Evaporation-induced Self-assembly Method Research Articles

Bifunctional vanadium doped mesoporous Co3O4 on nickel foam towards highly efficient overall urea and water splitting in the alkaline electrolyte

Developing more active and stable electrode materials for oxygen evolution reaction (OER) and urea oxidation reaction (UOR) is necessary for electrocatalytic water and urea oxidation which can be used to generate hydrogen. Here, a low-cost vanadium-doped mesoporous cobalt oxide on Ni foam (V/meso-Co/NF) electrodes are obtained via the grouping of an in-situ citric acid (CA)-assisted evaporation-induced self-assembly (EISA) method and electrophoretic deposition process, and work as highly efficient and long-lasting electrocatalytic materials for OER/UOR. In particular, V/meso-Co/NF electrodes require 329 mV overpotential to maintain a 50 mA/cm2, with exceptional long-term durability of 30 h. Interestingly, V/meso-Co/NF also exhibits excellent electrocatalytic UOR performance, reaching 50 and 100 mA/cm2 versus RHE at low potentials of 1.34 and 1.35 V, respectively. By employing the V/meso-Co/NF materials as both the anode and cathode, this urea electrolysis assembly V/meso-Co/NF-5 (+,−) reaches current densities of 100 mA cm−2 at 1.62 V in KOH/urea, which is nearly 340 mV lesser than classical water electrolysis. The V/meso-Co/NF-5 electrocatalysts also exhibit remarkable durability for electrocatalytic OERs and UORs. The obtained findings revealed that the synthesized V/meso-Co/NF might be a promising electrode materials for overall urea-rich wastewater management and H2 generation from wastewater.

Phyllosilicate-derived Ni catalysts with small nanoparticle size and strong metal-support interaction for efficient and robust decomposition of ammonia

Ammonia decomposition is a structure-sensitive reaction, so the difference in structure of similar catalysts may have a great impact on the catalytic performance of ammonia decomposition reaction. However, it is not clear which structural properties can play a role in ammonia decomposition reaction and the degree of influence on catalytic performance. To explore this question, ammonia evaporation-hydrothermal (AEH), impregnation (IM), and evaporation-induced self-assembly (EISA) methods were used to synthesize Ni/SiO2 catalysts to obtain carbon-free hydrogen from catalyzing NH3 decomposition reaction. Among the three, the Ni/SiO2 catalyst synthesized via ammonia evaporation-hydrothermal method is the smallest in terms of Ni nanoparticles (∼3.0 nm) and the strongest Ni-SiO2 interaction. For ammonia decomposition, it is the highest in activity and thermal stability. The NH3 conversion at 650 °C and 30 000 mL gcat−1h−1 (GHSV) over Ni/SiO2-AEH was close to 90 % and remained stable in an evaluation period of 60 h.

Thickness control of dispersion in opal photonic crystals

Opals are naturally occurring photonic crystals which can be formed easily using low-cost self-assembly methods. While the optical behaviour of opals has received significant attention over the last number of decades, there is limited information on the effect of crystal thickness on the optical properties they display. Here, the relationship between volume fraction and crystal thickness is established with an evaporation-induced self-assembly (EISA) method of formation. The extent to which thickness can be used to manipulate the optical properties of the crystals is explored, focusing on the change in the photonic band gap (PBG). Microscopical structural characterization and angle-resolved transmission spectroscopy are used to examine the quality of the photonic crystals formed using different volume fractions of polystyrene spheres, with thicknesses up to 37 layers grown from volume fractions of 0.125%. This work provides a direct correlation between sphere solution volume fraction and crystal thickness, and the associated optical fingerprint of opal photonic crystals. Maximum thickness is examined, which is shown to converge to a narrow range over several evaporation rates. We identify the criteria required to achieve thickness control in relatively fast evaporation induced self-assembly while maintaining structural quality, and the change to the spectroscopic signature to the (111) stopband and higher order (220) reflections, under conditions where a less ordered photonic crystals are formed.

