Gas Sorption Research Articles

Estimating Gas Sorption In Polymeric Membranes From The Molecular Structure: A Machine Learning Based Group Contribution Method For The Non-Equilibrium Lattice Fluid Model (ML-GC-NELF)

Since its inception, the non-equilibrium lattice fluid (NELF) model has become a vital tool in correlating and predicting the gas solubility behaviour in glassy polymeric membranes. But like its equilibrium variant, the NELF model is highly constrained by the availability of the pure polymer characteristic parameters, which are not always convenient to obtain as the need arises. In this study, we provide a proof-of-concept for building a machine learning-based group contribution method (ML-GC) for the Sanchez–Lacombe equation of state (EoS) pure polymer parameters. The ML-GC model was built using a modified version of the Marrero and Gani’s method, which incorporates machine learning regression into the GC parameterisation process. The final model was capable of reproducing the parameters of a randomly selected test set of polymers, with a diverse range of chemical structures. The resultant average AARD% of the predicted densities in this set is 5.59%, with no polymer exceeding 15%. Moreover, to test the model’s capabilities in estimating the parameters of high glass transition temperature polymers, we predicted a priori the characteristic parameters of 6 polyimides from the knowledge of their molecular structure. The ML-GC parameters were also incorporated into the NELF model to predict the infinite dilution solubility coefficients (S0) of some of these polymers and the results were validated against experimental data. Furthermore, the ML-GC-NELF model was also used for the first time to represent effectively the gas solubility isotherms in PIM-PI-SBI and PIM-PI-EA with relatively small magnitudes of the binary interaction parameters (kij). Despite the small data-set used herein, the model performance was satisfactory, however, as more data are being published in literature, the proposed ML-GC model has the potential of providing even more accurate predictions for a wider range of polymers, ultimately leading to lesser reliance on experimental data for modelling the gas sorption.

Studies of Isotopic Fractionation of D/H Water Ice in Lunar Regolith

In order to study the processes related to the origin and retention of water on the surface of the Moon, an experimental setup has been created at the Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences (GEOKHI RAS), for the analysis of (re)sublimation processes of water ice in a vacuum at low temperatures. The temperature range for (re)sublimation varies from –100 to 0°C. The setup is connected to an Isotope Ratio Mass Spectrometer (IRMS), which allows for measuring the isotopic composition of the vapor of the evaporating substance and providing an estimation of the (re)sublimation rate under specific physicochemical conditions. The direct introduction of gases into the mass spectrometer in real-time mode sets the developed setup apart from foreign counterparts. The setup is equipped with a transparent quartz window through which the surface of the studied substance can be heated using a halogen lamp, simulating the movement of solar rays on the surface of mineral grain compositions under conditions similar to those on the lunar surface. In addition to studying gas (de)sorption on the surfaces of mineral grains of various compositions, the setup can also be used for researching the (re)sublimation of gas hydrates and CO2.

Understanding ageing mechanism of carbon electrodes in double layer capacitors operating in organic electrolytes

Understanding the ageing mechanisms of porous carbon electrodes used in electrochemical double layers supercapacitors (EDLCs) is of high importance to improve their lifetime. In this work, we studied ageing of two different porous carbons with different pore size distribution and surface functionalities in 1.5 M tetraethyl ammonium tetrafluoroborate (Et4NBF4) in acetonitrile (AN) electrolyte. The combination of Raman spectroscopy, thermogravimetric analysis (TGA), gas sorption and electrochemical impedance spectroscopy techniques allowed us to identify two different behaviors depending on the porous carbon used. A microporous carbon experiences an ionic/electronic resistance increase leading to a capacitance fall off upon cycling, associated with pore clogging. This resulted from the electrolyte degradation taking place at the positive electrode combined with porous carbon oxidation. Differently, only an increase of the series resistance was observed for the mesoporous carbon tested, following the creation of defects at the positive carbon electrode.

