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Polymer Electrolyte Membrane Fuel Cells (PEMFC) is an electrochemical device that generates electrical energy from the reactions between hydrogen and oxygen. An effective thermal management is needed to preserve the fuel cell performance and durability. Cooling by water is a conventional approach for PEMFC. Balance between optimal operating temperature, temperature uniformity and fast cooling response is a continuous issue in the thermal management of PEMFC. Various cooling strategies have been proposed for water-cooled PEMFC and an approach to obtain a fast cooling response was tested by feeding the coolant at a high temperature. In this paper, the operating behaviour was characterized from the perspectives of temperature profiles, mean temperature difference, and cooling response time. A 2.4 kW water-cooled PEMFC was used and the electrical load ranged from 40 A–90 A. The operating coolant temperature was set to 50 °C where the maximum stack operating temperature is 60 °C. The stack temperature profiles, cooling response time, mean temperature difference and cooling rates to the load variation was analysed. The analysis showed that the strategy allowed a fast cooling response especially at high current densities, but it also promotes a large temperature gradient across the stack. [ABSTRACT FROM AUTHOR]

Ceramic membranes (CMs) with different pore sizes (0.14 μm CM1, 150 kDa CM2 and 5 kDa CM3) were tested as separators in two-chamber microbial fuel cells (MFCs). The performance and ionic gradient concentration of MFCs using CMs were compared with that of cation exchange membrane (CEM), Nafion 117. MFC with CMs exhibited a higher performance than that of CEM under batch operation. The highest power density of 1790 ± 60 mW/m 2 , columbic efficiency (CE) of 41 ± 10% and internal resistance of 102 ± 13 Ω were obtained for MFC with CM3 under batch mode operation. The highest power density, columbic efficiency and internal resistance of MFC with CEM were found to be 1225 ± 20 mW/m 2 , 21 ± 1% and 400 ± 10 Ω, respectively. The highest performance of MFC with CM3 was expected due to a higher porosity of CM3 (13.8%) compared with that of CM1 (11.0%) and CM2 (11.05%). MFCs operated with catholyte containing salt solution, phosphate buffer basal medium without carbon source and yeast extract (PBBM-SA), generated lower current than with phosphate buffer (PB) as catholyte. This difference was more significant in the MFCs with the CEM Nafion 117 than with ceramic membranes. The non-selective porous ceramic membranes improved the diffusion of protons in the presence of other high concentration cations and resulted in MFC with higher performance. Hence, the porous ceramic membrane is a potential candidate separator for the development of commercial scale MFCs. [ABSTRACT FROM AUTHOR]

Immobilized cell technology is a new technique to produce biogas. In the present study, an immobilized mixed-culture reactor (IMcR) in batch-mode operation was used for the production of hydrogen and methane simultaneously from glucose. Several factors, such as glucose concentration, temperature and fermentation time, were evaluated to determine the optimal conditions for hydrogen and methane production. Gas chromatography with a thermal conductivity detector (GC-TCD) and high-performance liquid chromatography (HPLC) were used to analyse the gas and effluent. The morphologies of the immobilized cells were characterized using scanning electron microscopy (SEM). The optimal conditions for hydrogen and methane production were obtained using a substrate with 5.0 g/L glucose at 60 °C for fermentation times of 48.0 h (hydrogen) and 72.0 h (methane). The maximum yields of hydrogen and methane at these optimal conditions were 37.0 ± 0.0 (×10 −3 ) mol/mol glu and 39.0 ± 0.0 (×10 −3 ) mol/mol glu, respectively. The chemical oxygen demand ( COD ) and pH gradually decreased with increasing fermentation time and temperature. However, the performance of the IMcR decreased over time due to cell damage and microorganism detachment from the cell. In conclusion, the IMcR system is a potential system for the simultaneous production of hydrogen and methane. [ABSTRACT FROM AUTHOR]

