Hydrothermal Co-reduction Research Articles

Magnetic field-enhanced radical intensity for accelerating norfloxacin degradation under FeCu/rGO photo-Fenton catalysis

• FeCu/rGO was facilely prepared via a one-step hydrothermal co-reduction process. • A strong synergistic effect between Fe and Cu species promoted NOR degradation. • Enhanced •OH and •O 2 – /•HO 2 were observed with an external magnetic field (200 mT). • The magnetic field further accelerated NOR removal (34.1%) and H 2 O 2 usage (27.0%). • The mechanism of magnetic field-improved FeCu/rGO photo-Fenton catalysis was proposed. Improving the efficiency of photo-induced carriers (e - /h + ) is one of the most effective routes to accelerate the heterogeneous photo-Fenton process. Herein, inspired by inverse Lorentz forces of opposite charges in a magnetic field, an external magnetic field intensified photo-Fenton catalysis for norfloxacin (NOR) degradation was constructed under visible light irradiation. The reduced graphene oxide-supported Fe-Cu bimetal (FeCu/rGO), obtained by employing common iron powder as a reducing agent, was served as a model catalyst. Impressively, the intensities of both carriers and radicals (•OH and •O 2 – /•HO 2 ) were increased after the normal photo-Fenton reactor was placed into two fixed permanent magnets (200 mT), leading to a 34.1% improvement in NOR removal. Meanwhile, the consumption of H 2 O 2 was also critically boosted (from 65.1% to 92.1%). Combined with theoretical studies, the enhanced radicals were not only resulted from accelerated carrier separation but also extended O-O and O–H bonds in H 2 O 2 and facilitated spin evolutions of 1 [HO•↑···↓•OH] → 3 [HO•↑···↑•OH] and 1 [HOO•↑···↓•H] → 3 [HOO•↑···↑•H]. This study offers an insight into the specific role of an external magnetic field in promoting heterogeneous photo-Fenton catalysis.

Novel Nanoarchitechtonics Olive-Like Pd/BiVO₄ for the Degradation of Gaseous Formaldehyde Under Visible Light Irradiation.

In this research, olive-like Pd/BiVO₄ was successfully prepared through a facile hydrothermal coreduction method for the photocatalytic degradation of formaldehyde under visible light irradiation. The structure, composition, and optical properties of the as-prepared Pd/BiVO₄ were characterized through X-ray diffraction, transmission electron microscopy, ultraviolet-visible spectrophotometry, X-ray photoelectron spectroscopy, and photoluminescence. In addition, the photocatalytic activities of Pd/BiVO₄ were evaluated through the photodegradation of formaldehyde. The experimental results demonstrated that the degradation efficiency of formaldehyde increased with increasing irradiation time. Moreover, 1.0 wt% Pd/BiVO₄ exhibited the highest photocatalytic performance for formaldehyde degradation in 180 min, with the formaldehyde degradation rate as high as 87.5%.

Synthesis and Phase Analysis of CuFeS2 Powders Prepared by Hydrothermal Method

In recent years, CuFeS2 optoelectronic materials are widely concerned by scientists because of their advantages of safety, non-toxicity and low price. In this work, the CuFeS2 powders were synthesized by simple hydrothermal co-reduction method, the effects of different heat treatment conditions and different sulfur sources on preparation of CuFeS2 phase were systematically studied with CuCl2·2H2O and FeCl3·6H2O as raw materials. The phase structure and surface morphology of the samples were analyzed by X-ray Powder diffractometer (XRD) and scanning electron microscope (SEM). It was found that when the sulfur source was sulfur powder, the sample crystallized well and has no impurity formation. With the reaction temperature extending to 220 °C, the diffraction peak intensity is obviously improved while the grain size decreases slightly with the increase of temperature. The extension of heat treatment temperature and holding time is favorable for preparation of CuFeS2 power and the impurity Fe3O4 crystal can be effectively eliminated by prolonging the time and increasing temperature. With the reaction temperature extending to 220 °C, the shorter the time required for Fe3O4 crystal to disappear. Therefore, the optimum heat treatment temperature for preparing CuFeS2 powder is 220 °C and the time is 20 h.