Molten salt method derived porous carbon with high energy density in KI-additive electrolyte

A series of porous carbons (PCs) with tunable surface areas were prepared by molten salt (NaCl/KCl) method with the assistance of CaCO3. Gas sorption analyses by N2 and CO2 show that the usage of CaCO3 leads to the increasement of in micropores and mesopores, thus enlarging the surface area up to 864 from 425 m2 g−1. Besides, numerous micropores (<0.6 nm) inaccessible to N2 can be detected by CO2. Supercapacitive performance for PCs was also investigated in aqueous KOH, H2SO4 and KI-additive (H2SO4 + KI) electrolytes as well. Combining the results of pore-structure analysis, the investigations on the relationship between specific capacitance and pore-size show that the minimum pore entrance for SO42−, K+ and I− are 0.4, 0.32 and 0.4 nm, respectively. Considering the naked/solvated ionic sizes of SO42− (0.38/0.58 nm), K+ (0.26/0.42 nm) and I− (0.39/0.66 nm), desolvation effect probably occurs in those aqueous electrolytes. Moreover, the effect of oxygen functionalities on the redox reaction was also investigated in this work. It is found that the quinone oxygen species is electrochemically active in both H2SO4 and KI-additive electrolytes. With the addition of KI in electrolyte, the prepared porous carbon-based supercapacitor possesses high specific energy of 55.7 Wh kg−1.

Engineering pore-size distribution of metal-loaded carbon catalysts by in situ cavitation for boosting electrochemical mass transfer

In addition to highly active catalytic sites, mass transfer, especially diffusion of the reactant/product also play important roles in supported electrocatalyst systems. However, compared with the morphologies and specific surface areas, the pore structures of the catalyst supports and their influence on catalytic mass transfer have received less attention. Herein, we propose a universal in situ cavitation strategy to regulate the pore size distributions on the metal-loaded carbon through nitro modification on the molecule-based precursors, without significantly changing the electronic structures of the active metal centers. Gas sorption experiments, electrocatalytic measurements and molecular dynamic simulations certified that the increasing mesopore/macropore ratios can remarkably facilitate the diffusion coefficient, enabling improved oxygen evolution kinetics with 71 mV overpotential dropping at 10 mA·cm−2 compared with the nitro-free counterpart. This work demonstrates that the pore size distributions of the catalyst support should be another nonnegligible parameter on boosting the overall electrocatalytic performance.

Symmetry-Mismatched SBU Transformation in MOFs: Postsynthetic Metal Exchange from Zn to Fe and Its Effects on Gas Adsorption and Dye Selectivity.

This research explores the alteration of metal-organic frameworks (MOFs) using a method called postsynthetic metal exchange. We focus on the shift from a Zn-based MOF containing a [Zn4O(COO)6] secondary building unit (SBU) of octahedral site symmetry (ANT-1(Zn)) to a Fe-based one with a [Fe3IIIO(COO)6]+ SBU of trigonal prismatic site symmetry (ANT-1(Fe)). The symmetry-mismatched SBU transformation cleverly maintains the MOF's overall structure by adjusting the conformation of the flexible 1,3,5-benzenetribenzoate linker to alleviate the framework strain. The process triggers a decrease in the framework volume and pore size alongside a change in the framework's charge. These alterations influence the MOF's ability to adsorb gas and dye. During the transformation, core-shell MOFs (ANT-1(Zn@Fe)) are formed as intermediate products, demonstrating unique gas sorption traits and adjusted dye adsorption preferences due to the structural modifications at the core-shell interface. Heteronuclear clusters, located at the framework interfaces, enhance the heat of CO2 adsorption. Furthermore, they also influence the selectivity of the dye size. This research provides valuable insights into fabricating novel MOFs with unique properties by modifying the SBU of a MOF with flexible organic linkers from one site symmetry to another.

Resonance and relaxation effects governing the sorption of O2 and CO2 in deionized water under dynamic conditions at 21 ± 1 °C