A biocathode microbial electrolysis cell (MEC) can be considered as an environmentally friendly and self-generative alternative to an abiocathode MEC for the cleaner production of hydrogen in a novel microbial electrolysis system. For the first time, this research focused on the development of the MEC biocathode out of sulphate-reducing bacteria (SRB) for the purpose of hydrogen production based on the previously proposed hypothesis. SRB were initially enriched from a mixed culture source during the ex-situ SRB enrichment stage. Two different MEC bioathodes- namely, the MEC origin (MEC-O) biocathode and the microbial fuel cell-MEC (MFC-MEC) biocathode- were then developed through two different enrichment procedures during the in-situ SRB enrichment stage. Hydrogen gas was the main product of the MEC-O biocathode with a low detection of methane, while methane was detected as the sole product of the MFC-MEC biocathode system. Therefore, the MEC-O biocathode system was selected during the enhancement stage to increase the biocathode MEC performance. It was shown in the study, that in the enhancement stage of the MEC-O biocathode, the concentration of sodium sulphate in the cathodic medium, the hydrogen supply during the enrichment stage and pH of the cathodic medium could significantly affect the MEC performance in terms of the hydrogen production rate, the onset potential for the hydrogen evolution reaction (HER) and the cathodic charge transfer resistance. The hydrogen production was improved significantly by about 6 times from 0.31 to 1.85 m 3 H 2 /(m 3 d) during the enhancement stage, while the methane production was totally hindered. The linear sweep voltammetry analysis displayed a 430-mV (equal to about 1 kWh/m 3 of energy input) reduction of the HER onset potential in the biocathode system compared to that of a non-inoculated graphite felt cathode. Moreover, the electrochemical impedance spectroscopy showed that the cathodic charge transfer resistance of the MEC biocathode reduced by 300 times compared to that of a non-inoculated graphite felt cathode. [ABSTRACT FROM AUTHOR]

Upscaling bioelectrochemical systems needs a proper operational mode to integrate them to the units operating in pilot and industrial scales. This study conducted a comprehensive investigation on combining the advantages of conventional batch and continuous operational modes in form of a simple and efficient looped configuration system, while reducing the drawbacks of each. In this regard, nine various recirculation batch (RB) systems with various recirculation to reactor volume ratios and with different recirculation flow rates were thoroughly evaluated and compared to the results of batch and continuous modes of operation. Recirculation rate and volume were both effective factors on system performance. The highest power density of 38 W/m 3 was achieved amongst the various studied RB systems, which showed 40% and 32% of improvement compared to batch and continuous systems respectively. Cyclic voltammetry test approved 3.6 and 2.1 times increment of oxidation peak in the optimised RB system compared to the batch and continuous systems respectively. Moreover, electrochemical impedance spectroscopy analysis showed the significant reduction of charge transfer resistance in RB system. Rather than high energy outputs, the proposed operational mode showed promising results on reducing the waste treatment duration by 12.5 and 3 times compared to the batch and continuous systems respectively while achieving the COD and pH close to the releasing requirements. [ABSTRACT FROM AUTHOR]

In this study, a single layer graphene oxide is successfully synthesized and used as a nano-filler in a self-fabricated sulfonated polyether ether ketone (SPEEK) to make a composite proton exchange membrane, graphene oxide/SPEEK (GO-SPEEK). The properties of GO-SPEEK, Nafion ® 117 and SPEEK are then compared to ascertain their selectivity to proton transport compared to both water and oxygen. GO-SPEEK was found to have the highest selectivity with a water uptake of 85.4%, proton conductivity of 1.48 × 10 −3 S cm −1 and oxygen diffusion coefficient of 1.154 × 10 −6 cm 2 s −1 . During tests in Microbial Fuel Cells (MFCs), the MFC system with Nafion ® 117 membrane produces the highest maximum power density (1013 mW m −2 ) followed by the MFCs with GO-SPEEK (902 mW m -2 ) and SPEEK (812 mW m −2 ) membranes. On the other hand, the MFC with GO-SPEEK membrane produces the highest coulombic efficiency (16.88%). The high efficiency and comparable maximum power density which is produced by the MFC with GO-SPEEK membrane, shows that GO-SPEEK membrane is a promising alternative membrane to replace the expensive Nafion ® 117 as a separator in the MFC. [ABSTRACT FROM AUTHOR]

