Template-assisted Hydrothermal Method Research Articles

Perovskites synthesized by soft template-assisted hydrothermal method: A bibliometric analysis and new insights

Hydrothermal synthesis is a technique which enables preparing many perovskites with specific crystal structures, chemical compositions, and morphologies. Thus, a bibliometric analysis of 1087 articles from the Scopus database (1975–2023) related to the keywords “perovskites” and “hydrothermal synthesis” was conducted using the VOSviewer software program. The results of the bibliometric analysis showed that the 1087 articles have 23,286 citations. Materials Letters has the highest number of publications (2.85%) regarding the journals in which these articles are published. China has the highest number of publications (34.50%) and citations (33.56%) related to these articles. Regarding the institutions affiliated with these articles, Jilin University in China concentrates 5.34% of the publications and 6.08% of the citations. In terms of authors, Han, G. has the highest number of publications (2.02%). Finally, the top three keywords with the highest number of occurrences were “perovskite”, “hydrothermal synthesis” and “scanning electron microscopy”. Based on bibliometric analysis, LaNiO3 perovskites were chosen to evaluate the influence of hydrothermal synthesis parameters on their morphologies and, consequently, how these morphologies affect their applications. Thus, the temperature and time ranges used for the synthesis parameters were 160–230 °C and 6–48 h, respectively. Furthermore, the pH range used was 7.6–13, and the mineralizers used to adjust the pH were ammonia, potassium hydroxide, and sodium hydroxide. The temperature and time ranges used for the calcination parameters were 550–800 °C and 2–6 h, respectively. Additionally, LaNiO3 perovskites obtained sphere, cube, rod, disc, and hollow morphologies. The soft templates used to obtain these morphologies were glycine, glycerin, isopropanol, polyvinylpyrrolidone (PVP), cetyltrimethylammonium bromide (CTAB), citric acid, and urea. The specific surface areas of the perovskites varied between 5.2 and 35.8 m2 g−1. Finally, the most common application for LaNiO3 perovskites was the methane reforming for hydrogen production.

Bi-phasic BiPO4 prepared through template-assisted hydrothermal method with enhanced electrochemical response for hybrid supercapacitor applications

Bi-phasic BiPO4 prepared through template-assisted hydrothermal method with enhanced electrochemical response for hybrid supercapacitor applications

Comparative investigation on the catalytic performance of HT/SBA-15 and SBA-15/HT composites for the isomerization of glucose to fructose

Hydrotalcites (HT) have a broad spectrum of applications as prosperous heterogeneous catalysts for diverse chemical transformations. The catalytic activity of HT-based materials can be tailored by introducing siliceous material into the internal or external framework. The surface modification of the HT framework with silica mesostructures leads to the formation of versatile Lewis base, Brønsted base and redox catalytic active sites. This work presents the comparative evaluation of the catalytic performance of HT/SBA-15 and SBA-15/HT composites for the isomerization of glucose to fructose using 1-butanol as a solvent. The composites with different external morphology were prepared by a modified template-assisted hydrothermal method, using different HT to SBA-15 proportions. The textural and morphological characterization results conferred the efficiency of the employed post-synthetic intercalation strategy to achieve the successful formation of HT/SBA-15 and SBA-15/HT composites. With optimal HT loading and surface basicity, the HTS-3 composite demonstrated the highest catalytic performance, resulting in good glucose conversions (54 %) with improved selectivity (>83 %). The observed high reactivity could be mainly attributed to the extensive dispersion of HT particles on the SBA-15 component, which contributes to a significant increase in textural properties and surface basicity. Furthermore, special attention is devoted to addressing such reactivity phenomena as active site selectivity, catalyst multifunctionality and multisite reactivity commonly encountered in mesoporous catalysis.