Canna-inspired superhydrophobic and icephobic regenerated cellulose based hierarchical intelligent colorimetric sensing film for food real-time visual monitoring

Unsafe food cause serious threat to public health and the economy, exploiting effective food quality assessment strategies has attracted concerns worldwide. Herein, inspired by Canna micro-nano hierarchical structure, a generic, facile, and highly processable roll-to-roll and solvent evaporation-induced self-assembly fabrication method is introduced to fabricate regenerated cellulose based superhydrophobic and icephobic hierarchical colorimetric sensing film for real-time visual monitoring of food freshness. The synergistic effect from macromolecular chains attraction and nanoscaled aggregation renders the colorimetric sensing film with excellent mechanical strength of 105.07 MPa and superhigh shear modulus of 17.28 GPa. Upon applied tension, the vigorous intermolecular interactions make the film extraordinary structure stability. The optimized colorimetric sensing film exhibits microscaled pores for sensing performance and three-dimensional nanoflower morphologies for superhydrophobic (water contact angle of 155.1 °and roll-off angle of 7.8°) and icephobic that delay the freezing time of 40 μL water droplets (45 s to 265 s) and reduce the bonding strength of ice (599.72 kPa to 45.53 kPa). What counts is the first time bestowed with icephobicity to food freshness colorimetric sensing film, which mitigating the interference of the covered ice layer against the colorimetric, and providing a more reasonable monitoring in food freshness. These results benefit for stimulating new design principles of colorimetric sensing films, and also provide promising applications in extremely cold environments.

Engineering the Interface and Interaction Structure on Highly Coke-Resistant Ni/CeO2-Al2O3 Catalyst for Dry Reforming of Methane

Designing and tailoring metal-support interaction in Ni-based catalysts with plentiful interfacial sites is of significant interest for achieving a targeted catalytic performance in dry reforming of methane (DRM), but remains as a challenging task. In this work, Ni/Al2O3 and Ni/CeO2-Al2O3 catalysts with the same strong metal-support interaction (SMSI) but distinct interface structure are developed by an improved evaporation-induced self-assembly method using pseudobohemite gel as aluminum source. Ni/CeO2-Al2O3 exhibits superior catalytic activity and stability in DRM in comparison with Ni/Al2O3. The highest CH4 and CO2 conversion reaches at 71.4% and 82.1% for Ni/CeO2-Al2O3, which are higher than that of 64.3% and 75.6% for Ni/Al2O3 at 700 °C. The SMSI effect in Ni/CeO2-Al2O3 provides more active interfacial sites with less coke deposition, and promotes the generation of active formate species which are the key intermediates for DRM. The findings of the present work could possibly pave the way for fabricating catalysts with SMSI strategy for efficient heterogeneous catalysis.

Superior thermally conductive, mechanically strong and electrically insulating nacre-mimetic chitosan/boron nitride nanosheet composite via evaporation-induced self-assembly method

The development of electronic devices and the strict application environment put forward more requirements on the heat dissipation materials. However, it is still a challenge for thermal management materials to simultaneously possess high thermal conductivity, strong mechanical property and excellent electrical insulation. Herein, inspired by the special structure and function of natural nacre, we report on a large-scale and high-performance nacre-mimetic composite with boron nitride nanosheet (BNNS) as the “brick” and chitosan as the “mortar” via a green, simple evaporation-induced assembly technique. The nacre-mimetic composite film presents high TC of 26.3 W/(m·K) and superior electrically insulating due to well-aligned BNNS and strong interface interaction. In addition, even at BNNS contents as high as 70 wt%, the composite films still possess a tensile strength of 104.5 MPa and a Young's modulus of 8.7 GPa. The composite film used as a thermal interface material for cooling LED chip demonstrates higher heat dissipation efficiency than commercial silicone pad. This approach of constructing nacre-mimetic composite film with an oriented structure offers potential applications for heat dissipation in new portable electronic equipment.

