γ-Al2O3 Surface Research Articles

XPS and DFT studies of γ-Al2O3 modified by NO

The modification of γ-Al2O3 after NO treatment and during the NO + H2 reaction was studied using X-ray photoelectron spectroscopy (XPS) and density functional theory. The XPS N1s spectra contain features with binding energies BE = 399.0 and 403.0 eV; the first is preserved, and the second disappears when NO is removed from the gas phase. The features were identified from experimental and modeled O-KLL regions of possible modification products − NAln oxynitrides (n = 3; 4) of the γ-Al2O3(110) surface and adsorbed states. Calculations show that NAln adsorbs NO, forming normal states with a distance to the surface d = 1.32–1.70 Å and distant (d-NO) states (d = 1.91–2.06 Å) in which the spin-polarized NO molecule is retained due to magnetic NAln and Coulomb interaction. An increase in the similarity of the O-KLL spectra in the sequence of NO/γ-Al2O3(110), NO/NAln and d-NO/NAln at an adsorption heat of ∼ 0.53, 1.33 and 1.26 eV, respectively, suggests that the modification includes the formation of NO/NAl4 corresponding to BE = 399.0 eV and d-NO/NAl4, which corresponds to BE = 403.0 eV and, being chemically unbound, is able to leave the surface in the absence of NO in the reaction medium.

Synthesis of gamma aluminum oxide nano-powder for adsorptive removal of nitrate from aqueous solutions

Nitrate pollution of surface and groundwater could be a worldwide issue resulting in the threat to the environment and public health. The removal of nitrate from water was carried out using gamma aluminum oxide (γ-Al2O3) nano powder. The nano powder was synthesized from aluminum oxide powder using the aqueous-based reflux method and applied for nitrate removal. The surface properties of the activated γ-Al2O3 were characterized using FTIR, XRD, and BET surface area analysis. Analysis of variance (ANOVA) was used to analyze nitrate removal to determine the appropriate regression model, which was found to be the quadratic model with a coefficient of determination (R2 = 0.99). The adsorption process was observed to be dependent on initial nitrate concentration, adsorbent dose, and time. The optimized nitrate removal efficiencies were 97.01% using a dose of 2.26 gL−1, an initial nitrate concentration of 10 mgL−1, and a contact time of 45 min. Additionally, the kinetics of nitrate ion adsorption was discussed based on pseudo-first order and pseudo-second order kinetic models. The experimental data fitted well with the pseudo-second order kinetic model, indicating that the adsorption mechanism is chemisorption. The equilibrium adsorption of nitrate experimental data followed the both Freundlich and Langmuir isotherm (R2 = 0.95), implying a homogeneous nature of the γ-Al2O3 surface sites. These results suggest further consideration of the practical application of γ-Al2O3 for nitrate treatment for domestic purposes.

The study of design and performance improvement of catalysts for the stepwise production of bicyclohexane from benzene and cyclohexene

Bicyclohexane is a hydrogen storage reagent with high hydrogen density and low boiling point. Compared with the hydrogenation of biphenyl, the alkylation of benzene and cyclohexene to cyclohexylbenzene and hydrogenation is a promising way to prepare cyclohexane on a large scale. The research and development of high-efficiency cyclohexyl benzene hydrogenation catalyst should be further developed based on mature alkylation technology. This paper used an acidified USY molecular sieve to catalyze the alkylation of benzene and cyclohexene to cyclohexylbenzene, which achieved 100% conversion and selectivity. Furthermore, Pt/TiO2/γ-Al2O3 catalyst is prepared by pre-deposition TiO2 film of different thicknesses on γ-Al2O3 surface and then supported with platinum particles by Atomic layer deposition (ALD). The role of TiO2 film in improving the cyclohexylbenzene hydrogenation performance of the catalyst is studied. TEM, CO pulse chemisorption, CO-DRIFTs, quasi-in situ XPS, H-D exchange, and H2-TPR characterization show that compared with Pt/γ-Al2O3, TiO2 thin films on Pt/TiO2/γ-Al2O3 do not change the dispersion of Pt particles, but can form new Pt-TiO2 interactions. The hydrogenation performance of cyclohexylbenzene was improved by increasing the electron density and the proportion of planar active sites on the surface of platinum and reducing the energy barrier of hydrogen spillover. The research provides theoretical support for further bicyclohexane organic liquid hydrogen storage reagent development. The relevant metal-support interaction regulation strategy can be applied to the development of efficient catalysts for other aromatic molecules hydrogenation.

