Comparative study on CeO2 catalysts with different morphologies and exposed facets for catalytic ozonation: performance, key factor and mechanism insight.

Morphology and facet effects of metal oxides in heterogeneous catalytic ozonation (HCO) are attracting increasing interests. In this paper, the different HCO performances for degradation and mineralization of phenol of seven ceria (CeO2) catalysts, including four with different morphologies (nanorod, nanocube, nanooctahedron and nanopolyhedron) and three with the same nanorod morphology but different exposed facets, are comparatively studied. CeO2 nanorods with (110) and (100) facets exposed show the best performance, much better than that of single ozonation, while CeO2 nanocubes and nanooctahedra show performances close to single ozonation. The underlying reason for their different HCO performances is revealed using various experimental and density functional theory (DFT) calculation results and the possible catalytic reaction mechanism is proposed. The oxygen vacancy (OV) is found to be pivotal for the HCO performance of the different CeO2 catalysts regardless of their morphology or exposed facet. A linear correlation is discerned between the rate of catalytic decomposition of dissolved ozone (O3) and the density of Frenkel-type OV. DFT calculations and in-situ spectroscopic studies ascertain that the existence of OV can boost O3 activation on both the hydroxyl (OH) and Ce sites of CeO2. Conversely, various facets without OV exhibit similar O3 adsorption energies. The OH group plays an important role in activating O3 to produce hydroxyl radical (∙OH) for improved mineralization. This work may offer valuable insights for designing Facet- and OV-regulated catalysts in HCO for the abatement of refractory organic pollutants.

Comparative study on Al-SBA-15 prepared by spray drying and traditional methods for bulky hydrocarbon cracking: Properties, performance and influencing factors.

Mesoporous aluminosilicates Al-SBA-15 with large pore sizes and suitable acid properties are promising substitutes to zeolites for catalytic cracking of bulky hydrocarbons without molecular diffusion limitation. The conventional processes to synthesize Al-SBA-15 are time-consuming and often suffer from low "framework" Al contents. Herein, Al-SBA-15 microspheres are synthesized using the rapid and scalable microfluidic jet spray drying technique. They possess uniform particle sizes (45-60 µm), variable surface morphologies, high surface areas (264-340 m2/g), uniform mesopores (3.8-4.9 nm) and rich acid sites (126-812 µmol/g) and high acid strength. Their physicochemical properties are compared with the counterparts synthesized using traditional hydrothermal and evaporation-induced self-assembly methods. The spray drying technique results in a higher incorporation of aluminum (Al) atoms into the silica "framework" compared to the other two methods. The catalytic cracking efficiencies of 1,3,5-triisopropylbenzene (TIPB) on the Al-SBA-15 materials synthesized using the three different methods and nanosized ZSM-5 are compared. The optimal spray-dried Al-SBA-15 exhibits the best performance with 100 % TIPB conversion, excellent selectivity (about 75 %) towards the formation of deeply cracked products (benzene and propylene) and high stability. The catalytic performances of the spray-dried Al-SBA-15 with varying Si/Al ratios are also compared. The reasons for the different performances of the different materials are discussed, where the mesopores, high acid density and strength are observed to play the most critical role. This work might provide a basis for the synthesis of mesoporous rich metal-substituted silica materials for different catalytic applications.

Deep Cracking of Bulky Hydrocarbons into Light Products via Tandem Catalysis over Uniform Interconnected ZSM-5@AlSBA-15 Composites.

Deep cracking of bulky hydrocarbons on zeolite-containing catalysts into light products with high activity, desired selectivity, and long-term stability is demanded but challenging. Herein, the efficient deep cracking of 1,3,5-triisopropylbenzene (TIPB) on intimate ZSM-5@AlSBA-15 composites via tandem catalysis is demonstrated. The rapid aerosol-confined assembly enables the synthesis of the composites composed of a continuous AlSBA-15 matrix decorated with isolated ZSM-5 nanoparticles. The two components at various ZSM-5/AlSBA-15 mass ratios are uniformly mixed with chemically bonded pore walls, interconnected pores, and eliminated external surfaces of nanosized ZSM-5. The typical composite with a ZSM-5/AlSBA-15 mass ratio of 0.25 shows superior performance in TIPB cracking with outstanding activity (≈100% conversion) and deep cracking selectivity (mass of propylene + benzene > 60%) maintained for a long time (> 6 h) under a high TIPB flux (2 mL h-1), far better (several to tens of times higher) than the single-component and physically mixed catalysts and superior to literature results. The high performance is attributed to the cooperative tandem catalytic process, that is, selective and timely pre-cracking of TIPB to isopropylbenzene (IPB) in AlSBA-15 and subsequently timely diffusion and deep cracking of IPB in nanosized ZSM-5.

