Hydrothermal Synthesis Conditions Research Articles

Seeds Combining Pyrrolidine Control the Framework Al Distribution of FER Zeolite to Enhance Its Performance in the Skeletal Isomerization of n-Butene

FER zeolites have a unique framework structure and acid distribution, and are widely studied as a catalyst for reactions such as n-butene skeletal isomerization and dimethyl ether carbonylation. The Brönsted acid site (BAS) located in the 10-member ring (10-MR) of FER zeolites serves as the active site for the isomerization reaction of skeletal n-butene to produce isobutene. This study prepared five types of FER zeolites using different methods: using pyrrolidine (PY) alone as a template; using Na-form FER as seeds (SN) or H-form FER as seeds without organic structure directing agents (OSDAs); and combining the seeds of SN or SH with PY as OSDAs. The differences in the structure and acid distribution of the five zeolites were investigated, as well as their catalytic performance for the skeletal isomerization of n-butene. Experiments and characterization results showed that under hydrothermal synthesis conditions, the FER-PY+SH zeolites synthesized by using both H-form zeolites seeds and pyridine exhibited the highest aluminum concentrations at T1 and T3 sites, along with the greatest BAS located in the 10-MR. This unique composition contributed to the highest selectivity of isobutene. The FER-PY+SH catalyst was continuously used for 720 h at 350 °C, 0.1 MPa, and an n-butene mass space velocity of 2.0 h−1 for three cycles of 2160 h. During this period, the conversion of n-butene was over 39%, while the selectivity of isobutene exceeded 95%. The FER-PY+SH catalyst exhibited excellent stability and activity.

How substrate surface area and surface curvature determine kinetics and titanate formation during non-hydrothermal alkali treatment of titanium microspheres

Titanium surface nanostructuring using alkali treatment gains significant attention in a wide range of fields, such as biomaterials, (photo)catalysis, (metal/ion) sorption, CO2 capture, electrochromism and sodium-ion batteries. Even though the physicochemical properties and application potentials of the surface nanostructures are fairly well understood, there is still debate about their exact formation mechanism, limiting knowledge based structural control through altered synthesis conditions. Moreover, this knowledge is largely focused on hydrothermal synthesis conditions, whereas non-hydrothermal conditions might provide benefits towards industrial application. Also the impact of substrate properties, rather than chemical reaction conditions, on the nanostructure formation is only limitedly reported in literature. This work reveals new fundamental knowledge of non-hydrothermal alkali treatment of titanium, using microspheres by implementing, for the first time, in-situ hydrogen measurement during alkali treatment in combination with the ex-situ determination of the sodium and oxygen content in the recovered alkali treated samples, providing critical information on the role of dissolution apart from the precipitation process. The effect of surface area and surface curvature on the dissolution and precipitation process, and the resulting impact on the physicochemical properties of the obtained titanate layer is studied. This shows the much larger impact on dissolution in contrast to precipitation, knowledge that is lacking in literature, but important when implementing alkali surface nanostructuring on complex (e.g. 3D printed) substrates, and considering the prospective shift from lab-scale to industry. The Ti dissolution step was found to be mainly controlled by the total surface area, while the rate determining step was found to be the titanate precipitation, not influenced by either surface area or particle size.The changes in oxygen content in the samples after transformation of titanate into TiO2 provided a novel method for its quantification. The microspheres were analysed chemically (Raman), structurally (XRD) and morphologically (SEM, MIP), screening the effect of surface area, particle size and reaction time on the growth behaviour of the titanate layer. The porous layer structurally corresponds to Na2Ti2O4(OH)2 for all evaluated conditions, with pores in the range of 10–600 nm. Increasing surface area and particle size results in local and non-uniform titanate growth, while titanate nanowire and strut formation between the microspheres were enhanced by reduced microsphere size and prolonged reaction times.

Crystallization of smooth amorphous calcium phosphate microspheres to core-shell hydroxyapatite microspheres.