Facile fabrication of superhydrophobic surfaces via spraying with silicone-urea copolymers

The microphase separation method is recognized as one of the most promising approaches to fabricate superhydrophobic surfaces (SHS), but it is still subjected to confined polymer materials, expensive instruments, and complicated techniques. Here we innovatively proposed a solvent evaporation-induced self-assembly method to produce SHS with facile prepared, environmentally friendly, ultrafast ambient temperature curable properties. In this study, a new category of silicone-urea copolymers was synthesized via step-growth polymerization of polydimethylsiloxane (PDMS) and different diisocyanates. The SHS induced by the microphase separation and solvent evaporation was then fabricated by spraying these copolymer solutions onto various substrates. It was discovered that the surface superhydrophobicity and morphology can be readily tuned by varying the spraying concentrations, diisocyantes, solvents, spraying heights, and molecular weight of PDMS. And those synthesized copolymers were assembled into micrometer-size fibers or spheres consisting of hierarchical microstructure using tetrahydrofuran as spraying solvent and 10–15 cm spraying height, and the contact angles of surfaces reached 119° and 153°, respectively. To further explore the possible formation mechanism of the SHS, small-angle scattering, and X-ray photoelectron spectroscopy were carried out to investigate the effects of the microphase separation and solvent evaporation. With the induced microscopic roughness caused by the copolymers, these prepared super-anti-wetting surfaces have been demonstrated for potential utilization in the field of waterproofing, self-cleaning, and antifouling aspects. This work provides an effective way for the potential large-scale preparation of superhydrophobic surfaces with environmentally friendly materials and straightforward techniques.

CTAB assisted evaporation-induced self-assembly to construct imidazolium-based hierarchical porous covalent organic polymers for ReO4-/TcO4- removal

Evaporation-induced self-assembly method (EISA) was a facile and reliable method to synthesize porous materials. Herein, we report a kind of hierarchical porous ionic liquid covalent organic polymers (HPnDNH2) under cetyltrimethylammonium bromide (CTAB) assisted by EISA for ReO4-/TcO4- removal. Unlike covalent organic frameworks (COFs), which usually needed to be prepared in a closed environment or with a long reaction time, HPnDNH2 in this study was prepared within 1 h in an open environment. It was worth noting that CTAB not only served as a soft template for forming pore, but also induced ordered structure, which was verified by SEM, TEM, and Gas sorption. Benefit from its hierarchical pore structure, HPnDNH2 exhibited higher adsorption capacity (690.0 mg g−1 for HP1DNH2 and 808.7 mg g−1 for HP1.5DNH2) and faster kinetics for ReO4-/TcO4- than 1DNH2 (without employing CTAB). Additionally, the material used to remove TcO4- from alkaline nuclear waste was seldom reported, because combining features of alkali resistance and high uptake selectivity was not easy to achieve. In this study, in the case of HP1DNH2, it displayed outstanding adsorption efficiency toward aqueous ReO4-/TcO4- in 1 mol L−1 NaOH solution (92%) and simulated Savannah River Site High-level waste (SRS HLW) melter recycle stream (98%), which could be a potentially excellent nuclear waste adsorbing material.

Synergetic catalysis of Pt/WN-TiO2 nanocomposites for selective hydrogenation of furfural to valuable furfuryl alcohol

Herein, WN-TiO2 with evenly distributed WN nanoparticles (NPs) were facilely synthesized thru one pot evaporation-induced self-assembly (EISA) and nitridation treatment method, as an active host material for precious Pt NPs. A number of characterization techniques were executed to explore the influence of the synthetic approach upon the surface and catalytic properties of the as-synthesized 2wt%Pt/TiO2 and 2wt%Pt/WN-TiO2 catalysts. As compared to 2wt%Pt/TiO2, the 2wt%Pt/WN-TiO2 catalyst exhibited outstanding performance in the selective hydrogenation reaction of Furfural (FAL) to Furfuryl alcohols (FOL) (conversion (97.8%) and selectivity (98.6%)). The 2wt%Pt/WN-TiO2 catalyst also exhibited an impressive recyclability performance for up to five recycles without significant deactivation in activity and selectivity. The superior catalytic hydrogenation performance can be ascribed to the specific nanostructure characteristics of the catalyst arose from the possible synergistic effect occurred between Pt and WN species of 2wt%Pt/WN-TiO2. Besides, the improved homogeneous dispersion of precious Pt NPs causes more exposed active sites of Pt0 species on the surface of 2wt%Pt/WN-TiO2, which is very beneficial for the improved hydrogenation of FAL to FOL.