Controllable Synthesis of Nanostructured Ca-P Coating on Magnesium Alloys via Sodium Citrate Template-Assisted Hydrothermal Method and Its Corrosion Resistance

In this study, a nanostructured needle-like hydroxyapatite (HA) coating was prepared by the sodium citrate template-assisted hydrothermal method on magnesium alloy (AZ31). The influence of sodium citrate on the composition, microstructure and corrosion behavior of the coatings was studied. The results showed that with the increase in the mole ratio of Ca/sodium citrate from 1 to 13, the coating gradually changed from the needle-like morphology of HA to the flake morphology of β-tricalcium phosphate (β-TCP), which was related to the existing form of citrate in the solution and the trend of complexation reaction. When the mole ratio of Ca/sodium citrate was 1, the HA coating sample with the nano needle-like morphology had a high corrosion resistance (Rt = 235.300 ± 3.584 kΩ·cm2), which was almost 200 times that of the naked AZ31 alloy. Moreover, the corrosion rates of the Ca-P coated AZ31 alloy stabilized at about 0.55 mm/year and could provide more than 56 days of corrosion protection to the samples, which approximated the degradation rate requirement for biomaterials used as bone fixture.

Hydrothermal synthesis of Au@SnO2 hierarchical hollow microspheres for ethanol detection

In this paper, Au@SnO2 hierarchical hollow microspheres were synthesized using template-assisted hydrothermal method, and utilized in ethanol detection. In the prepare process, Au@SnO2 hollow microspheres were synthesized by removing C-sphere template in high temperature annealing, before that, Au was embedded in the C-sphere template by regulating the amount of chloroauric acid. The surface morphological characterization and element content analysis of the samples were used to demonstrate structure and chemical state of all samples. The systematic gas sensing characterizations was carried out to learn the sensing performance of every sensor. The sensitivity (23.93) was three times higher than the pure SnO2 based sensor (8.48), and the optimal operating temperature was reduced to 240 °C. It presented excellent response/recovery time (4/48 s) additionally. These phenomenons indicated that Au increased the capacity of chemisorbed oxygen on the surface of sensitive materials (catalytic characteristic). In addition, the hierarchical structure of Au@SnO2 hollow microspheres also provided more active sites for sensing ethanol (structural characteristic). All the results showed that Au@SnO2 hierarchical hollow microspheres has a wide range potential application for ethanol detection.

Rational design direct Z-scheme BiOBr/g-C3N4 heterojunction with enhanced visible photocatalytic activity for organic pollutants elimination.

A rapid recombination of photo-generated electrons and holes, as well as a narrow visible light adsorption range are two intrinsic defects in graphitic carbon nitride (g-C3N4)-based photocatalysts. Inspired by natural photosynthesis, an artificially synthesized Z-scheme photocatalyst can efficaciously restrain the recombination of photogenerated electron–hole pairs and enhance the photoabsorption ability. Hence, to figure out the above problems, BiOBr/g-C3N4 composite photocatalysts with different mass ratios of BiOBr were successfully synthesized via a facile template-assisted hydrothermal method which enabled the BiOBr microspheres to in situ grow on the surface of g-C3N4 flakes. Furthermore, to explore the origin of the enhanced photocatalytic activity of BiOBr/g-C3N4 composites, the microstructure, photoabsorption ability and electrochemical property of BiOBr/g-C3N4 composites were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectroscopy (DRS), electrochemical impedance spectroscopy (EIS) and photocurrent (PC) response measurements. As a result, the introduction of BiOBr on g-C3N4 to constitute a direct Z-scheme heterojunction system can effectively broaden the light absorption range and promote the separation of photo-generated electron–hole pairs. Hence, compared with pure g-C3N4 and BiOBr, the resultant BiOBr/g-C3N4 composites exhibit the remarkable activity of photodegradated rhodamine B (RhB) and tetracycline hydrochloride (TC-HCl) under visible light irradiation. Simultaneously, the optimal BiOBr content of the BiOBr/g-C3N4 composites was obtained. The BiOBr/g-C3N4 composites exhibit an excellent photostability and reusability after four recycling runs for degradation RhB. Moreover, the active-group-trapping experiment confirmed that ·OH, ·O2− and h+ were the primary active groups in the degradation process. Based on the above research results, a rational direct Z-scheme heterojunction system is contrastively analyzed and proposed to account for the photocatalytic degradation process of BiOBr/g-C3N4 composites.

