Synthesis and characterization of novel magnetically separable NiFe2O4@AlMCM-41-Cu2O core-shell and its performance in removal of dye

The synthesis of magnetic NiFe₂O₄@AlMCM-41-Cu₂O core-shell as a new class of visible light driven photocatalyst was suggested. The magnetic NiFe₂O₄ core was prepared by solvothermal method. The intermediate AlMCM-41 shell was prepared by the method of liquid crystal templating mechanism and subsequently cuprous oxide (Cu₂O) nanoparticles (NPs) were synthesized in NiFe₂O₄@AlMCM-41core-shell via colloidal chemistry approach. The properties of prepared magnetic core-shell were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), nitrogen adsorption–desorption measurement and vibration sample magnetometer (VSM). Based on EDX results, the weight percentage (wt%) of NiFe₂O₄ core, MCM-41 shell and Cu₂O NPs were calculated to be 68.89, 30.55 and 0.56%, respectively. It consisted of mesoporous structure with a surface area of 687.00 m² g^?1, an average pore size of 2.95 nm and possessed excellent magnetic properties of 4.74 emu g^?1. The TEM results indicated that the NiFe₂O₄ as core were regular spheres with diameter of 68 nm, and the average thickness of AlMCM-41 shells was ～35 nm. The particles size of Cu₂O incorporated in core-shell was less than 5 nm. The photocatalytic activity was evaluated under visible light irradiation using the removal of methylene blue (MB) dye as a model reaction. The removal rate of MB achieved up to 90% after 60 min under visible light irradiation, and the NiFe₂O₄@AlMCM-41-Cu₂O can be recycled and reused.     

Highly dispersible and uniform size Cu2ZnSnS4 nanoparticles for photocatalytic application

Highly dispersible, uniform size (～7 nm) single-phase Cu₂ZnSnS₄ nanoparticles have been synthesized by hydrothermal method using non-toxic surfactant (oleic acid). High resolution transmission electron microscopy image indicates good crystallinity of the Cu₂ZnSnS₄ nanoparticles with the growth along (1 1 2) plane. X-ray photoelectron spectroscopy analyses suggested that the formation of with Cu, Zn, and Sn in +1, +2 and +4 oxidation states. The optical absorption spectrum of Cu₂ZnSnS₄ nanoparticles exhibits an absorption in the visible region and its optical band gap was found to be ～1.72 eV, which could be much more appropriate for photocatalytic application under visible light irradiation. These Cu₂ZnSnS₄ nanoparticles have been shown high photocatalytic degradation activity of methylene blue (MB) dye in the presence of visible light irradiation. The rate constant (k) value of Cu₂ZnSnS₄ nanoparticles is found to be 0.0144 min^?1. We have discussed the mechanism of dye degradation process that drives the photocatalytic degradation process. The reusability of the Cu₂ZnSnS₄ nanoparticles for the dye degradation is also demonstrated.     

High efficiency visible-light-driven Fe2O3-xSx/S-doped g-C3N4 heterojunction photocatalysts: Direct Z-scheme mechanism

Several nanoporous Fe_2 O_3-xSx/S-doped g-C_3 N_4(CNS) Z-scheme hybrid heterojuctions have been successfully synthesized by one-pot in situ growth of the Fe_2O_3-xSx particles on the surface of CNS. The characterization results show that S-doping in the g-C3 N4 backbone can greatly enhance the charge mobility and visible light harvesting capability. In addition, porous morphology of hybrid composite provides available open pores for guest molecules and also improves light absorbing property due to existence of multiple scattering effects. More importantly, the Fe_2 O_3-xSx nanoparticles formed intimate heterojunction with CNS and developed the efficient charge transfer by extending interfacial interactions occurred at the interfaces of both components. It has been found that the Fe_2 O_3-xSx/CNS composites have an enhanced photocatalytic activity under visible light irradiation compared with isolated Fe_2 O_3 and CNS components toward the photocatalytic degradation of methylene blue(MB). The optimal loaded Fe_2 O_3-xSx value obtained is equal to 6.6 wt% that provided 82% MB photodegradation after 150 min with a reaction rate constant of 0.0092 min~(-1) which was faster than those of the pure Fe_2 O_3(0.0016 min~(-1))and CNS(0.0044 min~(-1)) under the optimized operating variables acquired by the response surface methodology. The specific surface area and the pore volume of Fe_2 O_3(6.6)/CNS hybrid are 33.5 m~2/g and0.195 cm~3/g, which are nearly 3.8 and 7.5 times greater compared with those of the CNS, respectively. The TEM image of Fe_2 O_3(6.6)/CNS nanocomposite exhibits a nanoporous morphology with abundant uniform pore sizes of around 25 nm. Using the Mott-Schottky plot, the conduction and valence bands of the CNS are measured(at pH = 7) equal to-1.07 and 1.48 V versus normal hydrogen electrode(NHE), respectively.Trapping tests prove that ·OH-and ·O_2-radicals are major active species in the photocatalytic reaction.It has been established that formation of the Z-scheme Fe_2 O_3(6.6)/CNS heterojunction between CNS and Fe_2 O_3 directly produces ·OH as well as ·O_2-radicals which is consistent with the results obtained from trapping experiments.     