Unraveling the effects of Ce/Zr molar ratio in mesoporous CexZr1−xO2 on the performance of dry reforming of methane over the supported Ni catalysts

Ni supported on the ordered mesoporous CexZr1−xO2 with various Ce/Zr molar ratios prepared by a programmed evaporation-induced self-assembly method were employed for dry reforming of methane. The systematical techniques, including X-ray diffraction, N2 physisorption, Raman, transmission electron microscope, chemisorption, X-ray photoelectron spectroscopy, diffuse reflection Fourier transform infrared spectrum, thermogravimetric analysis, etc. were used to clarify the structure-activity relationship. It was found that the prepared catalysts all had highly ordered mesoporous structures, and compared to the sole ZrO2 and CeO2, the CeO2-ZrO2 composites exhibited the best thermal stability, stronger basicity, and greater oxygen migration. Especially, the composite with Ce/Zr ratio of 1/4 possessed the suitable basicity and most oxygen vacancies, which were closely related to the excellent anti-carbon ability. Moreover, its supported catalyst had the strongest metal-support interaction and highest Ni dispersion. Expectedly, the catalyst showed the superior activity and the robust stability for at least 1800 min

Optimization of the specific surface area of ordered mesoporous TiO2 yields a high response to humidity

Owing to their unique surface adsorption characteristics, the controlled synthesis of highly ordered mesoporous materials with high adsorption traits is of utmost importance. In the present work, ordered mesoporous TiO2 (OMT) with tunable channels was prepared via a facile soft-templet evaporation-induced self-assembly (EISA) method. The effect of phenol-formaldehyde resins (PF) and the ratio of triblock copolymer (F127) and tetrabutyl titanate (TBOT) on the OMT surface was studied by BrunauerEmmettTeller (BET) and scanning electron microscopy (SEM) analysis. The samples without PF resol did not offer any ordered mesoporous formation, while a highly ordered mesoporous structure was obtained for samples with PF resol. For the prepared samples, the specific surface area SSA∼141–254 m2/g, average pore size SP∼5.3–9.8 nm and pore volume VP∼0.29–0.45 cm3/g were obtained by controlling the ratio of F127 and TBOT. For 95% relative humidity (RH), the OMT with optimum specific surface area (SSA∼220 m2/g) and small pore size (SP∼5.3 nm) showed a high response (SR∼3.5 ×105), fast response time (26 s) and good long-term stability (over 90 days). Finally, the structure, morphology and chemical composition of the samples were determined by XRD, SEM, HRTEM, and XPS techniques to predict and authenticate the plausible sensing mechanism.

Supramolecular glasses with color-tunable circularly polarized afterglow through evaporation-induced self-assembly of chiral metal–organic complexes

The fabrication of chiral molecules into macroscopic systems has many valuable applications, especially in the fields of optical displays, data encryption, information storage, and so on. Here, we design and prepare a serious of supramolecular glasses (SGs) based on Zn-L-Histidine complexes, via an evaporation-induced self-assembly (EISA) strategy. Metal-ligand interactions between the zinc(II) ion and chiral L-Histidine endow the SGs with interesting circularly polarized afterglow (CPA). Multicolored CPA emissions from blue to red with dissymmetry factor as high as 9.5 × 10−3 and excited-state lifetime up to 356.7 ms are achieved under ambient conditions. Therefore, this work not only communicates the bulk SGs with wide-tunable afterglow and large circular polarization, but also provides an EISA method for the macroscopic self-assembly of chiral metal–organic hybrids toward photonic applications.

