Activation Energy For Hydrolysis Research Articles

Enhanced hydrolysis of MgH₂ by transition metal oxides and NaH: Performance, mechanisms, and optimization

MgH₂ is recognized as a promising material for hydrogen production due to its high hydrogen density, abundant availability, and non-polluting hydrolysis by-products, making it a viable hydrogen source for fuel cells. This study, for the first time, investigates the hydrogen production performance of the MgH₂-MOx-NaH (M = Ti, Zr, Mo, Fe, V, Bi) system, which exhibits remarkable hydrolysis properties in aqueous solutions. A series of MgH₂-MOx-NaH composite powders were synthesized via mechanical ball milling. The results revealed that V₂O₅-NaH and Bi₂O₃-NaH significantly enhanced the hydrolysis performance of MgH₂ for hydrogen production. Specifically, Bi₂O₃-NaH and V₂O₅-NaH effectively refined MgH₂ particles and mitigated agglomeration during the milling process. Hydrolysis tests demonstrated that the conversion rate and the hydrogen generation rate (mHGR) of composites initially increased with ball milling time and then decreased. The maximum hydrolysis hydrogen production yield and conversion rate for MgH₂-Bi₂O₃-NaH and MgH₂-V₂O₅-NaH composites occurred at a ball milling duration of 10 hours, and reached up to 1354.1 mL g⁻¹ (88.5 %) and 1273.5 mL g⁻¹ (81.8 %), respectively, within 8 minutes. Kinetic tests of hydrolysis hydrogen production showed that the reaction rate and hydrogen conversion increased with elevated hydrolysis temperatures. The activation energies for the hydrolysis of MgH₂-MOx-NaH (M = Ti, Zr, Mo, Fe, V, Bi) were calculated from the hydrolysis-hydrogen production curves using the Arrhenius formula, yielding values of 41.32, 37.66, 36.40, 34.60, 30.80, and 27.17 kJ mol⁻¹, respectively. The lower activation energies for hydrolysis indicate improved reaction kinetics, suggesting that the incorporation of transition metal oxides and sodium hydride effectively enhances both the hydrolytic conversion and reaction rate of MgH₂.

Development of Cost-Effective Sn-Free Al-Bi-Fe Alloys for Efficient Onboard Hydrogen Production through Al–Water Reaction

Leveraging the liquid-phase immiscibility effect and phase diagram calculations, a sequence of alloy powders with varying Fe content was designed and fabricated utilizing the gas atomization method. Microstructural characterizations, employing SEM, EDS, and XRD analyses, revealed the successful formation of an incomplete shell on the surfaces of Al-Bi-Fe powders, obviating the need for Sn doping. This study systematically investigated the microstructure, hydrolysis performance, and hydrolysis process of these alloys in deionized water. Notably, Al-10Bi-7Fe exhibited the highest hydrogen production, reaching 961.0 NmL/g, while Al-10Bi-10Fe demonstrated the peak conversion rate at 92.99%. The hydrolysis activation energy of each Al-Bi-Fe alloy powder was calculated using the Arrhenius equation, indicating that a reduction in activation energy was achieved through Fe doping.

Engineering of the ferrite-based support for enhanced performance of supported Pt, Pd, Ru, and Rh catalysts in hydrogen generation from NaBH4 hydrolysis

