Hydrothermal Method Research Articles

Photoelectrocatalytic property and DFT calculations of TiO2 with broadened infrared light absorption by Gd2O3:Er3+

In this paper, erbium-doped gadolinium oxide rare earth oxide nanoparticles (Gd2O3:Er3+) with good light absorption capacity from the visible to the infrared region were prepared by polyol method, and then compounded with TiO2 by hydrothermal method. SEM, TEM, XPS, UV-vis and electrochemical workstation were used to study the morphology, structure, UV-vis light absorption and photoelectrochemical (PEC) properties of Gd2O3:Er3+/TiO2. The results showed that the Gd2O3:Er3+ spherical nanoparticles with a particle size of about 15 nm were uniformly distributed on the surface of the TiO2 nanorod array, and the Gd2O3:Er3+/TiO2 nanocomposites had good light absorption capacity in the infrared region. Furthermore, the photocurrent densities of Gd2O3/TiO2 and Gd2O3:Er3+/TiO2 were 2.08 and 2.75 times higher than those of TiO2, respectively, manifesting that the broadening of infrared light absorption can improve the PEC property of TiO2. Meanwhile, the DFT calculation results showed that the energy band of Gd2O3:Er3+/TiO2 was significantly narrower than that of TiO2, indicating that Gd2O3:Er3+/TiO2 had a redshift phenomenon of UV-vis absorption. The calculation results of state density showed that the f orbital of Gd2O3:Er3+ intersected with the d orbital of TiO2, indicating that there is an electron transfer between Gd2O3:Er3+ and TiO2.

Comparison between pool boiling system of graphene quantum dots and nitrogen-doped graphene quantum dots suspended in binary base fluids

Using nanofluids instead of conventional heat transfer fluids as a passive method is a well-established and widely used technique by researchers to increase the rate and thermal performance of engineering equipment. In this study, the hydrothermal method with a bottom-up approach was used for the synthesis of graphene quantum dots and nitrogen-doped graphene quantum dots. Then, nanofluid samples were prepared in a two-step process, by adding nanoparticles to binary base fluids of deionized water and ethylene glycol in volume concentrations of (50:50) and (60:40), in four concentrations of 100, 200, 500, and 1000 ppm. In order to better understand the boiling heat transfer mechanism and measure its characteristics such as critical heat flux and heat transfer coefficient, an experimental system was designed and built. Nanofluids based on graphene quantum dots have unique features such as compatibility with the environment, economic efficiency, high stability and suitable heat transfer capability. For this reason, their selection in the pool boiling heat transfer process, in addition to saving energy, is introduced as one of the most effective options for improving CHF and HTC. The tests were performed under saturated conditions, atmospheric pressure, and on a vertical flat and polished copper thermal plate. Prepared nanofluids GQDs and N: GQDs based on DI-water maintained their apparent stability for two months. For GQDs nanofluids at an optimal concentration of 500 ppm with a volume ratio of (60:40) DI-water and EG, compared to DI-water, the greatest increase in CHF and HTC is 90.69, 85.011 % and for N: GQDs at a concentration of 500 with a volume ratio (50:50) DI-water and EG, 75.37 and 78.17 % compared to DI-water.

Core-shell structured MgCo2O4@Ni(OH)2 nanorods as electrode materials for high-performance asymmetric supercapacitors

In the field of energy storage, supercapacitors have received extensive attention in recent years. However, achieving the expected electrochemical performance and energy density of supercapacitors is still a huge challenge. The design and synthesis of binder-free composite electrode with core–shell structure is an effective strategy to improve the electrochemical performance of supercapacitors. In this paper, a heterogeneous core–shell structured and binder-free electrode material MgCo2O4@Ni(OH)2 (MCO@NH) grown on nickel foam (NF) is prepared by a simple hydrothermal and oil bath method. The unique core–shell structure makes the MCO@NH have a large specific surface area, which provides abundant active sites for ion transport and storage, thereby improving the electrochemical performance. The MCO@NH/NF nanocomposite demonstrates a high specific capacitance (Cs) of 1583 F g−1 at 1 A/g. A solid-state asymmetric supercapacitor (ASC) assembled with MCO@NH/NF and active carbon (AC) exhibits excellent energy density (45 Wh kg−1 at 457.5 W kg−1) and outstanding capacitance (89.51 %) and coulombic efficiency (97.8 %) after 12,000 cycles, evidencing its good operation stability and potential practical applications. Therefore, the prepared core–shell MCO@NH/NF electrode can be a promising candidate for energy storage devices.