Structural evolution of robust Ni3Fe1 alloy on Al2O3 in dry reforming of methane: Effect of iron-surplus strategy from Ni1Fe1 to Ni3Fe1

Bimetallic Ni−Fe alloy catalyst offers boosting effect for dry reforming of methane (DRM) by strong interaction between Ni and Fe. However, the facile segregation of iron species from the alloy particles remains an open challenge. Herein, in pursuit of a stable Ni−Fe alloy, Ni1Fe1/Al2O3 and Ni3Fe1/Al2O3 catalysts were developed by an evaporation-induced self-assembly method. Ni1Fe1/Al2O3 exhibited superior stability to Ni3Fe1/Al2O3 at 600 °C for 50 h. The structural evolution of Ni−Fe alloys existed on Ni1Fe1/Al2O3 and Ni3Fe1/Al2O3 in DRM, leading to the generation of Ni3Fe1/Al2O3 and Ni/Al2O3, respectively, where the equimolar alloy provided sufficient FeOx in the dealloying process. Compared to Ni3Fe1/Al2O3, Ni1Fe1/Al2O3 possessed smaller amounts of coke deposition with lower graphitization, which is beneficial to realloying of the segregated FeOx for Ni−Fe alloy. Furthermore, the two catalysts presented distinct pathways for coke deposition, where CO and CH4 dissociation concurrently occurred on Ni3Fe1/Al2O3, while only CH4 dissociation appeared on Ni1Fe1/Al2O3.

Mesoporous TiO2 Coatings Regulate ZnO Nanoparticle Loading and Zn2+ Release on Titanium Dental Implants for Sustained Osteogenic and Antibacterial Activity.

Two major issues are currently hindering the clinical practice of titanium dental implants for the lack of biological activities: immediate/early loading risks and peri-implantitis. To solve these issues, it is urgent to develop multifunctional implants modified with effective osteogenic and antibacterial properties. Zinc oxide nanoparticles (ZnO NPs) possess superior antibacterial activity; however, they can rapidly release Zn2+, causing cytotoxicity. In this study, a potential dental implant modification was creatively developed as ZnO nanoparticle-loaded mesoporous TiO2 coatings (nZnO/MTC-Ti) via the evaporation-induced self-assembly method (EISA) and one-step spin coating. The mesoporous TiO2 coatings (MTCs) regulated the synthesis and loading of ZnO NPs inside the nanosized pores. The synergistic effects of MTC and ZnO NPs on nZnO/MTC-Ti not only controlled the long-term steady-state release of Zn2+ but also optimized the charge distribution on the surface. Therefore, the cytotoxicity of ZnO NPs was resolved without triggering excessive reactive oxygen species (ROS). The increased extracellular Zn2+ further promoted a favorable intracellular zinc ion microenvironment through the modulation of zinc transporters (ZIP1 and ZnT1). Owing to that, the adhesion, proliferation, and osteogenic activity of bone mesenchymal stem cells (BMSCs) were improved. Additionally, nZnO/MTC-Ti inhibited the proliferation of oral pathogens (Pg and Aa) by inducing bacterial ROS production. For in vivo experiments, different implants were implanted into the alveolar fossa of Sprague-Dawley rats immediately after tooth extraction. The nZnO/MTC-Ti implants were found to possess a higher capability for enhancing bone regeneration, antibiosis, and osseointegration in vivo. These findings suggested the outstanding performance of nZnO/MTC-Ti implants in accelerating osseointegration and inhibiting bacterial infection, indicating a huge potential for solving immediate/early loading risks and peri-implantitis of dental implants.

Mesostructured γ-Al2O3-Based Bifunctional Catalysts for Direct Synthesis of Dimethyl Ether from CO2

In this work, we propose two bifunctional nanocomposite catalysts based on acidic mesostructured γ-Al2O3 and a Cu/ZnO/ZrO2 redox phase. γ-Al2O3 was synthesized by an Evaporation-Induced Self-Assembly (EISA) method using two different templating agents (block copolymers Pluronic P123 and F127) and subsequently functionalized with the redox phase using an impregnation method modified with a self-combustion reaction. These nanocomposite catalysts and their corresponding mesostructured supports were characterized in terms of structural, textural, and morphological features as well as their acidic properties. The bifunctional catalysts were tested for the CO2-to-DME process, and their performances were compared with a physical mixture consisting of the most promising support as a dehydration catalyst together with the most common Cu-based commercial redox catalyst (CZA). The results highlight that the most appropriate Pluronic for the synthesis of γ-Al2O3 is P123; the use of this templating agent allows us to obtain a mesostructure with a smaller pore size and a higher number of acid sites. Furthermore, the corresponding composite catalyst shows a better dispersion of the redox phase and, consequently, a higher CO2 conversion. However, the incorporation of the redox phase into the porous structure of the acidic support (chemical mixing), favoring an intimate contact between the two phases, has detrimental effects on the dehydration performances due to the coverage of the acid sites with the redox nanophase. On the other hand, the strategy involving the physical mixing of the two phases, distinctly preserving the two catalytic functions, assures better performances.