First-Principles Calculations of the Effect of γ-Alumina Surface Hydroxyl Structures on the Location and Dechlorination of a Platinum Precursor.

The interaction between Pt precursors and alumina support is an important step in synthesizing Pt/Al2O3 catalysts, while an in-depth understanding of the interaction is still lacking. Herein, density functional theory (DFT) calculations were performed to simulate the coordination of H2PtCl6 with different surface hydroxyl groups, revealing the influence of the γ-Al2O3 surface hydroxyl structure on the position of the Pt precursor and the removal of Cl ligands. After drying, the interaction mechanism between [PtCl6]2- and alumina support involves hydrogen bonds and van der Waals forces, which are the main driving forces for the structural transformation from [PtCl6]2- coordinated with the surface hydroxyl group into the PtClx(OH)y species (OH is the γ-Al2O3 surface group). HO-μ1-AlVI and H2O-μ1-AlVI on the (100) surface with electrophilicity facilitate hauling and activating the electron-rich [PtCl6]2-, but the nucleophilic (110) surface has a weaker interaction with [PtCl6]2-. Combining free energy and electronic property analysis, the stable structures on the (100) surface after drying treatment are PtCl4(OH)2 and PtCl3(OH)3, while only PtCl4(OH)2 structures can be formed on the (110) surface. This study can deepen our understanding of the interaction mechanism between Al-hydroxyl groups and Pt precursors, providing a theoretical reference for the precise placement of Pt active phases and the construction of metal-support interfaces.

Electrolytes for solid state lithium batteries in the [N13pip]ClO4-LiClO4-Al2O3 system for solid state lithium batteries

The transport, electrochemical, structural, and thermal properties of electrolytes in the ternary system [N13pip]ClO4-LiClO4-γ-Al2O3 (N13pip is N-methyl-N-ethyl-piperidinium cation) were investigated at the molar ratio [N13pip]ClO4:LiClO4 = 0.82:0.18. The addition of alumina leads to a change in the thermodynamic properties of the [N13pip]ClO4-LiClO4 system that can be explained by a partial transfer of lithium perchlorate from the organic phase to the surface of γ-Al2O3. The highest ionic conductivity of 6.2∙10–4 S/cm at 110 °C was observed for the composition containing the volume fraction (f) of γ-Al2O3 equal to 0.5. The increase in conductivity compared to the binary system 0.82[N13pip]ClO4-0.18LiClO4 is achieved due to the amorphization of the organic salt near the salt/LiClO4/oxide interfaces. Galvanostatic cycling with Li electrodes shows that composites with f = 0.5 are stable at 110 °C for at least 68 charge/discharge cycles, and the electrolyte is shown to be electrochemically stable up to 5 V. This system can be used as a solid-state electrolyte in lithium-ion current sources.

