CoNi Nanoparticles/CNT Composite as Effective Anode for Direct Urea Fuel Cells

CoNi nanoparticles/CNTs composite is introduced as workable anode in the direct urea fuel cells. The proposed anode was prepared by calcination under argon atmosphere of a dried cobalt acetate/nickel acetate/CNTs/ethanol slurry at 850 oC. The composition of the metal nanoparticles was optimized by synthesizing composites having different cobalt contents compared to nickel. The results indicated that the best performance is attributed to the anode containing nanoparticles having 10 wt% Co as the corresponding generated power was 3.95 mW/m2 which is 40 folds compared to that obtained from pristine nickel nanoparticles-containing anode (0.09 mW/m2).This Publication was made possible by NPRP grant # [8-1344-1-246] from the Qatar National Research Fund (a member of Qatar Foundation). The findings achieved herein are solely the responsibility of authors

Applicable anode based on Co3O4–SrCO3 heterostructure nanorods-incorporated CNFs with low-onset potential for DUFCs

Besides the high-current density, lower onset potential of urea electrooxidation is key parameter which influences the direct urea fuel cell performance. In the present article, low-onset potential has been reported for nickel-free (NF) electrocatalyst in urea electrooxidation. The nickel-free electrocatalyst: Co3O4–SrCO3 heterostructure nanorods-incorporated carbon nanofibers (CNFs) were synthesized by electrospinning technique, followed by calcination of electrospun mat composed of strontium acetate, cobalt acetate, and poly(vinyl alcohol) sol–gel in inert environment at 750 °C. Physiochemical characterizations confirmed the formation of Co3O4–SrCO3 heterostructure nanorods-incorporated CNFs. The electrochemical activity of resultant nickel-free electrocatalyst toward the electrooxidation of urea in alkaline medium is evaluated using cyclic voltammetry measurements (CV). Co3O4–SrCO3 heterostructure nanorods-incorporated CNFs reveals high-current density of 21.33 mA/cm2 at low-fuel concentration. Notably, the low-onset potential has been observed, showing a good application prospect in direct urea fuel cells.This Publication was made possible by NPRP grant # [8-1344-1-246] from the Qatar National Research Fund (a member of Qatar Foundation). The findings achieved herein are solely the responsibility of authors

ZnO@C (core@shell) microspheres derived from spent coffee grounds as applicable non-precious electrode material for DMFCs

Although numerous reports have introduced non precious electrocatalysts for methanol oxidation, most of those studies did not consider the corresponding high onset potential which restricts utilization in real fuel cells. In this study, an −90 mV [vs. Ag/AgCl] onset potential non-precious electrocatalyst is introduced as an applicable anode material for the direct methanol fuel cells. Moreover, the proposed material was prepared from a cheap and abundantly existing resource; the spent coffee grounds. Typically, the spent coffee grounds were facilely converted to core@shell (ZnO@C) microspheres through a two-step approach, involving chemical activation and a subsequent calcination at temperature of 700 °C. Activation of the carbon derived from the spent coffee grounds was performed with ZnCl2 which acts as pore-forming agent as well as a precursor for the ZnO. The structure and morphology were characterized by (XRD), (SEM), and (TEM) analyses while the electrochemical characterizations was evaluated by cyclic voltammetry (CV) technique. Besides the comparatively very low onset potential, the introduced microspheres exhibited relatively high current density; 17 mA/cm2. Overall, based on the advantages of the green source of carbon and the good electrocatalytic activity, the spent coffee grounds-derived carbon can be considered a promise anode material for the DMFCs.This Publication was made possible by NPRP grant # [8-1344-1-246] from the Qatar National Research Fund (a member of Qatar Foundation). The findings achieved herein are solely the responsibility of authors

Leaching of Some Essential and Non-Essential Heavy Metals from Modern Glazed Ceramic Crockeries Imported into Qatar from China, India and Spain

In this study, the leaching potential of ceramic crockeries available in Qatar market has been evaluated using inductively coupled plasma mass spectrometry (ICP-MS). Ceramic crockeries decorated with glaze matter containing various essential (Zinc, Iron, and Barium, etc.) and non-essential heavy metals (lead and cadmium) can adulterate the foodstuff and/or can release deadly metals into the food substance. Chines, Indian, and Spanish ceramic crockeries were randomly selected from the products available in the local Qatari market and analyzed to determine the level of leachable essential and non-essential heavy metals. Leaching studies were performed according to the ASTM 738-94 standard test methods for specific metals leaching into 4% acetic acid solutions over 24 hours exposure time. ASTM 738-94 is a precise and standard method and particularly designed for the determination of some heavy metals extracted by acetic acid from the glazed ceramic surface. Results show that all the ceramic crockeries contain both leachable essential and non-essential heavy metals. However, the concentration of these heavy metals is not potentially high to cause any adverse effect on human health

Strong improvement of permeability and rejection performance of graphene oxide membrane by engineered interlayer spacing