Photocatalytic hydrogen production by biomimetic indium sulfide using Mimosa pudica leaves as template

Biomimetic sulfur-deficient indium sulfide (In2.77S4) was synthesized by a template-assisted hydrothermal method using leaves of Mimosa pudica as a template for the first time. The effect of this template in modifying the morphology of the semiconductor particles was determined by physicochemical characterization, revealing an increase in surface area, decrease in microsphere size and pore size and an increase in pore volume density in samples synthesized with the template. X-ray photoelectron spectroscopy (XPS) analysis showed the presence of organic sulfur (SO/SC/SH) and sulfur oxide species (SO2, SO32−, SO42−) at the surface of the indium sulfide in samples synthesized with the template. Biomimetic indium sulfide also showed significant amounts of Fe introduced as a contaminant present on the Mimosa pudica leaves. The presence of these sulfur and iron species favors the photocatalytic activity for hydrogen production by their acting as a sacrificial reagent and promoting water oxidation on the surface of the templated particles, respectively. The photocatalytic hydrogen production rates over optimally-prepared biomimetic indium sulfide and indium sulfide synthesized without the organic template were 73 and 22 μmol g−1, respectively, indicating an improvement by a factor of three in the templated sample.

Ferromagnetism in High-Surface-Area ZnO Nanosheets Prepared by a Template-Assisted Hydrothermal Method**Supported by the National Key Research and Development Program of China under Grant No 2016YFA0201001, the National Natural Science Foundation of China under Grant No 11574071, the Natural Science Foundation for Outstanding Young Researcher in Hebei Province under Grant No E2016210093, and the Natural Science Foundation of Hebei Province under

High-surface-area ZnO nanosheets are prepared using a template-assisted hydrothermal method. A saturation moment as high as 0.02 emu/g is obtained for the ZnO nanosheets. Both photoluminescence spectroscopy and x-ray photoelectron spectroscopy demonstrate the existence of abundant oxygen vacancies on the surfaces of the nanosheets. In addition, the oxygen vacancy concentration increases with an increasing nanosheet surface area. The results show that the origin of the room-temperature ferromagnetism is closely related with a large surface area and oxygen vacancies of the nanosheets. This finding suggests that the high-surface-area ZnO nanosheets are promising to be applied to spintronic devices.

Rational construction of bowl-like MnO2 nanosheets with excellent electrochemical performance for supercapacitor electrodes

Rational construction of unique hierarchical nanostructured electrodes with excellent electrochemical performance is a promising solution to satisfy the increasing demand of supercapacitors with high energy density. In this work, a novel nanostructure of bowl-like MnO2 nanosheets with ultra-thin thickness (about 4 nm) has been successfully designed by a simple template-assisted hydrothermal method. The composition and morphology of the obtained bowl-like nanostructures have been characterized by FESEM, TEM, XRD, XPS and N2 adsorption-desorption. Such novel nanostructures present several advantages, such as large surface area, compact contacts, reduced interior space, additional electroactive sites for reversible redox reactions and short/unimpeded diffusion channels for ions/electron transport. When evaluated as electrode materials, bowl-like MnO2 nanosheets exhibit a specific capacitance of 379 F g−1 at a current density of 0.5 A g−1, a capacitance retained ratio of 60.5% from 0.5 to 10 A g−1 and 87.3% capacitance retention after 5000 cycles. Moreover, a possible mechanism for the excellent electrochemical performance of the novel bowl-like nanostructures compared with hollow particles has been systematically studied. We believe that this strategy can open up an avenue and appropriate idea for the rational construction of other transition metal oxides with high performance for the practical supercapacitor applications.