Al-doped ZnO Nanostars for Electrochemical miRNA-21 Biosensors

The accurate and cost-effective detection of miRNAs, which are strongly associated with numerous diseases and disorders, poses significant technical challenges due to their small size, low concentration, and sequence similarity. In this study, we address these challenges by developing an Al-doped ZnO nanostar working electrode for electrochemical biosensors targeting miRNA-21 detection, employing a simple hydrothermal growth method. The introduction of Al doping modifies the nanostructure of the nanostars, enhancing their affinity for DNA probing and enabling tunability of the working electrode’s conductivity. This enhancement is achieved through the formation of a high-density, uniformly distributed nanostar structure, leading to improved electron transfer rates and increased surface area for miRNA binding. The nanostar biosensors, optimized with the appropriate Al content, exhibit satisfactory analytical properties, including a wide linear range from 1 pM to 10 nM, a low detection limit of 3.98 pM, reproducibility, and excellent selectivity for miRNA assays. Notably, real-time detection is achievable, demonstrating promising potential for point-of-care testing.

Hydrogen generation by water splitting of formic acid assisted supramolecular self-assembled g-C3N4 nanostructures

The photocatalytic hydrolysis reaction primarily unfolds on the material's surface, making the material's morphology and microstructure critical for the catalytic efficiency of photocatalysts. In this paper, a formic acid-assisted melamine hydrothermal self-assembly method is explored to prepare g-C3N4 photocatalysts with a unique morphology. The impact of sintering temperature on the morphology of the g-C3N4 photocatalysts are explored and the effect of formic acid concentration on the XRD and FTIR was analyzed. Findings reveal that the g-C3N4 nanostructures photocatalyst possesses fibrous tubular and nanosheet structures, boasting a heightened specific surface area (32.9 m2/g) and a more refined graphite-like crystalline framework. When synthesized with a 0.15 M concentration of formic acid, the g- C3N4 nanostructured photocatalyst achieved a hydrogen production rate (1289.4 μmol h-1 g-1), which is approximately 4.8 times greater than that of bulk g-C3N4 (264.7 μmol h-1 g-1). This work provides a simple method for preparing high-performance g-C3N4 based photocatalysts for visible light hydrolysis hydrogen production.

Unveiling the promotion role of ZnO on Zn-Al spinel oxide for CO2 hydrogenation

The Zn-Al spinel oxide stands out as one of the most active catalysts for high-temperature methanol synthesis from CO2 hydrogenation. However, the structure-activity relationship of the reaction remains poorly understood due to challenges in atomic-level structural characterizations and analysis of reaction intermediates. In this study, we prepared two Zn-Al spinel oxide catalysts via coprecipitation (ZnAl-C) and hydrothermal (ZnAl-H) methods, and conducted a comparative investigation in the CO2 hydrogenation reaction. Surprisingly, under similar conditions, ZnAl-C exhibited significantly higher selectivity towards methanol and DME compared to ZnAl-H. Comprehensive characterizations using X-ray diffraction (XRD), Raman spectroscopy and electron paramagnetic resonance (EPR) unveiled that ZnAl-C catalyst had abundant ZnO species on its surface, and the interaction between the ZnO species and its ZnAl spinel oxide matrix led to the formation of oxygen vacancies, which are crucial for CO2 adsorption and activation. Additionally, state-of-the-art solid-state nuclear magnetic resonance (NMR) techniques, including ex-situ and in-situ NMR analyses, confirmed that the surface ZnO facilitates the formation of unique highly reactive interfacial formate species, which was readily hydrogenated to methanol and DME. These insights elucidate the promotion effects of ZnO on the ZnAl spinel oxide in regulating active sites and reactive intermediate for CO2-to-methanol hydrogenation reaction, which is further evidenced by the significant enhancement in methanol and DME selectivity observed upon loading ZnO onto the ZnAl-H catalyst. These molecular-level mechanism understandings reinforce the idea of optimizing the ZnO-ZnAl interface through tailored synthesis methods to achieve activity-selectivity balance.