3D Carbon Microspheres with a Maze-Like Structure and Large Mesopore Tunnels Built From Rapid Aerosol-Confined Coherent Salt/Surfactant Templating.

Hierarchically porous carbons with tailor-made properties are essential for applications wherein rich active sites and fast mass transfer are required. Herein, a rapid aerosol-confined salt/surfactant templating approach is proposed for synthesizing hierarchically porous carbon microspheres (HPCMs) with a maze-like structure and large mesopore tunnels for high-performance tri-phase catalytic ozonation. The confined assembly in drying microdroplets is crucial for coherent salt (NaCl) and surfactant (F127) dual templating without macroscopic phase separation. The HPCMs possess tunable sizes, a maze-like structure with highly open macropores (0.3-30 µm) templated from NaCl crystal arrays, large intrawall mesopore tunnels (10-45 nm) templated from F127, and rich micropores (surface area >1000 m2 g-1 ) and oxygen heteroatoms originated from NaCl-confined carbonization of phenolic resin. The structure formation mechanism of the HPCMs and several influencing factors on properties are elaborated. The HPCMs exhibit superior performance in gas-liquid-solid tri-phase catalytic ozonation for oxalate degradation, owing to their hierarchical pore structure for fast mass transfer and rich defects and oxygen-containing groups (especially carbonyl) for efficient O3 activation. The reactive oxygen species responsible for oxalate degradation and the influences of several structure parameters on performance are discussed. This work may provide a platform for producing hierarchically porous materials for various applications.

Surfactants Used in Colloidal Synthesis Modulate Ni Nanoparticle Surface Evolution for Selective CO2 Hydrogenation.

Colloidal chemistry holds promise to prepare uniform and size-controllable pre-catalysts; however, it remains a challenge to unveil the atomic-level transition from pre-catalysts to active catalytic surfaces under the reaction conditions to enable the mechanistic design of catalysts. Here, we report an ambient-pressure X-ray photoelectron spectroscopy study, coupled with in situ environmental transmission electron microscopy, infrared spectroscopy, and theoretical calculations, to elucidate the surface catalytic sites of colloidal Ni nanoparticles for CO2 hydrogenation. We show that Ni nanoparticles with phosphine ligands exhibit a distinct surface evolution compared with amine-capped ones, owing to the diffusion of P under oxidative (air) or reductive (CO2 + H2) gaseous environments at elevated temperatures. The resulting NiPx surface leads to a substantially improved selectivity for CO production, in contrast to the metallic Ni, which favors CH4. The further elimination of surface metallic Ni sites by designing multi-step P incorporation achieves unit selectivity of CO in high-rate CO2 hydrogenation.

Cobalt-Promoted Noble-Metal Catalysts for Efficient Hydrogen Generation from Ammonia Borane Hydrolysis.

Ammonia borane (AB) has been regarded as a promising material for chemical hydrogen storage. However, the development of efficient, cost-effective, and stable catalysts for H2 generation from AB hydrolysis remains a bottleneck for realizing its practical application. Herein, a step-by-step reduction strategy has been developed to synthesize a series of bimetallic species with small sizes and high dispersions onto various metal oxide supports. Superior to other non-noble metal species, the introduction of Co species can remarkably and universally promote the catalytic activity of various noble metals (e.g., Pt, Rh, Ru, and Pd) in AB hydrolysis reactions. The optimized Pt0.1%Co3%/TiO2 catalyst exhibits a superhigh H2 generation rate from AB hydrolysis, showing a turnover frequency (TOF) value of 2250 molH2 molPt-1 min-1 at 298 K. Such a TOF value is about 10 and 15 times higher than that of the monometal Pt/TiO2 and commercial Pt/C catalysts, respectively. The density functional theory (DFT) calculation reveals that the synergy between Pt and CoO species can remarkably promote the chemisorption and dissociation of water molecules, accelerating the H2 evolution from AB hydrolysis. Significantly, the representative Pt0.25%Co3%/TiO2 catalyst exhibits excellent stability, achieving a record-high turnover number of up to 215,236 at room temperature. The excellent catalytic performance, superior stability, and low cost of the designed catalysts create new prospects for their practical application in chemical hydrogen storage.