The behavior of water samples (deionized, deaerated and washed with He) was investigated in dynamics by physicochemical and electrochemical methods. The susceptibility of water samples to sorption of O2 and CO2 from air depends on their pretreatment. Sorption of O2 and CO2 accompanied by the desorption of dissolved helium is a multivariable nonlinear process, presumably, based on resonance and relaxation phenomena within the surface layer. Sorption of O2 and CO2 in water is considered as an interaction between gas molecules and ensembles of H2O molecules, which is assumed to be based on resonance effects. Sorption of gases leads to a, decrease in the surface tension at the water/gas interface. The effect is most pronounced in case of He-washed samples. The decrease in the surface energy upon CO2 absorption and the increase in the relaxation properties of the water surface are probably factors that facilitate sorption of gases, including O2. A fraction of sorbed O2 are contained in nanobubbles formed via water surface relaxation. A change in the viscosity of water samples during the sorption of gases may serve as a relaxation factor favorably affecting the formation and stability of nanobubbles in the surface layer and in bulk water. Irradiation of water with a laser light at λ = 633 nm can generate nano-cavities in the laser beam. In case of very low dissolved O2 concentrations, nanobubbles have no noticeable effect on the oxygen reduction reaction. Water samples washed with helium demonstrate a higher physical and chemical activity compared to other water samples, the activity being manifested in sorption properties. Electrochemical properties of water samples - deionized, deaerated and washed with He - are somewhat different. This is primarily due to the different content of dissolved O2 in the samples. Nonempirical simulations helped in clarifying the experimental data. The key factor that predetermines stability and/or collapse of nanobubbles is the organization of the hydrogen-bond network of water that strongly depends on the presence of water ions and foreign particles. In the case of both deionized water and water washed with He, HCO3-anion cannot participate in stabilization of nanobubbles. On the other hand, OH– anions can stabilize nanobubbles.

Effect of Linker Substituent Nature on Performance of Active Sites in UiO-66: Combined FT-IR and DFT Study.

The nature of organic linker substituents plays an important role in gas sorption and separation as well as in catalytic applications of metal-organic frameworks. Zirconium-based UiO-66 is one of the most tunable members of this class of materials. However, the prediction of its properties is still not a fully solved problem. Here, the infrared spectroscopic measurements using highly sensitive CO probe molecules, combined with DFT calculations, are used in order to characterize the performance of different acidic sites caused by the presence of different organic linker substituents. The proposed model allowed differentiation between various active sites over the UiO-66 and clarification of their behavior. The experimental IR bands related to CO adsorption can be unambiguously assigned to one type of site or another. The previously undescribed highly red-shifted band is attributed to CO adsorbed on coordinatively unsaturated zirconium sites through an O atom. The results confirm the lower and higher Lewis's acidity of coordinatively unsaturated Zr sites on linker defects in the UiO-66 structure when electron-withdrawing and electron-donating groups are, respectively, included in a terephthalate moiety, whilst the Brønsted acidity of zirconium oxo-cluster remains almost unchanged.

WO3 dispersed on a titanium porous clay heterostructure as a highly efficient visible light-active photocatalyst

Nanocomposites of WO3-dispersed titanium-porous clay heterostructures (W/Ti-PCH) from montmorillonite raw clay were synthesized and reported for the first time in this paper. The nanocomposite was prepared by impregnating tungstophosphoric acid into the titanium-porous clay heterostructure (Ti-PCH). The physicochemical features of the nanocomposite were characterized by using X-ray diffraction (XRD), scanning electron microscopy energy dispersive X-ray spectroscopy (SEM-EDS), high-resolution transmission electron microscopy (HRTEM), UV–visible diffuse reflectance UV–visible spectroscopy (UV-DRS), X-ray photoelectron spectroscopy (XPS) and gas sorption analyses. Identification using XRD and XPS revealed that the dispersion of WO3 anchored on the Ti-PCH surface led to an increase in the band gap energy of the material from 3.1 eV in Ti-PCH to 3.22 eV in W/Ti-PCH. The improved characteristics support the excellent photocatalytic activity for RhB degradation, as 99.99 % removal was achieved after 15 min of treatment.

