In this work, Ni foam supported hierarchical NiCo2O4 nanomaterials are successfully prepared through a hydrothermal process and subsequent calcination process, then the hierarchical NiCo2O4 is ...converted to hierarchical NiCo2S4 through a hydrothermal anion exchange process. The hierarchical nanomaterials are constructed by a nanorod core and nanoribbons shell. The morphology evolution mechanism of the hierarchical NiCo2O4 is studied by exploratory experiments, the results show that the morphology evolution from nanorod to hierarchical nanostructure undergo a solid–solid process, and the calcination temperature is crucial for the formation of the hierarchical nanostructure. The hierarchical NiCo2O4 and NiCo2S4 nanomaterials are both used as electrocatalysts for methanol oxidation reaction in alkaline electrolyte, and the electrocatalytic activity of the NiCo2S4 is higher than that of the NiCo2O4. Cycling test shows the good stability of the NiCo2S4, and the slight loss of activity during cycling is caused by the surface oxidation of NiCo2S4 in alkaline electrolyte. This work indicate that the hierarchical NiCo2S4 is a promising non-noble metal electrocatalyst for direct methanol fuel cells.
Display omitted
•Hierarchical NiCo2O4 and NiCo2S4 nanostructures are grown on Ni foam.•The morphology evolution of the hierarchical nanostructure is researched.•The NiCo2S4 shows a better electrocatalytic activity than that of the NiCo2O4.•The surface oxidation of NiCo2S4 causes the loss of activity during cycling test.
0.9KNbO3-0.1Ba(Nb1/2Ni1/2)O3-δ (KBNNO) powder was synthesized through one step hydrothermal method at 200 °C. The effect of KOH concentration (1 M-18 M) and the effect of reaction time (30 ...min-12 h) on phase evolution and powder morphology were investigated. To get maximum perovskite phase atleast 10 M KOH concentration and 12 h soaking time were required. Characterization by X-ray diffraction, Raman spectroscopy, FESEM, TEM and XPS confirms the phase, structure, morphology and composition. The Powder morphology varies from spherical to irregular shape, to rod like nature, to cube shape when KOH concentration of the starting solution in the range of 4-6 M, 8-12 M and 14-18 M, respectively. UV–vis absorption spectroscopy indicates that KBNNO has significant absorption in the visible range compared to that of KNbO3. The photocatalytic degradation of Rhodamine B (RhB) shows an enhanced photocatalytic activity of KBNNO in comparison with KNbO3 synthesized under similar conditions. Finally, a mechanism for the enhanced charge separation and photodegradation is proposed.
Display omitted
•0.9KNbO3-0.1(BaNb1/2Ni1/2O3-δ) (KBNNO) synthesized by hydrothermal method at 200 °C.•The maximum perovskite phase obtained at 10 M KOH conc and 12 h reaction time.•KOH concentration has significant effect on particle morphology and phase composition.•UV–vis absorption spectra show significant absorption in visible region.•KBNNO has dye degradation efficiency almost double to that of KNbO3.
In diagenetic solutions, ammonium may be incorporated into smectites as an exchangeable cation and become fixed within the interlayer space of illites and other white micas. To study the potential ...impact of NH4+ on the smectite-to-illite transformation reaction, a series of hydrothermal experiments were carried out at 100, 150 and 200 °C, spanning reaction duration from 15 to 90 days, and two NH4+ concentrations (0.1 and 0.2 M). The solids resulting from these alteration experiments were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), and transmission and analytical electron microscopy (TEM and AEM). The XRD analysis revealed that, under the specified experimental conditions, smectite incorporates NH4+ in the structure, leading to the formation of non-swelling layers, resulting in partial transformation to illite layers and producing packets of disordered illite/smectite (I/S). In addition, a minor XRD peak at ∼10 Å suggests the formation of discrete illite crystals. The FTIR spectra demonstrated the uptake of NH4+, with deformation bands observed at 1400 and 1430 cm−1, corresponding to exchangeable NH4+ in smectite and fixed NH4+ in high-charge layers, respectively. TEM analysis revealed that smectite particles exhibited wavy stacks comprising a few layers with abundant defects and lateral discontinuities. The interlayer spacing in these particles ranged from 12 to 15 Å and became thinner and more plate-like with increasing temperature and time. Moreover, they contained inclusions of 10–10.3 Å layers, either as discrete layers or in packets of several layers, indicating the formation of disordered mixed-layer illite-smectite. Lateral transitions from 12 to 15 Å to 10 Å layers were frequently observed and interpreted as reaction fronts due to local rearrangement. At 150 and 200 °C, isolated packets of 10 Å layers were identified as discrete illite crystals that precipitated directly from solution. Analysis of the chemical composition of individual particles revealed an increase in octahedral charge (MgVI for AlVI substitution) in smectite particles, followed by increase in tetrahedral charge in I/S particles. Interlayer NH4+ played a stabilizing role in the high-charge layers and favored the smectite-to-illite conversion process.