Boosting solar-driven N2 to NH3 conversion using defect-engineered TiO2/CuO heterojunction photocatalyst

Ammonia (NH3) is one of the important energy sources for sustainable chemical products and carbon-free energy carriers. Artificial N2 photofixation is one of the promising approaches for the clean production of NH3 using photocatalysts in N2-dissolved water as a hydrogen source. We prepared defect-engineered TiO2/CuO heterojunction photocatalysts by the simple evaporation-induced self-assembly (EISA) method followed by post-thermal annealing under inert gas flow. The formation of a type-Ⅱ using TiO2 and CuO facilitated light absorption in near IR to UV light and the separation of photoexcited electron-hole pairs. In addition, the further post-thermal annealing under N2 gas flow resulted not only in an increase in crystallinity for the photoactive Anatase TiO2 and Tenorite CuO in the bulk but also in the in-situ formation of Ti3+ defect sites on the TiO2 surface. The increased crystallinity enhanced the photoexcited charge transport, while the defect sites improved N2 adsorption and activation, promoting the photocatalytic conversion of N2 to NH3. The defect-engineered TiO2/CuO photocatalysts exhibited a high NH3 production rate (1.575 μ mol g−1h−1) under visible light irradiation (λ≥ 420 nm) without any sacrificial agent, this value is 9.4 times and 2.5 times higher than those obtained with pristine TiO2 and TiO2/CuO photocatalysts, respectively. This work clearly demonstrates the synergistic effect of heterojunction and defect-engineering and provides insights into how each strategy can affect solar-driven NH3 production.

Solvent-Free Catalytic Hydrotreatment of Alcell Lignin Using Mono- and Bimetallic Ni(Mo) Catalysts Supported on Mesoporous Alumina

Technical lignins are an attractive and renewable source for the production of aromatic chemicals. However, efficient depolymerization of technical lignins to valuable low-molecular-weight chemicals is challenging due to its recalcitrant nature. Here, we report the use of nonprecious metal-based, monometallic Ni (prereduced) and bimetallic NiMo (in situ sulfided) catalysts supported on mesoporous alumina, either as such or doped with Si, Mg, or Ti, for a solvent-free catalytic hydrotreatment (batch, 400 °C, 4 h reaction time, 100 bar initial H2 pressure) of Alcell lignin to obtain oils enriched in biobased chemicals like alkylphenols and the parent phenol. These are important building blocks in the chemical industry and are currently obtained from fossil resources. The catalysts were prepared by a one-pot evaporation-induced self-assembly (EISA) method and characterized by various techniques [N2 physisorption, X-ray diffraction (XRD), temperature-programmed desorption (TPD), temperature-programmed reduction (TPR), and transmission electron microscopy (TEM)]. The best result was obtained using a monometallic Ni catalyst with an ordered mesoporous alumina support doped with Ti, giving an oil yield of 57 wt % with 10 wt % alkylphenols on lignin intake. By comparison, it was shown that the mesoporous structure of alumina is crucial for enhanced lignin oil yields.

Ordered mesoporous Ni-La2O3/Al2O3 catalysts towards efficient plasma-assisted dry reforming of methane

Plasma-assisted dry reforming of methane reaction provides a promising way to produce syngas with unity H2/CO ratio as one important chemical feedstock. Aiming to establish a match between CH4 and CO2 activation rates to suppress carbon deposition under combining plasma and catalyst, the design of reasonable and efficient catalytic materials is great of importance. Herein, we reported that the addition of La enhanced the reducibility of Ni2+ species and promoted Ni dispersion over the highly ordered mesoporous 10Ni5LaAl-one pot catalyst. In comparison to 10Ni5La/Al prepared by the incipient wetness impregnation (IWI) method and 10NiAl-one pot prepared by one pot solvent evaporation-induced self-assembly (EISA) method, the 10Ni5LaAl-one pot catalyst exhibited the highest catalytic activity for syngas production (H2/CO ratio of 0.98) and the strongest coke-resistance ability in the plasma-assisted DRM reaction. Meanwhile, excellent stability performance was obtained within 90 h for the catalyst owing to the higher discharge power, efficient capacitance and lower apparent activation energy of CO2 under plasma condition. And possible reaction mechanism of the10Ni5LaAl-one pot was proposed during plasma-catalytic DRM process.