The application of the biocathode for hydrogen production in a Microbial Electrolysis Cell (MEC) is a promising alternative to precious metal catalysts. However, biocathodes are still in the improvement and development stages and require a deep understanding of the bioelectrochemical mechanisms involved. In this review, the results of biocathode MEC experiments and studies in the literature on biocathode development methods were summarised; furthermore, used carbon sources and substrates in biocathodic compartments and microbial communities on the biocathode were characterised. Based on the respective articles that were examined, biocathode MEC may be developed and initiated in one of three categories: (I) half biological two-chambered biocathode MEC; (II) full biological two-chambered biocathode MEC; (III) full biological single-chambered biocathode MEC. In addition, various mixed cultures capable of producing hydrogen were identified, and predominant species were detected. Desulfovibrio paquesii , Desulfovibrio G11 and Geobacter sulfurreducens were also successfully tested as pure cultures in biocathode MECs. Further studies are necessary for an acute and experimental comprehension of the transfer of electrons and the energy conservation mechanism involved in the biocathode MEC, which may provide a cost-effective and practical implementation of this technology. [ABSTRACT FROM AUTHOR]

The spray drying process is considered a conventional method to convert liquids to powders with some but at an acceptable level of degradation and oxidation of volatile compounds. Spray drying is based on the preparation, homogenization, atomization, dispersion and subsequently dehydration of the solution. Wall deposition is a key processing problem in the spray dryer particles that indirectly affects the quality and quantity of the product. The degree of wall deposition is affected by several factors including operating parameters, type and size of spray dryer and the spray dryer wall properties. The development of wall depositions in the spray dryer deteriorates the yield of the products and hence increases the costs of manufacturing and maintenance. And constructive models are very resourceful in understanding the mechanism of wall deposition which will result in direct economic benefits to the food industry. The aim of this review is to give a physical and chemical description of the wall deposition mechanism and introduce the classified models to simulate and visualize this behavior in spray dryers. [ABSTRACT FROM AUTHOR]

Direct carbon fuel cell (DCFC) is a high-temperature fuel cell which operates directly from solid carbon. From the past research, it is proven to be capable of achieving nearly 100% theoretical efficiency. Thus, DCFC commercialization would change the course of power generation industry into a more sustainable and environmental friendly means of generating electricity. Although biomass constitutes of carbon (C), they exist in different forms, making them unsuitable to be used directly as fuel in DCFC. For that purpose, heat treatment such as pyrolysis is utilized in converting the biomass into biochar which possesses slightly different physicochemical properties, such as higher C% and large surface area. It was found that, palm shell pyrolyzed at 750 °C, with heating rate of 10 °C/min and residence time of 1 hour produced a highly potential biochar for DCFC application. [ABSTRACT FROM AUTHOR]

Abstract: Oxygen Reduction Reactions (ORR) are one of the main factors of major potential loss in low temperature fuel cells, such as microbial fuel cells and proton exchange membrane fuel cells. Various studies in the past decade have focused on determining a method to reduce the over potential of ORR and to replace the conventional costly Pt catalyst in both types of fuel cells. This review outlines important classes of abiotic catalysts and biocatalysts as electrochemical oxygen reduction reaction catalysts in microbial fuel cells. It was shown that manganese oxide and metal macrocycle compounds are good candidates for Pt catalyst replacements due to their high catalytic activity. Moreover, nitrogen doped nanocarbon material and electroconductive polymers are proven to have electrocatalytic activity, but further optimization is required if they are to replace Pt catalysts. A more interesting alternative is the use of bacteria as a biocatalyst in biocathodes, where the ORR is facilitated by bacterial metabolism within the biofilm formed on the cathode. More fundamental work is needed to understand the factors affecting the performance of the biocathode in order to improve the performance of the microbial fuel cells. [Copyright &y& Elsevier]