Glutamic based self-assembly urchin microsphere structure metal organic framework for gas sorption and aluminium ion sensing applications

Bio-molecules based self-assembled nano range metal-organic frameworks (MOFs) potential materials used in recent compact applications. For its structural tunability, large void area, pore volumes and eco-friendly nature. In this work, we report the same composition but different synthesized method glutamic acid cobalt node-based metal-organic compounds GACo1 and GACo2. In this material, GACo2 has the property of a nanocrystalline nature, this fundamental combination forms self-assembly uniform well-developed porous 3D urchin-like microsphere architectures with the dimension of 1.5 µm. The sorption analysis declares N2 adsorbed in the amount of 1544 ccg−1 and surface area is 2695 m2 g−1 without supercritical CO2 treatment. Interestingly, GACo2 MOF acts as a fluorescence probe for Al3+ metal ions in the aqueous phase with high selectivity and sensitivity. The KSV value and detection limit of material were 2.13 × 103 M−1 and 0.0547 × 10−7 M respectively, Also, the limit of detection is significantly lower than the WHO recommendation of Al3+ ion for drinking water ((7.41310−3 M)). Interestingly, the turn-on-sensing ability of GACo2 MOF for Al3+ ions in an aqueous medium was achieved even in the presence of a change in the pH of the solution.

In-situ gas contents of a multi-section coal seam in Sydney basin for coal and gas outburst management

The gas content is crucial for evaluating coal and gas outburst potential in underground coal mining. This study focuses on investigating the in-situ coal seam gas content and gas sorption capacity in a representative coal seam with multiple sections (A1, A2, and A3) in the Sydney basin, where the CO2 composition exceeds 90%. The fast direct desorption method and associated devices were described in detail and employed to measure the in-situ gas components (Q1, Q2, and Q3) of the coal seam. The results show that in-situ total gas content (QT) ranges from 9.48 m3/t for the A2 section to 14.80 m3/t for the A3 section, surpassing the Level 2 outburst threshold limit value, thereby necessitating gas drainage measures. Among the gas components, Q2 demonstrates the highest contribution to QT, ranging between 55% and 70%. Furthermore, high-pressure isothermal gas sorption experiments were conducted on coal samples from each seam section to explore their gas sorption capacity. The Langmuir model accurately characterizes CO2 sorption behavior, with fit coefficients (R2) greater than 0.99. Strong positive correlations are observed between in-situ gas content and Langmuir volume, as well as between residual gas content (Q3) and sorption hysteresis. Notably, the A3 seam section is proved to have a higher outburst propensity due to its higher Q1 and Q2 gas contents, lower sorption hysteresis, and reduced coal toughness f value. The insights derived from the study can contribute to the development of effective gas management strategies and enhance the safety and efficiency of coal mining operations.

Synthesis Zeolite Y From Lapindo Mud With Variations Filling Autoclave And Ratio Molar Si/Al

Lapindo mud contains Silicate (SiO2), and Aluminum oxide (Al2O3) that can be utilized to synthesize zeolite Y. Zeolite Y was synthesized from Lapindo mud via the smelting and hydrothermal method, respectively. The thermal activation of Lapindo mud was achieved by leaching smelting at 550oC for 2 hours with NaOH to achieve thed desire adding SiO2, NaOH and aging for 48 hours. The effects of various parameters on the synthesis were investigated. The samples were characterized with X-ray Fluorescence (XRF), X-Ray Diffraction (XRD), Fourier Transformation Infrared Spectroscopy (FTIR) and Gas Sorption Analyzer (GSA). Zeolite Y with high crystallinity was synthesized under optimized conditions, such as filling autoclave 90% and a SiO2/ Al2O3 molar ratio of 15.

Revaluating coal permeability-gas pressure relation under various gas pressure differential conditions