Rational design of titanium-doped Y zeolite for hydrodenitrogenation of aromatic N-heterocyclic compounds

Ti modified Y zeolites with different Ti content were synthesized by in-situ hydrothermal crystallization method and used as the support of hydrodenitrogenation (HDN) catalyst. The forms of Ti species in the zeolites and the effect of Ti incorporation on the active metal states of the corresponding catalysts were investigated by XRD, UV–Vis DRS, XPS, HAADF-STEM, ICP-OES, Py-FTIR, H2-TPR, HRTEM, and DFT calculation. The results show that the incorporation of in-situ Ti species into Y zeolite led to a decrease in the Brønsted acid sites (BAS) /Lewis acid sites (LAS) value of the corresponding catalyst, but effectively enhanced the stacking layer number of the WS2 active phase by weakening the interaction between the active metals and the supports, which is manifested in the improvement of the hydrogenolysis activity and the decrease of the hydrogenation activity of the catalyst. When the hydrogenolysis activity and hydrogenation activity in the catalyst match to a certain extent, that is, the BAS/LAS value and the stacking layer number of the active phase reach an appropriate value, the HDN catalyst exhibited the highest catalytic activity. The NiW/Y-0.1Ti catalyst with suitable amount of BAS and stacking layer number of active phase showed the maximum kHDN values (11.7 × 10-4 mol·g−1·h−1 and 3.9 × 10-4 mol·g−1·h−1) and TOFs (1.91 h−1 and 1.04 h−1) of quinoline and indole HDN.

Study of Cu@MIL-101(Fe) Adsorbent for the Enhancement of CO Adsorption: Effective Cu+ Capacity and π complexation

In this study, a series of π-complexed CO adsorbents of xCu@MIL-101(Fe) were successfully prepared by hydrothermal and low-temperature reduction methods, which the objective was to overcoming the difficulties of stable and highly dispersed Cu+ loading. At the same time, the physical and chemical properties of the adsorbents were deeply analyzed using various characterization techniques, and the effects of different metal sites on CO adsorption were explored using molecular dynamics simulations. The results demonstrated that incorporating Cu+ augmented the adsorbent's thermal stability and enhanced the CO adsorption performance through competitive coordination. Notably, the CO adsorption reached a maximum of 2.66 mmol/g when the Cu loading reached 20 wt%. This study presents a novel approach for developing efficient, stable, and cost-effective Cu+ π-complexed CO adsorbents.

Strong electron coupling effect of non-precious metal Schottky junctions enhanced square meter level photocatalytic hydrogen evolution

Photocatalytic hydrogen production technology utilizes solar energy to decompose water into hydrogen, helping to alleviate the pressure of energy depletion. Engineering of non-precious metal nanomaterials as cocatalysts can play a significant role in low-cost, sustainable, and large-scale photocatalytic hydrogen production. Herein, MnCdS-Vs/NiCo2S4 (MCSN) Schottky junction nanomaterials with strong electron coupling effect were prepared by a two-step hydrothermal method and successfully applied to a square meter hydrogen evolution device. The optimized MCSN material demonstrated high hydrogen evolution activity of 34.28mmolg-1 h-1, which is 9.34 and 685.60 times higher than that of pure MnCdS-Vs and NiCo2S4, respectively. More importantly, in a square meter (1 m2) flat-plate reactor, MCSN produced H2 evolution approximately 201mmol in 5h, showcasing its potential for large-scale applications. In-situ XPS and DFT calculations demonstrated that MnCdS-Vs interacts with NiCo2S4 to produce a strong electron coupling effect and form a Schottky junction. It promotes the facilitated the directional migration of photogenerated electrons from MnCdS-Vs to NiCo2S4, but also effectively suppressed electron backflow through the Schottky barrier. Furthermore, the abundance of sulfur vacancies enhanced visible light absorption capability, further improving photocatalytic hydrogen evolution performance. This work delves into the role of defect engineering and Schottky junction design in enhancing photocatalytic performance, providing new insights into transitioning photocatalytic hydrogen production technologies from small-scale laboratory experiments to large-scale practical applications.