Advanced magnetic adsorbents for enhanced phosphorus and fluoride removal from wastewater: Mechanistic insights and applications

A novel mesoporous magnetic nanoparticle adsorbent, Fe3O4@CSH-AAO, was synthesized using the atomization-precipitation method, effectively removing phosphorus (P) and fluoride (F) from wastewater, particularly from the recirculating water of wet-process phosphoric acid. The adsorbent achieved removal efficiencies of 99.6 % for P and 73.5 % for F under conditions of 20 g/L adsorbent dosage, pH ≈ 4, with initial P and F concentrations at 115 mg/L and 38 mg/L, respectively. Equilibrium adsorption data indicated that the adsorption kinetics followed the pseudo-second-order model for F and the pseudo-first-order model for P. The adsorption isotherms fitted the Langmuir model for P and the Freundlich model for F, with maximum adsorption capacities of 37.86 mg P/g and 6.764 mg F/g at pH 4 and 298 K. The surface properties, functionality, and crystallinity were analyzed using BET, SEM, TEM, XRD, and XRF. Furthermore, XPS analyses and molecular dynamics (MD) simulations elucidated that surface Ca in CSH and the exposed Al atoms on the γ-Al2O3 (110) surface serve as optimal adsorption sites for P and F. The steric hindrance imposed by phosphorus contributes to its preferentially higher adsorption capacity over fluoride. This study not only presents an effective method for the removal of phosphorus and fluoride suitable for practical applications but also provides deep insights into the adsorption mechanism, highlighting the pivotal role of steric hindrance in facilitating ion adsorption.

Adsorption properties of N2O and NF3 on γ-Al2O3 (110) surface: A DFT study

To alleviate the environmental pressure caused by SF6 emissions, SF6/N2 has been widely used in power systems as a replacement gas. In case of abnormal equipment failure, SF6/N2 will decompose and produce many kinds of toxic and harmful gases, so it is necessary to place molecular sieves to safeguard the insulation performance of the equipment. Since γ-Al2O3 is the main component of molecular sieves, the adsorption of N2O and NF3 on the surface of γ-Al2O3 (110) is systematically calculated in this paper using density functional theory to investigate the adsorption energy, charge transfer, density of states (DOS), electrons density difference (EDD), electron localization function (ELF) and frontier molecular orbital theory for their stable configurations. The calculated results show that although N2O adsorption on γ-Al2O3 (110) is slightly stronger than NF3, both gases have weak interactions with γ-Al2O3 (110) and thus may both be physisorbed. This paper deepens the basic understanding of adsorbent adsorption of SF6/N2 decomposition gases in power equipment, and provides a theoretical basis for the optimisation study of adsorbents required for equipment with SF6/N2 as the insulating medium.

Effect of Residence Time and Carrier Gas on the Dehydrogenation of n-Hexane over Alumina-supported Chromium Catalyst

CrOx/γ-Al2O3 catalyst was prepared by incipient wetness impregnation method, and the influence of residence time and carrier gas on the dehydrogenation of n-hexane were studied. It is found that n-hexane dehydrogenation over CrOx/γ-Al2O3 catalyst with H2 as carrier gas exhibits totally different catalytic behaviors with that of diluting n-hexane with N2. When diluting feed with N2, the selectivity to dehydrogenation product is promoted while the cracking reaction is exhibited with reducing residence time. However, the selectivity to dehydrogenation product is significantly decreased while the isomerization of n-hexane is promoted when using H2 as carrier gas. It is proposed that H2 undergoes dissociation on the dehydrogenation active site, and further facilitates the olefinic dehydrogenation products to form carbocation, which performing isomerization reaction on the acid site on the γ-Al2O3 surface. Therefore, the isomerization of n-hexane is promoted in cost of the selectivity to dehydrogenation product when using H2 as carrier gas.

Chemical activation of atom-precise Pd3 nanoclusters on γ-Al2O3 supports for transfer hydrogenation reactions.