•Smectite transforms into illite under alkaline (NH4+) hydrothermal solutions by NH4+ adsorption at the interlayer spaces.•Dissolution and NH4+ fixation convert smectite to illite, increasing AlIV and MgVI, and forming disordered I/S structures.•The process is further enhanced with higher temperature, prolonged reaction times, and increased NH4+ concentration.
•A new cadmium phosphomolybdate crystal compound was designed and synthesized by hydrothermal synthesis method.•Structural analysis shows that the compound has a 4, 8-connected inorganic open ...topology (412·612·84)(46)2.•Taking the synthesis of aspirin as the probe reaction, the catalytic activity of the synthesized product was studied.
To green-catalyze the synthesis of aspirin, we designed and synthesized a novel and unreported cadmium phosphomolybdate crystal compound (C2N2H10)4{Cd3P4Mo6O26(OH)52}·6H2O as a catalyst for the synthesis reaction of aspirin using hydrothermal synthesis, and structurally characterized. Single-crystal X-ray diffraction analysis showed that the compound has a 4,8-connected inorganic open topology (412·612·84)(46)2. The optimal process conditions for the reaction of salicylic acid and acetic anhydride were determined by screening the catalyst dosage, temperature, and reaction time. The reaction temperature was set at 80 °C, the catalyst dosage was 0.09 g, and the reaction time was 25 min. The industry's most often utilized catalyst for aspirin manufacturing is concentrated sulfuric acid, which has strong oxidizing and corrosive qualities, resulting in difficult issues such as low synthetic product yield, large equipment needs, and substantial environmental damage. The experimental results of the (C2N2H10)4{Cd3P4Mo6O26(OH)52}·6H2O catalytic synthesis of aspirin reveal that as a solid acid catalyst, its catalytic activity is similar to the commonly used catalyst concentrated H2SO4. Synthetic catalysts, on the other hand, have the advantages of high efficiency, selectivity, conversion rate, ease of recovery, and the ability to be recycled several times without polluting equipment, all of which are consistent with modern ``green'' catalysts. The results of this work suggest that the supramolecular compounds of polymetallic oxonate that we designed and produced hydrothermally can serve as catalysts in drug synthesis reactions to mitigate environmental pollution, hence providing new opportunities for the development of environmentally friendly medications.
Display omitted
This paper reports the synthesis of various molar concentrations of iron (Fe)-doped TiO2 nanoparticles and their efficient use as potential photocatalysts for photocatalytic ...degradation of toxic and harmful chemical, paranitrophenol. The nanoparticles were synthesized by a novel and facile ultrasonic assisted hydrothermal method and characterized in detail by various analytical techniques in terms of their morphological, structural, compositional, thermal, optical, pore size distribution, etc properties. The photocatalytic activities of the as-prepared Fe-doped TiO2 nanoparticles were examined under visible light illumination using para-nitrophenol as target pollutant. By detailed experimental findings revealed that the Fe dopant content crucially determines the catalytic activity of TiO2 nanoparticles. The maximum degradation rate of para-nitrophenol observed was 92% in 5h when the Fe3+ molar concentration was 0.05mol%, without addition of any oxidizing reagents. The prepared nanoparticles demonstrated excellent photocatalytic response because of their small size, excellent crystalline structure, increase in threshold wavelength response and maximum separation of photogenerated charge carriers. Further, the determination of reaction intermediates has also been carried out and plausible mechanism of photocatalytic degradation of para-nitrophenol has been proposed.
The fluorophosphate compounds A3Fe4(PO4)2F9 (A = K+ and NH4+) were found to exhibit a channel framework constructed from {Fe4O8F10} tetrahedral clusters and PO4 tetrahedra, featuring a tetramer ...chain structure along the a-axis. Here these two compounds were synthesized by a fluorine-rich hydrothermal method. The purity of the samples was characterized by single crystal and powder XRD, EDS, and FT-IR measurements. The results of magnetic and heat capacity measurements confirmed that both compounds possess an antiferromagnetic ordering at ∼10 K and ∼6 K with Weiss temperatures of −341.5(8) K and −334.3(5) K, respectively, indicating strong spin frustration in the systems due to large frustration factors of ∼34 and ∼56. The presence of spin frustration is suggested to arise from the competition of very close magnetic interactions within the tetrahedral Fe4 clusters.
Two isostructural compounds A3Fe4(PO4)2F9 (A = K+ and NH4+) with a tetrahedral Fe4 cluster spin chain structure show strong geometrically frustrated effect. Display omitted
•Two fluorophosphate compounds A3Fe4(PO4)2F9 (A = K+ and NH4+) are obtained by a fluorine-rich hydrothermal method.•These compounds exhibit a channel framework constructed by the {Fe4O8F10} tetrahedral clusters.•These compounds show strong spin frustration effect.