Fabrication of graphene-fullerene hybrid by self-assembly and its application as support material for methanol electrocatalytic oxidation reaction

Graphene-fullerene hybrids were facilely fabricated by self-assembly of graphene oxide (GO) and multi-substituted fulleropyrrolidines (PyrC60). The hybrids (GO-PyrC60) were applied as support materials to deposit Pd nanoparticle catalyst by a simple hydrothermal co-reduction approach. The as-prepared electrocatalysts (Pd/RGO-PyrC60) were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), respectively. The RGO-PyrC60 hybrid supported Pd catalyst with the optimal ratio of RGO to PyrC60, exhibited much enhanced electrocatalytic activity and stability toward methanol oxidation reaction (MOR) compared to the RGO alone supported Pd as well as commercial Pd/C. The introduction of fulleropyrrolidine as spacer between graphene layers could increase the electrocatalytic activity and improve the long-term stability. This strategy may contribute to developing graphene-fullerene hydrids as effective support materials for advanced electrocatalysts.

In situ synthesis of PtPd bimetallic nanocatalysts supported on graphene nanosheets for methanol oxidation using triblock copolymer as reducer and stabilizer

A facile hydrothermal co-reduction strategy has been demonstrated to in situ synthesize PtPd bimetallic nanocatalysts supported on graphene nanosheets (PtPd/GNs) with triblock pluronic copolymer P123 as both reducer and stabilizer. The nucleation mode and morphology of the PtPd bimetallic nanoparticles were tuned simply by changing the molar ratio of Pt and Pd precursor. Defect investigation upon graphene nanosheets predicts that the synergetic role between P123 and PtPd may have great influence on generating defects in graphene, which inducing the in situ loading of PtPd bimetallic nanocatalysts at the defect sites. Compared with the common process to assemble nanocatalysts in pre-synthesized graphene substrate, the one-pot in situ assembly is more facile, cost-effective, and ensuring the effective control of the location and distribution of PtPd nanocatalysts. Both of the PtPd/GNs showed enhanced electrocatalytic performances towards methanol oxidation reaction (MOR) in acidic media, among which Pt1Pd1/GN (Pt/Pd molar ratio 1/1) exhibited the highest specific activity, mass activity, stability and best CO tolerance for MOR. The synthetic process without any seeds, templates, or toxic organic solvent and extra reducer, turns out a promising method to construct the Pt-based nanocatalysts for direct methanol fuel cells (DMFCs).

Oxygen Electroreduction Catalyzed by Palladium Nanoparticles Supported on Nitrogen-Doped Graphene Quantum Dots: Impacts of Nitrogen Dopants

Palladium nanoparticles supported on nitrogen-doped graphene quantum dots (NGQD) were synthesized by hydrothermal coreduction of palladium salts, citric acid, and urea at 160 °C for up to 12 h. Transmission electron microscopic studies showed that in the resulting PdNGQD nanocomposites, small palladium nanoparticles clustered into superstructures of 100 nm and larger. X-ray photoelectron spectroscopic studies showed that the NGQDs contained only p-type pyridinic and pyrrolic nitrogen centers, and although the total concentrations of nitrogen dopants were rather consistent (ca. 10 at. %) among the series of samples, the relative abundance of pyrrolic (pyridinic) nitrogens increased (decreased) with prolonging reaction duration, suggesting thermal conversion of pyridinic nitrogens into pyrrolic ones. The binding energy of the Pd 3d electrons was found to increase accordingly, probably due to enhanced electron withdrawing by the more acidic pyrrolic nitrogens. This suggests apparent interactions between pall...

MnO2/reduced graphene oxide nanoribbons: Facile hydrothermal preparation and their application in amperometric detection of hydrogen peroxide

In the present work, graphene oxide nanoribbons (GONRs) were synthesized via the longitudinal unzipping of multi-walled carbon nanotubes (MWCNTs) nanoparticles with the aid of strong oxidants. The MnO2/reduced graphene oxide Nanoribbons (MnO2/rGONRs) composites were successfully fabricated by means of a reproducible and single-step hydrothermal co-reduction of KMnO4 and GONRs. The morphology and composition of as-prepared materials were studied by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy and X-ray diffraction (XRD). The as-prepared MnO2/rGONRs were employed in fabricating a nonenzymatic electrochemical sensor for the sensitive detection of hydrogen peroxide (H2O2). The electrochemical properties of the MnO2/rGONRs modified glassy carbon electrode (MnO2/rGONRs/GCE) were studied by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The developed nonenzymatic electrochemical sensor exhibited well-defined amperometric response towards H2O2 in a wide linear range of 0.25–2245μM, and a detection limit of 0.071μM (S/N=3) could be obtained. And the proposed sensor also displayed excellent electrochemical analytical performance, acceptable reproducibility, high accuracy, and great anti-interference ability. The proposed sensor was applied for the determination of H2O2 in real sample of fetal bovine serum (FBS), and acceptable accuracy and recovery could be obtained.