Deposition of atom-precise nanoclusters onto solid supports is a promising route to synthesize model heterogeneous catalysts. However, to enhance nanocluster-support interactions, activation of the nanoclusters by removal of surface ligands is necessary. Thermal treatment to remove surface ligands from supported metal nanoclusters can yield highly active heterogeneous catalysts, however, the high temperatures employed can lead to poor control over the final size and speciation of the nanoclusters. As an alternative to high-temperature thermal treatments, chemical activation of [Pd3(μ-Cl)(μ-PPh2)2(PPh3)3]+ (Pd3) nanoclusters on γ-Al2O3 supports under mild reaction conditions has been demonstrated in this work. Hydride-based reducing agents such as NaBH4, LiBH4, and LiAlH4 have been examined for the activation of the Pd3 nanoclusters. The structural evolution and speciation of the nanoclusters after activation have been monitored using a combination of XAS, XPS, STEM-EDX mapping, and solid-state NMR techniques. The results indicate that treatment with borohydride reducing agents successfully removed surface phosphine and chloride ligands, and the extent of size growth of the nanoclusters during activation is directly correlated with the amount of borohydride used. Borate side products remain on the γ-Al2O3 surface after activation; moreover, exposure to high amounts of NaBH4 resulted in the incorporation of B atoms inside the lattice of the activated Pd nanoclusters. LiAlH4 treatment, on the other hand, led to no significant size growth of the nanoclusters and resulted in a mixture of Pd single-atom sites and activated nanoclusters on the γ-Al2O3 surface. Finally, the catalytic potential of the activated nanoclusters has been tested in the transfer hydrogenation of trans-cinnamaldehyde, using sodium formate/formic acid as the hydrogen donor. The catalytic results showed that smaller Pd nanoclusters are much more selective for hydrogenating trans-cinnamaldehyde to hydrocinnamaldehyde, but overall have lower activity compared to larger Pd nanoparticles. Overall, this study showcases chemical activation routes as an alternative to traditional thermal activation routes for activating supported nanoclusters by offering improved speciation and size control.

Discovery of highly efficient dual-atom catalysts for propane dehydrogenation assisted by machine learning.

Propane dehydrogenation (PDH) is a highly efficient approach for industrial production of propylene, and the dual-atom catalysts (DACs) provide new pathways in advancing atomic catalysis for PDH with dual active sites. In this work, we have developed an efficient strategy to identify promising DACs for PDH reaction by combining high-throughput density functional theory (DFT) calculations and the machine-learning (ML) technique. By choosing the γ-Al2O3(100) surface as the substrate to anchor dual metal atoms, 435 kinds of DACs have been considered to evaluate their PDH catalytic activity. Four ML algorithms are employed to predict the PDH activity and determine the relationship between the intrinsic characteristics of DACs and the catalytic activity. The promising catalysts of CuFe, CuCo and CoZn DACs are finally screened out, which are further validated by the whole kinetic reaction calculations, and the highly efficient performance of DACs is attributed to the synergistic effects and interactions between the paired active sites.

Atomic-level mechanism of CO2-promoted oxidation of alumina-forming alloys

The high-temperature oxidation of the NiAl alloy in the CO2 and O2 atmospheres is comparatively studied by a combination of electron microscopy characterization and first-principles calculations. It is shown that CO2 accelerates the oxidation of NiAl alloy by the formation of a highly porous γ-Al2O3 scale that is non-protective and follows the linear growth law. By contrast, the NiAl oxidation in O2 results in a double-layered oxide scale consisting of an outer columnar γ-Al2O3 layer and an inner equiaxed α-Al2O3 layer, which is protective and follows parabolic growth law. Our first-principles calculations show that this accelerated NiAl oxidation in the CO2 can be attributed to more ready decomposition of adsorbed CO2 than adsorbed O2 into atomic oxygen on defective γ-Al2O3 surfaces, which leads to the inward γ-Al2O3 growth by the infiltration of gaseous CO2 through the cracked oxide scale toward the exposed NiAl alloy. These results provide new insights into the atomic origin of CO2-promoted alloy oxidation.

Accumulation of Ag(0) Single Atoms at Water/Mineral Interfaces during Sunlight-Induced Reduction of Ionic Ag by Phenolic DOM.

