ABSTRACT
In this paper, Fe@SiO2 nanoparticles (α-Fe nanoparticles coated with SiO2 shell) were synthesized at room temperature using the modified Stöber method combined with potassium borohydride (KBH4) reduction process. The present study depicts the facile synthesis of Fe@SiO2 without the presence of surfactants and stabilizers. In this experiment, KBH4 acted both as a reducing agent for iron salt and a catalyst for hydrolysis and polycondensation of tetraethylorthosilicate (TEOS). The Fe@SiO2 nanoparticles were characterized using X-ray diffraction method, specific surface area (BET) technique, transmission electron microscope (TEM), and vibrating sample magnetometer (VSM). The optimal mass ratio of Fe in the form of anhydrous ferric chloride (FeCl3) and SiO2) in the form of TEOS was 4:1. α-Fe-Fe nanoparticles (size of about 45 nm) were coated with approximately 10 nm thick SiO2 shells. Moreover, Fe/SiO2 (Fe0 nanoparticles supported by silica nanoparticles) was synthesized to compare the results. Due to the silica shells, Fe cores cannot be oxidized when dipped in the concentrated sulfuric acid, and hence, the removal of Cr(VI) was not weakened in the acidic environment.
ABSTRACT
Non-carbon materials are considered as the promising candidates for carbon-based catalyst support to increase the durability of proton exchange membrane fuel cells (PEMFCs). Due to the high stability and good electrical conductivity of TiO2, M-doped TiO2 (M is transition metals: Mo, Ru, V, W) is an emerging candidate for Pt nanoparticles support on the cathode side of PEMFCs. In this research, the synthesis mechanism of Ti0.7Ir0.3O2 nanostructure by the one-step hydrothermal method at low temperature was studied. We found that by only controlling the pH of the precursor solution, Ti0.7Ir0.3O2 can be synthesized with different morphology and phase selection without any formation of mixed oxides. In particular, Ti0.7Ir0.3O2 nanostructure synthesized at pH = 0 exhibited concomitant anatase, brookite, and rutile phases. The spherical particles of diameter 20-40 nm, cubic particles of 30-50 nm in side-length and rod-like particles with 70 nm in length and 20 nm in diameter represented the anatase, brookite, and rutile phases respectively. At a pH value of 1 or 2, the majority of spherical nanoparticles were homogeneous at 15-20 nm in diameter. It was observed that the electronic conductivity of novel Ti0.7Ir0.3O2 nanostructure was significantly higher than that of the undoped TiO2. Thus the promising properties of this new nanostructure open a new path to the much-needed fuel cell applications.
ABSTRACT
This study was focused on a new strategy by investigating whether the novel Ti0.7Mo0.3O2 material can be used as a conductive support for PtRu to prevent carbon corrosion and improve catalyst activity as the novel Ti0.7Mo0.3O2 support has some functional advantages. The 30 wt% PtRu/Ti0.7Mo0.3O2 catalyst showed the highest current density at the complete potential, which is approximately 12-fold and 1.4-fold higher than that of the commercial 20 wt% Pt/C (E-TEK) and 30 wt% PtRu/C (JM) catalysts, respectively, at 0.6 V (NHE) toward the methanol oxidation (MOR). Our data suggest that this enhancement is a result of the electronic Pt structure change upon its synergistic interaction with Ti0.7Mo0.3O2 support and the improved mass transport kinetics of PtRu/Ti0.7Mo0.3O2 compared to the carbon support (Pt or PtRu). The PtRu/Ti0.7Mo0.3O2 catalyst exhibited a much higher stability than carbon-supported catalysts because of the strong metal/support interactions between the Pt particles and Ti0.7Mo0.3O2, the inherent structural and chemical stability, and the corrosion resistance of the Ti0.7Mo0.3O2 in acidic and oxidative environments.
ABSTRACT
The degradation of Pt-based catalysts is considered as the main barrier to the commercialization of fuel cells. M-doped TiO2 (M is a transition metal) has been investigated to improve the stability of electrocatalysts. Recently, W-doped TiO2 materials have been found as a good catalyst support for the photocatalyst applications but their application in Proton-exchange membrane fuel cell application has rarely been reported. In addition, the agglomeration of nanoparticles, which are synthesized from the organic precursor, has been reported. Here, we report Ti0.7W0.3O2 nanoparticles prepared via a one-step solvothermal method with inorganic precursors without using surfactants or stabilizers for restricting nanoparticle agglomeration. The properties of the material were measured by XRD, TEM, BET, and electronic conductivity. The mean particle size of â¼5 nm, the high specific surface area of 126.471 m2/g and a moderate electronic conductivity of 0.014 S/cm were obtained for the sample prepared at 220 °C for 4 h. It was observed that using inorganic precursors to prevent particle agglomeration is more advantageous compared to organic precursors as mentioned in previous reports.
ABSTRACT
This article describes the synthesis and characterization of tin-doped indium oxide (ITO) and platinum nanoparticles deposited on ITO. For different calcination temperatures, the tin-doped indium oxide nanoparticles (ITO NPs) were synthesized successfully by a nonaqueous sol-gel method with indium acetylacetonate and tin bis(acetylacetonate) dichloride in oleylamine as the precursors. The ITO sample that calcinated at 500 °C exhibited a spherical morphology with a narrow range of the particle size distribution (15-20 nm). Moreover, the electrical conductivity of the sample (1.242 S/cm) was higher than many different non-carbon supports. In addition, 20% platinum nanoparticles (Pt NPs) were also deposited uniformly on the ITO supports via chemical reduction process using NaBH4 as the reducing agent. The size of Pt NPs was about 5 nm and the crystalline structure of ITO supports remained unchanged.