Calcium phosphates (Ca-P) represent a significant class of biological minerals found in natural hard tissues. Crystallization through phase transformation of a metastable precursor is an effective strategy to guide the growth of crystalline Ca-P with exceptional functionality. Despite extensive research on Ca-P, the exact process during the crystallization of amorphous particles to hydroxyapatite (HA) remains elusive. Herein, pure HA microspheres with a core-shell structure are crystallized via dissolution and re-crystallization of smooth amorphous calcium phosphate (ACP) microspheres. The transformation is initiated with the increase of the hydrothermal treatment time in the presence of sodium trimetaphosphate and l-glutamic. The underlying mechanisms along with the kinetics of such transformation are explored. Nanocrystalline areas are formed on the smooth ACP microspheres and crystallization advances via nanometre-sized clusters formed by directional arrangement of nanocrystalline whiskers. Our findings shed light on a crucial but unclear stage in the genesis of HA crystals, specifically under the conditions of hydrothermal synthesis.

Lignin-hydrothermal fabrication of 3D hierarchical porous carbon for energy storage application

In this groundbreaking study, the Taguchi-Probability method is employed to optimize the energy storage performance of porous hierarchical carbon (PHC) by investigating lignin doping and controlling hydrothermal synthesis conditions. The findings indicate that optimal lignin contents range from 63 to 70 % carbon, 0.75–1.0 % nitrogen, <2.0 % sulfur, and < 30 % oxygen, with varying hydrogen percentages. Ideal hydrothermal conditions involve a temperature of 220 °C, duration of 18 h, concentration of 80 g/L, and pH of 4. Remarkably, pH has the most significant impact (33.30 %) on energy storage enhancement, followed by reaction time (24.73 %), concentration, and temperature. These results highlight the pivotal role of hydrothermal conditions in enhancing PHC's energy storage capabilities, offering promising avenues for sustainable energy storage solutions.

Hydrothermally Synthesized ZnCr- and NiCr-Layered Double Hydroxides as Hydrogen Evolution Photocatalysts.

The layered double hydroxides (LDHs) of transition metals are of great interest as building blocks for the creation of composite photocatalytic materials for hydrogen production, environmental remediation and other applications. However, the synthesis of most LDHs is reported only by the conventional coprecipitation method, which makes it difficult to control the catalyst's crystallinity. In the present study, ZnCr- and NiCr-LDHs have been successfully prepared using a facile hydrothermal approach. Varying the hydrothermal synthesis conditions allowed us to obtain target products with a controllable crystallite size in the range of 2-26 nm and a specific surface area of 45-83 m2∙g-1. The LDHs synthesized were investigated as photocatalysts of hydrogen generation from aqueous methanol. It was revealed that the photocatalytic activity of ZnCr-LDH samples grows monotonically with the increase in their average crystallite size, while that of NiCr-LDH ones reaches a maximum with intermediate-sized crystallites and then decreases due to the specific surface area reduction. The concentration dependence of the hydrogen evolution activity is generally consistent with the standard Langmuir-Hinshelwood model for heterogeneous catalysis. At a methanol content of 50 mol. %, the rate of hydrogen generation over ZnCr- and NiCr-LDHs reaches 88 and 41 μmol∙h-1∙g-1, respectively. The hydrothermally synthesized LDHs with enhanced crystallinity may be of interest for further fabrication of their nanosheets being promising components of new composite photocatalysts.

