•A facile and scalable chemical synthesis strategy is proposed.•The NiCo2O4 materials display a high surface area and porosity.•The NiCo2O4 electrode shows a high specific capacitance and rate ...capability.•The AC-NiCo2O4 capacitor exhibits a high Ragone behavior and high cycling stability.
Highly porous nickel cobaltite (NiCo2O4) materials have been synthesized via a facile and scalable chemical synthesis route. The obtained NiCo2O4 material displays a typical secondary submicron/micron-sized (0.1–2μm) agglomerate morphology, exhibiting large surface area (190.1m2g−1) and high porosity (1.136cm3g−1). The fabricated NiCo2O4 electrode shows high specific capacitance (351Fg−1 at 1Ag−1) and high-rate capability (82.1% capacitance retention at 8Ag−1), which is superior to many reported NiCo2O4 materials. Further, the assembled AC-NiCo2O4 aqueous hybrid capacitor exhibits high power and energy densities (2805Wkg−1, 6.8Whkg−1 at 8Ag−1) and high cycling stability (15% loss after 5000 cycles at 1.5Ag−1). The high-performance of the NiCo2O4 materials is attributed to their large surface area and highly porous structure which contribute to rich surface electroactive sites and easy ions transport pathways for facile electrochemical reactions.
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•Acid-treated TiO2 nanoblet is used to prepare supported Pt catalyst (Pt/TiNB-ac).•Pt/TiNB-ac shows very high activity for low-temperature oxidation of HCHO.•TiNB-ac has rough ...surface, abundant chemisorbed oxygen and hydroxyl species.•More metal-support interface active sites are present in Pt/TiNB-ac catalyst.
In this work, two kinds of novel Pt/TiO2 catalysts were prepared by impregnation method using hydrothermally synthesized TiO2 nanobelt (TiNB) and sulfuric acid-treated TiO2 nanoblet (TiNB-ac) as supports, and their catalytic properties were investigated in the oxidation of formaldehyde. It was found that Pt/TiNB-ac exhibits much higher catalytic activity, which can efficiently convert formaldehyde to CO2 and H2O at ambient temperature. The addition of water vapor into the feed stream can further promote the catalytic activity of Pt/TiNB-ac catalyst. A variety of characterization results showed that TiNB-ac possesses much rougher surface, and more defect sites (including abundant chemisorbed oxygen and surface hydroxyl species) due to the treatment by sulfuric acid. These features should be beneficial to achieve high dispersion of Pt nanoparticles on the rough-surface of TiNB-ac, to produce more interface active sites like Pt-O(OH)x-Ti species through the interaction between the Pt naoparticles and the surface hydroxyl species of TiNB-ac support, thus resulting in the formation of highly efficient Pt/TiNB-ac catalyst for the oxidation of formaldehyde under mild conditions.
MgFe2O4 with inverse spinel structure is demonstrated to be an efficient support for constructing practical potential Pt catalyst (Pt/MgFe2O4). The resultant Pt/MgFe2O4 exhibits excellent catalytic ...behavior in CO oxidation under normal temperature and humidity. TOF calculated based on the content of Pt is 0.131 s–1. The excellent performance of Pt/MgFe2O4 attributes to the presence of surface undercoordinated lattice oxygens on MgFe2O4 support. These oxygens could participate in the initial CO oxidation and then be recovered under O2 conditions. Over this Pt/MgFe2O4 catalyst, CO catalytic oxidation should mainly follow a redox mechanism.
Mesoporous nickel cobaltite (NiCo2O4) nanoparticles have been synthesized via a facile hydrothermal strategy with the assistance of sodium dodecyl sulfate (SDS) soft template (ST). Their ...physicochemical properties have been characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectra (EDS), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS) and nitrogen sorption measurements. Their electrocatalytic performances have been examined by cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) tests. The obtained NiCo2O4 materials exhibit a typical nanoscale crystalline hexagonal morphology with specific surface area (SSA) and mesopore volume of 88.63 m2 g−1 and 0.298 cm3 g−1. Impressively, the SDS-assisted NiCo2O4 electrode shows a catalytic current density of 125 mA cm−2 and 72% retention for consecutive 1000 s at 0.6 V in 1 M KOH and 0.5 M CH3OH electrolytes towards methanol (CH3OH) electrooxidation, which is better than the one without SDS assistance. The pronounced electrocatalytic activity is largely ascribed to their higher surface intensities of Co and Ni species and superior mesoporous nanostructures, which provide the richer electroactive sites and faster electrochemical kinetics, leading to the enhanced electrocatalytic activity.
•SDS enhances mesoporous structures and surface electroactive sites.•SDS-assisted NiCo2O4 electrode shows faster electrochemical kinetics.•SDS-assisted NiCo2O4 electrode exhibits enhanced electrocatalytic activity.•Surface physicochemical properties strongly affect electrocatalytic behavior.