A series of M/NiCo-Ferrite (M: Pt, Pd, Ru, and Rh) nanoparticles were successfully synthesized, through a facile sol–gel auto-combustion followed by impregnation-reduction approach, as a catalyst for hydrogen generation from hydrolysis of NaBH4. All synthesized samples were characterized by XRD, N2 adsorption–desorption method, ICP-OES, FE-SEM, and EDX analysis. Compared to the other samples, it was observed that the Rh/NiCo-Ferrite sample exhibited higher particle distribution and surface area. To evaluate the hydrogen generation rate, the hydrolysis was carried out at a temperature of 35 °C, with an aqueous solution containing 5 wt.% NaBH4 and 3 wt.% NaOH. The experimental findings indicate that the Rh/NiCo-Ferrite sample exhibited a superior rate of hydrogen generation, with an average value of 11,667 mL/min.gcat, compared to the other samples studied. Enhanced catalytic properties may be responsible for its high activity. In addition, the activation energy of hydrolysis of sodium borohydride over the Rh/NiCo-Ferrite sample was 54.5 kJ/mol which is lower than the activation energy of many Ferrite-based catalysts. Moreover, the re-usability test of the Rh/NiCo-Ferrite sample denoted a decline in the catalytic activity after 4 recycling experiments due to the alterations in morphology and the reduction in the quantity of active phase.

Enhanced hydrolysis of NaBH4 using cobalt sulphide for hydrogen production

The generation of pollution free hydrogen through NaBH4 hydrolysis using the suitable low cost catalysts is promising technique for sustainable green energy production. Herein, we report the facile synthesis of cobalt sulphide (CoS) using the hydrothermal technique and catalysed hydrolysis of NaBH4 for hydrogen generation. CoS nanoparticles show obvious catalytic performance with hydrogen generation rate (HGR) of 328 mL min−1 g−1cat at 25 °C in 2.9 % (1.5 g) NaBH4. Importantly, owing to low activation energy for hydrolysis of about 58.8 kJ mol−1 and efficient hydrolysis, CoS nanoparticles enables the NaBH4 hydrolysis with HGR of 319 mL min−1 g−1cat at 50 °C with 0.1 g NaBH4. The HGR is significantly enhanced from 119 mL min−1 g−1cat in dark to 214 mL min−1 g−1cat in illumination with 0.5 g NaBH4 and 60 mg catalysts. Finally, the present findings advocate the development of sulphide based non-precious catalysts for solar light driven hydrolysis of NaBH4.

Effects of solution concentration and water amount on hydrogenation performance of MgH2

Hydride hydrolysis reaction is a promising method for on-site hydrogen production with high capacity. However, ensuring a certain amount of water and the formation of a passivation layer in the produced material is crucial to interrupt the reaction. In this experimental study, multiple hydrolysis experiments using chloride solutions at concentrations of 0.1 M, 0.5 M, and 1 M were investigated. Hydrolysis kinetics curves were measured at different temperatures. The resulting hydrolyzed products underwent analysis of phase and morphology using XRD and SEM scanning techniques, and the hydrolysis mechanism was examined. The results demonstrated that the hydrolysis activation energy for the 0.1 M, 0.5 M, and 1 M MgCl2 solutions was determined to be 42.62 ± 7, 37.4 ± 0.6, and 27.1 ± 0.5 kJ/mol, respectively, establishing the impact of concentration on the hydrolysis kinetics. Moreover, water reduction tests conducted under the original conditions revealed that using 0.1 M FeCl3 and 0.1 M AlCl3 solutions with 5 mL water yielded a hydrolysis yield of 1500 mL/g, and the conversion rate can reach 97 % in 2 mL of water in 0.5 M FeCl3 solution. These remarkable hydrolysis properties of MgH2 are significant for the study of related magnesium-based alloy hydrides.

In Situ Preparation of 2D Co-B Nanosheets@1D TiO2 Nanofibers as a Catalyst for Hydrogen Production from Sodium Borohydride