Progress of ZnS and its Powder Morphology Synthesized by Chemical Route

As the most wide band gap in II-VI compound semiconducting materials, ZnS has many advantages of low-price, innocuity and excellent electro-optical, piezoelectric and pyroelectric properties. ZnS powder with wurtzite structure was synthesized by hydrothermal co-reduction from ZnCl2and Sulfur powder. The phase was characterized by X-ray diffraction (XRD), while the size and morphology of the product were characterized by field emission scanning electron microscope (FESEM). The results show that, the powders grow mainly along (0 1 8), (1 1 0), (1 1 24) crystal planes, and the ZnS powders were polygonal nanoflakes with sizes of about 100~300 nm in length or small particles less than 100 nm.

The Phase and Morphology of Cu2ZnSnSe4 Nanopowders by Hydrothermal Method

Quaternary compound Cu2ZnSnSe4 (CTZSe) which belonged to I2‐II‐IV‐VI4 group, without rare elements, can be considered as the perfect material for absorbing layer in eco‐friendly solar cells due to low cost and high efficiency. The CTZSe powders were synthesized by hydrothermal coreduction method from metal chlorides and SeO2 with reducing agent hydrazine hydrate at 160~200°C. The phases of obtained products were analyzed by X‐ray diffraction (XRD) and the size and morphology were observed by field emission scanning electron microscope (FESEM). Experimental results show that well crystallized Cu2ZnSnSe4 powders without Se impurities can be obtained by reacting at 200°C for 90 h. The three strong XRD peaks of these products are corresponding to (112), (204), and (312) crystal planes, respectively. The morphologies of these products mostly show irregular polygon flakes with about 30~40 nm thickness and 50~200 nm diameters.

Excited state assisted three-photon absorption based optical limiting in nanocrystalline Cu2Se and FeSe2

Transition metal selenides (FeSe2 and Cu2Se) are synthesized by the hydrothermal co-reduction method. XRD results revealed the crystalline nature of their single phase and the elemental compositions are obtained using EDS. TEM images of the as-prepared samples show the formation of nanorods of 10–20nm diameter in case of iron selenide and nanoparticles of 10–35nm diameter in case of copper selenide. The energy bandgap values are calculated using tauc plots obtained from UV–Visible absorption spectra. The open aperture Z-scan measurements carried out using 5ns pulses at 532nm revealed that the samples showed excellent optical limiting behavior owing to strong nonlinear absorption (NLA). Through numerical simulations, the mechanism of NLA is found to be effective three-photon absorption which has significant contribution from excited state absorption.

Au–Pd Alloy and Core–Shell Nanostructures: One-Pot Coreduction Preparation, Formation Mechanism, and Electrochemical Properties

It is a known fact that Pd-based bimetallic nanostructures possess unique properties and excellent catalytic performance. In this work, the Au-Pd alloy and core-shell nanostructures have been prepared by a simple one-pot hydrothermal coreduction route, and their formation process and mechanism are discussed in detail. A reducing capacity-induced controlled reducing mechanism is proposed for the formation process of Au-Pd bimetallic nanostructures. CTAB plays a key role in the formation of alloy Au-Pd nanostructures. When CTAB is absent, the products are typical core-shell nanostructures. Moreover, the as-prepared nanostructures exhibit excellent electrocatalytic ORR performance in alkaline media, especially for Au-Pd alloy nanostructures. The overpotential of oxygen reduction gets reduced significantly, and the peak potential is positive-shifted by 44 and 34 mV in comparison with the core-shell ones and Pd/C catalyst, respectively. Thus, the controllable preparation and excellent electrocatalytic properties will make them become a potentially cheaper Pd-based cathodic electrocatalyst for DAFCs in alkaline media.

Study on Synthesis of Ni-S Powders Synthesized by Hydrothermal Co-Reduction

The technologies of synthesizing Ni-S powders from 0.001 mol NiCl2•6H2O and 0.001 mol sulfur (S) powder were investigated at 95,105,120,140 and 160 °C. The phases and morphology of the products were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) respectively. Experimental results show that, the Ni-S powders prepared at 120~160 °C from NiCl2•6H2O and S powder have the same major phase NiS. These products have flakes or unregular shape grains with sizes of 100~200nm. However, the product powder prepared at 105 °C has the major phase Ni3S2 without obvious impurity phases and only grains with size less than 200nm. No Nickel sulfides can be synthesized at 95 °C under the experimental conditions. It can be found that the NiS phase appears in the products powders obtained at higher temperatures while Ni3S2 obtained at lower temperature.