Approaches to the design of efficient and stable catalysts for biofuel reforming into syngas: doping the mesoporous MgAl2O4 support with transition metal cations.

The mesoporous MgAl2O4 support is promising for the design of efficient and stable to coking catalysts for natural gas and biofuel reforming into syngas. This work aims at doping this support with transition metal cations (Fe, Cr, Ti) to prevent the incorporation of Ni and rare-earth cations (Pr, Ce, Zr), loaded by impregnation, into its lattice along with providing additional sites for CO2 activation required to prevent coking. Doped MgAl1.9Me0.1O4 (Me = Fe, Ti, Cr) mesoporous supports prepared by the one-pot evaporation-induced self-assembly method with Pluronic P123 triblock copolymers were single-phase spinels. Their specific surface area varies in the range of 115-200 m2 g-1, decreasing to 90-110 m2 g-1 after successive addition of the supporting nanocomposite active component 10 wt% Pr0.3Ce0.35Zr0.35O2 + (5 wt% Ni + 1% Ru) by impregnation. Mössbauer spectroscopy for iron-doped spinels confirmed the spatially uniform distribution of Fe3+ cations in the lattice without clustering being mainly located at the octahedral positions. Fourier-transform infrared spectroscopy of the adsorbed CO molecules was performed to estimate the surface density of metal sites. In methane dry reforming, the positive effect of MgAl2O4 support doping was observed from both a higher turn-over frequency as compared with the catalyst on the undoped support as well as the highest efficient first-order rate constant for the Cr-doped catalyst as compared with published data for a variety of Ni-containing catalysts based on the alumina support. In the reaction of ethanol steam reforming, the efficiency of catalysts on the doped supports is comparable, while exceeding that of Ni-containing supported catalysts reported in the literature. Coking stability was provided by a high oxygen mobility in the surface layers estimated by the oxygen isotope heteroexchange with C18O2. A high efficiency and coking stability were demonstrated in the reactions of methane dry reforming and ethanol dry and steam reforming in concentrated feeds for the honeycomb catalyst with a nanocomposite active component on the Fe-doped MgAl2O4 support loaded on the FeCrAl-alloy foil substrate.

Ordered mesoporous Ni–Mg–Al2O3 as an effective catalyst for CO2 reforming of CH4

The Ni based catalysts have been considered as promising candidates for the CO2 reforming of CH4 (CRM). However, they have suffered from two challenging issues of sintering and carbon accumulation. In order to overcome these drawbacks, a series of ordered mesoporous Ni-xMg-Al2O3 catalysts (x was the mole ratio of Mg/(Mg + Al)) with different Mg contents were synthesized by an improved one-pot evaporation-induced self-assembly method. The effect of Mg on the physicochemical property and catalytic performance of Ni-xMg-Al2O3 catalysts for CRM was investigated. The catalysts were characterized by XRD, H2-TPR, XPS, TEM, NH3-TPD, and N2 adsorption-desorption at low temperature. The results showed that the introduction of Mg into the Ni–Al2O3 maintained well the ordered mesoporous structure and enhanced the interaction between Ni and Al2O3, which could effectively restrict the thermal agglomeration of Ni nanoparticles. In addition, the acid sites were decreased with the introduction of Mg, which was beneficial for resistance to carbon accumulation, and then improving the CRM performance. Among Ni-xMg-Al2O3 catalysts, Ni–3Mg–Al2O3 presented the highest catalytic activity and stability. Under the conditions of 750 °C and GHSV = 32000 mL g−1 h−1, the conversion of CH4 and CO2 could reach 81.97% and 89.11% without deactivation for 20 h.