Heterostructured Fe3O4/Bi2O2CO3 photocatalyst: Synthesis,characterization and application in recyclable photodegradation of organic dyes under visible light irradiation

Heterostructured Fe₃O₄/Bi₂O₂CO₃ photocatalyst was synthesized by a two-step method. First, Fe₃O₄ nanoparticles with the size of ca. 10 nm were synthesized by chemical method at room temperature and then heterostructured Fe₃O₄/Bi₂O₂CO₃ photocatalyst was synthesized by hydrothermal method at 180 °C for 24 h with the addition of 10 wt% Fe₃O₄ nanoparticles into the precursor suspension of Bi₂O₂CO₃. The pH value of synthesis suspension was adjusted to 4 and 6 with the addition of 2 M NaOH aqueous solution. By controlling the pH of synthesis suspension at 4 and 6, sphere- and flower-like Fe₃O₄/Bi₂O₂CO₃ photocatalysts were obtained, respectively. Both photocatalysts demonstrate superparamagnetic behavior at room temperature. The UV–vis diffuse reflectance spectra of the photocatalysts confirm that all the heterostructured photocatalysts are responsive to visible light. The photocatalytic activity of the heterostructured photocatalysts was evaluated for the degradation of methylene blue (MB) and methyl orange (MO) in aqueous solution over the photocatalysts under visible light irradiation. The heterostructured photocatalysts prepared in this study exhibit highly efficient visible-light-driven photocatalytic activity for the degradation of MB and MO, and they can be easily recovered by applying an external magnetic field.     

Synthesis of dual Z-scheme photocatalyst ZnFe2O4/PANI/Ag2CO3 with enhanced visible light photocatalytic activity and degradation of pollutants

The ZnFe₂O₄/PANI/Ag₂CO₃ photocatalyst was synthesized by the co-precipitation method. The composition, morphology and optical properties of the synthesized photocatalyst were characterized. Compared with pure Ag₂CO₃, ZnFe₂O₄, PANI/Ag₂CO₃ and ZnFe₂O₄/Ag₂CO₃, ZnFe₂O₄/PANI/Ag₂CO₃ has the best photocatalytic ability of bisphenol A can reach 86.36% under 40 min of light, and it has a certain ability to be reused. At the same time, after 1 h of light, the degradation rate of Nitrobenzene can reach 90%. The reason for the increased catalytic ability of ZnFe₂O₄/PANI/Ag₂CO₃ can be attributed to the extended absorption capacity of the visible light region and the efficient separation of electron-hole pairs.     

A comparison study of hydrogen storage properties of as-milled Sm5Mg41 alloy catalyzed by CoS2 and MoS2 nano-particles

The influences of the catalysts of CoS₂ and MoS₂ nano-particles on microstructure and hydrogen storage behaviors of as-milled Sm₅Mg₄₁ alloy have been compared in this work. The Sm₅Mg₄₁ + 5 wt.% M (M = CoS₂, MoS₂) alloys were prepared by milling the mechanical ground as-cast Sm₅Mg₄₁ alloy powders (particle size ≤ 75 μm) with 5 wt.% CoS₂ or MoS₂ nano-particles (particle size ≤ 30 nm), respectively. The results demonstrate that the CoS₂ and MoS₂ nanoparticles are embedded into the alloy surface, which is nanostructure containing some crystal defects, such as dislocation, grain boundary and twin etc. Those microstructures play a beneficial role in reducing the total potential barrier that the hydrogen absorption or desorption reactions must overcome, hence improving the hydrogen storage kinetics of the alloys. The as-milled alloys are composed of Sm₅Mg₄₁ and SmMg₃ phases, and ball milling refines their crystal grains. The MgH₂ and Sm₃H₇ phases appear after hydrogenation, while Mg and Sm₃H₇ phases exist after dehydrogenation. The dehydriding activation energy of M = CoS₂ and MoS₂ alloys are 101.67 and 68.25 kJ/mol H₂ respectively. The initial hydrogen desorption of M = CoS₂ and MoS₂ alloys are 252.9 °C and 247.8 °C. The hydrogenation and dehydrogenation enthalpy changes of M = MoS₂ alloy are a little smaller than that of M = CoS₂ alloy. Therefore, the catalyst MoS₂ can improve the as-milled Sm₅Mg₄₁ alloy in hydrogen storage property more effectively than CoS₂.     

