ carbonyl complex RuCl₂(CO)(PPh₃)₂. The in situ formed carbonyl complex RuCl₂(CO)(PPh₃)₂ was thoroughly characterized by equilibrium, spectrophotometric, IR, and electrochemical techniques. Under equilibrium conditions, the rate and dissociation constants for the dissociation of PPh₃ from RuCl₂(PPh₃)₃ were found to be favorable for the formation of the carbonyl complex RuCl₂(CO)(PPh₃)₂. The rates of complexation for the formation of RuCl₂(CO)(PPh₃)₂ were found to follow an overall second-order kinetics being first order in terms of the concentrations of both carbon monoxide and RuCl₂(PPh₃)₂. The determined activation parameters corresponding to the rate constant (ΔH^# = 35.9 ± 2.5 kJ mol⁻¹ and ΔS^# = −122 ± 6 J K⁻¹ mol⁻¹) and thermodynamic parameters corresponding to the formation constant (ΔH° = −33.5 ± 4.5 kJ mol⁻¹, ΔS° = −25 ± 8 J K⁻¹ mol⁻¹, and ΔG° = −25.7 ± 2.0 kJ mol⁻¹) were found to be highly favorable for the formation of the complex RuCl2(CO)(PPh3)2. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 359–369, 2008     

Microcalorimetric studies of dodecacarbonyl(diiron)ruthenium and dodecacarbonyl(iron)diruthenium. Enthalpy contribution of heterometallic metal—metal bonds

Microcalorimetic measurements at 520–550 K of the heats of thermal decomposition of Fe₂Ru(CO)₁₂, FeRu₂(CO)₁₂ and Ru₃(CO)₁₂ lead to values of the standard enthalphy of formation (ΔH^o_f, c/kJ mol^-1) as follows: Fe₂Ru(CO)₁₂  (1820 ± 14); FeRu₂(CO)₁₂  (1891 ± 16); Ru₃(CO)₁₂  (1903 ± 18). Enthalpies of sublimation are estimated and the ironruthenium bond enthalpy contribution is derived as E(FeRu)  (95 ± 20) kJ mol^-1.     

Variable‐Temperature Infrared Spectroscopy Studies on the Thermodynamics of CO Adsorption on the Zeolite Ca–Y

Variable temperature FT–IR spectroscopy (in the range of 298–380 K) is used to study the thermodynamics of formation of Ca²⁺???CO carbonyl species upon CO adsorption on the faujasite‐type zeolite Ca–Y, and also the (temperature‐dependent) isomerization equilibrium between carbonyl and isocarbonyl (Ca²⁺???OC) species. The standard enthalpy and entropy changes involved in formation of the monocarbonyl species resulted to be ΔH⁰=?50.3 (±0.5) kJ mol^?1 and ΔS⁰=?186 (±5) J mol^?1 K^?1, respectively. Isomerization of the (C‐bonded) Ca²⁺???CO carbonyl to yield the (O‐bonded) Ca²⁺???OC isocarbonyl involves an enthalpy change =+11.4 (±1.0) kJ mol^?1. These results are compared with previously reported data for the CO/Sr–Y system; and also, a brief analysis of enthalpy–entropy correlation for CO adsorption on zeolites and metal oxides is given.     

Promoting CO2 Electroreduction to Multi-Carbon Products by Hydrophobicity-Induced Electro-Kinetic Retardation

Advancing the performance of the Cu-catalyzed electrochemical CO₂ reduction reaction (CO₂RR) is crucial for its practical applications. Still, the wettable pristine Cu surface often suffers from low exposure to CO₂, reducing the Faradaic efficiencies (FEs) and current densities for multi-carbon (C₂₊) products. Recent studies have proposed that increasing surface availability for CO₂ by cation-exchange ionomers can enhance the C₂₊ product formation rates. However, due to the rapid formation and consumption of *CO, such promotion in reaction kinetics can shorten the residence of *CO whose adsorption determines C₂₊ selectivity, and thus the resulting C₂₊ FEs remain low. Herein, we discover that the electro-kinetic retardation caused by the strong hydrophobicity of quaternary ammonium group-functionalized polynorbornene ionomers can greatly prolong the *CO residence on Cu. This unconventional electro-kinetic effect is demonstrated by the increased Tafel slopes and the decreased sensitivity of *CO coverage change to potentials. As a result, the strongly hydrophobic Cu electrodes exhibit C₂₊ Faradaic efficiencies of ≈90 % at a partial current density of 223 mA cm⁻², more than twice of bare or hydrophilic Cu surfaces.     