Embryonic zeolite-directed synthesis of ZSM-34 and SSZ-13 zeolites

The use of an organic structure-directing agent (OSDA) makes zeolite synthesis expensive and environmentally non-friendly. Seeded zeolite synthesis offers an environmentally benign alternative that avoids using an OSDA while providing a high purity, crystallinity, and yield in the product. In this study, we report using embryonic zeolites (EZs) as efficient seeds to obtain industrially important zeolites such as ZSM-34 and SSZ-13 in an OSDA-free synthesis system. Our results showed that zeolites ZSM-34, SSZ-13 and LTL could be obtained depending on the Al/Si ratio in the synthesis system. The synthesis time was considerably shorter than other ZSM-34 and SSZ-13 syntheses methods reported in the literature, achieving more than 90% crystallinity. The physicochemical analysis showed that highly crystalline zeolites with characteristics similar to the OSDA synthesized counterparts were obtained. Furthermore, the EZs seeding approach is facile, low cost, and environmentally friendly, provided the synthesis is OSDA-free. In addition, the EZs seeds can be obtained under hydrothermal synthesis conditions. The method can be potentially applied to the synthesis of other zeolite types.

Ni/Mn electroactive nanohybrids physic-chemical properties for ulterior new generation of supercapacitors

In this paper, highly mesoporous hierarchical mono- and bi- Ni and/or Mn based hydroxide and/or carbonate nanohybrids were synthesized using a facile free template hydrothermal method and investigated as high-performance electroactive nanomaterials for ulterior new generation of supercapacitors. Controlling the Ni/Mn precursors molar ratio and the growth conditions can offer preponderances for performances enhancing via a comparative products physic-chemical properties which were carried out using different techniques like: XRD, FTIR, Raman, XPS, HRTEM/FESEM, EDS, UV–visible and BET. The structural results confirmed the formation of MnCO3, α-3Ni(OH)2·2H2O and Ni(HCO3)2 phases in the synthesized nanomaterials, with different morphologies (nanofibers, nanocubes, porous micro/nanoflowers) depending on the hydrothermal synthesis conditions. Meanwhile, the influence of Ni and Mn transition metal species co-existence on the resulting composition and their optical properties were also discussed. Moreover, their electrochemical measurements were also performed in a 6 M KOH aqueous electrolyte using three electrode system. The results show that 2Ni(HCO3)2/MnCO3 nanohybrid exhibited the highest specific capacitance (capacity) of 2777 F g−1 at 5 mV s−1 (320 mAh.g−1 at 1 A g−1) with high rate capability. This excellent electrochemical kinetics performance is ascribed to the optimized composition of Ni/Mn and its unique nanostructured configuration with intercalated ions, indicating a great potential of this new kind of nanohybrids to deliver both high energy density and high power density in future energy storage devices.

Optimization of hydrothermal synthesis conditions of Bidens pilosa-derived NiFe2O4@AC for dye adsorption using response surface methodology and Box-Behnken design.

The presence of stable and hazardous organic dyes in industrial effluents poses significant risks to both public health and the environment. Activated carbons and biochars are widely used adsorbents for removal of these pollutants, but they often have several disadvantages such as poor recoverability and inseparability from water in the post-adsorption process. Incorporating a magnetic component into activated carbons can address these drawbacks. This study aims to optimizing the production of NiFe2O4-loaded activated carbon (NiFe2O4@AC) derived from a Bidens pilosa biomass source through a hydrothermal method for the adsorption of Rhodamine B (RhB), methyl orange (MO), and methyl red (MR) dyes. Response surface methodology (RSM) and Box-Behnken design (BBD) were applied to analyze the key synthesis factors such as NiFe2O4 loading percentage (10-50%), hydrothermal temperature (120-180 °C), and reaction time (6-18 h). The optimized condition was found at a NiFe2O4 loading of 19.93%, a temperature of 135.55 °C, and a reaction time of 16.54 h. The optimum NiFe2O4@AC demonstrated excellent sorption efficiencies of higher than 92.98-97.10% against all three dyes. This adsorbent was characterized, exhibiting a well-developed porous structure with a high surface area of 973.5 m2 g-1. Kinetic and isotherm were studied with the best fit of pseudo-second-order, and Freundlich or Temkin. Qmax values were determined to be 204.07, 266.16, and 177.70 mg g-1 for RhB, MO, and MR, respectively. By selecting HCl as an elution, NiFe2O4@AC could be efficiently reused for at least 4 cycles. Thus, the Bidens pilosa-derived NiFe2O4@AC can be a promising material for effective and recyclable removal of dye pollutants from wastewater.