Aerosol Spray Drying Guided Synthesis of Ultrasmall Alloyed Bimetallic Nanoparticles Supported on Silica for Catalytic Semihydrogenation.

Supported bimetallic nanoparticles (NPs) with ultrasmall sizes and homogeneous alloying are attractive for catalysis. However, facile synthesis of this type of material remains very challenging. Here, the aerosol drying impregnation method for rapid, scalable, and general synthesis of silica-supported bimetallic NPs is proposed. The method relies on aerosol spray drying to promote the mixing and dispersing of binary metal precursors on SiO2 . It is capable of controlling the composition and size of bimetallic NPs and avoids the use of expensive metal complex salts and complicated experiment procedures. Twelve permutations combining a noble metal (Pd, Ru, and Pt) and a base one (Fe, Co, Ni, and Cu) with ultrasmall sizes (1.4-2.2 nm in average size), uniform dispersion, and good alloying are synthesized. Interesting activity and selectivity trends in catalytic semihydrogenation of phenylacetylene over the supported Pd-based NPs can be observed. The silica-supported PdNi NPs deliver both high activity and styrene selectivity. Spectroscopic and density functional theory calculation results reveal the improved chemoselectivity originated from the suitably down-shifted d-band center of the PdNi NPs inducing an increased energy barrier for overhydrogenation and a weakened styrene adsorption.

Oxygen vacancies and interfacial iron sites in hierarchical BiOCl nanosheet microflowers cooperatively promoting photo-Fenton.

Controllable active site construction, crystal structure regulation and efficient charge separation are core issues in heterogeneous photo-Fenton. Herein, abundant oxygen vacancies and well-dispersed interfacial iron sites are simultaneously constructed in hierarchical nanosheet-assembled BiOCl microflowers. The composites exhibit superior performance in photo-Fenton oxidation of carbamazepine (10 mg L-1) with a low H2O2 concentration (1.3 mM). The high performance highly depends on the synergistic effects between oxygen vacancies and iron species. Rather than modulating the valence band, the involvements of oxygen vacancies and iron species could modify the conduction band of BiOCl. The presence of oxygen vacancies promotes the migration of photo-generated electrons and accelerates the redox cycling of ≡Fe(III)/≡Fe(II) to boost the activation of H2O2 to generate hydroxyl radicals, and oxygen vacancies can be well preserved after cyclic use. This work provides understanding on efficient utilization of oxygen vacancies and interfacial iron sites to assist photo-Fenton and the underlying electron transfer mechanism.

Amorphous iron oxides anchored on BiOCl nanoplates as robust catalysts for high-performance photo-Fenton oxidation.

Semiconductor supported iron oxides are highly promising catalysts to remove organic pollutants in photo-Fenton. Development of robust composite catalysts with both high activity and stability is essential. In this work, amorphous iron oxide layers are uniformly and tightly anchored on two-dimensional (2D) BiOCl nanoplates through post precipitation-deposition and subsequent low-temperature thermal treatment at 150-350 °C. A low iron loading amount (1-2 wt.%) is sufficient to make the resulted composite (BiOCl-Fe) catalysts superior in photo-Fenton oxidation of phenol (10 mg/L) with high mineralization efficiency (up to about 80% in 60 min). The low-temperature thermal treatment can significantly enhance the stability of catalysts with much less iron leached and high photo-Fenton performance maintained. The intimate contact between the amorphous iron oxide layers and the 2D BiOCl nanoplates could guarantee the fluent electron transfer and efficient activation of H2O2 at interfaces. Compared with the pristine BiOCl, the BiOCl-Fe catalysts possess faster separation of the charge carriers. The predominant active species turns from O2•- in photocatalysis to HO• in the photo-Fenton catalysis. This research could provide enhanced understanding on the synthesis of robust catalysts and the structure optimization of BiOCl supported iron oxides for photo-Fenton.

Superhydrophilic three-dimensional porous spent coffee ground reduced palladium nanoparticles for efficient catalytic reduction.