Identifying changes in coal permeability with gas pressure and accurately codifying mean effective stresses in laboratory samples are crucial in predicting gas-flow behavior in coal reservoirs. Traditionally, coal permeability to gas is assessed using the steady-state method, where the equivalent gas pressure in the coal is indexed to the average of upstream and downstream pressures of the coal, while ignoring the nonlinear gas pressure gradient along the gas flow path. For the flow of a compressible gas, the traditional method consistently underestimates the length/volume-averaged pressure and overestimates mean effective stress. The higher the pressure differential within the sample, the greater the error between the true mean pressure for a compressible fluid and that assumed as the average between upstream and downstream pressures under typical reservoir conditions. A correction coefficient for the compressible fluid pressure asymptotes to approximately 1.3%, representing that the error in mean pressure and effective stress can be on the order of approximately 30%, particularly for highly pressure-sensitive permeabilities and compressibilities, further amplifying errors in evaluated reservoir properties. We utilized this volume-averaged pressure and effective stress to correct permeability and compressibility data reported in the literature. Both the corrected initial permeability and the corrected pore compressibility were found to be smaller than the uncorrected values, due to the underestimation of the true mean fluid pressure, resulting in an overestimation of reservoir permeability if not corrected. The correction coefficient for the initial permeability ranges from 0.6 to 0.1 (reservoir values are only approximately 40% to 90% of laboratory values), while the correction coefficient for pore compressibility remains at approximately 0.75 (reservoir values are only approximately 25% of laboratory value). Errors between the uncorrected and corrected parameters are quantified under various factors, such as confining pressure, gas sorption, and temperature. By analyzing the evolutions of the initial permeability and pore compressibility, the coupling mechanisms of mechanical compression, adsorption swelling, and thermal expansion on the pore structure of the coal can be interpreted. These findings can provide insights that are useful for assessing the sensitivity of coal permeability to gas pressure as truly representative of reservoir conditions.

A thermostable calcium-based metal–organic framework for efficient capture and separation of acetylene from ternary mixture

High-efficiency and eco-friendly selective separation of C2H2 from industrial gaseous mixtures such as CO2 and CH4 is of great importance in the purification and production of downstream commodity chemicals. Herein, we report a thermostable calcium-based metal–organic framework, namely NUM-20, which could preferentially capture C2H2 from C2H2-containing gaseous mixtures. NUM-20 exhibits a higher capacity and preferential adsorption behavior of C2H2 versus the competing gases including CO2 and CH4, as reflected by single component gas sorption isotherms and the heat of adsorption. The IAST selectivity calculations indicate that NUM-20 possesses multiple component separation capacity, and the transient breakthrough simulations were performed to validate the capture and separation of C2H2 from multiple components. Furthermore, computational simulations were carried out to unveil the host–guest interactions under the molecular-level. This study on Ca-based MOF materials will enrich the three-dimensional Ca-based MOF adsorbents for gas capture and separation applications and address the industrial challenging separation process.

Optimization of Mass and Light Transport in Nanoparticle-Based Titania Aerogels.

Aerogels composed of preformed titania nanocrystals exhibit a large surface area, open porosity, and high crystallinity, making these materials appealing for applications in gas-phase photocatalysis. Recent studies on nanoparticle-based titania aerogels have mainly focused on optimizing their composition to improve photocatalytic performance. Little attention has been paid to modification at the microstructural level to control fundamental properties such as gas permeability and light transmittance, although these features are of fundamental importance, especially for photocatalysts of macroscopic size. In this study, we systematically control the porosity and transparency of titania gels and aerogels by adjusting the particle loading and nonsolvent fraction during the gelation step. Mass transport and light transport were assessed by gas permeability and light attenuation measurements, and the results were related to the microstructure determined by gas sorption analysis and scanning electron microscopy. Mass transport through the aerogel network was found to proceed primarily via Knudsen diffusion leading to relatively low permeabilities in the range of 10-5-10-6 m2/s, despite very high porosities of 96-99%. While permeability was found to depend mainly on particle loading, the optical properties are predominantly affected by the amount of nonsolvent during gelation, allowing independent tuning of mass and light transport.

Significance of organo-mineralogical constituents on pore distribution, fractals and gas sorption mechanism of Permian shale beds in Korba sub-basin of the Son-Mahanadi Valley, India