In this study, 2D Co-B nanosheet-decorated 1D TiO2 nanofibers (2D Co-B NS-decorated 1D TiO2 NFs) are synthesized via electrospinning and an in situ chemical reduction technique. The as-prepared catalyst showed excellent catalytic performance in H2 generation from sodium borohydride (SBH). When compared to naked Co-B nanoparticles, the catalytic activity of the 2D Co-B NS-decorated 1D TiO2 NFs catalyst for the hydrolysis of SBH is significantly enhanced, as demonstrated by the high hydrogen generation rate (HGR) of 6020 mL min−1 g−1 at 25 °C. The activation energy of hydrolysis was measured to be 30.87 kJ mol−1, which agreed with the reported values. The catalyst also showed good stability. Moreover, the effects of SBH, catalyst concentration, and temperature on the catalytic performance of 2D Co-B NS-decorated 1D TiO2 NFs were studied to gain a comprehensive understanding of the dehydrogenation mechanism of SBH. Based on these findings, we conclude that 2D Co-B NS-decorated 1D TiO2 NFs are effective catalytic materials for the dehydrogenation of SBH.

Weak Temperature Dependence of the Relative Rates of Chlorination and Hydrolysis of N2O5 in NaCl–Water Solutions

We have measured the temperature dependence of the ClNO2 product yield in competition with hydrolysis following N2O5 uptake to aqueous NaCl solutions. For NaCl-D2O solutions spanning 0.0054-0.21 M, the ClNO2 product yield decreases on average by only 4 ± 3% from 5 to 25 °C. Less reproducible measurements at 0.54-2.4 M NaCl also fall within this range. The ratio of the rate constants for chlorination and hydrolysis of N2O5 in D2O is determined on average to be 1150 ± 90 at 25 °C up to 0.21 M NaCl, favoring chlorination. This ratio is observed to decrease significantly at the two highest concentrations. An Arrhenius analysis reveals that the activation energy for hydrolysis is just 3.0 ± 1.5 kJ/mol larger than for chlorination up to 0.21 M, indicating that Cl- and D2O attack on N2O5 has similar energetic barriers despite the differences in charge and complexity of these reactants. In combination with the measured preexponential ratio favoring chlorination of 300-200+400, we conclude that the strong preference of N2O5 to undergo chlorination over hydrolysis is driven by dynamic and entropic, rather than enthalpic, factors. Molecular dynamics simulations elucidate the distinct solvation between strongly hydrated Cl- and the hydrophobically solvated N2O5. Combining this molecular picture with the Arrhenius analysis implicates the role of water in mediating interactions between such distinctly solvated species and suggests a role for diffusion limitations on the chlorination reaction.

Shoreline Drying of Microseira (Lyngbya) wollei Biomass Can Lead to the Release and Formation of Toxic Saxitoxin Analogues to the Water Column.

The harmful, filamentous cyanobacteria Microseira (Lyngbya) wollei produces several toxic analogues of saxitoxin (Lyngbya wollei toxins 1-6, or LWTs 1-6), grows in shallow water, and can deposit significant biomass on nearby shorelines. Here, we show that the LWTs are stable in the biomass during subsequent drying but that the process facilitates the later release of LWTs upon return to the water column. Under basic conditions, LWTs hydrolyzed to generate products that were significantly more neurotoxic than the initial toxins. Aqueous LWTs were subjected to conditions of covarying temperature and pH, and their degradation rates and products were determined at each condition. LWTs 1, 5, and 6 degraded faster at pH ≥ 8 at all temperatures. Their degradation products, which included decarbamoyl saxitoxin and LWT 4, were consistent with a base-catalyzed hydrolysis mechanism and represented a net increase in total biomass toxicity normalized against the equivalent toxicity of saxitoxin. The corresponding pre-exponential terms and activation energies for hydrolysis were obtained for pH 6-10 over the temperature range 10-40 °C. A locally weighted scatterplot smoothing (LOWESS) regression was developed to predict the loss of parent toxins and subsequent products in the water column under conditions corresponding to those commonly encountered in cyanobacterial blooms.