Template-assisted hydrothermally synthesized iron-titanium binary oxides and their application as catalysts for ethyl acetate oxidation

Iron-titanium binary oxides were synthesized by template-assisted hydrothermal method. The effect of the variation in the Fe/Ti ratio and the temperature of hydrothermal treatment on the phase composition, structural, textural and redox characteristics of thus obtained materials was studied by Nitrogen physisorption, XRD, SEM, HRTEM, XPS, Raman, UV–vis, FTIR and Moessbauer spectroscopy and TPR with hydrogen. The contribution of various features of the samples on their catalytic behaviour in total oxidation of ethyl acetate as a representative VOC was in the focus of the discussion. The binary materials represent a complex mixture of pure and substituted anatase and/or hematite phases with different dispersion and proportion, which can be controlled by both the variation in the Fe/Ti ratio and the temperature of hydrothermal treatment. The stabilization of finely dispersed hematite-like particles in the vicinity of Fe3+ substituted in titania was considered as an important factor for the improvement of the catalytic activity and selectivity in total oxidation of ethyl acetate and it is favoured by the lower Fe/Ti ratio and the lower temperature of the hydrothermal treatment.

One-pot synthesis and photoluminescence properties of core/porous-shell olive-like BaWO4 microstructure by a template-assisted hydrothermal method

Core/porous-shell olive-like crystalline BaWO4 is synthesized by a combined simple hydrothermal method and soft template approach. The prepared product shows an olive-like shape with diameter of ∼2 μm, length of ∼4 μm, and the thickness of the shell of about 65 nm, which are orderly assembled by many nanoparticles. A possible formation mechanism of olive-like BaWO4 microstructure involving interfacial recognization of ions, nucleation, aggregation, in situ growth and Ostwald ripening process is proposed. Polyacrylic acid sodium (PAAS) as a template plays an important role in inducing the nucleation and growth of olive-like BaWO4 microcrystalline. Other shapes of BaWO4 microcrystalline are also fabricated by varying the concentration of PAAS and Ba2+. The olive-like product with a core-shell structure which exists a large number of pores on crystal surface shows excellent photoluminescence property, which have potentially applied prospects in fields such as light display systems etc.

Synthesis of ZnO inverse opals with high crystalline quality by a three-dimensional colloidal crystal template-assisted hydrothermal method over a seed layer

In this paper, zinc oxide (ZnO) inverse opal structures were fabricated on a seed layer using three-dimensional (3D) colloidal crystal templates. The 3D colloidal crystal templates hindered the diffusion of zinc ions during hydrothermal growth thereby restricting the formation of porous ZnO structures at typical Zn2+ concentrations leading to rods. Instead of porous ZnO microstructures, ZnO nanobowl films were exclusively grown using the 3D colloidal templates on the photoresist-patterned seed layer at the initial Zn2+ concentrations. 3D porous ZnO with different filling fractions were successfully created by a hydrothermal method at a Zn2+ concentration of 0.15 M with different adjuvants. The addition of sodium citrate yielded ZnO having inverse opal structures and showing variable reflection peaks according to the photonic stop band, which were controlled by the diameter of the template colloidal spheres. ZnO inverse opals prepared with sodium citrate as an adjuvant also showed superior ultraviolet photoluminescence intensity values compared to their adjuvant-free and polyethylenimine counterparts. The hydrothermal method resulted in ZnO inverse opal structures with significantly enhanced crystalline quality compared to those prepared by electrodeposition methods. ZnO inverse opals prepared by large-diameter colloidal crystal templates showed slightly better properties than those prepared using small-diameter templates. The ZnO inverse opals conformally coated by a thin layer of TiO2 were used as photoanodes for water splitting. The ZnO inverse opals prepared by the hydrothermal method showed significantly higher photocurrent values than those synthesized by electrodeposition. These ZnO inverse opals showed maximum photocurrent values of ca. 0.9 mA cm−2 comparable to the best results of other ZnO-based microstructures.