In this study, shale samples obtained from the Korbasub-basin of Central India have been evaluated for the significance of organo-inorganic constituents in terms of their source potential of gas genesis, pore-matrix setup, and gas adsorption and desorption. The samples were analysed for various properties, such as megascopic features, lithological variations, depositional facies, and sources of organic and inorganic sediments. Also, maceral content, mineralogical constituents, kerogen type, pore distribution, pore structure, fractal characteristics and gas storage capacity were examined. The analysis revealed a trend of alternating bands of carbonaceous matter, silts, intercalations, and fluvial bedding lithofacies patterns indicating that the sediments were deposited under fluvio-terrestrial-lacustrine depositional conditions. Ternary facies analysis of maceral composition and van Krevelen diagram suggested the evolutionary path of type IV kerogen and are thermally matured source material located within the dry hydrocarbon generation window. Evaluation of pore types and pore structures using BET sorption plots (hysteresis H3 and isotherm type IV) revealed the presence of cylindrical, slit and combined cylindrical-slit pores with two distinct fractal characteristics. The discrete macerals underwent partial decomposition during transportation and mixing with inorganic components (clay and minerals), which influenced organic matter preservation, gas genesis, pore fractals and storage mechanism. The chemical index of alteration (CIA – 88.36 to 91.97), weathering (CIW – 96.60 to 98.80) and compositional variation (ICV – 0.31 to 0.70) demonstrated the influence of partial decomposition and strong weathering patterns on the organo-inorganic matter. A significant correlation was observed between pore fractals and elemental composition, particularly related to the resistance of weathering elements such as MgO, Al2O3, Fe2O3, SiO2, P2O5, TiO2, etc., which partially contributed to the formation of pore rugged surfaces. Microscopic and XRD analyses were employed to determine the mineral type, grain shape and size, and their amount leading to the development of the shales brittleness index (MBI). The importance of brittle characteristics, governed by minerals and clays within the shale, is discussed in relation to the hydro-fracturing technique for permeability enhancement. The results of high-pressure methane sorption indicated a moderate gas storage potential. The variation in sorption capacity (VL – 6.65 to 8.25 cc/g) is described through relationships with the ICV, pore diameter, pore volume, liptinite and total maceral content. Fractal dimensions D1 (2.4571–2.5611) and D2 (2.5804–2.7529) exhibited a direct relationship with adsorption properties, indicating the presence of rugged surfaces associated with meso- and macro-scale pores, which primarily control gas storage in shale. This research offers detailed insights into shale gas, providing valuable information for CBM and petroleum operators engaged in methane gas exploration and production. While commercial CBM production has been ongoing in India for over a decade, the exploration and understanding of shale gas reservoir characteristics are still in progress. This investigation adds significant value and highlights the extensive opportunities for research and potentially commercially recovering shale gas in the Korba sub-basin.

Natural gas desorption versus laboratory gas adsorption with pore shrinkage

To perform hydro-mechanical experiments on sorptive geomaterials, the gas is injected into bulk of the specimen to re-saturate it representing its in-situ state, and adsorption is monitored until gas equilibrium is reached. We show in this study that this experimental procedure does not reflect the in-situ state of the sample leading to potentially significant errors. We measured the carbon dioxide (CO2) adsorption capacity of the coal specimen (free of gas) and its powder with different particle sizes and compared the results with field desorption data. Experimental results indicate an increase in coal adsorption capacity with decrease in coal particle size. Interestingly, the field data exhibits much higher desorbed gas amount compared to laboratory-measured adsorption capacity of coal powder with smallest measurable particle size under the same gas pressure. To shed light on the observation of field desorption – laboratory adsorption hysteresis, the micro-scale gas adsorption experiments combined with X-ray micro-Computed Tomography (XRCT) measurements were conducted where an intact specimen was imaged before (dry state) and after Krypton injection. The analysis of the XRCT images indicates that the Krypton adsorption closes/reduces the aperture of pre-existing fractures in the specimen. In addition, the Krypton diffuses only in a small region near pre-existing fractures despite its adsorption measurement indicating gas equilibrium and specimen saturation. This observation proposes that significant portion of pores exposed to Krypton experienced a size reduction by swelling resulting in partial saturation of the specimen. This patrial saturation at laboratory conditions evidently cannot resemble the in-situ state of gas sorption capacity.

Application of image-based diffusion coefficients in multi-scale simulation of coalbed methane reservoirs

Gas diffusion in coalbed methane (CBM) reservoirs is a multi-scale process. It can be a dominant factor in long-term gas production performance. Producing coalbed methane requires a detailed understanding of diffusion behaviours and their contribution to production. This paper develops a core-scale model based on micro-CT images. Our model considers free and adsorbed gas diffusion, sorption, and viscous flow. It also includes the effect of swelling, gas moisture, and effective stress. Following that, it is used to simulate gas flow on micro-CT images. The simulation results quantify the influence of effective stress on gas diffusion in coal. The core-scale model is then coupled to the large-scale simulation, where we compare the gas production curves against the result based on the assumption of a constant diffusion coefficient. This model can be used to calculate the effective diffusion coefficient from a micro-CT image and to predict the production performance at the reservoir scale reliably using a coupled multi-scale approach.

