Activated carbon nanofibers as an alternative cathode catalyst to platinum in a two-chamber microbial fuel cell

This paper evaluated the oxygen reduction reaction (ORR) in a microbial fuel cell (MFC) system by using chemically and physically activated electrospun carbon nanofibers (ACNFs) in an MFC and comparing their performance with that of plain carbon paper. The chemical and physical activation was carried out by KOH reagents and CO₂ gas to increase the electrode surface area and the catalytic activity. As a result, it was found that the MFC with the chemically activated carbon nanofibers (ACNFs) exhibited better catalytic activity than that of the physically activated ACNFs. Chemically ACNFs with 8 M KOH were found to be one of the most promising candidates for the ORR and could generate up to 3.17 times more power than that of the carbon paper. The ACNFs with 8 M KOH exhibited 78% more power generation than that of the physically activated ACNFs and exhibited 16% more power generation than the chemically activated ACNFs with 4 M KOH. The power per cost of ACNFs with 8 M KOH is 2.65 times greater than that of the traditionally used platinum cathode. Thus, ACNFs are a good alternative catalyst to Pt for MFCs.     

Development and application of vanadium oxide/polyaniline composite as a novel cathode catalyst in microbial fuel cell

Polyaniline (Pani), vanadium oxide (V₂O₅), and Pani/V₂O₅ nanocomposite were fabricated and applied as a cathode catalyst in Microbial Fuel Cell (MFC) as an alternative to Pt (Platinum), which is a commonly used expensive cathode catalyst. The cathode catalysts were characterized using Cyclic Voltammetry and Linear Sweep Voltammetry to determine their oxygen reduction activity; furthermore, their structures were observed by X‐ray Diffraction, X‐ray Photoelectron Spectroscopy, Brunauer–Emmett–Teller, and Field‐Emission Scanning Electron Microscopy. The results showed that Pani/V₂O₅ produced a power density of 79.26 mW/m², which is higher than V₂O₅ by 65.31 mW/m² and Pani by 42.4 mW/m². Furthermore, the Coulombic Efficiency of the system using Pani/V₂O₅ (16%) was higher than V₂O₅ and Pani by 9.2 and 5.5%, respectively. Pani–V₂O₅ also produced approximately 10% more power than Pt, the best and most common cathode catalyst. It declares that Pani–V₂O₅ can be a suitable alternative for application in a MFC system. Copyright © 2013 John Wiley & Sons, Ltd.     

Effect of pre-treatment and biofouling of proton exchange membrane on microbial fuel cell performance

Nafion^® 117, as the most popular proton exchange membrane, has been studied with regards to the effect of pre-treatment and biofouling for bioelectricity production and wastewater treatment, in dual chamber microbial fuel cells. The obtained results showed that maximum generated power was obtained using pre-treated Nafion^® 117, at approximately 100 mW/m². However, maximum generated power for untreated Nafion^® 117 and biofouled Nafion^® 117 were 52.8 mW/m² and 20.9 mW/m², respectively. Furthermore, the columbic efficiency of pre-treated Nafion^® 117 was 2.32 and 4.15 times higher than untreated and biofouled Nafion^® 117, respectively. Obtained results demonstrated that the pre-treatment of the proton exchange membrane is necessary to reach higher powers, and biofouling is a major obstacle for proton exchange membranes in dual chamber MFCs.     

Copper-phthalocyanine and nickel nanoparticles as novel cathode catalysts in microbial fuel cells

In this study, four different catalysts (i.e., carbon black, nickel nanoparticle (Ni)/C, Phthalocyanine/C and copper-phthalocyanine/C), were tested in a two-chamber Microbial Fuel Cell (MFC) and their performances were compared with Pt as the common cathode catalyst in MFC. The characterization of catalysts was done by TEM, XPS and EDX and their electrochemical characteristics were compared by cyclic voltammetry (CV) and Linear Sweep Voltammetry (LSV). The results proved that copper phthalocyanine and nickel nanoparticles are potential alternatives catalyst for Pt. Even copper-phthalocyanine generated power is almost the same as Pt. The CV and LSV results reported high electrochemical activity of these catalysts. The maximum power density and coulombic efficiency was achieved by copper-phthalocyanine/C as 118.2 mW/m² and 29.3%.     