Advanced membranes fabricated from multilayer/laminated graphene oxide (GO) are promising in water treatment applications as they provide very high flux and excellent rejection of various water pollutants. However, these membranes have limited viability, and suffer from instabilities and swelling due to the hydrophilic nature of GO. In this work, the permeability and rejection performance of laminated GO membranes were improved via functionalization with ethylenediamine (EDA) and polyethyleneimine (PEI). The membranes are fabricated via the pressure-assembly stacking technique, and their structure is well characterized. The performance, rejection, and stability of the fabricated functionalized GO membranes were evaluated. Pillaring the GO layers using diamine and polyamine resulted in exceptionally high water permeability of 113 L/m2h (LMH) compared to only 28 LMH for the pristine GO membrane while simultaneously satisfying high rejection of multivalent salts of 79.4, 35.4, and 19.6 % for Na2SO4, MgCl2, and NaCl, respectively. The results obtained indicate that proper functionalization of GO provides a roadmap for the potential commercialization of such advanced membranes in water treatment applications.</p

Engineering of magnetically separable ZnFe2O4@ TiO2 nanofibers for dye-sensitized solar cells and removal of pollutant from water

Abstract In this study, magnetic Zinc Ferrite (ZnFe2O4)@TiO2 nanofibers were prepared by low cost and nontoxic route; hydrothermal technique followed by electrospinning process. The prepared magnetic ZnFe2O4@TiO2 nanofibers were morphologically and structurally analyzed by X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), and thermal gravimetric analysis (TGA). The prepared magnetic ZnFe2O4@TiO2 nanofibers were utilized as photoanode for the fabrication of dye-sensitized solar cells (DSSCs) and presented applicable performance with 4.2% overall conversion efficiency with high short circuit current density (JSC) of 10.16 mA/cm2. The maximum ∼42% incident photo-to-current conversion efficiency (IPCE) value was also recorded at 520 nm. In addition, ZnFe2O4@TiO2 nanofibers were not only possessed the good conversion efficiency, but also shown excellent photocatalytic efficiency with magnetic properties towards the dye remediation. Prepared ZnFe2O4@TiO2 nanofibers can be considered as a promising material for energy conversion and environmental applications

Capacitance of MnO2 Micro-Flowers Decorated CNFs in Alkaline Electrolyte and Its Bi-Functional Electrocatalytic Activity toward Hydrazine Oxidation

Well-dispersed MnO2 micro-flowers were grown directly on carbon nanofibers via a simple hydrothermal technique without any template. Structure and morphology were characterized by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM) equipped with rapid energy dispersive analysis X-ray (EDX). The appealed characterization techniques specified that the obtained material is carbon nanofibers decorated by MnO2 micro-flowers. Super capacitive performance of the MnO2 micro-flowers decorated CNFs as active electrode material was evaluated by cyclic voltammetry (CV) in alkaline medium and yield a reasonable specific capacitance of 120 Fg−1 at 5 mV s−1. As an electrocatalyst for hydrazine oxidation, the MnO2 micro-flowers decorated CNFs showed high current density. The impressive bi-functional electrochemical activity of MnO2 micro-flowers decorated CNFs is mainly attributed to its unique architectural structure.This Research was financially supported by National Research Foundation of Korea (NRF) Grant funded by the Korean Government (MSIP) (No. 2014R1A4A1008140

Enhanced oxygen evolution reaction on polyethyleneimine functionalized graphene oxide in alkaline medium

Practical applications of metal free catalysts are hindered by their innate poor stability for electrocatalytic application. Accordingly, in this study, synthesis and functionalization of graphene oxide via a modified Tour's method (GOT) with different amine containing molecules results in excellent catalytic performance and stability toward OER in alkaline medium. The as-synthesized polyethyleneimine GOT electrode (P-GOT), produced current densities of 10, 50 and 100 mA/cm2 at overpotentials of 240, 350 and 420 mV, respectively, with small Tafel slope of 47 mV/dec. The X-ray diffraction analysis (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) analysis confirms the successful functionalization of GOT by ethylenediamine (E) and polyethyleneimine (P) molecules, respectively. Morphological studies based on field emission scanning electron microscopy (FESEM) confirm that the modification via covalent bonding preserved the original wrinkled and layered structure of GOT. The P-GOT with cross-linked amine can expose more active sites and is not easy to peel off, which corresponds to attaining lower charge transfer resistance (1.01Ω cm2) and remarkable current stability in 1.0 M KOH solution, compared to the pristine GOT and E-GOT electrodes. From this perspective, our results therefore provide a valuable route for development and practical application of metal free catalytic materials for water oxidation reaction

Critical Behavior of La0.8Ca0.2Mn1−xCoxO3 Perovskite (0.1 ≤ x ≤ 0.3)

The critical properties of La0.8Ca0.2Mn1−xCoxO3 (x = 0, 0.1, 0.2 and 0.3) compounds were investigated by analysis of the magnetic measurements in the vicinity of their critical temperature. Arrott plots revealed that the paramagnetic PM-ferromagnetic (FM) phase transition for the sample with x = 0 is a first order transition, while it is a second order transition for all doped compounds. The critical exponents β, γ and δ were evaluated using modified Arrott plots (MAP) and the Kouvel-Fisher method (KF). The reliability of the evaluated critical exponents was confirmed by the Widom scaling relation and the universal scaling hypothesis. The values of the critical exponents for the doped compounds were consistent with the 3D-Heisenberg model for magnetic interactions. For x = 0.1, the estimated critical components are found inconsistent with any known universality class. In addition, the local exponent n was determined from the magnetic entropy change and found to be sensitive to the magnetic field in the entire studied temperature range.This work has been supported by the Tunisian Ministry of Scientific Research and Technology and Institute Neel at Grenobl