High performance magnetically recoverable g-C3N4/Fe3O4/Ag/Ag2SO3 plasmonic photocatalyst for enhanced photocatalytic degradation of water pollutants

The g-C₃N₄/Fe₃O₄/Ag/Ag₂SO₃ nanocomposites have been successfully fabricated by facile refluxing method. The as-obtained products were characterized by XRD, EDX, SEM, TEM, UV–vis DRS, FT–IR, TGA, PL, and VSM techniques. The results suggest that the Ag/Ag₂SO₃ nanoparticles have anchored on the surface of g-C₃N₄/Fe₃O₄ nanocomposite, showing strong absorption in the visible region. The evaluation of photocatalytic activity indicates that for the g-C₃N₄/Fe₃O₄/Ag/Ag₂SO₃ (40%) nanocomposite, the degradation rate constant was 188 × 10^?4 min^?1 for rhodamine B, exceeding those of the g-C₃N₄ (16.0 × 10^?4 min^?1) and g-C₃N₄/Fe₃O₄ (20.2 × 10^?4 min^?1) by factors of 11.7 and 9.3, respectively. The results showed that the nanocomposite prepared by refluxing for 120 min has the superior photocatalytic activity and its activity decreased with rising the calcination temperature. The trapping experiments confirmed that superoxide ion radical was the main active species in the photocatalytic degradation process. Also, it was demonstrated that the magnetic photocatalyst has considerable activity in degradation of one more dye pollutant. Finally, the reusability of the photocatalyst was evaluated by five consecutive catalytic runs. This work may open up new insights into the utilization of magnetically separable nanocomposites and provide new opportunities for facile fabrication of g-C₃N₄-based plasmonic photocatalysts.     

A new scale for optimized cryogenic magnetocaloric effect in ErAl2@Al2O3 nanocapsules

The Er Al_2@Al_2O_3nanocapsules with Er Al_2core and Al_2O_3shell were synthesized by modified arc-charge technique.The typical core-shell structure of the nanocapsules was confirmed by high resolution transmission electron microscopy and X-ray photoelectron spectroscopy.Transmission electron microscopy analysis shows the irregular sphere of the nanocapules with an average diameter of 26 nm.Magnetic investigation revealed the Curie temperature of Er Al_2@Al_2O_3nanocapsules at 20 K and the typical superparamagnetic behavior between blocking temperature and Curie temperature.Based on the blocking temperature and average diameter,the magnetocrystalline anisotropy constant of Er Al_2@Al_2O_3nanocapsules was estimated to illustrate the magnetic contribution to the-S_M.The large-S_Mof 14.25 J/(kg K)was obtained under 50 k Oe at 5 K.A vital parameterˇwas introduced in the present work to scale the optimized magnetic characteristics and the optimized mechanism was discussed in detail according to classical superparamagnetic theory.The results demonstrate that the optimal-S_Mwill be obtained when the magnetic parameterˇis close to the theoretical coefficient.     

Highly enhanced and stable activity of defect-induced titania nanoparticles for solar light-driven CO2 reduction into CH4

Photocatalytic reduction of CO₂ to fuel offers an exciting opportunity for helping to solve current energy and global warming problems. Although a number of solar active catalysts have been reported, most of them suffer from low product yield, instability, and low quantum efficiency. Therefore, the design and fabrication of highly active photocatalysts remains an unmet challenge. In the current work we utilize hydrogen-doped, blue-colored reduced titania for photocatalytic conversion of CO₂ into methane (CH₄). The photocatalyst is obtained by exposure of TiO₂ to NaBH₄ at 350 °C for 0.5 h. Sensitized with Pt nanoparticles, the material promotes solar spectrum photoconversion of CO₂ to CH₄ with an apparent quantum yield of 12.40% and a time normalized CH₄ generation rate of 80.35 μmol g^?1 h^?1, which to the best of our knowledge is a record for photocatalytic-based CO₂ reduction. The material appears intrinsically stable, with no loss in sample performance over five 6 h cycles, with the sample heated in vacuum after each cycle.     