Silver (Ag) undergoes a complex and dynamic Ag+/Ag0 cycle under environmental conditions. The Ag+ → Ag nanoparticles (AgNPs) transformation due to the combined actions of sunlight, O2, and dissolved organic matter has been a well-known environmental phenomenon. In this study, we indicate that this process may be accompanied by a pronounced accumulation of Ag(0) single atoms (Ag-SAs) on the minerals' surfaces. According to spherical aberration-corrected scanning transmission electron microscopy and high-energy-resolution X-ray adsorption fine structure analyses, humic acid (HA) and phenol (PhOH) can induce Ag-SAs accumulation, whereas oxalic acid causes only AgNPs deposition. Ag-SAs account for more than 20 wt % of total Ag(0) on the γ-Al2O3 surfaces during HA- and PhOH-mediated photolysis processes. HA also causes Ag-SAs to accumulate on two other prevalent soil minerals, SiO2 and Fe2O3, and the fractions of Ag-SAs are about 15 wt %. Our mechanism studies suggest that a phenolic molecule acts as a reducing agent of Ag+ and a stabilizer of Ag-SAs, protecting Ag-SAs against autocatalytic nucleation.

The chemical state and Cu+ stability for three-way catalytic performance of Cu-added Al2O3 catalysts

Cu-added γ-Al2O3 (CuAl) catalysts having varying Cu loadings (3, 5, 8, and 10 mol%) were prepared at 900 °C. The effects of the copper oxidation states and the stability of these states under oxidizing and reducing atmospheres were examined. The use of these materials as three-way catalysts (TWCs) was also assessed. Analyses by X-ray diffraction and transmission electron microscopy indicated that copper oxide species were well dispersed and formed a solid solution in a surface layer of the γ-Al2O3. The TWC activity was found to increase with the addition of copper, and the 8 mol% CuAl catalyst showed very high performance despite being heat-treated at high temperatures. In the case of the 10 mol% CuAl catalyst, the excess Cu loading resulted in the precipitations of copper species on the γ-Al2O3 surface, which decreased catalytic activity. The oxidation states also differed between these catalysts. X-ray absorption fine structure and temperature-programmed reduction data demonstrated variations in copper oxidation states among the catalysts before and after oxidation and reduction treatments. The 8 mol% CuAl catalyst had a high Cu+/Cu2+ ratio and contained stable Cu+ species during both oxidation and reduction trials. The stability of the copper oxidation states is evidently a factor affecting catalytic activity.

CuII-Hfur–imidazole] compounds as precursors of efficient hydrogenation and reductive alkylation catalysts in flow systems

The reaction of copper(II) acetate with furoic acids (2Hfur / 3Hfur) and imidazole (Im) in methanol resulted in mononuclear complexes [Cu(fur)2(Im)2(H2O)]·L (fur- = 2fur- (1, 2), 3fur- (3); L = MeCN (1)) whose structures were determined by direct single crystal X-ray analysis. It was found for the first time that copper nanoparticles immobilized on the surface of γ-Al2O3 obtained by chemical reduction of 1, 2 and 3 (pre-deposited on the surface from solution) with sodium tetrahydroborate show high selectivity of mono- and dihydrogenation of tricyclo[5.2.1.02,6]deca-3,8-diene (dicyclopentadiene, DCPD). The catalytic activity tests show a high selectivity (97 %) of the catalyst obtained from an ethanolic solution of complex 1 in the reaction of partial hydrogenation to DHDCPD under continuous process conditions even at high conversion values (up to 96 %) and with an excess of hydrogen, whereas the catalyst obtained from an aqueous solution of complex 1 showed 98 % total hydrogenation product (THDCPD) selectivity. The catalysts based on all the complexes 1–3 were successfully used in reactions of nitrobenzene (NB) reduction to aniline (AN) and in the reductive alkylation of nitrobenzene with isobutanol (i-BAN) 100 % yields of aniline and N-isobutylaniline were obtained at LHSV 0.16 h−1.