Bipyridine‐Assisted Assembly of Au Nanoparticles on Cu Nanowires To Enhance the Electrochemical Reduction of CO2

We report a new strategy to prepare a composite catalyst for highly efficient electrochemical CO₂ reduction reaction (CO₂RR). The composite catalyst is made by anchoring Au nanoparticles on Cu nanowires via 4,4′‐bipyridine (bipy). The Au‐bipy‐Cu composite catalyzes the CO₂RR in 0.1 m KHCO₃ with a total Faradaic efficiency (FE) reaching 90.6 % at ?0.9 V to provide C‐products, among which CH₃CHO (25 % FE) dominates the liquid product (HCOO^?, CH₃CHO, and CH₃COO^?) distribution (75 %). The enhanced CO₂RR catalysis demonstrated by Au‐bipy‐Cu originates from its synergistic Au (CO₂ to CO) and Cu (CO to C‐products) catalysis which is further promoted by bipy. The Au‐bipy‐Cu composite represents a new catalyst system for effective CO₂RR conversion to C‐products.     

Time‐Resolved Thermodynamic Profile upon Photoexcitation of a Nitrospiropyran in Cycloalkanes and of the Corresponding Merocyanine in Aqueous Solutions

The photoconversion of 2′,3′‐dihydro‐6‐nitro‐1′,3′,3′‐trimethylspiro[2H‐1‐benzopyran‐2,2′‐indole] ( Sp ) to its open merocyanine form ( Mc ) in a series of aerated cycloalkanes (cyclopentane, cyclohexane, and trans‐ and cis‐decalin) and of the protonated merocyanine ( McH ⁺ ) to Sp in aqueous solution were studied by laser‐induced optoacoustic spectroscopy (LIOAS). The +(11±2) ml mol⁻¹ expansion determined for the ring closure is due to deprotonation of McH ⁺ plus the reaction of the ejected proton with the monoanion of malonic acid (added to stabilize Mc ), an intrinsic expansion and a small electrostriction term. The energy difference between Sp and initial McH ⁺ is (282±110) kJ mol⁻¹. An intrinsic contraction of −(47±15) ml mol⁻¹ occurs upon ring opening, forming triplet ³Mc in the cycloalkanes, whereas no volume change was detected for the ³Mc to Mc relaxation. Electrostriction decreases the ³Mc energy, (165±18) kJ mol⁻¹, to 135 kJ mol⁻¹. The difference in the values of the ring‐opening ( Sp to Mc ) reaction enthalpy in cycloalkanes as derived from the temperature dependence of the Sp ⇌ Mc equilibrium, (29±8) kJ mol⁻¹, and from the LIOAS data, −(9±25) kJ mol⁻¹, is due to the formation of Mc‐Sp aggregates during steady‐state measurements. The Sp ‐sensitized singlet molecular oxygen, O₂(¹Δ_g), quantum yield (average Φ_Δ=0.58±0.03) derived from the near‐IR emission of O₂(¹Δ_g), was taken as a measure of Mc production in the cycloalkanes. These solvents, albeit troublesome in their handling, provide an additional series for the determination of structural volume changes in nonaqueous media, besides the alkanes already used.     

The isomolecular exchange reaction Ga2S(g) + In2S(g) = 2 InGaS(g)

Equilibria involving the molecules Ga₂S(g), In₂S(g), and InGaS(g), by the reaction Ga₂S(g) + In₂S(g) = 12InGaS(g) were investigated between 1060–1350 K by the Knudsen-effusion, mass-spectrometric method. The reaction enthalpy at 298 K was calculated to be 0±1 kJ mol⁻¹. The enthalpy of formation of InGaS at 298 K and the enthalpy of atomization of InGaS at 298 K were calculated to be 80±18 kJ mol⁻¹ and 710±18 kJ mol⁻¹, respectively. The equilibrium constant and the enthalpy of reaction indicated that the three gaseous molecules have a bent triatomic structure in which S is a center atom and no bond between metals.     

CO在Ag掺杂的氧化锰八面体分子筛上吸附的TAP研究

利用产物瞬时分析反应器中进行的单脉冲实验, 考察了393～493 K温度范围内CO在Ag掺杂的氧化锰八面体分子筛上的吸附行为. 实验表明: CO在催化剂表面发生化学吸附, 并与晶格氧反应生成CO₂. 通过对该过程反应物及产物脉冲响应曲线的模拟, 得到了各基元反应的动力学参数. CO和CO₂在该催化剂表面的脱附活化能分别为83和31 kJ/mol, CO与晶格氧的反应活化能为116 kJ/mol.     