Numerical simulation of the magnetic field and Joule heating effects on force convection flow through parallel-plate microchannel in the presence of viscous dissipation effect

The effects of Joule heating, Hartman, Brinkman, and Reynolds numbers on the flow pattern and thermal characteristics of force convection flow through a parallel-plate microchannel are investigated in various nanoparticles volume fraction. Water–Al₂O₃ is considered as the working nanofluid while taking viscous dissipation effect (VDE) into account. The mid-section of the microchannel is heated with a constant uniform heat flux and influenced by a magnetic field with a uniform strength. The effective thermal conductivity and viscosity of nanofluid are calculated through a new correlation in which the influence of Brownian motion is considered. A control volume finite different scheme, along with the SIMPLE algorithm, is adopted to conduct the numerical analyses and solve the discrete equations. Contour plots of streamlines and isotherms are presented to graphically display the impact of the investigated variables. Furthermore, the values of the Nusselt number for the minimum temperature and maximum velocity are calculated and presented through figures. The results show that all of the Brinkman, Joule, nanofluid concentration, and Hartmann numbers have decreasing effect on the heat transfer. The conclusion is supported by the fact that all the aforementioned factors increase the temperature throughout the flow field. The higher the flow field temperature, the lower the heat transfer from the wall. Higher Brinkman number leads to the friction intensification between flow layers due to considering VDE. It can be said about the Joule heating that, since this term has an inverse relation with the squared velocity, increase in Joule number is followed by a reduction of heat transfer from the walls. Also, an increase in the nanofluid concentration increases the temperature throughout the microchannel leading to heat transfer deterioration.     

A Numerical Study on the Forced Convection of Laminar Nanofluid in a Microchannel with Both Slip and No-Slip Conditions

This article provides numerically study of the thermal performance of a microchannel, cooled with either pure water or a Cu-water nanofluid, while considering the effects of both slip and no-slip boundary conditions on the flow field and heat transfer. The microchannel is partially heated at a constant temperature and cooled by forced convection of a laminar flow at a relatively lower temperature. The effects of pertinent parameters such as Reynolds number, solid volume fraction, and slip velocity coefficient on the thermal performance of the microchannel are studied. The results of the numerical simulation indicate that the heat transfer rate is significantly affected by the solid volume fraction and slip velocity coefficient at high Reynolds numbers.     

Design,Synthesis, and Fabrication of Chitosan/Hydroxyapatite Composite Scaffold for Use as Bone Replacement Tissue by Sol–Gel Method

Journal of Inorganic and Organometallic Polymers and Materials - Injuries or bone defects are phenomena that are harmful to human health. In the field of bone scaffold tissue engineering,...     

Ranking the key parameters of immersion precipitation process and modeling the resultant membrane structural evolution

Key parameters coupling with the instantaneous nucleation concept (ie, the Big Bang analogy) was used to model immersion precipitation process. The merits of the acquired model were verified via comparing its predictions with experimental results of two well‐prepared and characterized cellulose acetate (CA) and polyacrylonitrile (PAN) membranes. A morphology predictable map, ΔPη^?1 versus ?₁, was constructed, where ΔP, η and ?₁ are osmotic pressure difference between nonsolvent and dope solution, dope viscosity and intruded nonsolvent volume fraction into the dope, respectively. The phase separation map, ΔPη^?1 (proportional with apparent system diffusivity with the unit of time^?1) versus ?₁ showed three regimes which, at least qualitatively, depicted the correct morphological evolution trends of the studied systems. Phase separation in regime one of CA membrane with the longest delayed time or lowest ΔPη^?1, led to bead‐like morphology. CA membrane with the shortest elapsed time or highest ΔPη^?1, separated to finger‐like morphology in regime three. Finally, phase separation in the intermediate regime of CA membrane, ended up to sponge‐like morphology. Phase separation time scales of the PAN membranes versus intruded nonsolvent into the dope solution were located in finger‐like region of the CA membrane, which its downward transition lowered the fingers population. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Artificial microcracking of granites subjected to salt crystallization aging test

Bulletin of Engineering Geology and the Environment - Salt crystallization-induced decay of Vardavard granodiorite and Shirkouh monzogranite, two Iranian building stones, were assessed with two...