Abstract: The microbial fuel cell (MFC) is a very promising technology for generating electrical energy from anaerobic fermentation of organic and inorganic matter in wastewater using microorganisms as biocatalysts while simultaneously treating the wastewater. However, the overall low performance of the MFC compared to other more established fuel cell technologies and the high cost of its components compared to the low value of the wastewater it treated, are the two major barriers to commercialization. In recent years, MFC’s performance has been improved by using among other things, cheaper nano-composite materials such as nano-structured carbon in the electrodes that are more conductive and mechanically stabile with larger surface area and higher electrochemical catalytic activity compared to the conventional Pt on carbon. However, the nano-structured carbon electrodes have also been reported to have some serious drawbacks such as toxicity to the microbial consortium in the biofilm attached on its surface, which reduces performance of the MFC. This paper tries to highlight the broad-spectrum of different nano-composite materials that have been used as electrode material in the MFC in recent years. [Copyright &y& Elsevier]

Abstract: The urgent need to address the twin problems of the modern world, energy insecurity caused by fossil fuel depletion and climate change caused by global warming from carbon dioxide emission and the greenhouse effect has led to among other things the emergence of fuel cell technology as a green energy technology that could generate cleaner and highly efficient energy. Microbial fuel cell (MFC), an emerging dual function, bioenergy conversion device, that not only treats wastewater but also generates electricity, has caught much attention of both fuel cell and bioenergy researchers. Until today, the commercialization of MFC has been restricted mainly due to its high cost and low power density. Many challenges still remain to be conquered, in order to improve the performance and commercialization of MFC. It is generally known that ion exchange membrane in MFC is one of the main factors that could significantly affect the cost and performance of MFC. This review provides an overview of several important membrane characteristics, which include membrane internal resistance, membrane biofouling, pH splitting, oxygen diffusion, and substrate loss across the membrane. The negative impact of these characteristics on MFC performance, are discussed. Moreover, this review concerns the types of membrane that have been applied in MFC systems, such as cation exchange membranes, anion exchange membranes, membraneless technology, polymer/composite membranes, and porous membranes. The future trend of membrane development for MFC applications is also discussed. [Copyright &y& Elsevier]

Abstract: 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%. [Copyright &y& Elsevier]

Abstract: Anode materials are important in the power generation of microbial fuel cell. In this study, polyaniline was used as a conducting polymer anode in two chambers MFC. XPS and SEM were used for the characterization of functional groups of anode materials and the morphology. The power generation of microbial fuel cell was elevated by the modification of anode by nitric acid, ethylenediamine, and diethanolamine. The time that MFC reaches its maximum power generation was shortened by modification. Moreover the SEM photos prove that, it causes better attachment of microorganisms as biocatalysts on electrode surface. The best performance of among the MFCs with different anode electrodes, was the system working by polyaniline modified by ethylenediamine as that generated power of 136.2 mW/m2 with a 21.3% Coulombic efficiency. [Copyright &y& Elsevier]

Abstract: Deposition behavior of spray dried full cream milk, skim milk and whey particles were observed in a pilot scale dryer. Particle surface dominated with fats exhibit gradual decrease in deposition fluxes when transition from the initial adhesion to the subsequent cohesion mechanism. Whey protein, however, displayed significant differences in the adhesion and cohesion fluxes. Reduction of particle deposition on low energy chamber wall surface is more significant for the hydrophobic whey particles. Further analysis shows that the reduction in droplet–wall contact energy is larger for the more hydrophobic droplet, delineating weaker adhesion interaction. The results suggest that the hydrophobicity of the depositing particles in an important consideration when using lower chamber wall with lower surface energy. This is in addition to the effect of particle rigidity and deposition strength as reported previously. [Copyright &y& Elsevier]