The standard enthalpies of formation of cyclohexylamine and cyclohexylamine hydrochloride

The standard enthalpy of combustion of cyclohexylamine has been measured in an aneroid rotating-bomb calorimeter. The value ΔH_o^o(c-C₆H₁₁NH₂, 1) = ?(4071.3 ± 1.3) kJ mol^?1 yields the standard enthalpy of formation ΔH_f^o(c-C₆H₁₁NH₂, 1) = ?(147.7 ± 1.3) kJ mol^?1. The corresponding gas-phase standard enthalpy of formation for cyclohexylamine is ΔH_f^o(c-C₆H₁₁NH₂, g) = ?(104.9 ± 1.3) kJ mol^?1. The standard enthalpy of formation of cyclohexylamine hydrochloride, ΔH_f^o(c-C₆H₁₁NH₂·HCl, c) = ?(408.2 ± 1.5) kJ mol^?1, was derived by combining the measured enthalpy of solution of the salt in water, literature data, and the ΔH_c^o measured in this study. Comment is made on the thermochemical bond enthalpy H(CN).     

The enthalpies of formation of CH3Mn(CO)5 and of CH3Re(CO)5, and the strengths of the CH3Mn and CH3Re bonds

From measurements of the heats of iodination of CH₃Mn(CO)₅ and CH₃Re(CO)₅ at elevated temperatures using the ‘drop’ microcalorimeter method, values were determined for the standard enthalpies of formation at 25° of the crystalline compounds: ΔH^o_f[CH₃Mn(CO)₅, c] = ?189.0 ± 2 kcal mol^?1 (?790.8 ± 8 kJ mol^?1), ΔH^o_f[Ch₃Re(CO)₅,c] = ?198.0 ± kcal mol^?1 (?828.4 ± 8 kJ mo^?1). In conjunction with available enthalpies of sublimation, and with literature values for the dissociation energies of MnMn and ReRe bonds in Mn₂(CO)₁₀ and Re₂(CO)₁₀, values are derived for the dissociation energies: D(CH₃Mn(CO)₅) = 27.9 ± 2.3 or 30.9 ± 2.3 kcal mol^?1 and D(CH₃Re(CO)₅) = 53.2 ± 2.5 kcal mol^?1. In general, irrespective of the value accepted for D(MM) in M₂(CO)₁₀, the present results require that, D(CH₃Mn) = $\text{1}\text{2}$D(MnMn) + 18.5 kcal mol^?1 and D(CH₃Re) = $\text{1}\text{2}$D(ReRe) + 30.8 kcal mol^?1.     

In Situ Reconstruction of a Hierarchical Sn‐Cu/SnOx Core/Shell Catalyst for High‐Performance CO2 Electroreduction

The electrochemical CO₂ reduction reaction (CO₂RR) to give C₁ (formate and CO) products is one of the most techno‐economically achievable strategies for alleviating CO₂ emissions. Now, it is demonstrated that the SnO_x shell in Sn_2.7Cu catalyst with a hierarchical Sn‐Cu core can be reconstructed in situ under cathodic potentials of CO₂RR. The resulting Sn_2.7Cu catalyst achieves a high current density of 406.7±14.4 mA cm^?2 with C₁ Faradaic efficiency of 98.0±0.9 % at ?0.70 V vs. RHE, and remains stable at 243.1±19.2 mA cm^?2 with a C₁ Faradaic efficiency of 99.0±0.5 % for 40 h at ?0.55 V vs. RHE. DFT calculations indicate that the reconstructed Sn/SnO_x interface facilitates formic acid production by optimizing binding of the reaction intermediate HCOO* while promotes Faradaic efficiency of C₁ products by suppressing the competitive hydrogen evolution reaction, resulting in high Faradaic efficiency, current density, and stability of CO₂RR at low overpotentials.     

Thermal homolytic fission of the MoMo bond in (h5 -C5H5)2Mo2(CO)6

Kinetic studies of reactions of the MoMo bonded complex (h⁵-C₅H₅)₂Mo₂(CO)₆ in decalin show that it undergoes reversible homolytic fission and that the activation enthalpy required to break the MoMo bond is 135.9 ± 2.2 kJ mol^?1.     

The standard enthalpy of formation of silver pivalate

The standard enthalpy of combustion of crystalline silver pivalate, (CH₃)₃CC(O)OAg (AgPiv), was determined in an isoperibolic calorimeter with a self-sealing steel bomb, Δ_c H ⁰ (AgPiv, cr)= −2786.9±5.6 kJ mol⁻¹. The value of standard enthalpy of formation was derived for crystalline state: Δ_f H ⁰(AgPiv,cr)= −466.9±5.6 kJ mol⁻¹. Using the enthalpy of sublimation, measured earlier, the enthalpy of formation of gaseous dimer was obtained: Δ_f H ⁰(Ag₂Piv₂,g)= −787±14 kJ mol⁻¹. The enthalpy of reaction (CH₃)₃CC(O)OAg(cr)=Ag(cr)+(CH₃)₃CC(O)O^.(g) was estimated, Δ_r H ⁰=202 kJ mol⁻¹.     