Electrophoretic deposition of MXene coating on Mg alloy 2,5 PDCA-LDH film for enhanced anticorrosion/wear

Two-dimensional (2D) MXene, employed as protective coatings for anticorrosion and wear resistance, outperforms most state-of-the-art 2D nanomaterials. In this work, MgAl-LDH film modified with the 2,5 PDCA inhibitor was synthesized on Mg alloy AZ31 via in-situ hydrothermal methods. Subsequently, MXene Ti3C2 at various concentrations was electrophoretically deposited onto the as-prepared 2,5 PDCA-LDH film. The successful incorporation of the 2,5 PDCA inhibitor resulted in MgAl-LDH nanosheets with a low growth angle, facilitating the electrophoretic deposition of MXene Ti3C2. After deposition, Ti3C2 nanomaterials uniformly coated the 2,5 PDCA-LDH film, forming a protective barrier against corrosive species while simultaneously establishing a lubricating layer. Notably, Ti3C2 nanosheets exhibit a tendency to self-agglomerate at higher concentrations, resulting in the 1.0 wt% Ti3C2 coating displaying the highest anticorrosion and lubrication capacities.

Plasma-sprayed high entropy alloy coating with novel MoS2 /resin hybrid sealant: Tribological and corrosion characterization

Sealing treatment provides a strategy for the long-term performance of thermal spray coatings under actual working conditions. However, common sealants are mainly limited to improving the corrosion resistance of coatings, neglecting applications in more complex environments where they are subject to simultaneous corrosion and wear. Herein, a novel organic-inorganic hybrid composite sealant, composed of self-lubricating MoS2 nanoparticles and environmentally friendly waterborne silicone modified acrylic resin (WBS-ACR), was successfully prepared in the pores and micro-defects of plasma-sprayed HEA coatings by one-step hydrothermal method. The results indicate that MoS2 nanosheets are uniformly synthesized in resin materials through precursor hydrothermal reactions. The hybrid sealants are filled densely in the micro-defects of HEA coatings with a maximum penetration depth greater than 180 μm. The tribological and electrochemical results indicate that the hybrid sealant exhibits similar anti-wear performance, but two orders of magnitude lower corrosion currents than that of pure MoS2 sealant. In comparison to the pure resin sealant, the hybrid sealant retains its excellent corrosion resistance while increasing its wear resistance. The superior comprehensive performance of the novel organic-inorganic hybrid sealant could expand the application of thermal spray coatings into new fields.

Construction of Co-MOF Electrochemical Sensor and Application of it in recognizing and distinguishing Naphthylamine Isomers

A 3D Co-MOF:[Co(μ2-O)(L)4]n (Co-1, HL= nicotinic acid) was synthesized hydrothermal method. Co-1 was used as electrode materials modified onto a glass carbon electrode(GCE) to assemble Co-1/GCE. It served as an electrochemical sensor for recognizing and distinguishing aromatic amines isomer 1-naphthylamine(1-NA) and 2-naphthylamine(2-NA). The recognition potentials of 1-NAand 2-NA were 0.84 V and 0.74 V with the limits of detection (LOD) 1.025 μM and 0.875 μM, respectively, Furthermore, Co-1/GCE has high selectivity and excellent sensitivity towards 1-NAand 2-NAin mimic waste organic environment. An outstanding recognition and distinguish ability can be observed.

Comparative study of microwave-assisted and hydrothermal hydroxyapatite synthesis from neutralization slag: Optimization, energy, and adsorption

The study proposes the utilization of microwave-assisted methods for converting neutralization slag (NS) into hydroxyapatite (HAP), offering an alternative to the conventional hydrothermal method. The microwave-assisted approach addresses the challenges encountered in hydrothermal reactions, such as particle agglomeration, reduced specific surface area, prolonged reaction time, high temperature requirements, and inadequate saturation adsorption capacity. By employing the response surface methodology with a Box-Behnken design, the study found that the microwave-assisted method significantly reduced the synthesis time from 90 to 25 min and the temperature from 120 °C to 56 °C. Furthermore, the microwave method consumed only 1/43 of the energy utilized in hydrothermal synthesis. To assess the performance of the synthesized HAP, various detection methods were utilized, including XRD, SEM-EDS, FTIR, Zeta potential, and ICP, which analyzed the crystal structure, crystallinity, morphology, chemical composition, and surface charge of HAP. The BET method was used to measure the specific surface area, further confirming the successful synthesis of HAP. The HAP synthesized through this microwave-assisted method exhibited a saturation adsorption capacity of up to 98.4 mg/g of fluoride ions from vanadium industrial raffinate. This study demonstrates that the microwave-assisted method provides a viable solution for reducing energy consumption and enhancing HAP synthesis efficiency for wastewater treatment in the vanadium industry.