Robust catalyst 3D microarchitectures by digital light printing with ceramic particle–polymer composites

This study entailed the development of an advanced photocatalyst model characterized by high efficiency and ease in dispersion and retrieval processes. This model incorporates a multiscale-hierarchical open-cell structure integrated with nanostructured materials, effectively targeting the removal of organic compounds from wastewater. The fabrication of the specimens was achieved through a combined approach of additive manufacturing and chemical synthesis. The open-cell structure, composed of photopolymerized polymers and synthesized nanocrystals, displays a notable aspect ratio, an extensive surface area, and a significant porosity. These features facilitate the concurrent entry of fluid and light into the core of the framework, leading to enhanced light scattering and activation of photoinduced redox reactions on organic contaminants adhered to the anatase TiO2 surface. The photocatalytic performance was quantified through a spectroscopic analysis, monitoring the absorbance changes associated with organic pollutant degradation. In addition, the influence of open-cell structures on nanomaterial growth under hydrothermal synthesis conditions was explored using finite element method simulations, with findings corroborated by microscopic examination. The functional effectiveness of the novel photocatalyst was assessed through compression tests, analysis of changes pre- and post-reaction, and evaluations of reusability. The developed 3D photocatalyst offers straightforward installation, relocation, and operation, presenting a resilient and effective solution for employing nanoscale catalysts while significantly reducing secondary contamination risks from nanomaterials in aquatic environments. This innovative structure holds potential for application in diverse sectors, including hydrogen production, water decomposition, CO2 capture, and biomedicine.

Controllable synthesis and morphology-dependent light emission efficiency of Zn2GeO4 nanophosphors.

Zn2GeO4 is considered a very promising alternative to current luminescent semiconductors. Previous results suggest that its emitted wavelength may depend on different variables, such as particle size and morphology, among others. In this work, we have prepared pure and highly homogeneous Zn2GeO4 nanorods under hydrothermal synthesis conditions with a willemite-like structure. Their luminescent properties have been explored and their band gap is estimated, which are distinct from those of previously reported Zn2GeO4 bulk particles. Therefore, our results identify particle morphology as a crucial factor for maximizing and fine-tuning the luminescence of Zn2GeO4 nano-phosphors.

Strong green upconversion emission from submicron spindle-shaped SrMoO4:Yb3+,Er3.

Upconversion luminescence (UCL) is a fluorescence process where two or more lower-energy photons convert into a higher-energy photon. Lanthanide (Ln3+)-doped UCL materials often suffer from weak luminescence, especially when directly synthesized by a hydrothermal (HT) process due to the existing hydroxyl group and undesirable arrangement of dopants within host lattices which quench luminescence and limit energy transfer. Therefore, additional heat treatment processes are required to enhance their UCL emission, even though direct hydrothermal synthesis without further heat treatment has the advantages of low energy consumption, fast synthesis, and wide applicability to generate UCL materials. In this study, via a HT process without annealing, we have produced Yb3+ and Er3+ co-doped SrMoO4 submicron spindles with a strong green UCL emission which can be seen with the naked eye, which HT produced oxide-based UCL materials often fail to demonstrate. We have investigated different HT synthesis conditions, such as temperature, time, pH and dopant composition, which control the nucleation, growth, lattice structure arrangement, and ultimately their UCL properties through XRD, SEM, EDS and UCL measurements. The bright green UCL from the SrMoO4:Yb,Er submicron spindles is further enhanced by post-synthesis annealing within a molten NaNO3/KNO3 system to prevent particle size growth. The green UCL intensity from the annealed SrMoO4:Yb,Er submicron spindles surpasses samples produced by the solid-state method and is comparable to that from the commercial NaYF4:Yb,Er sample. We have further studied the temperature-dependent luminescence of both the HT-prepared and molten-salt annealed SrMoO4:Yb,Er submicron spindle samples. The strong UCL from our SrMoO4:Yb,Er submicron spindles could warrant their candidacy for bioimaging and anticounterfeiting applications.