Hydrolysis susceptibility and carbamate formation for a low moisture-absorbing, siloxane-modified cyanate ester resin matrix (TC410) material used for composite space applications

Siloxane-modified cyanate ester resins are ideal matrix materials for next-generation, high-precision composites used for radomes and satellite structures. They provide extremely low moisture uptake, excellent microcracking resistance, and protection from atomic radiation. However, cyanate ester resins have been shown to be susceptible to hydrolysis during cure, which may significantly impact both mechanical and thermal performance. In this investigation, we evaluate the cure kinetics and hydrolysis susceptibility of a siloxane-modified prepreg system (TC410/M55J). DSC tests verified that the Ea of polymerization for the TC410 system is 65 KJ/mol. Samples were also exposed to moisture during cure at several temperatures, and FTIR was used to follow changes in the carbonyl peak absorption intensity to compare the rate kinetics and activation energy for hydrolysis leading to carbamate formation (52 KJ/mol). DMA tests of composites exhibited significantly reduced Tg’s with increasing moisture levels during cure. TGA of these cured samples exhibited both a significant decrease in the onset of the thermal decomposition temperature as well as an increase in the relative degree of volatiles generated at low temperature. Flatwise tension strength tests showed a linear reduction in strength with decreasing Tg, at an equivalent trend to previous work on an M55J/RS3C system indicating a similar mechanism. However, the added margin provided from the higher initial FWT strength in the TC410 system allows for larger decreases in Tg before significant degradation occurs. Laminates manufactured on composite mandrels resulted in parts with larger decreases in the tool-side Tg of the part when compared to the bag-side Tg, with the differential depending on the initial moisture content of the tool. AFM was shown to selectively identify these carbamate-affected regions by showing that the recession behavior of these less cross-linked areas was greater than in areas where the resin was properly cured. Composites with increased carbamate formation resulted in increasing warpage of the part with elevated temperature exposure due to variations in stress relaxation. This effect should be considered when manufacturing precision, high-dimensional stability composite hardware.

Bilayer MOF@MOF and MoO species functionalization to access prominent stability and selectivity in cascade-selective biphase catalysis

• MoO x @UiO-66@MoO x @UiO-bpy showed well stability and selectivity in cascade-selective catalysis. • Micro-mesopores and increased surface area facilitated molecules diffusion. • Bilayer structure offered platform to capture-convert intermediates to target product. • Cyclopentene oxide hydrolysis activation energy was further reduced. • Mechanism of cyclopentene oxidation over MoO x @UiO-66@MoO x @UiO-bpy was proposed. A novel bilayer metal-organic framework ( viz. , MOF@MOF, based on Zr-MOFs via epitaxial growth of UiO-bpy on preformed UiO-66) assembled with two-dimensional MoO x species was designed and synthesized. The MoO x @UiO-66@MoO x @UiO-bpy composite would improve substrates/products diffusion, avoid active metals leaching, and crucially provide a new platform via trapping intermediates and regulating the desired reaction direction. As confirmed via characterization results, MoO x @UiO-66@MoO x @UiO-bpy with micro-/mesopores and strong acid sites (Lewis and Brønsted) exhibited good thermal and chemical stability. The bilayer MoO x @UiO-66@MoO x @UiO-bpy was further tested in cascade-selective biphase cyclopentene oxidation and exhibited 10.3% cyclopentene conversion and 16.9% glutaric acid selectivity higher than those of MoO x @UiO-66, due to its large specific surface area, high content of MoO x species, micro-/mesoporous structure, and bilayer catalytic effect. Its good reusability (> 10 runs) in the solvent-free-biphase cyclopentene oxidation suggested multidimensional encapsulation of active species in bilayer MOFs providing new idea for designing high-selectivity/stability heterogeneous catalysts. Besides, a set of reaction kinetic models with detailed kinetic parameters and a detailed reaction mechanism were provided, reconfirming the key to develop the technology of cyclopentene to glutaric acid was to conquer cyclopentene oxide hydrolysis activation energies (E 2 and E 4 ). Compared to our previous study, E 2 and E 4 values were decreased 93.8 and 31.7 kJ⋅mol −1 , respectively.