Chemistry of NOx and HNO3 Molecules with Gas-Phase Hydrated O.− and OH− Ions

The gas-phase reactions of O ^{. −}(H₂O)_n and OH⁻(H₂O)_n, n=20–38, with nitrogen-containing atmospherically relevant molecules, namely NO_x and HNO₃, are studied by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry and theoretically with the use of DFT calculations. Hydrated O ^{. −} anions oxidize NO ^. and NO₂ ^. to NO₂⁻ and NO₃⁻ through a strongly exothermic reaction with enthalpy of −263±47 kJ mol⁻¹ and −286±42 kJ mol⁻¹, indicating a covalent bond formation. Comparison of the rate coefficients with collision models shows that the reactions are kinetically slow with 3.3 and 6.5 % collision efficiency. Reactions between hydrated OH⁻ anions and nitric oxides were not observed in the present experiment and are most likely thermodynamically hindered. In contrast, both hydrated anions are reactive toward HNO₃ through proton transfer from nitric acid, yielding hydrated NO₃⁻. Although HNO₃ is efficiently picked-up by the water clusters, forming (HNO₃)_0–2(H₂O)_mNO₃⁻ clusters, the overall kinetics of nitrate formation are slow and correspond to an efficiency below 10 %. Combination of the measured reaction thermochemistry with literature values in thermochemical cycles yields ΔH_f(O⁻(aq.))=48±42 kJ mol⁻¹ and ΔH_f(NO₂⁻(aq.))=−125±63 kJ mol⁻¹.     

Frontispiece: Induced-Fit-Identification in a Rigid Metal-Organic Framework for ppm-Level CO2 Removal and Ultra-Pure CO Enrichment

Removing CO₂ from crude syngas via physical adsorption is an effective method to yield eligible syngas. However, the bottleneck in trapping ppm-level CO₂ and improving CO purity at higher working temperatures are major challenges. Here we report a thermoresponsive metal–organic framework ( 1 a-apz ), assembled by rigid Mg₂(dobdc) ( 1 a ) and aminopyrazine (apz), which not only affords an ultra-high CO₂ capacity (145.0/197.6 cm³ g⁻¹ (0.01/0.1 bar) at 298 K) but also produces ultra-pure CO (purity ≥99.99 %) at a practical ambient temperature (T_A). Several characterization results, including variable-temperature tests, in situ high-resolution synchrotron X-ray diffraction (HR-SXRD), and simulations, explicitly unravel that the excellent property is attributed to the induced-fit-identification in 1 a-apz that comprises self-adaption of apz, multiple binding sites, and complementary electrostatic potential (ESP). Breakthrough tests suggest that 1 a-apz can remove CO₂ from 1/99 CO₂/CO mixtures at practical 348 K, yielding 70.5 L kg⁻¹ of CO with ultra-high purity of ≥99.99 %. The excellent separation performance is also revealed by separating crude syngas that contains quinary mixtures of H₂/N₂/CH₄/CO/CO₂ (46/18.3/2.4/32.3/1, v/v/v/v/v).     

Photo-thermal Cooperative Carbonylation of Ethanol with CO2 on Cu2O-SrTiCuO3-x

Carbonylation of ethanol with CO₂ as carbonyl source into value-added esters is of considerable significance and interest, while remains of great challenge due to the harsh conditions for activation of inert CO₂ in that the harsh conditions result in undesired activation of α-C−H and even cleavage of C−C bond in ethanol to deteriorate the specific activation of O−H bond. Herein, we propose a photo-thermal cooperative strategy for carbonylation of ethanol with CO₂, in which CO₂ is activated to reactive CO via photo-catalysis with the assistance of *H from thermally-catalyzed dissociation of alcoholic O−H bond. To achieve this proposal, an interfacial site and oxygen vacancy both abundant SrTiCuO_3-x supported Cu₂O (Cu₂O-SrTiCuO_3-x) has been designed. A production of up to 320 μmol g⁻¹ h⁻¹ for ethyl formate with a selectivity of 85.6 % to targeted alcoholic O−H activation has been afforded in photo-thermal assisted gas-solid process under 3.29 W cm⁻¹ of UV/Vis light irradiation (144 °C) and 0.2 MPa CO₂. In the photo-driven activation of CO₂ and following carbonylation, CO₂ activation energy decreases to 12.6 kJ mol⁻¹, and the cleavage of alcoholic α-C−H bond has been suppressed.