Abstract: Optical and photoelectrochemical (PEC) properties of a TiO2 thin film electrode doped with a new variation of ruthenium–(4,4′dimethyl-2,2′-bipyridine)–isothiocyanato–tungsten[bis-(phenyl-1,2-ethilenodithiolenic)] bimetallic complex (BM) were investigated. Physical adsorption process was used to immobilise the BM on the TiO2 thin film. Crystalline structure and surface morphology of the thin films were examined using scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy-dispersive X-ray (EDX) techniques. N3 commercial dye was also used as a dopant to the TiO2 films for comparison. Light absorption spectra and bandgap energy of the thin films were determined using UV–vis spectroscopy. Light absorption of the TiO2 thin film doped with BM was better than the TiO2 doped with the N3 commercial dye. Band edges of the TiO2 thin film and the BM were determined via cyclic voltammetry (CV) measurements. Top-edge of the BM valence band (VB) was more positive than the bottom edge of the conduction band (CB) of the TiO2 film (vs. NHE). PEC analysis indicated that photocurrent of TiO2 doped with the BM electrode was higher than TiO2 doped with the N3 in the beginning of illumination process, but the performance was defeated after a while. Based on the optical properties and the PEC analyses, BM has potential to be used as dye sensitisers for a PEC cell. [Copyright &y& Elsevier]

Abstract: Momentous amount of glycerol is produced as a by-product during bio-diesel production by the transesterification of vegetable oils, which are available at low cost in large supply from renewable raw materials. As hydrogen is a clean energy carrier, conversion of glycerol to hydrogen is one among the most attractive ways to make use of glycerol. In this study, the catalytic production of hydrogen by steam reforming of glycerol has been experimentally performed in a fixed-bed reactor. The performance of this process was evaluated over 10wt% Ni supported alumina xerogel catalysts. Ni is impregnated over alumina xerogel which was pretreated at different temperatures of 700°C, 800°C, 900°C and 1000°C. For a comparative purpose, the steam reforming experiments were conducted under same operating conditions, i.e., reaction temperature of 600°C, atmospheric pressure and 1:6 glycerol to water molar ratio where we are getting 100% glycerol conversion in all the runs. The results showed that the hydrogen production increased with the increase in the treatment temperature of the support. The highest amount of hydrogen produced was attained over 10wt% Ni doped alumina xerogel pretreated at 1000°C. The catalytic enhancement over the best catalyst system is due to the thermal stability of the support which is treated at highest temperature. Sol gel method of preparation is implemented in the support development and different catalyst systems used in the reforming process were characterized using X-ray powder diffraction, BET surface area and SEM analysis. [Copyright &y& Elsevier]

Abstract: Bilayer photoanodes were prepared onto glass substrates (FTO) in order to improve generated photocurrents using UV–vis light by water splitting process. A comparative study of photocatalytic was performed over the films surface using Fe2O3, WO3 and mixture of bicomponents (Fe2O3:WO3). Different types of films were prepared using Fe2O3, WO3 and bicomponents (mixture) on FTO substrates. The films were grown by sol gel method with the PEG-300 as the structure-directing agent. The photo-generated of the samples were determined by measuring the currents and voltages under illumination of UV–vis light. The morphology, structure and related composition distribution of the films have been characterized by SEM, XRD and EDX respectively. Photocurrent measurements indicated surface roughness as the effective parameter in this study. The deposited surfaces by bicomponents or mixture are flat without any feature on the surface while the deposited surfaces by WO3 appears rough surface as small round (egg-shaped particles) and cauliflower-like. The surface deposited by Fe2O3 show rough no as well as WO3 surface. The deposited surfaces by WO3 reveal the higher value of photocurrent measurement due to surface roughness. Indeed, the roughness can be effective in increasing contact surface area between film and electrolyte and diffuse reflection (light scattering effect). The solution (Fe2O3:WO3) shows the low photocurrent value in compare to WO3 and Fe2O3 hat it may be due to decomposition the compound at 450±1°C to iron-tungstate Fe2(WO4)3. [Copyright &y& Elsevier]