Quantification and kinetic study of the main compounds in biocrude produced by hydrothermal carbonization of lignocellulosic biomass

The biomass hydrothermal carbonization (HTC) reaction pathway to the formation of primary and secondary hydrochar is proposed in this study. Total sugars were the main product in biocrude at low temperature; their concentration decreased as the temperature increased, producing organic acids and furans. Kinetic study reveals that the hydrolysis activation energy increased as hemicellulose content decreased. Indeed, a value of 63.08 kJ/mol was found for biomass rich in hemicellulose (avocado stone) while for biomass composed of a hemicellulose-cellulose mixture (agave bagasse) the value was 85.02 kJ/mol, and for α-cellulose it was 136.24 kJ/mol. Contrastively, the activation energy for furans formation was higher than that for organic acids in any case. A proposed14-reactions mechanism adequately describes the HTC process considering intermediate to final products (R2 > 0.98). The higher heating value (HHV) of hydrochars was between 22 and 26 MJ/kg, with an energy densification of 34 to 49% compared to the corresponding feedstock.

Metal-Free Supramolecular Catalytic Hydrolysis of Ammonia Borane through Cucurbituril Nanocavitands

Ammonia borane (AB) is considered a potential "on-board" hydrogen storage material. However, its implementation as a hydrogen reservoir in fuel cells is lacking due to the extremely slow release of hydrogen at room-temperature hydrolysis. In this study, a metal-free supramolecular strategy is demonstrated at room temperature to increase the hydrolysis rate and yield of hydrogen along with significant reduction in ammonia release by using cucurbit[5/8]uril (CB5/CB8) nanocavitands as catalysts. The complex of AB with CB stabilizes the ammonium ion at the host portals, which reduces ammonia release and enhances hydrogen yield. The complexation brings down the activation energy of hydrolysis from 103.8 to ∼27.5 kJ mol-1 (for CB5), a value close to the Pt/Pd nanoparticle-based catalysts reported so far. The high catalytic performance and reusability of CB catalysts at very low concentration make AB a promising supramolecular alternative for a sustainable "on-board" energy source.

Surface reaction of the hafnium precursor with a linked amido-cyclopentadienyl ligand: A density functional theory study

We studied heteroleptic Hf precursors with a linked amido-cyclopentadienyl ligand by density functional theory (DFT) calculation to enable high-temperature atomic layer deposition processes. The thermolysis and hydrolysis of Hf precursors were simulated to expect thermal stability and reactivity with hydroxyl groups. The effects of alkyl groups in the precursors were also investigated. We constructed the hydroxylated HfO2 surface and then simulated the surface reactions of the precursors. The precursors with the linked ligand showed higher activation energies for thermolysis and lower activation energies for hydrolysis as compared with CpHf(NMe2)3. The precursors with the linked ligand also showed low activation energies for the serial ligand exchange reactions on the HfO2 surface, significantly lower than those of CpHf(NMe2)3. Therefore, the DFT calculation suggests that the Hf precursors with the linked ligand are promising due to their thermal stability and reactivity better than CpHf(NMe2)3.

Mono-substituted polyoxometalate clusters@Zr-MOFs: Reactivity, kinetics, and catalysis for cycloolefins-H2O2 biphase reactions

Abstract Advanced heterogeneous catalytic materials, mono-substituted polyoxometalate clusters@Zr-MOFs (i.e., M-POM@Zr-MOFs, M= Co or Cu), with multi-acid sites, effective catalytic sites, stable active sites, and directive selectivity are reported and applied in liquid (cycloolefin)-liquid (H2O2) biphase selective oxidation system. One of the M-POM@Zr-MOFs crystals, Co-POM@UiO-bpy, when acted as the catalyst for cyclopentene selective oxidation, displayed excellent catalytic ability (76.3 % cyclopentene conversion and 95.0 % glutaric aicd selectivity) and superior cycling stability. Further investigation uncovered that this excellent catalytic performance could be assigned to the cooperative catalysis of metal clusters (i.e., Zr-OH(OH2)) in Zr-MOFs host framework, the gust Co-POM molecules, and the functional groups (viz., bipyridines). Moreover, for the first time, a set of mechanism steps for cyclopentene oxidation with detailed kinetic parameters (i.e., reaction rate constants (k1∼5) and activation energies (E1∼5)) were proposed, and it was indicated that the key to develop this reaction is to reduce cyclopentene oxide hydrolysis activation energy (E2 and E4). This work provides a new option for the development of POM@MOFs catalysts and supplies a new perspective for cycloolefins selective oxidation to dicarboxylic acids.