Preparation of Ga\(_{2}\)O\(_{3}\)-modified sulfated zirconia mesopore and its application on cellobiose hydrolysis

Heterogeneous catalyst plays vital role in biomass processing due to slow rate of biological and naturally pathway processes. Solid acid sulfated zirconia (SZ) is a promising catalyst with properties that can be tuned up. Sulfated zirconia was successfully modified by 2%, 5% and 10% (wt.) Ga2O3 (xGa-SZ; x = 2, 5 and 10) via template-assisted sol-gel method. The catalysts were characterized through various method (XRD, SEM-EDS and Gas Sorption analysis) and applied on hydrolysis of cellobiose, a model compound of cellulose. Diffraction pattern showed xGa-SZ formed completely tetragonal phase whereas un-promoted SZ contains mixed phase of monoclinic and tetragonal. Acidity evaluation via gravimetric method using ammonia as probe molecule indicates the Ga2O3 promoted sulfated zirconia has larger acidity. The SEM-EDS results confirmed the presence of Gallium element on the surface of promoted xGa-SZ. Gas sorption analysis shows specific surface area is improved (83 m2∙g-1 to 123 m2∙g-1) and increased pore radii (36 Å to 56 Å). The adsorption-desorption isotherm displayed pattern of meso-porosity material. At higher T and longer time, SZ yield more glucose than xGa-SZ. However, at shorter time, 2Ga-SZ and 10Ga-SZ show better hydrolysis performance. The solid acid 10Ga- SZ shows potential performance as heterogeneous catalyst for cellobiose conversion in modest conditions.

Effect of Gas-Phase Nitric Oxide Adsorption on ORR Activity of Fe-N-C Catalysts

Significant progress has been made in recent years in developing platinum group metal-free catalysts, particularly so-called Fe-N-C materials, for the oxygen reduction reaction (ORR) in polymer electrolyte fuel cells.1 However, further improvement in both activity and, especially, durability are still necessary for practical applications. One of the major factors that hinder the further enhancement of the catalysts is the lack of clear understanding of the nature of the active sites in the Fe-N-C catalysts due to the complexity of the Fe-N-C catalysts’ composition and structure. Gaseous nitric oxide was reported to be a suitable probe molecule that can bond to Fe and impede the ORR of the Fe-N-C catalysts.2,3 In this work, the effect of nitric oxide gas-phase adsorption on Fe-N-C catalyst redox feature and ORR activity for a variety of Fe-N-C catalysts from different origin will be investigated. The implication of these results on the nature of the ORR active sites of the Fe-N-C catalysts will be discussed.AcknowledgementsThis work was supported by the U.S. Department of Energy (DOE), Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office (HFTO) under the auspices of the Electrocatalysis Consortium (ElectroCat 2.0). This work was partially authored by Argonne, a U.S. Department of Energy (DOE) Office of Science laboratory operated for DOE by UChicago Argonne, LLC under contract no. DE-AC02-06CH11357.References X.X. Wang, M.T. Swihart, and G. Wu, "Achievements, challenges, and perspectives on cathode catalysts in proton exchange membrane fuel cells for transportation", Nature Catalysis, 2 (2019) 578-589.J.L. Kneebone, et al., "A Combined Probe-Molecule, Mossbauer, Nuclear Resonance Vibrational Spectroscopy, and Density Functional Theory Approach for Evaluation of Potential Iron Active Sites in an Oxygen Reduction Reaction Catalyst", J. Phys. Chem. C 121 (2017) 16283-16290.P. Boldrin, D. Malko, A. Mehmood, U.I. Kramm, S. Wagner, S. Paul, N. Weidler, A. Kucernak, “Deactivation, reactivation and super-activation of Fe-N/C oxygen reduction electrocatalysts: Gas sorption, physical and electrochemical investigation using NO and O2”, Applied Catalysis B: Environmental 292 (2021) 120169.