Chain scission modification mode in plasma catalytic n-undecane decomposition: In situ probing of intermediates and reaction pathways

To provide insight into the mechanism of plasma-catalytic long-chain alkane oxidation from the aspect of chain scission, n-undecane (C11H24) decomposition over γ-Al2O3 and Ag/γ-Al2O3 were investigated in a coaxial dielectric barrier discharge (DBD) reactor. The highest n-undecane conversion (89.7 %) and CO2 selectivity (SCO2, 40.0 %) were achieved in Plasma + Ag/γ-Al2O3 system. It was found that the simultaneous activation of O3 and C11H24 played a very important role in chain scission, which could be promoted by the formation of Ag-O-Al entity introduced by the strong interaction between Ag and γ-Al2O3. Different chain scission behaviors and reaction pathways were proposed by a combined analysis of GC-MS and in-situ DRIFTS. In Plasma + Ag/γ-Al2O3 system, the reaction of chain scission and oxidation preferred to take place in the middle of the chain, producing the ketone and aldehyde species with low carbon number, which were easy to be converted to CO2 and H2O. Instead, without the highly efficient activation of O3 and C11H24, the oxidation of the C11H24 over the surface of γ-Al2O3 was more likely to take place on the edge of the chain, leading to the accumulation of long-chain aldehyde, which lower values of C11H24 conversion and SCO2 (45.6 % and 21.7 %, respectively) in Plasma + γ-Al2O3 system.

SYNTHESIS AND CHARACTERIZATION OF γ-Al2O3@MgO SORBENT FOR EFFICIENT Pb REMOVAL FROM AQUEOUS SOLUTIONS

This study focuses on enhancing the adsorption capacity for lead ions by introducing MgO onto the surface of γ-Al2O3, forming γ-Al2O3@MgO. The γ-Al2O3 nanoparticles were synthesized via the sol-gel method on a citrate template. MgO was incorporated onto the surface of the γ-Al2O3 nanoparticles, with varying MgO concentrations (5%, 10%, and 15% by weight), achieved through the absorption of magnesium ions onto the material's surface followed by sintering at 773K. The findings indicated that both the γ-Al2O3 and MgO crystalline phases exhibit a cubic structure (Fd3m symmetry group), which is formed within the sample. Although the specific surface area diminished from 166 m2/g to 135 m2/g, the surface basicity increased proportionally to the amount of MgO incorporated into the sample. The impacts of various absorption conditions such as pH, adsorbent mass, and contact time on the Pb2+ ion adsorption capacity was systematically examined. Optimal conditions (pH=7, adsorption time of 8 hours) highlighted that the γ-Al2O3 material containing 10% MgO by weight showcased the highest Pb2+ adsorption capacity at 145 mg/g, surpassing the adsorption capacity of 135 mg/g for the γ-Al2O3 material.

Theoretical and experimental study on the dehydrogenation of propane by oxygen vacancy caused by γ-Al2O3 with the assistance of S

As a nontoxic and cheap catalyst, the Al2O3 catalyst can be used to catalyze the propane dehydrogenation (PDH) process. However, due to its poor activity, it has been used as a catalyst carrier rather than catalysis. In this work, the experimental results indicate that γ- Al2O3-(110)-S catalysts can improve the yield of propane dehydrogenation more effectively than γ-Al2O3-(110) catalyst. We investigate the potential barrier of propane dehydrogenation reaction catalyzed by Al2O3-(110) under different conditions and found that the substitution of the S atom for partial O atom can modify the acid-base properties of the surface active site of γ-Al2O3-(110), thus reducing the reaction energy barrier. In particular, the yield of the reaction can be further improved by the active sites of oxygen vacancies generated by removing partial S atoms in γ-Al2O3-(110)-S, which is consistent with our theoretical calculation results. At the same time, theoretical calculation shows that Cu clusters can effectively remove the S atoms on the surface of γ-Al2O3-(110)-S and form oxygen vacancies. This strategy provides a new path to form oxygen vacancies on γ-Al2O3-(110), which opens up a new way for the study of propane dehydrogenation.