The use of functional biodegradable wastes to treat environmental problems would create minimal extra burden to our environment. In this paper, we propose a sustainable and practical strategy to turn spent coffee ground (SCG) into a multifunctional palladium-loaded catalyst for water treatment instead of going into landfill as solid waste. Bleached delignified coffee ground (D-SCG) has a porous structure and a good capability to reduce Pd (II) to Pd (0). A large amount of nanocellulose is formed on the surface of SCG after bleaching by H2O2, which anchors and disperses the palladium nanoparticles (Pd NPs). The D-SCG loaded with Pd NPs (Pd-D-SCG) is superhydrophilic, which facilitates water transport and thus promotes efficient removal of organic pollutants dissolved in water. Pd-D-SCG exhibits excellent room temperature catalytic activity for the removal of 4-nitrophenol (4-NP) and methylene blue (MB) in water and shows good chemical stability and recyclability in water, with no obvious decrease even after five repeated cycles.

Microdroplet confined assembly enabling the scalable synthesis of titania supported ultrasmall low-valent copper catalysts for efficient photocatalytic activation of peroxymonosulfate.

The synthesis of highly dispersed low-valent copper catalysts is very challenging because they are prone to oxidation and sintering. Herein, scalable synthesis of ultrafine Cu(0)/Cu(i) catalysts supported on mesoporous titania microspheres is enabled by a one-step microdroplet confined assembly method. The extremely fast solute assembly in the microdroplet induces excellent metal precursor dispersion, reduces sol-gel crosslinking, and creates wrinkled microspheres with surface crusts and hollow cavities. This structural architecture allows the generation of an inner reductive gas environment during calcination in air to reduce Cu(ii) and create oxygen vacancy (OV) sites in titania. The obtained catalysts exhibit excellent performance in the photocatalytic activation of peroxymonosulfate (PMS) for pollutant degradation. The Cu(0) species with a surface plasmon resonance effect and OV-rich anatase facilitate efficient solar light utilization and charge separation. The intimate interface between Cu(i)/Cu(0) and anatase enables fast electron transfer and timely copper redox cycling to promote the activation of PMS.

An acid-base molecular assembly strategy toward N-doped Mo2C@C nanowires with mesoporous Mo2C cores and ultrathin carbon shells for efficient hydrogen evolution.

Molybdenum carbides are promising electrocatalysts for the hydrogen evolution reaction (HER). Rational design of morphology, composition and interfacial structure in Mo2C materials is essential to enhance their HER performance. Herein, an acid-base molecular assembly strategy is demonstrated for the synthesis of novel N-doped Mo2C@C core-shell nanowires (NWs) composed of mesoporous Mo2C cores with interconnected crystalline walls and ultrathin carbon shells. The strong interactions between the two precursors, adenine (Ade) and phosphomolybdic acid (PMA), lead to the formation of inter-molecular hybrid NWs during a hydrothermal process. The subsequent pyrolysis leads to confined growth of crystalline Mo2C NWs with inter-crystal mesopores (5 ~ 10 nm), formation of ultrathin carbon shells (~1.5 nm in thickness), and effective N doping. Such a structure architecture can provide abundant active sites, fast and diverse mass and electron transport paths, as well as stable reaction interfaces. The typical N-doped Mo2C@C NWs exhibit high HER performance with a low overpotential of 136 mV at 10 mA cm-2, a small Tafel slop of 58 mV dec-1, excellent durability and outstanding anti-poisoning performance against CO and H2S gases. Furthermore, the influences of several important factors, including the pyrolysis temperature, hydrothermal temperature and precursor mass ratio, on the morphology, composition and structural configuration of the resulted materials are elucidated and correlated with their HER performance. This work may provide a general strategy for the synthesis of other nanoscale metal carbides for various catalytic applications.

Study on the Stability, Evolution of Physicochemical Properties, and Postsynthesis of Metal-Organic Frameworks in Bubbled Aqueous Ozone Solution.