This study aims to develop a decision model to optimise the oil palm biomass value chains by minimising the environmental impact whiles generating economy value from their bioproducts. The model considers two major components, namely, a fuzzy analytic hierarchy (FAHP) framework and a multi-objective optimisation model. Both components will be used by integrating the priorities of the environmental and economic impacts obtained from experts' judgement with the multi-objective optimisation model to generate an optimal solution based on expert's judgement. The framework used to study different case study for the oil palm industry in Peninsular Malaysia. Results show that a maximum profit of 267,116,398 USD per year can be achieved. However, to minimise the environmental impact, a 34% cut of the profit is needed to reduce 91% of CO 2 emissions generated and 97% of water consumption. Moreover, the model generates optimal pathways by selecting the processing facilities that are needed in the value chain to achieve the objectives. The biomass or bio-product distribution networks around Peninsular Malaysia are also presented in this paper. Several scenarios are discussed to observe the effects on the optimal value chain solutions by manipulating the production level. On the basis of the results, the interactions of the environment–food–energy–water nexus are investigated. Therefore, this study can contribute to the improvement of oil palm industry policies while addressing sustainability issues through the proposed value chain model. • Demonstrate economic optimisation of oil palm biomass value chain. • Biomass value chain with the least negative impacts to the elements in the nexus. • Experts' opinions are incorporated into decision-making model. • Uncover the interactions between biomass value chain with elements in the nexus. [ABSTRACT FROM AUTHOR]

The bioanode is important for a microbial electrolysis cell (MEC) and its robustness to maintain its catalytic activity affects the performance of the whole system. Bioanodes enriched at a potential of +0.2 V (vs. standard hydrogen electrode) were able to sustain their oxidation activity when the anode potential was varied from −0.3 up to +1.0 V. Chronoamperometric test revealed that the bioanode produced peak current density of 0.36 A/m 2 and 0.37 A/m 2 at applied potential 0 and +0.6 V, respectively. Meanwhile hydrogen production at the biocathode was proportional to the applied potential, in the range from −0.5 to −1.0 V. The highest production rate was 7.4 L H 2 /(m 2 cathode area)/day at −1.0 V cathode potential. A limited current output at the bioanode could halt the biocathode capability to generate hydrogen. Therefore maximum applied potential that can be applied to the biocathode was calculated as −0.84 V without overloading the bioanode. [ABSTRACT FROM AUTHOR]

Fabrication of solid oxide fuel cell (SOFC) components via a simple and economical technique is critical to lower the overall manufacturing cost of SOFCs. Thus, screen-printing is widely used to fabricate SOFC components having thickness in the range of 10–100 µm. Fabrication of optimized screen-printing inks is highly significant for the production of high quality films with improved performance. The effect of solid, binder, solvent and dispersant on the ink rheological properties and performance of resultant films must be deeply understood for the fabrication of optimized screen-printing inks. These effects can be optimized by measuring the rheological properties of inks such as viscosity, yield stress, thixotropy and viscoelasticity for application at a specific printer setting. Understanding the relationship between the composition and rheology of the inks may enhance the properties and performance of the resultant screen-printed films. Furthermore, these parameters can be correlated to the film properties such as mechanical strength, electrical conductivity and electrochemical properties of the resultant films. The focus of this review paper is to understand the underpinning science of ink rheology and processing conditions of screen-printing inks for the fabrication of high performance SOFC electrodes and/or electrolyte. [ABSTRACT FROM AUTHOR]

The cathode reaction is one of the most important limiting factors in bioelectrochemical systems even with precious metal catalysts. Since aerobic bacteria have a much higher affinity for oxygen than any known abiotic cathode catalysts, the performance of a microbial fuel cell can be improved through the use of electrochemically-active oxygen-reducing bacteria acting as the cathode catalyst. These consume electrons available from the electrode to reduce the electron acceptors present, probably conserving energy for growth. Anaerobic bacteria reduce protons to hydrogen in microbial electrolysis cells (MECs). These aerobic and anaerobic bacterial activities resemble those catalyzing microbially-influenced corrosion (MIC). Sulfate-reducing bacteria and homoacetogens have been identified in MEC biocathodes. For sustainable operation, microbes in a biocathode should conserve energy during such electron-consuming reactions probably by similar mechanisms as those occurring in MIC. A novel hypothesis is proposed here which explains how energy can be conserved by microbes in MEC biocathodes. [ABSTRACT FROM AUTHOR]