High triethylamine-sensing properties of NiO/SnO2 hollow sphere P–N heterojunction sensors

Triethylamine (TEA) gas sensor with high response and selectivity was fabricated successfully with PN heterojunction consisted of n-type SnO2 hollow spheres and p-type NiO nanoparticles. SnO2 hollow spheres were synthesized by a template-assisted hydrothermal method. The NiO/SnO2 P–N junction was formed by depositing NiO nanoparticles onto the surface of SnO2 hollow sphere sensors via a pulsed laser deposition (PLD) process. The response of NiO/SnO2 sensor is up to 48.6 when exposed to 10ppm TEA gas, which is much higher than that of pristine SnO2 hollow spheres and most of other reported TEA sensors. The detection limit can also be as low as 2ppm-level. Moreover, the optimal operating temperature is down to 220°C, and 40°C lower than that of the pristine SnO2 hollow sphere sensor. These good sensing performances mainly attribute to the formation of depletion layer at the P–N junction interface in the NiO/SnO2 sensor, which makes great variation of resistance in air and TEA gas. Thus, the combination of n-type SnO2 hollow spheres and p-type NiO nanoparticles provides an effective strategy to design new TEA gas sensors.

Hydrothermal Synthesis of Tetragonal BaTiO<SUB>3</SUB> Nanotube Arrays with High Dielectric Performance

Tetragonal Barium titanate (BaTiO3) nanotube arrays have been prepared using the template-assisted hydrothermal method combined with an annealing process. The in-situ chemical conversion of TiO2 nanotube array templates ensured that BaTiO3 maintained the morphology of the nanotube architectures. Moreover, X-ray diffraction and Raman spectrum characterization were used to confirm that the BaTiO3 nanotube arrays had a tetragonal phase after the use of a simple annealing technique. Typical hysteresis loops showed their ferroelectricity, with the remanent polarization and coercive fields being 2.57 microC/cm2 and 2.52 kV/cm, respectively. The relative dielectric constant of the tetragonal BaTiO3 nanotube arrays reached up to 1000 and the dielectric loss was as low as 0.02 at 1 kHz at room temperature.

Magnetic properties of Co0.5Zn0.5Fe2O4 nanopowders prepared by means of the template-assisted hydrothermal method

Abstract In the present article, nickel cobalt ferrite (Co0.5Zn0.5Fe2O4) nanoparticles were synthesized using a template-assisted hydrothermal method. Carboxymethyl cellulose was used as the templating agent for controlling the morphology of the Co0.5Zn0.5Fe2O4 nanoparticles. The synthesized nanoparticles were characterized using X-ray diffraction, scanning electron microscopy, and a vibrating sample magnetometer. The results indicated that the morphology of the nanoparticles changed from granular and superparamagnetic to platelike and ferromagnetic with the addition of the template. The Co0.5Zn0.5Fe2O4 nanoparticles synthesized without the template exhibited a saturation magnetization and coercivity 2.81 T and 0.2 kA · m– 1, while when the template was used, the saturation magnetization and coercivity increased to 3.13 T and 76.6 kA · m– 1 as the template proportion increased to 0.3.

Magnetic Properties of Co0.5Zn0.5Fe2O4Nanoparticles Synthesized by a Template-Assisted Hydrothermal Method

In the present paper, nickel cobalt ferrite (Co0.5Zn0.5Fe2O4) nanoparticles were synthesized using a template-assisted hydrothermal method. Carboxymethyl cellulose was used as the templating agent for controlling the morphology of the Co0.5Zn0.5Fe2O4nanoparticles. The synthesized nanoparticles were characterized using X-ray diffraction, scanning electron microscopy, and a vibrating sample magnetometer. The results indicated that the morphology of the nanoparticles changed from granular and superparamagnetic to platelike and ferromagnetic with the addition of the template. The Co0.5Zn0.5Fe2O4nanoparticles synthesized without the template exhibited a saturation magnetization and coercivity 2.81 T and 0.2 kA⋅m−1, while when the template was used, the saturation magnetization and coercivity increased to 3.13 T and 76.6 kA⋅m−1as the template proportion increased to 0.3.

Synthesis of SnO2 hollow nanostructures with controlled interior structures through a template-assisted hydrothermal route

A simple in situ template-assisted hydrothermal method has been developed to prepare SnO(2) hollow nanostructures with controlled interior texture. The shell number and core size have an impact on the electrochemical performance of the samples when used as anode materials for lithium-ion batteries.