Design of Copper Microfabricated Potentiometric Sensor for in‐line Monitoring of Neostigmine Degradation Kinetics

AbstractThe quality of pharmaceutical products is critical for human health. Drug development requires tools to assess the presence of degradation products and contaminants during the manufacturing and storage processes. Accelerated stress degradation and kinetic studies play a vital role in predicting final product stability. This work describes the design of potentiometric sensor based on copper microfabricated electrodes for in‐line tracking the degradation kinetics of neostigmine. The proposed electrochemical technique provides a continuous profile for the hydrolysis of NEO under different temperatures and pH. The hydrolysis activation energy was found to be 18.88 kcal mol−1 which was aligned with the reported hydrolysable ester values. Consequently, the kinetic data analysis is crucial to predict the optimum analysis and storage conditions.

Kinetics study of enzymatic hydrolysis of Tetraselmis chuii using Valjamae model

The Tetraselmis chuii microalgae have a potential as an alternative raw material for producing bioethanol, because of its low lignin and high carbohydrate content. The purpose of this research is to study the kinetics of enzymatic hydrolysis of Tetraselmis chuii using Valjamae model. This experiment was carried out with a variety of enzymes (cellulase, xylanase, and cellulase-xylanase mixture, enzyme concentrations (10, 20, and 30% w/w), times (10, 20, 30, and 40 min), and temperatures (40 and 45 °C). The results show that the activation energy of hydrolysis using cellulase-xylanase mixture is 27,253 J/mol, xylanase 116,121J/mol, and cellulose 140,914 J/mol. At 45 °C, the concentration of the cellulase-xylanase mixture increased (10, 20, and 30% w/w), the reaction rate constants (0.028, 0.110, and 0.171 1/min) as well as the fractal exponents (0.4, 0.6, and 0.7). Thus, the glucose production rate is higher, where at 40 minutes produces higher yields (23.5, 25.5, 28.5, and 32.5%). In this study, the constant rate of Tetraselmis chuii hydrolysis using cellulase-xylanase mixture at 45 °C is 0.1714 1/min; higher than the one conducted at 40°C which is 0.1454 1/min. The kinetic parameters of the enzymatic hydrolysis are expected to help in bioreactor design.

Rapid catalytic hydrolysis performance of Mg alloy enhanced by MoS2 auxiliary mass transfer

Mg10Ni-MoS2 composites were synthesized, and the amount of molybdenum disulfide (MoS2) and ball milling time was optimized to obtain rapid initial kinetics with high conversion yield at room temperature in simulated seawater. The microstructures and H2 generation thermodynamics were comprehensively investigated to demonstrate the main influential factors on excellent initial hydrolysis performance. Mg10Ni-5 wt%MoS2-15 min can generate 493.3 mL·g-1 H2 at 298 K with 58% yield in 20 s. The H2 generation capabilities of Mg10Ni-5 wt% MoS2-15 min are 569 mL·g-1 H2 and 67%, which are higher than those of Mg10Ni (495 mL·g-1 H2, 56%) in 2 min. The lowest hydrolysis activation energy (18.74 kJ·mol-1) can be achieved by Mg10Ni-5 wt%MoS2, which means low energy consumption. Mg10Ni with higher specific surface area (4.04 m2⋅g-1) than that of Mg10Ni-5wt.%MoS2-15 min (0.78 m2⋅g-1) presents worse H2 generation performance, indicating that higher specific surface area is the secondary determinant for superior initial hydrolysis kinetics and higher conversion yield compared with the added MoS2. The added MoS2 with specific morphologic structure can provide auxiliary mass transfer paths, which shorten the transfer distance and destroy the continuous colloidal layer. Mg-rich alloys optimized for rapid and efficient H2 production performance are expected to be applied large-scale H2 generators.