The Morphology and Phases of Cu-In-2Se Powders Prepared by Hydrothermal Method

Cu-In-2Se powders were synthesized by hydrothermal co-reduction method from CuCl2.2H2O, InCl3.4H2O and SeO2 at 95～200 °C in deionized water. The morphology and phases of the products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) respectively. Experimental results show that, CuInSe2 can be obtained at 120～200 °C, the major phase of the products synthesized at 120～200 °C are all the same. However the noticeable impurity phase In(OH)3 still exists in the product powders. The In(OH)3 phase decreases with the increasing of reacting temperature. The product powder obtained at 200 °C has fine and homogeneous particles with diameters of about 500 nm.

Study on the Morphology and Phases of Cu-Se Powders Synthesized by Hydrothermal Co-Reduction

Cu-Se compound powders are synthesized by hydrothermal co-reduction from CuSO4•5H2O and SeO2 in deionized water at 120～200 °C. The phases and morphology of the products were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) respectively. Experimental results show that, the CuSe phase can be synthesized at 120,150,180 and 200 °C, however, the purity phases become more with the temperature decreasing. It indicates that the reaction is more incomplete at lower temperature. Hexagonal flakes with side length 100～400 nm can be observed in the products at 150,180 and 200 °C, among which only the product prepared at 180 °C has the hexagonal flakes with good dispersity and homogeneous size with 200 nm length.

The Morphology and Phases of Ni-Se Powders Prepared by Hydrothermal Method

Ni-Se powders synthesized by hydrothermal co-reduction method from NiCl2.6H2O and SeO2 at 95～220 °C. The phases and morphology of the products were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) respectively. Experimental results show that, Ni0.85Se can be synthesized at 95～220 °C while noticeable impurities appeared at lower reaction temperatures. The products with single-phase Ni0.85Se obtained at 200 and 220 °C show hollow sphere structures with diameters of about 150 ~ 700 nm, which have complete and regular shape but no holes.

Selective synthesis and magnetic properties of uniform CoTe and CoTe2 nanotubes

Uniform CoTe and CoTe2 nanotubes could be successfully synthesized via a facile hydrothermal co-reduction route based on the precipitate slow-release controlled process.

Synthesis and characterization of Cu 2Se prepared by hydrothermal co-reduction

Cu 2Se compounds were synthesized by hydrothermal co-reduction at 150–200 °C from CuSO 4·5H 2O and SeO 2 in deionized water. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and field emission scanning electron microscope (FESEM). Experimental results show that, the product powders with Cu 2Se phase obtained at 180 and 200 °C almost consist of regular hexagonal flakes which grow along (1 1 1) crystal plane. The side lengths between 100 and 200 nm of hexagonal flakes synthesized at 180 °C are much smaller than those of the product with 1.3–2 μm side length at 200 °C.

Preparation and characterization of nanostructured Bi2Se3 and Sn0.5-Bi2Se3

Nanostructured Bi2Se3 and Sn0.5-Bi2Se3 were successfully synthesized by hydrothermal coreduction from SnCl2·H2O and the oxides of Bi and Se. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and field emission scanning electron microscope (FESEM). Bi2Se3 powders obtained at 180°C and 150°C consist of hexagonal flakes of 50–150 nm in side length and nanorods of 30–100 nm in diameter and more than 1 μm in length. The product obtained at 120°C is composed of thin irregular nanosheets with a size of 100–200 nm and several nanometers in thickness. The major phase of Sn0.5-Bi2Se3 synthesized at 180°C is similar to that of Bi2Se3. Sn0.5-Bi2Se3 powders are primarily nanorod structures, but small amount of powders demonstrate irregular morphologies.

Synthesis and characterization of SnSe 2 hexagonal nanoflakes

Single phase SnSe 2 was synthesized at 180 °C by hydrothermal co-reduction method from SnCl 2·2H 2O== and SeO 2, its morphology and growth direction were investigated. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and field emission scanning electron microscope (FESEM). Experimental results show that, the SnSe 2 powder almost consists of regular and homogenous hexagonal nanoflakes which grow along (0001) crystal plane, these nanoflakes are about 600–700 nm in side length and 30–40 nm in thickness.

Direct growth of novel alloyed PtAu nanodendrites

A novel nanostructure of a PtAu catalyst, alloyed PtAu nanodendrites, has been synthesized via a reproducible single-step hydrothermal co-reduction of Pt and Au inorganic precursors and shows exceptionally high catalytic activity towards the electrooxidation of formic acid.