THE INFLUENCE OF THE SYNHTETIC WAY OF LAYERED-TYPE MANGANSESE DIOXIDE ON THE PROPERTIES OF CATHODE MATERIALS FOR AQUEOUS ZINC-ION BATTERIES

This research presents an analysis of physico-chemical, structural and electrochemical properties of cathode materials for aqueous zinc-ion batteries based on manganese dioxide with birnessite-type structure in dependence on the conditions of hydrothermal synthesis. The manganese oxides obtained are capable to the reversible zin ions intercalation into the crystal lattice because of large interlayer distances. They were considered two approaches of synthesis: a reaction between manganese sulfate and potassium permanganate at 160 °С (MnO2-I) and a hydrothermal treatment of potassium permanganate solution at 220 °С (MnO2-II). From the structural analysis it was shown that both methods allow obtaining the birnessite-type manganese dioxide. At the same time, electrochemical properties of cathodes obtained differ in the models of aqueous zinc-ion batteries. MnO2-II material demonstrate higher initial specific capacity (180 mAh∙g-1 at current density 0.3 A∙g-1) while its cyclic stability is on 40% lower than for MnO2-I material. This can be explained with higher surface area of the active material and lower crystallinity.

Hydrothermal Synthesis of Calcium Silicates on the Recovery of Phosphorus from Phosphorite

Calcium silicates with nanosized needle-like structure have been obtained from phosphorite by hydrothermal synthesis. Phosphorus is recovered from phosphorite as sodium phosphate solution under conditions of autoclave treatment of phosphorite with alkaline solution in the presence of silicon dioxide at 250°C. This approach enables involvement of low-phosphorus raw materials into non-waste processing owing to the synthesis of calcium silicates suitable in many branches of industry. Thus prepared phosphate solutions are applicable in agriculture and, after appropriate purification, in food industry. Hydrothermal synthesis conditions have been determined: temperature of 250–300°C, leaching time of 3 h, and NaOH concentration of 150 kg/m3.

PHASE FORMATION IN ALKALINE TITANOSILICATE SYSTEMS DURING HYDROTHERMAL SYNTHESIS

The investigations in the polycomponent high alkaline systems – TiO2–H2SO4–Na2SiO3–NaOH–H2O and TiO2–H2SO4–(NH4)2SO4–Na2SiO3–NaOH–H2O under hydrothermal synthesis conditions have been carried out to provide new products with the given technical properties. It has been shown that by directed selection of structure-forming components, in particular titanium compounds, together with optimal parameters of hydrothermal treatment of the obtained precursor, it is possible to form compounds with the given phase and chemical composition, morphology and particle size. It was found that the rate of structural transformations during synthesis depends on the phase composition of titanosilicate precursors. During their hydrothermal treatment, alkaline and thermal hydrolysis with subsequent dehydration of hydrolyzed phases of titanium (IV) and silicon take place. The process is accompanied by localization of free bonds providing formation of Ti–O–Si–O-bridges and their subsequent transformation into structured new formations.

Highly efficient catalyst of Crednerite CuMnO2 for PMS activation: Synthesis, performance and mechanism