Effects of ZrO2 addition on phase stability and photocatalytic activity of ZrO2/TiO2 nanoparticles

ZrO₂/TiO₂ nanoparticles with various Zr/Ti ratios (0–0.9) were prepared by a polymer complex solution method (PCSM). The prepared samples were characterized using transmission electron microscopy (TEM), the Brunauer, Emmett & Teller (BET) method, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). The ZrO₂/TiO₂ photocatalyst showed a high specific area and small crystal size. The XRD pattern for the Zr/Ti = 0.1 sample indicated that the addition of ZrO₂ stabilized the anatase phase of TiO₂ up to 800 °C. The photocatalytic activity of Zr/Ti = 0.1 sample was higher than that of the TiO₂ sample and commercially available Degussa P25. The high photocatalytic activity can be attributed to stronger adsorption in the visible light region, higher specific area, smaller crystal size and increased surface OH groups.     

Magnetic separation and adsorptive performance for methylene blue of mesoporous NiFe2O4/SBA-15 nanocomposites

Magnetic NiFe₂O₄/SBA-15 nanocomposites were synthesized by a facile impregnation method, and NiFe₂O₄ nanoparticles presented spinel phase structure and existed in the mesopores of SBA-15. Partial mesopores were blocked by NiFe₂O₄ nanoparticles and micropores formed, which the capillarity of micropores played a decisive role for methylene blue (MB) adsorption. The saturation magnetization increased from 2.34 emu g^?1 to 10.03 emu g^?1 with the NiFe₂O₄ content, while the specific surface area decreased from 552.18 m² g^?1 to 260.40 m² g^?1 and pore volume decreased from 1.13 cm³ g^?1 to 0.49 cm³ g^?1. MB adsorption could be improved by optimizing the NiFe₂O₄ content of the nanocomposites. MB could be adsorbed completely in 60 min with the optimum nanocomposites and could be separated easily from water by magnetic separation technique.     

Synthesis of polyaniline-modified Fe3O4/SiO2/TiO2 composite microspheres and their photocatalytic application

Polyaniline-modified Fe₃O₄/SiO₂/TiO₂ composite microspheres have been successfully synthesized by sol–gel reactions on Fe₃O₄ microspheres followed by the chemical oxidative polymerization of aniline. The synthesized multilayer-structured composites were characterized by TEM, XRD, TGA, UV–vis diffuse reflectance spectra and magnetometer. The photocatalytic activity was evaluated by the photodegradation of methylene blue under visible light. The effect of polyaniline (PANI) amounts on the photocatalytic activity was investigated. The photocatalytic activity results show that the Fe₃O₄/SiO₂/TiO₂ composites with about 2.4 wt.%–4.1 wt.% PANI could show higher photocatalytic efficiency than that of Fe₃O₄/SiO₂/TiO₂. Furthermore, the PANI-Fe₃O₄/SiO₂/TiO₂ photocatalyst could be easily recovered using a magnet.     

Structural and optical properties of sol gel derived Cu2ZnSnS4 nanoparticles

The spherical Cu₂ZnSnS₄ nanoparticles with the average diameters (～8–10 nm) have been synthesized by sol gel method. The effects of solvents and reaction temperatures on the properties of the as-synthesized nanoparticles were investigated. The X-ray diffraction shows as grown Cu₂ZnSnS₄ nanoparticles exhibit kesterite crystal structure along preferential orientation (1 1 2) plane. The crystalline nature of nanoparticles was improved in ethylene glycol solvent with the increase in reaction temperature. Rietveld refinement study was performed and structural parameters were determined for the Cu₂ZnSnS₄ nanoparticles. The Raman spectra show the main characteristic peak of A₁ vibrational mode which confirmed the formation of Cu₂ZnSnS₄ phase in all the samples. Scanning electron micrographs depict the irregular aggregate formation of nanoparticles in methanol solvent and uniformly distributed aggregates of nanoparticles with ethylene glycol solvent. Transmission electron microscopy results show the synthesis of polycrystalline porous nanostructures and uniform spherical nanoparticles in methanol and ethylene glycol solvents respectively at the temperature of 250 °C. UV–vis absorption spectra indicated the broad absorption in visible range and the band gap of the nanoparticles was found to 1.38 and 1.45 eV which is suitable for absorbing the solar radiation. The obtained results revealed ethylene glycol as a suitable solvent and 250 °C as the favorable synthesis temperature.     