Thermoelectric properties of polycrystalline pristine and Pb-doped SnS materials using a conventional hydrothermal method

Thermoelectric properties of polycrystalline pristine and Pb-doped SnS materials using a conventional hydrothermal method

One-step preparation of Z-scheme g-C3N4 nanorods/TiO2 microsphere with improved photodegradation of antibiotic residue

Graphitic carbon nitride nanorods/titanium dioxide microspheres (g-C3N4 NRs/TiO2 MSs) Z-scheme heterojunctions were simply prepared by a one-step hydrothermal method, which showed improved visible-light-induced photocatalytic activity for the degradation of tetracycline hydrochloride (TC-HCl). The photodegradation activity of g-C3N4 NRs/TiO2 MSs is 6.6 and 1.9 times better than that of pristine g-C3N4 and TiO2, which is assigned to the unique morphology and formed heterojunction. Hydroxyl radical (⋅OH) and superoxide radical (⋅O2−) were the main species for TC-HCl photodegradation according to capture experiments, and a possible mechanism is proposed. This study provides an effective reference for the preparation of binary heterostructures with excellent photocatalytic activity from a simplified process.

Boosting piezocatalytic efficiency: Thin carbon layer-modified ZnO for superior rhodamine B degradation

This study aims to enhance the piezocatalytic activity of ZnO by modifying it with a thin carbon layer (TCL). The composite catalysts were synthesized using a simple hydrothermal method. The tightly adhered TCL served as an effective electron transfer medium, enabling the rapid migration of piezoinduced charge carriers from the ZnO to the catalyst surface, thereby facilitating the catalytic degradation of Rhodamine B (RhB). The optimized TCL/ZnO sample exhibits an RhB degradation rate 13.4 times higher than that of pure ZnO. This work demonstrates that TCL/ZnO has significant potential in piezocatalytic water purification and offers new insights into the design of efficient piezocatalytic materials.

Insight into interfacial engineering for enhancing the synergistic effect of piezo-photocatalytic hydrogen peroxide production

Constructing heterojunctions represents a prevalent approach for enhancing piezo-photocatalytic performance. However, it remains challenging due to contradictory charge polarity and a poor active site. In this study, we employed an in situ hydrothermal method to fabricate a ZnIn2S4-BiOCl compact heterojunction with interfacial chemical bonding. Experimental and theoretical calculations demonstrate that the interfacial chemical bond (Bi-S bond) creates a strong interfacial electronic effect between the heterojunctions, acting as strain centers and charge transfer channels to enhance coordinated piezoelectric and photoelectric fields, thereby facilitating charge transfer. Additionally, interfacial bonding induces dynamic surface reconstruction and redistribution of electron density, improving reactant activation and charge exchange while reducing reaction barriers. Consequently, ZB-4 catalyst exhibits exceptional piezoelectric photocatalytic performance for pure water to H2O2 conversion (1987.33 μmol g-1·h-1), which is 5.85 times than that of pure BiOCl. This study presents a valuable strategy for enhancing positive coordination between heterojunctions and the photocatalytic piezoelectric effect.

Synergistic integration of MoS2 nanopetals and SnO2 quantum dots for enhanced supercapacitor performance

This study presents the synthesis and electrochemical application of MoS2 nanopetals/SnO2 quantum dots (MS/SQD) nanocomposites. Employing a hydrothermal method for MoS2 and a simple mixing process for SnO2 using thiourea and tin chloride dihydrate, we engineered a nanocomposite that significantly enhances supercapacitor performance. Characterization through XRD, FE-SEM, FE-TEM, and XPS confirmed the optimal morphology and structural integrity of the MS/SQD. Electrochemical evaluations using a three-electrode system highlighted the nanocomposite’s exceptional electrochemical attributes: it achieved a specific capacitance of up to 505 F·g−1 at 1 A·g−1 and maintained 350 F·g−1 at a high current density of 10 A·g−1, with nearly 99% capacity retention after 5,000 cycles. The novelty lies in the synergistic effects of SnO2 quantum dots, which enhance the MoS2 nanopetal’s structural integrity, conductivity, and electrochemical reactivity, thereby improving charge transfer efficiency and ion diffusion. These findings underscore the MS/SQD nanocomposite’s potential for high-performance energy storage applications.