Exploring highly efficient and stable transition metal-based catalysts is significant for the heterogeneous catalysis of peroxymonosulfate (PMS) in contaminants removal during water purification. Herein, we developed a series of Crednerite CuMnO2 catalysts by tuning the hydrothermal synthesis conditions and applied them to catalyze PMS to degrade Orange I (OI). Hydrothermal temperature, hydrothermal reaction time, and NaOH dosage had a great influence on the catalytic performance of catalysts, but different synthetic raw materials had little diversity. Amongst, CMO-160°C-110mmol-24h exhibited the optimal PMS activation effect due to the promoted surface oxygen mobility and electron conduction. Regardless of the wide pH range of 5-9, the coexistence of Inorganic anions and humic acid, the inhibition of OI removal was not significant. Additionally, CMO-160°C-110mmol-24h showed low metal ion leaching and noticeable reusability, implying a great potential application of the CMO-160°C-110mmol-24h/PMS system in practical wastewater engineering. Mechanism studies indicated that surface hydroxyl groups, Cu+/Cu2+ and Mn2+/Mn3+ redox couples were key active sites for PMS activation. Both free radical pathways (•OH, SO4•−, O2•−) and non-free radical pathways (1O2 and electron transfer) were detected in the oxidation reaction, with non-free radical pathways as major contributors. The possible degradation pathway of OI was proposed, and the toxicity of intermediates was assessed. Overall, this study provided an important strategy for the construction of efficient and stable PMS catalysts in wastewater treatment.

Tailoring hydroxyapatite morphology via the effect of divalent cations on the hydrolysis of α-TCP: Oriented crystal growth towards the application in water treatment

The hydrothermal synthesis method to produce calcium hydroxyapatite (HA) of controlled morphology without the use of organic additives is developed in this study. The influence of smaller (Mg2+, Mn2+) and larger (Sr2+, Ba2+) ions on the hydrolysis of α-TCP and crystal growth of HA particles was investigated. It was revealed that both the hydrothermal synthesis conditions (temperature, time) and the nature and concentration of the foreign ion affected the phase purity and morphology of the final products. Of all the ions investigated, Mn2+ had the highest, and Sr2+ had the lowest inhibiting effect on the hydrolysis process of α-TCP. Under certain synthesis conditions, we were able to obtain samples consisting of plate-like or rod-like particles only. The dye adsorption test revealed that the adsorption of plate-like particles for cationic dyes was more efficient, possibly, due to the higher surface area (SBET). Upon normalizing the test results to SBET, it became apparent that the electrostatic attraction between HA particles and dye molecules also impacted the adsorption efficiency. Rod-like particles had a higher ratio of exposed (a,m)-planes and hence lower zeta potential, resulting in increased adsorption of the cationic dye.

Phase (1T/2H) dependent electromagnetic wave absorbing performance of flower-like MoS2 nanosheets

A study was carried out to determine the phase-dependent electromagnetic wave (EMW) absorption performance of MoS2 particles via systematically diversified hydrothermal synthesis conditions such as time, temperature, precursor molarity, and oxalic acid concentration. The formation of mixed-phase structure was verified depending on the presence of the characteristic diffraction peaks belong to 1T (trigonal, P3̅m1 space group) and 2H (hexagonal, P63/mmc space group) phases in the X-ray diffraction (XRD) patterns. Phase-pure 2H-MoS2 was obtained at 200 °C after 12 h of reaction and using 5 mmol oxalic acid. Microscopic examinations indicate that MoS2 particles formed by assembling several nanosheets to create a flower-like morphology. The size, shape, and the distance between the nanosheets were observed to change with increasing temperature, time, and acid concentration. The band gap was found to be modified depending on the phase distribution and decreased from 1.54 eV (2H) to a minimum of 0.64 eV (1T/2H) with the formation of the 1T (metallic) phase. Finally, the minimum reflection loss was measured as − 67.73 dB (99.9999 % of absorption at 9.05 GHz) with an effective absorption bandwidth (EAB) of 3.52 GHz for the sample composed of 1T/2H mixed-phased structure.