Kinetic Models for Glucosamine Production by Acid Hydrolysis of Chitin in Five Mushrooms

In this paper, glucosamine was produced by acid hydrolysis of five mushrooms. The glucosamine yields were investigated, and the optimum conditions were obtained as follows: acid type, sulfuric acid; acid concentration, 6 M; ratio of raw material to acid volume, 1 : 10; hydrolysis temperature, 100°C; and time, 6 h. Under these conditions, the glucosamine conversion from chitin content reached up to 92%. The results of hydrolysis kinetics indicated that hydrolysis of five mushrooms to glucosamine followed zero-order kinetics. Moreover, the relatively low activation energy for hydrolysis of straw mushroom (18.31 kJ/mol) and the highest glucosamine yield (56.8132 ± 3.5748 mg/g DM, 0.9824 g/g chitin) indicated that hydrolysis of straw mushroom was energy-saving. Thus, sulfuric acid hydrolysis of straw mushroom for glucosamine production should be considered as an efficient process for the future industrial application. However, further study is needed for glucosamine purification.

Hydrolysis of Chloramphenicol Catalyzed by Clay Minerals under Nonaqueous Conditions.

Soil contamination with antibiotics has raised great environmental concerns, while the abiotic degradation of antibiotics on drought soil particles has been largely ignored. In this study, we examined the transformation of chloramphenicol (CAP) on phyllosilicates under nonaqueous conditions. A significant hydrolysis of CAP mediated by kaolinite occurred under moderate relative humidities (RH: 33-76%) with the half-lives of 10-20 days. By contrast, incubation with montmorillonite did not result in detectable degradation of CAP. Infrared and Raman spectroscopies together with density functional theory calculations suggested that the surface-catalyzed CAP hydrolysis was mainly attributed to the basal plane hydroxyl groups of kaolinite, which formed hydrogen-bond interactions with the carbonyl of CAP such that the hydrolysis activation energy of CAP was greatly reduced. Neither the Brønsted nor the Lewis acidity was the determinant for the hydrolysis reaction. The surface moisture content played an essential role in CAP hydrolysis. Specifically, water facilitated the mass transfer of CAP over the low-RH range, whereas excessive water competed for the reactive hydroxyl sites. These results highlight an important but long-overlooked abiotic transformation pathway for antibiotics in field soil, where the soil moisture is low and the microbial activity is suppressed.

Molecular orbital studies of the initial process of gallium oxide chemical vapor deposition: micro-hydrolysis of triethylgallium

Gallium-doped zinc oxide films prepared by atomic layer deposition have received much attention. When triethylgallium is hydrolyzed on the surface of zinc hydroxide, a multi-layered metal oxide film containing a specific amount of gallium at a controlled position is formed. In this study, to elucidate the micro-hydrolysis mechanism of triethylgallium, reaction mechanisms involving one or two water molecules were investigated by molecular orbital calculations. The complete hydrolysis of triethylgallium occurs in three steps with the first partial hydrolysis being the rate limiting step. The activation energy of hydrolysis by two molecules of water is ∼10 kcal mol−1 lower than that with one molecule of water for all steps. The addition of further water molecules significantly decreases the activation energy because the transition state is stabilized by hydrogen bonding between the water molecules. These results suggest the hydrolysis reaction proceeds spontaneously under mild conditions by controlling the concentration of water molecules.