Metal-organic frameworks (MOFs) are highly promising in many areas. Their application and postsynthesis under strong oxidative environments are emerging. However, the stability, physicochemical property evolution, and possible postmodification and postsynthesis of MOFs in strong oxidative solutions are largely unknown. In this paper, the behaviors of a series of MOFs in bubbled aqueous ozone (O3) solutions are studied. The chosen MOFs are categorized into trimesic type including MIL-101(Fe) and MIL-96(Al); terephthalic type including MOF-74(Co), UiO-66(Zr), MIL-53(Al), and MIL-101(Cr); and imidazole type including ZIF-67(Co) and ZIF-8(Zn), based on the ligand structure. The intrinsic stability and evolution of the physicochemical properties of these MOFs during aqueous O3 treatment are elucidated using structural, morphological, textural, thermal, and spectroscopic analyses. Several stable, metastable, and instable MOFs are identified. The critical parameters that determine the stability and capability for postsynthesis of these MOFs in aqueous O3 solutions are discussed. The stability follows the general order of trimesic-type > terephthalic-type ≫ imidazole-type MOFs because of the distinct antioxidation capability of the ligands. The effects of the ligand, metal cation, and their coordination number on stability are discussed. MIL-100(Fe), MIL-96(Al), and MOF-74(Co) are stable in aqueous O3. UiO-66(Zr), MIL-53(Al), and MIL-101(Cr) are metastable that their porosity, particle size, and crystallinity can be postmodified. ZIF-67(Co) and ZIF-8(Zn) are instable and can be gradually and completely disassembled. Their particle size and morphology and surface groups can be tuned by controlling the treatment time. Postsynthesis of metal hydroxides from ZIF-67(Co) and gradual release of dissolved zinc ion from ZIF-8(Zn) are achievable. The stable MIL-96(Al) shows promising performance in catalytic ozonation for degrading 4-nitrophenol, and the α-Co(OH)2 derived from treating ZIF-67(Co) shows highly promising performance in the electrocatalytic oxygen evolution reaction (OER).

Highly dispersed titania-supported iron oxide catalysts for efficient heterogeneous photo-Fenton oxidation: Influencing factors, synergistic effects and mechanism insight.

Titania (TiO2) supported iron oxides (Fe-TiO2) are ideal catalysts to be applied in heterogeneous photo-Fenton oxidation (HPFO) for wastewater treatment because of the capabilities of TiO2 in photocatalysis and iron oxides in interfacial H2O2 activation. It is important to understand the influences of the structural parameters of Fe-TiO2 catalysts and the complicated interplay between TiO2 and iron oxides on the performance of HPFO. In this paper, a series of Fe-TiO2 catalysts are obtained through a facile solid-phase synthesis method. The iron loading content and the calcination temperature are systematically adjusted to tune the crystal phase, size, anatase/rutile ratio and density of oxygen vacancy (OV) site of TiO2, the dispersing state of iron species, and the interfacial structure of the Fe-TiO2 catalysts. Then, the performance of these catalysts in HPFO for degrading methylene blue (MB) are comparatively studied. Correlations between the performance and various structural properties of the catalysts are clarified. The interplay between TiO2 and iron oxides in the HPFO process is elucidated. The insight reaction mechanism is also discussed. Under optimized conditions (an iron loading of 1 wt% and a temperature of 600 °C), Fe-TiO2 catalysts with iron lattice doping, well-dispersed ultrasmall α-Fe2O3 nanoparticles, appropriate anatase/rutile ratios and abundant OV sites can be obtained. The anatase-rutile-Fe2O3 heterojunction, ultrasmall α-Fe2O3 nanoparticles and OV sites in the optimized catalysts work synergistically to improve the charge migration and interfacial activation of H2O2, leading to superior HPFO performance for MB degradation and mineralization.

Sintering- and oxidation-resistant ultrasmall Cu(I)/(II) oxides supported on defect-rich mesoporous alumina microspheres boosting catalytic ozonation.

Supported copper oxides with well-dispersed metal species, small size, tunable valence and high stability are highly desirable in catalysis. Herein, novel copper oxide (CuOx) catalysts supported on defect-rich mesoporous alumina microspheres are developed using a spray-drying-assisted evaporation induced self-assembly method. The catalysts possess a special structure composed of a mesoporous outer layer, a mesoporous-nanosphere-stacked under layer and a hollow cavity. Because of this special structure and the defective nature of the alumina support, the CuOx catalysts are ultrasmall in size (1 ~ 3 nm), bivalent with a very high Cu+/Cu2+ ratio (0.7), and highly stable against sintering and oxidation at high temperatures (up to 800 °C), while the wet impregnation method results in CuOx catalysts with much larger sizes (~15 nm) and lower the Cu+/Cu2+ ratios (~0.29). The catalyst formation mechanism through the spray drying method is proposed and discussed. The catalysts show remarkable performance in catalytic ozonation of phenol wastewaters. With high-concentration phenol (250 ppm) as the model organic pollutant, the optimized catalyst delivers promising catalytic performance with 100% phenol removal and 53% TOC removal in 60 min, and a high cyclic stability. Superoxide anion free radicals (⋅O2-), singlet oxygen (1O2) and hydroxyl radicals (⋅OH) are the predominant reactive species. A detailed structure-performance study reveals the surface hydroxyl groups and Cu+/Cu2+ redox couples play cooperatively to accelerate O3 decomposition generating reactive radicals. The plausible catalytic O3 decomposition mechanism is proposed and discussed with supportive evidences.