Adsorption mechanism of As2O3 on metal oxides (CaO, γ-Al2O3, α-Fe2O3): A density functional theory study

Arsenic (mainly As2O3) removal is one of the key concerns in the ultra-clean emissions of coal-fired flue gas. Facing the no consensus on the adsorption mechanism of As2O3 on typical metal oxides (CaO, γ-Al2O3 and α-Fe2O3) and the influence mechanism of SO2 on that, this work adopted the DFT calculation to conduct the systematic study from multiple perspectives, including adsorption energy, EDD, PDOS, Gibbs free energy and FMO. The results show As2O3 adsorption on CaO (001), γ-Al2O3 (001) and α-Fe2O3 (001) surface are mainly chemisorption, where that on CaO (001) surface is strongest. The adsorption ability of the metal oxides to As2O3 under 0–1173.15 K satisfies CaO (001) > γ-Al2O3 (001) > α-Fe2O3 (001). SO2 competes with As2O3 for adsorption active sites, and that on CaO is greater than α-Fe2O3 (001) and γ-Al2O3 (001). The newly formed adsorption sites are less active for As2O3 adsorption after SO2 adsorbed on the three metal oxides surfaces. The γ-Al2O3 (001) and α-Fe2O3 (001) surface with pre-adsorbed SO2 decreases the stability of hexahedral As2O3, which benefits for the adsorption occurrence.

A density functional theory study on how γ-Al2O3 – Boehmite transformation affects carbon evolution during aqueous-phase reaction

Gamma-alumina (γ-Al2O3), one of the most common materials, is commercially used in many catalytic applications, including the active catalyst and support. However, the problem of fast deactivation makes the utilization of the γ-Al2O3 challenging. This work elucidates the mechanism of coke formation consisting of coke deposition and evolution on γ-Al2O3(110) surfaces in differential conditions, including; clean and hydroxylation γ-Al2O3(110) in terms of partial and fully hydroxylation of OH/γ-Al2O3(110) and AlOOH(010), respectively. We demonstrated that the γ-Al2O3(110) surface is proper for atomic coke deposition and dimerization in the initial state, where the presence of OH species promotes the coke evolution to higher coke, Cn (where n ≥ 3). Also, the higher coke formation thermodynamically preferred the cyclic form to the aliphatic one. The electron transfer from substrates to adsorbed coke illustrates the role of the electron donor of catalyst surfaces corresponding to the electron acceptor of adsorbed cokes.

The Morphologically Controlled Synthesis and Application of Mesoporous Alumina Spheres.

The control of alumina morphology is crucial yet challenging for its various applications. Unfortunately, traditional methods for preparing alumina particles suffer from several limitations such as irregular morphology, poor dispersibility, and restricted application areas. In this study, we develop a novel method for preparing spherical mesoporous alumina using chitin and Pluronic P123 as mixed templates. The effects of reaction temperature, time, and the addition of mixed templates on the phase structure, micromorphology, and optical absorption properties of the samples were investigated. The experimental results indicate that lower temperature and shorter reaction time facilitated the formation of spherical mesoporous alumina with excellent CO2 adsorption capacity. The periodic density functional theory (DFT) calculations demonstrate that both the (110) and (100) surfaces of γ-Al2O3 can strongly adsorb CO2. The difference in the amount of CO2 adsorbed by Al2O3 is mainly due to the different surface areas, which give different numbers of exposed active sites. This approach introduces a novel strategy for utilizing biological compounds to synthesize spherical alumina and greatly enhances mesoporous alumina's application efficiency in adsorption fields. Moreover, this study explored the electrochemical performance of the synthesized product using cyclic voltammetry, and improved loading of electrocatalysts and enhanced electrocatalytic activity were discovered.