A new strategy for the preparation of porous zinc ferrite nanorods with subsequently light-driven photocatalytic activity

Porous zinc ferrite (ZnFe₂O₄) nanorods have been synthesized by the thermal decomposition of ZnFe₂(C₂O₄)₃ nanorods precursor, which was prepared by template-, surfactant-free solvothermal method. The morphology and structure of the obtained ZnFe₂(C₂O₄)₃ nanorods precursor and porous ZnFe₂O₄ nanorods were characterized by X-ray powder diffraction, transmission electron microscopy, field emission scanning electron microscopy and high-resolution transmission electron microscopy. The results indicated that the as-synthesized ZnFe₂O₄ retained the precursor morphology of 1D nanorods with diameters of 100–200 nm and lengths of several micrometers and plenty of nanoparticles were interconnected to each other to form porous nanorods. The as-prepared ZnFe₂O₄ nanorods as a kind of subsequently light-driven photocatalyst exhibited good photocatalytic decomposition activity for methylene blue (MB).     

Co2(OH)3Cl nanoparticles as new-type electrode material with high electrochemical performance for application in supercapacitor

In this work, we report the preparation of Co₂(OH)₃Cl nanoparticles with average size of ～20 nm and well-defined cubic shape at room temperature by an epoxide precipitation route. It was found that the as-prepared Co₂(OH)₃Cl nanoparticles could be used as a promising new electrode material for application in redox supercapacitors due to its high electrochemical performance. It presented superior specific capacitance of 783 F g^?1 at low current density of 2.8 A g^?1, while it had a high value of 604 F g^?1 at high current density of 56.6 A g^?1, proving its excellent high rate performance. Its 75% capacitance retention after 10,000 cycles of charge–discharge demonstrated its long-life span. According to characterization results, the possible mechanism for the electrochemical process that Co₂(OH)₃Cl nanoparticles underwent was proposed as a process of Co₂(OH)₃Cl → β-Co(OH)₂ → CoOOH ? Co₃O₄.     

Controlled synthesis of mesoporous α-Fe2O3 nanorods and visible light photocatalytic property

Porous α-Fe₂O₃ nanorods with typical pore size of 2–4 nm were controlled prepared by a facile hydrothermal process of Fe(NO₃)₃·9H₂O aqueous solution in the presence of NaOH, followed by a calcination treatment. Contrast experiments indicate that the morphology and crystalline structure of the hydrothermal products depend greatly on the quantity of NaOH. Hematite nanoparticles and microplates were respectively obtained under conditions without or with excess NaOH. The porous α-Fe₂O₃ nanorods exhibit a high BET surface area of 105.1 m² g^?1 and a pore volume of 0.13 m³ g^?1. UV–vis measurement shows wide absorption to visible light and an obvious blue-shift of the adsorption edge due to the quantum size effect. The visible-light photocatalytic performances of the as-prepared samples were evaluated by photocatalytic decolorization of methylene blue at ambient temperature. The results indicate that the photocatalytic activity of the porous α-Fe₂O₃ nanorods is superior to hematite nanoparticles and platelets and exhibit good reusable feature. The photocatalytic process of porous structure is determined to be pseudo-first-order reaction with apparent reaction rate constant of 1.04 × 10^?2 min^?1. And the optimum photocatalyst dosage is 20 mg per 100 mL of dye solution. The porous α-Fe₂O₃ nanorods are considered potential photocatalyst for practical application due to the excellent photocatalytic behavior and good reusability.     

Template-free hydrothermal derived cobalt oxide nanopowders: Synthesis,characterization, and removal of organic dyes

Pure spinel cobalt oxide nanoparticles were prepared through hydrothermal approach using different counter ions. First, the pure and uniform cobalt carbonate (with particle size of 21.8–29.8 nm) were prepared in high yield (94%) in an autoclave in absence unfriendly organic surfactants or solvents by adjusting different experimental parameters such as: pH, reaction time, temperature, counter ions, and (Co²⁺:CO₃^2?) molar ratios. Thence, the spinel Co₃O₄ (with mean particle size of 30.5–47.35 nm) was produced by thermal decomposition of cobalt carbonate in air at 500 °C for 3 h. The products were characterized by powder X-ray diffraction (XRD), Fourier transform infrared (FTIR), transmission electron microscope (TEM), scanning electron microscope (SEM), and thermal analysis (TA). Also, the optical characteristics of the as-prepared Co₃O₄ nanoparticles revealed the presence of two band gaps (1.45–1.47, and 1.83–1.93 eV). Additionally, adsorption of methylene blue dye on Co₃O₄ nanoparticles was investigated and the uptake% was found to be >99% in 24 h.     