The catalytic properties of iron oxide supported platinum catalysts (Pt/Fe2O3), prepared by a colloid deposition route, were investigated for the complete oxidation of formaldehyde. It is found that ...all the Pt/Fe2O3 catalysts calcined at different temperatures (200–500°C) were active for the oxidation of formaldehyde. Among them, the catalysts calcined at lower temperatures (i.e., 200 and 300°C) exhibited relatively high catalytic activity and stability, which could completely oxidize HCHO even at room temperature. Based on a variety of physical–chemical characterization results, it is proposed that the presence of suitable interaction between Pt particles and iron oxide supports, which is mainly in the form of Pt–O–Fe bonds, should play a positive role in determining the catalytic activity and stability of the supported Pt/Fe2O3 catalysts.
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► The nature of silica supports can affect the chemical states and catalytic properties of Pt nanoparticles. ► Fumed silica supported platinum catalyst is highly active for HCHO ...oxidation. ► Fumed silica supported platinum catalyst contains more metallic Pt species. ► The activation of molecular oxygen can be achieved at room temperature.
Three kinds of silica materials, including fumed SiO2, porous granular SiO2 and mesoporous SBA-15, were adopted to prepare supported Pt catalysts by impregnation method. The catalytic properties of these silica supported Pt catalysts (Pt/SiO2) were investigated for the complete oxidation of formaldehyde (HCHO). Among them, fumed SiO2 supported Pt catalyst (Pt/f-SiO2) shows very high catalytic activity, which could completely oxidize HCHO even at ambient temperature. According to the results of catalyst characterization, it was proposed that the nature of silica supports could affect the particle size and the chemical states of platinum species and then further influence the redox property of Pt/SiO2 catalysts. Compared with other silica supported Pt catalysts, Pt/f-SiO2 catalyst possesses higher ratio of metallic Pt species, which might be a key factor in improving its capability to activate molecular oxygen and consequently to oxidize HCHO at low temperature.
The effect of polyethylene glycol (PEG) additive on the synthesis of TS-1 zeolites was investigated by changing the addition amount of PEG and the crystallization time. Adding suitable amount of PEG ...may effectively inhibit the generation of unfavorable anatase, and result in the formation of TS-1 zeolites enriched tetrahedral framework Ti species with a short crystallization time (1.5 days). The resultant TS-1 zeolites showed significant improvement in catalyzing epoxidation of 1-hexene with H
2
O
2
as oxidant. A turnover frequency (TOF) up to 161 h
−1
could be obtained over the anatase-free TS-1 zeolite, much higher than the conventional TS-1 zeolite (TOF: 95 h
−1
). This work demonstrated that using a small amount of PEG additive could be beneficial for the formation of anatase-free TS-1 zeolites, which may have great potential for the catalytic application in H
2
O
2
-mediated olefin epoxidation.
A series of amine-modified ZrSBA-15 supported PdAu bimetallic nanoparticle (NP) catalysts were prepared, and their catalytic properties were studied for the dehydrogenation of formic acid in aqueous ...solution without any additives. The catalytic activities of the supported PdAu catalysts varied with the change of amines and Pd/Au ratios. The optimized catalyst achieves a very high efficiency under ambient conditions, and even works well at a temperature near the freezing point of the solution. During the preparation process of the catalysts, different organic amines could coordinate with the cations of Au and Pd to produce metal complexes with different structure stabilities and redox properties, and finally result in the formation of PdAu NPs with different particle sizes and dispersion states. The co-existence of small PdAu alloy NPs and the suitable amino groups within the single solid support could provide highly efficient bifunctional sites for synergistically activating FA molecules to produce H 2 and CO 2 .
Rationally controlling the morphology and microstructure of the zeolite crystals could play a significant role in optimizing their physicochemical properties and catalytic performances for ...application in various zeolite-based heterogeneous catalysis processes. Among different controlling strategies, the utilization of zeolite growth modifiers (ZGMs), which are molecules capable of altering the anisotropic rates of crystal growth, is becoming a promising approach to modulate the morphology and microstructural characteristics of zeolite crystals. In this mini-review, we attempt to provide an organized overview of the recent progress in the usage of several easily available polymer-based growth modifiers in the synthesis of some commonly used microporous zeolites and to reveal their roles in controlling the morphology and various physicochemical properties of zeolite crystals during hydrothermal synthesis processes. This review is expected to provide some guidance for deeply understanding the modulation mechanisms of polymer-based zeolite growth modifiers and for appropriately utilizing such a modulation strategy to achieve precise control of the morphology and microstructure of zeolite crystals that display optimal performance in the target catalytic reactions.
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