Slow and Sustained Release of Carbonate Ions from Amino Acids for Controlled Hydrothermal Growth of Alkaline-Earth Carbonate Single Crystals.

Alkaline-earth metal carbonate materials have attracted wide interest because of their high value in many applications. Various sources of carbonate ions (CO3 2-), such as CO2 gas, alkaline-metal carbonate salts, and urea, have been reported for the synthesis of metal carbonate crystals, yet a slow and sustained CO3 2- release approach for controlled crystal growth is much desired. In this paper, we demonstrate a new chemical approach toward slow and sustained CO3 2- release for hydrothermal growth of large alkaline-earth metal carbonate single crystals. Such an approach is enabled by the multiple hydrolysis of a small basic amino acid (arginine, Arg). Namely, the amino groups of Arg hydrolyze to form OH- ions, making the solution basic, and the hydrolysis of the guanidyl group of Arg is hydrothermally triggered to produce urea and ammonia, followed by the hydrolysis of urea to produce CO2 and ammonia and then the release of CO3 2- because of the reaction between CO2 and the OH- ions hydrolyzed from ammonia. Such a CO3 2- release behavior enables the slow and controlled growth of various carbonate single crystals over a wide range of pH values. The growth of uniform rhombohedron MgCO3 single crystals with variable morphologies and crystal sizes is studied in detail. The influences of reaction temperature, solution pH, precursor type, and concentration on the morphology and size of the resulting MgCO3 crystals are elucidated. The crystal evolution mechanism is also proposed and discussed with various supportive data.

Degradation of Acetaminophen via UVA-induced advanced oxidation processes (AOPs). Involvement of different radical species: HO, SO4- and HO2/O2.

In this work, UVA radiation that is part of solar light is taken as the irradiation source and radicals (HO, SO4- and HO2/O2-) are generated through activation of hydrogen peroxide (H2O2), sodium persulfate (Na2S2O8) and Bismuth catalyst (BiOCl), respectively. The distinguished performance in removing acetaminophen (ACTP), a model pharmaceutical pollutant, by these three radicals was compared for the first time. Effect of pH, halide ions concentration and interfacial mechanism have been investigated in detail. Interestingly, results show that heterogeneous UVA/BiOCl process has higher degradation efficiency than homogeneous UVA/H2O2 and UVA/Na2S2O8 systems whatever the solution's pH. To explain these results, second order reaction rate constant (kradical, ACTP) have been determined with laser flash photolysis (LFP) or radical scavenging experiments. The strongly interfacial-depended HO2/O2- radicals have the lowest second order rate constant with ACTP but highest steady state concentration. BiOCl is much easier activated by UVA, and outstanding ACTP mineralization can be achieved. Combination of BiOCl and Na2S2O8 exhibits synergistic effects rather than antagonism effects with H2O2. This study highlights the relative effective utilization of solar light through interfacial directed BiOCl photocatalysis and its synergistic effects with traditional oxidants.

Scalable Synthesis of Uniform Mesoporous Aluminosilicate Microspheres with Controllable Size and Morphology and High Hydrothermal Stability for Efficient Acid Catalysis.