Application of a Response Surface Method for the Optimization of the Hydrothermal Synthesis of Magnetic NiCo2O4 Desulfurization Catalytic Powders

In this study, nickel cobaltate (NiCo2O4) powders are employed as a catalyst in conjunction with persulfate for the development of a catalytic oxidation system to enhance fuel desulfurization. The hydrothermal synthesis conditions of NiCo2O4 powders, which significantly influenced the desulfurization efficiency, were optimized using a response surface methodology with a Box–Behnken design. These conditions were ranked in the following order: calcination temperature &gt; hydrothermal temperature &gt; calcination time &gt; hydrothermal time. Through the optimization process, the ideal preparation conditions were determined as follows: a hydrothermal temperature of 143 °C, hydrothermal time of 6.1 h, calcination temperature of 330 °C, and calcination time of 3.7 h. Under these optimized conditions, the predicted desulfurization rate was approximately 85.8%. The experimental results closely matched the prediction, yielding a desulfurization rate of around 84%, with a minimal error of only 2.1%. To characterize the NiCo2O4 powders prepared under the optimal conditions, XRD, SEM, and TEM analyses were conducted. The analysis revealed that the microscopic morphology of NiCo2O4 exhibited a rectangular sheet structure, with an average particle size of 20 nm. Additionally, fan-shaped NiCo2O4 particles were observed as a result of linear and bundle agglomerations. Thus, this work is innovative in its ability to synthesize nano-catalysts using hydrothermal synthesis in a controllable manner and establishing a correlation between the hydrothermal synthesis conditions and catalytic activity.

Novel physical sunscreen from one-dimensional TiO[formula omitted] nanowire: Synthesis, characterization and the effects of morphologies and particle size for use as a physical sunscreen

The performance of the one-dimensional (1D) morphology as an inorganic UV filter for sunscreens of titanium dioxide (TiO2) was evaluated in this research. The 1D TiO2 nanowires were prepared using solid TiO2 and 10 M NaOH as precursors via a modified hydrothermal method, followed by calcination at 400–900°C for 5 h. The influences of TiO2 loading, hydrothermal time and calcination temperature were studied on the morphologies of the as-prepared samples. The morphologies of the TiO2 nanowires were investigated using SEM and TEM techniques. The results found all the variables directly affected the particle size and shape of the TiO2 nanowires. The hydrothermal synthesis conditions using a TiO2 loading of 0.2 g at 220°C for 24 h (HTiO2) resulted in a particle size that was the longest and narrowest in length and diameter, respectively. The first product from the hydrothermal synthesis is H2Ti3O7, which can transform into TiO2(B) (TiO2@400), anatase (TiO2@700) and rutile (TiO2@900) by calcination at 400, 700 and 900 °C, respectively. The calcined samples were selected for a porcine skin penetration study. The 1D morphology particles were localized on the stratum corneum of the skin, while the comparison spherical particle penetrated the deeper layer. From the SPF test, the highest SPF is TiO2 anatase.

Boosting Methanol-Mediated CO2 Hydrogenation into Aromatics by Synergistically Tailoring Oxygen Vacancy and Acid Site Properties of Multifunctional Catalyst.

Even though the direct hydrogenation of CO2 into aromatics has been realized via a methanol-mediated pathway and multifunctional catalyst, few works have been focused on the simultaneously rational design of each component in multifunctional catalyst to improve the performance. Also, the structure-function relationship between aromatics synthesis performance and the different catalytic components (reducible metal oxide and acidic zeolite) has been rarely investigated. Herein, we increase the oxygen vacancy (Ov ) density in reducible Cr2 O3 by sequential carbonization and oxidation (SCO) treatments of Cr-based metal-organic frameworks. Thanks to the enriched Ov , Cr2 O3 -based catalyst affords high methanol selectivity of 98.1 % (without CO) at a CO2 conversion of 16.8 % under high reaction temperature (350 °C). Furthermore, after combining with the acidic zeolite H-ZSM-5, the multifunctional catalyst realizes the direct conversion of CO2 into aromatics with conversion and selectivity as high as 25.4 % and 80.1 % (without CO), respectively. The property of acid site in H-ZSM-5, especially the Al species that located at the intersection of straight and sinusoidal channels, plays a vital role in enhancing the aromatics selectivity, which can be precisely controlled by varying the hydrothermal synthesis conditions. Our work provides a synergistic strategy to boost the aromatics synthesis performance from CO2 hydrogenation.