Improved electrochemical hydrogen storage capacity of Ti45Zr38Ni17 quasicrystal by addition of ZrH2

Ti₄₅Zr₃₈Ni₁₇ + xZrH₂ (x = 5, 10, 15 and 20 wt%) composite materials are produced by ball milling for 20 min. The results of XRD measurement show that the composite materials contain icosahedral quasicrystal phase (I-phase), FCC phase with a Ti₂Ni type crystal and C14 Laves phase. After adding ZrH₂, the composite materials include not only the individual phases mentioned above, but also the ZrH phase. These composite materials are used as the negative electrode material of the nickel-metal hydride batteries. The electrochemical hydrogen storage characteristics of the material after adding ZrH is investigated. The Ti₄₅Zr₃₈Ni₁₇ + xZrH₂ (x = 5, 10, 15 and 20 wt%) composite material has reached the maximum discharge capacity (83.2 mA h/g) when x equals 10. This maximum discharge capacity is much higher than that of Ti₄₅Zr₃₈Ni₁₇ alloy without ZrH. After adding ZrH_2, the high-rate discharge ability and the cycling stability are enhanced simultaneously. The improvement of the electrochemical properties can be attributed to the synergistic effects of ZrH₂, and the synergistic effects in the composite electrodes are probably attributed to the entry of most of hydrogen atoms from weakly bond strength of the Zr-H to the I-phase structure in electrochemical reaction.     

CeO2-Cu2O composite nanofibers: Synthesis,characterization photocatalytic and electrochemical application

The present study describes fabrication and electrochemical classification of one-dimensional CeO₂-Cu₂O nanofibers for photocatalysis and supercapacitor application. The utilized CeO₂-Cu₂O composite was prepared by sol–gel electrospinning method using Polyvinylpyrrolidone (PVP), Ce(NO₃)₃?6H₂O and Cu(CH₃COO)₂ as precursors. The physicochemical properties of the synthesized samples were characterized using special characterization approaches such as X-ray diffractometer (XRD), energy dispersive X-ray analysis (EDX), electron probe microanalysis (EPMA) and scanning electron microscopy (SEM). As compared to pristine CeO₂, the UV–vis spectrum of CeO₂-Cu₂O composite exhibited the absorption peak which shifted to higher wavelength. The photocatalytic activity results indicated the substantial degradation of MB dye by ～92% over the surface of CeO₂-Cu₂O nanocomposite catalyst under visible light illumination. The CeO₂-Cu₂O composite possessed higher photocatalytic activity and electrochemical capacitance than the pristine samples as supercapacitor electrode materials. The CeO₂-Cu₂O composite exhibits a specific capacitance of 329.64 F g^?1 at 5 mV s^?1, which is higher than that of the pristine CeO₂ (192.5 F g^?1) nanofibers. These results suggest the applicability of fabricated composite nanofibers as visible light active photocatalyst and as electrode material for supercapacitors.     

Hydrolytic dehydrogenation of ammonia borane catalyzed by poly(amidoamine) dendrimers-modified reduced graphene oxide nanosheets supported Ag0.3Co0.7 nanoparticles

Poly(amidoamine) dendrimers-modified reduced graphene oxide nanosheets (PAMAM/rGO) composite was selected as a carrier of heterogeneous Ag_0.3Co_0.7 nanoparticles in order to obtain an excellent catalyst for ammonia borane (AB) hydrolysis. During the synthetic processes, GO could easily assembled with PAMAM by the electrostatic and hydrogen-bonding interactions. Structural characterization revealed that Ag_0.3Co_0.7 bimetallic nanoparticles with uniform size distribution of 5 nm are well dispersed on PAMAM/rGO composite architecture. Ag_0.3Co_0.7@PAMAM/rGO was found to be a highly active and reusable catalyst in hydrogen generation from the hydrolysis of AB with a turnover frequency value (TOF) of 19.79 mol_H2 min^–1 mol_M^–1 at 25.0 ± 0.1 °C and retained 75.4% of their initial activity with a complete release of hydrogen in five runs. The relatively high TOF value and low apparent activation energy (34.21 kJ mol^–1) make these Ag_0.3Co_0.7@PAMAM/rGO NPs as a high-efficient catalyst for catalytic dehydrogenation of AB facilitating the development of practically applicable energy storage materials.