Electrocatalytic activity of porous nanostructured Fe/Pt-Fe electrode for methanol electrooxidation in alkaline media

An electrochemical approach to fabricate a nanostructured Fe/Pt-Fe catalyst through electrodepo-sition followed by galvanic replacement is presented. An Fe/Pt-Fe nanostructured electrode was prepared by deposition of Fe-Zn onto a Fe electrode surface, followed by replacement of the Zn by Pt at open-circuit potential in a Pt-containing alkaline solution. Scanning electron microscopy and energy-dispersive X-ray techniques reveal that the Fe/Pt-Fe electrode is porous and contains Pt. The electrocatalytic activity of the Fe/Pt-Fe electrode for oxidation of methanol was examined by cyclic voltammetry and chronoamperometry. The electrooxidation current on the Fe/Pt-Fe catalyst is much higher than that on flat Pt and smooth Fe catalysts. The onset potential and peak potential on the Fe/Pt-Fe catalyst are more negative than those on flat Pt and smooth Fe electrodes for methanol electrooxidation. All results show that this nanostructured Fe/Pt-Fe electrode is very attractive for integrated fuel cell applications in alkaline media.     

Study of triplet kinetic of thermal decomposition reaction and sensitivity to impact and electrostatic discharge of HMX polymorphs

Journal of Thermal Analysis and Calorimetry - The polymorphs of HMX explosive show the different sensitivities to heat, friction, impact, shock, electrostatic charge, etc. Knowledge and...     

The catalytic effect of Ag/CNTs nanocomposite on the ignition reaction of Mg/KNO3 pyrotechnic by determination of the kinetic triplet

Journal of Thermal Analysis and Calorimetry - The ignition reaction of Mg/KNO3 was improved with addition of Ag/CNTs nanocomposite as catalyst. The nanoparticles of Ag(0) was deposited on the...     

Photodegradation of 2-nitrophenol catalyzed by CoO, CoS and CoO/CoS nanoparticles

The nanoparticles of CoO, CoS and CoO/CoS composite are synthesized using precipitation method. The X-ray diffraction, UV–Vis absorption spectroscopy, energy dispersive X-ray spectroscopy, scanning electron microscopy and FT-IR spectroscopy are used to characterize the prepared nanoparticles. The EDX analysis shows the formation of CoO_0.67S_0.33 composite. The XRD pattern indicates the hexagonal structure for nanocomposite. The formation of Co–O and Co–S bonds is confirmed by FT-IR spectra. The band-gap energies of 2.97, 3.06 and 2.91 eV are obtained from UV–Vis spectra of CoO, CoS and CoO/CoS nanoparticles, respectively. The results of photodegradation of 2-nitrophenol show that the photoreactivity order of nanocatalysts is CoO/CoS > CoO > CoS. The pseudo first-order kinetic rate constants of 6.4 × 10^?3, 4.3 × 10^?3 and 12.2 × 10^?3 min^?1 are obtained for CoO, CoS and CoO/CoS nanoparticles, respectively, at photodegradation reaction conditions of pH 10, 30 mg/L of 2-NP and 1.3 g/L of the catalyst. The proposed nanocomposite shows an acceptable reusability and stability against photocorrosion in four-cycle photodegradation experiments.     

High‐Efficiency Conversion of Trimethylsilyl Ethers to Their Corresponding Ethers using Carbon‐Based Solid Acid as a New Catalyst in Heterogeneous Mixtures

Carbon‐based solid acid was used as a new catalyst for conversion of trimethylsilyl ethers to their corresponding ethers in heterogeneous mixtures. The experiments were done moderately at room temperature, and high yields in suitable times were obtained under these conditions.     

H-point standard addition method for simultaneous determination of cobalt(II) and zinc(II) ions

The H-point standard addition method (HPSAM) was applied to the simultaneous determination of zinc(II) and cobalt(II). This method is based on the difference in the absorbance of methylthymol blue complexes of Zn(II) and Co(II) at pH 6 using different wavelength pairs. The results showed that Zn(II) and Co(II) can be determined simultaneously with concentration ratios of 20:1 and 1:7.5. Under working conditions, the proposed method was successfully applied to the simultaneous determination of zinc and cobalt in synthetic, drinking water and vitamin samples.     

Kinetic Spectrophotometric Determination of Trace Amounts of Nitrite by Catalytic Reaction between Methylthymol Blue and Bromate

A kinetic spectrophotometric method for determination of trace nitrite in two dynamic ranges (2–100 and 100–500 ng/mL) based on its catalytic effect on the reaction between methylthymol blue and potassium bromate in acidic (sulfuric acid) media is described. The reaction was monitored spectrophotometrically by measuring the decreasing color of methylthymol blue at 437 nm by the fixed‐time method of 4.0 min at 30°C. The detection limit is 0.6 ng/mL, and the relative standard deviations for 50.0 and 250.0 ng/mL nitrite are 1.6% and 1.3%, respectively. The method was used for the determination of nitrite in water samples.     

An empirical method for predicting detonation pressure of CHNOFCl explosives

This paper describes a new method for prediction of the Chapman-Jouguet detonation pressures of CHNOFCl explosives using the heat of detonation, Q_det, the number of moles of gaseous products of detonation per gram of explosive, α, and the average molecular weight of gaseous products, M. The equation has the form: P_CJ=15.88α(MQ_det)^1/2ρ₀²−11.17, where P_CJ is the Chapman-Jouguet detonation pressure and ρ₀ the loading density. Calculated P_CJ by this procedure show good result with respect to measured detonation pressure for any pure or mixture of ideal and some of less ideal CHNOFCl explosives at ρ₀>0.8 g/cm³.     

Electro-oxidation of methanol catalysed by porous nanostructured Fe/Pd-Fe electrode in alkaline medium

Nanostructured Fe/Pd-Fe catalysts are prepared first by the deposition of Fe-Zn onto the Fe electrode surface, followed by replacement of the Zn by Pd at open circuit potential in a Pd-containing alkaline solution. The surface morphology and composition of coatings are determined by scanning electron microscopy and energy dispersive X-ray techniques. The results show that the Fe/Pd-Fe coatings are porous structure and the average particle size of Pd-Fe is low, in the range of 30–80 nm. The electrocatalytic activity and stability of Fe/Pd-Fe electrodes for oxidation of methanol are examined by cyclic voltammetry and chronoamperometry techniques. The new Fe/Pd-Fe catalyst has higher electrocatalytic activity and better stability for the electro-oxidation of methanol in an alkaline media than flat Pd and smooth Fe catalysts. The onset potential and peak potential on Fe/Pd-Fe catalysts are more negative than that on flat Pd and smooth Fe electrodes for methanol electro-oxidation. All results show that the nanostructured Fe/Pd-Fe electrode is a promising catalyst towards methanol oxidation in alkaline media for fuel cell applications.