Mesoporous aluminosilicates are promising solid acid catalysts. They are also excellent supports for transition metal catalysts for various catalytic applications. Synthesis of mesoporous aluminosilicates with controllable particle size, morphology, and structure, as well as adjustable acidity and high hydrothermal stability, is very desirable. In this work, we demonstrate the scalable synthesis of Al-SBA-15 microspheres with controllable physicochemical properties by using the microfluidic jet-spray-drying technology. The productivity is up to ∼30 g of dried particles per nozzle per hour. The Al-SBA-15 microspheres possess uniform controllable micron sizes (27.5-70.2 µm), variable surface morphologies, excellent hydrothermal stability (in pure steam at 800 °C), high surface areas (385-464 m2/g), ordered mesopore sizes (5.4-5.8 nm), and desirable acid properties. The dependence of various properties, including particle size, morphology, porosity, pore size, acidity, and hydrothermal stability, of the obtained Al-SBA-15 microspheres on experimental parameters including precursor composition (Si/Al ratio and solid content) and processing conditions (drying and calcination temperatures) is established. A unique morphology transition from smooth to wrinkled microsphere triggered by control of the Si/Al ratio and solid content is observed. The particle formation and morphology-evolution mechanism are discussed. The Al-SBA-15 microspheres exhibit high acid catalytic performance for aldol-condensation reaction between benzaldehyde and ethyl alcohol with a high benzaldehyde conversion (∼56.3%), a fast pseudo-first-order reaction rate (∼0.1344 h-1), and a high cyclic stability, superior to the commercial zeolite acid (H-ZSM-5). Several influencing factors on the catalytic performance of the obtained Al-SBA-15 microspheres are also studied.

A Bimetallic Fe-Mn Oxide-Activated Oxone for In Situ Chemical Oxidation (ISCO) of Trichloroethylene in Groundwater: Efficiency, Sustained Activity, and Mechanism Investigation.

Bimetallic Fe-Mn oxide (BFMO) has been regarded as a promising activator of peroxysulfate (PS), the sustained activity and durability of BFMO for long-term activation of PS in situ, however, is unclear for groundwater remediation. A BFMO (i.e., Mn1.5FeO6.35) was prepared and explored for PS-based in situ chemical oxidation (ISCO) of trichloroethylene (TCE) in sand columns with simulated/actual groundwater (SGW/AGW). The sustained activity of BFMO, oxidant utilization efficiency, and postreaction characterization were particularly investigated. Electron spin resonance (ESR) and radical scavenging tests implied that sulfate radicals (SO4•-) and hydroxyl radicals (HO•) played major roles in degrading TCE, whereas singlet oxygen (1O2) contributed less to TCE degradation by BFMO-activated Oxone. Fast degradation and almost complete dechlorination of TCE in AGW were obtained, with reaction stoichiometry efficiencies (RSE) of ΔTCE/ΔOxone at 3-5%, much higher than those reported RSE values in H2O2-based ISCO (≤0.28%). HCO3- did not show detrimental effect on TCE degradation, and effects of natural organic matters (NOM) were negligible at high Oxone dosage. Postreaction characterizations displayed that the BFMO was remarkably stable with sustained activity for Oxone activation after 115 days of continuous-flow test, which therefore can be promising catalyst for Oxone-based ISCO for TCE-contaminated groundwater remediation.

A Molecular Foaming and Activation Strategy to Porous N-Doped Carbon Foams for Supercapacitors and CO2 Capture.

Hierarchically porous carbon materials are promising for energy storage, separation and catalysis. It is desirable but fairly challenging to simultaneously create ultrahigh surface areas, large pore volumes and high N contents in these materials. Herein, we demonstrate a facile acid-base enabled in situ molecular foaming and activation strategy for the synthesis of hierarchically macro-/meso-/microporous N-doped carbon foams (HPNCFs). The key design for the synthesis is the selection of histidine (His) and potassium bicarbonate (PBC) to allow the formation of 3D foam structures by in situ foaming, the PBC/His acid-base reaction to enable a molecular mixing and subsequent a uniform chemical activation, and the stable imidazole moiety in His to sustain high N contents after carbonization. The formation mechanism of the HPNCFs is studied in detail. The prepared HPNCFs possess 3D macroporous frameworks with thin well-graphitized carbon walls, ultrahigh surface areas (up to 3200 m2 g-1), large pore volumes (up to 2.0 cm3 g-1), high micropore volumes (up to 0.67 cm3 g-1), narrowly distributed micropores and mesopores and high N contents (up to 14.6 wt%) with pyrrolic N as the predominant N site. The HPNCFs are promising for supercapacitors with high specific capacitances (185-240 F g-1), good rate capability and excellent stability. They are also excellent for CO2 capture with a high adsorption capacity (~ 4.13 mmol g-1), a large isosteric heat of adsorption (26.5 kJ mol-1) and an excellent CO2/N2 selectivity (~ 24).