Fast Reduction of 4-Nitrophenol and Photoelectrochemical Hydrogen Production by Self-Reduced Bi/Ti3C2Tx/Bi2S3 Nanocomposite: A Combined Experimental and Theoretical Study.

The distinctive properties of 2D MXenes have garnered significant interest across various fields, including wastewater treatment and photo/electro-catalysis. The integration of inexpensive semiconductor nanostructures with 2D MXenes offers a promising strategy for applications such as wastewater treatment and photoelectrochemical hydrogen production. In this study, we employed an in situ hydrothermal method to immobilize 1D Bi2S3 nanorods and self-reduced metallic bismuth nanoparticles (Bi NPs) onto Ti3C2Tx MXene nanosheets, resulting in the formation of a Bi/Bi2S3/Ti3C2Tx (0D/1D/2D) composite catalyst, which demonstrates an outstanding efficacy in both the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) and photoelectrochemical hydrogen production. Remarkably, a 4-NP reduction efficiency of 100% was achieved only in 4 min with a reduction rate of 1.14 min-1, which is outstanding, and it is ∼3.8 times faster than pristine Bi2S3 nanorods (0.3 min-1). Furthermore, the photoelectrochemical assessment reveals that the Bi/Bi2S3/Ti3C2Tx catalyst displays remarkable hydrogen evolution reaction (HER) efficiency in an alkaline electrolyte. It exhibits a significantly lower overpotential and Tafel slope of 73 mV and 84 mV/dec, respectively, compared to pristine Bi2S3 nanorods, which are found to be 129 mV and 145 mV/dec under light illumination. The superior reduction performance of 4-NP and charge transfer mechanism is further investigated through density functional theory (DFT) calculations, alongside validation using various microscopic and spectroscopic techniques. Interestingly, the DFT analysis revealed modifications in the partial density of states of Bi2S3 within the band gap region due to the successful anchoring of Ti3C2Tx nanosheets and metallic Bi NPs, facilitating efficient charge transport and separation across the local junctions. Ultraviolet photoelectron spectroscopy provided insights into band alignment and interfacial charge transfer across the Bi/Bi2S3/Ti3C2Tx junction on a microscopic scale. This work is significant for the development of MXene-based hybrid catalysts, and it provides a deeper understanding of the reduction mechanism of organic pollutants and superior charge transport in the hybrid system for photoelectrochemical hydrogen production.

Halloysite-derived hierarchical cobalt silicate hydroxide hollow nanorods assembled by nanosheets for highly efficient electrocatalytic oxygen evolution reaction

The oxygen evolution reaction (OER) is regarded as the bottleneck of electrolytic water splitting. Thus, developing robust earth-abundant electrocatalysts for efficient OER has received a great deal of attention and it is an ongoing scientific challenge. Herein, hierarchical hollow nanorods assembled with ultrathin mesoporous cobalt silicate hydroxide nanosheets (denoted as CoSi) were successfully fabricated, using the silica nanotube derived from halloysite as a sacrificial template, via a simple hydrothermal method. The resulting cobalt silicate hydroxide nanosheets stack with thicknesses ∼10 nm, as confirmed by transmission electron microscopy. The elaborated nanoarchitecture possesses a high specific surface area (SSA) allowing good exposure to the cobalt active centers exhibiting superior catalytic activity vs analogs synthesized using sodium silicate. Among all as-prepared CoSi samples, those synthesized at 150°C (CoSi-150) exhibited the minimum overpotential of ∼347 mV at a current density of 10 mA cm–2. In addition, CoSi-150 also exhibited superior performance against typical cobalt-based catalysts, and its surface hydroxyl groups were beneficial for the enhancement of OER performance. Furthermore, the CoSi-150 showed excellent durability and stability after the 105 s chronopotentiometry test in 1 M KOH. This design concept provides a new strategy for the low-cost preparation of high-quality cobalt water splitting electrocatalysts.