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Proton Exchange Membrane Fuel Cell (PEMFC) is powered by chemical reaction of oxygen gas with hydrogen gas as main fuel, to produce electricity and water, while operating at lower temperatures, which make it easy to operate and handle. PEMFC can power a large range of electrical equipment, from electronics devices to cars, buses, submarines as well as stationary power plants. This study presented the procedure of computational simulation and modelling of PEMFC with ANSYS Fluent. The geometry was designed with ANSYS design modeler, while meshing was performed in workbench meshing and solver in Fluent. For this study, two models with isothermal and non-isothermal conditions were considered. The isothermal condition is set at 323K and operated at 1 atm whereas the non-isothermal condition is set to operate at 353K and 3 atm. The voltage values were varying from 0.4V to 0.9V, where the open circuit voltage was set at 1.05V. The polarization curve of the PEMFC indicated the performance of the fuel cell, which also is the focus of this study. The effects of temperature and pressure towards the performance of the PEMFC were also studied and evaluated.

Cu-Zn-V-Al oxide composite catalysts were prepared using a co-precipitation method to investigate hydrogen and carbon monoxide yield of a methanol reforming reaction. The mass compositions of metals were initially determined on the Simplex Centroid statistical design. The effects of various metal compositions on the physicochemical properties of the catalyst were studied via X-ray diffractogram (XRD), temperature-programmed reduction (TPR) analyses, and reaction. XRD revealed crystals in the samples. Crystalline CuO in Cu30V30Al40 formed with the addition of zinc oxide at the metal loading below 30 wt%. A combination of zinc oxide and vanadia, however, had no Zn-V complex crystal but its scanning electron microscopy image showed the formation of string structures (AS). The catalyst that contained the AS exhibited a broad hydrogen reduction peak in the TPR analysis. Vanadium at a loading below 40 wt% with various zinc and cuprum compositions also formed small ASs and exhibited single TPR peaks. A reaction yield study revealed the optimum compositions of metal oxides when the data was fitted by response surface plots. The catalysts with high content of AS were not at the peaks however. Cu-Zn based catalysts showed the highest hydrogen yield for the reaction temperature of between 150 oC to 225 oC and vanadia-promoted catalyst with AS only appeared to be the optimum catalyst at the higher temperature. ABSTRAK: Mangkin komposit oksida Cu-Zn-V-Al disediakan menggunakan kaedah pemendakan bersama untuk mengkaji hasil hidrogen dan karbon monoksida daripada tindak balas pembentukan semula metanol. Komposisi jisim logam-logam dikenal pasti terlebih dahulu menggunakan reka bentuk statistik Simplex Centroid. Pelbagai kesan komposisi logam terhadap sifat-sifat mangkin kimia-fizikal dikaji menerusi analisis-analisis pembelauan sinar-X (XRD) dan program penurunan suhu teratur (TPR), dan tindak balas kimia. Hasil analisis XRD menzahirkan kristal pada sampel-sampel. Hablur CuO terbentuk dalam Cu30V30Al40 dengan penambahan zink oksida pada muatan logam kurang daripada 30% berat. Gabungan zink oksida dan vanadia walau bagaimanapun tidak menghasilkan hablur kompleks Zn-V, namun imbasan imej mikroskop elektron menunjukkan pembentukan struktur tetali (AS). Mangkin yang mengandungi AS menunjukkan penurunan puncak hidrogen yang lebar dalam analisis TPR. Vanadium pada muatan berat logam kurang daripada 40% berbanding komposisi zink dan kuprum juga membentuk AS kecil dan menghasilkan puncak-puncak TPR tunggal. Hasil tindak balas kajian menunjukkan komposisi optimum oksida logam apabila data ujikaji dipadankan dengan menggunakan plot permukaan respon. Mangkin yang mempunyai kandungan AS tertinggi bagaimanapun tidak berada pada puncak. Mangkin berasaskan Cu-Zn menunjukkan hasil hidrogen tertinggi bagi suhu tindak balas antara 150 oC hingga 225 oC dan mangkin yang ditambah vanadia bersama AS pula muncul sebagai mangkin optimum pada suhu lebih tinggi.

Plasticisers have been widely used as additives in polymer applications, including pharmaceuticals, food processing, and electrochemical sensing, to improve the mechanical and physicochemical properties of the polymers. Recent developments using alternatives to the conventional phthalate ester plasticisers, such as water, ionic liquids (ILs) and deep eutectic solvents (DES), have opened new avenues for expanding plasticiser use into other potential areas such as ion exchange membranes. Owing to the unique properties of plasticisers that promote a higher amount of amorphous phase within the intermolecular structural of the polymer, combinations of plasticisers and polymers improve a polymeric film's ionic conductivity while maintaining film flexibility and thermal stability. Hence, this review paper intends to provide an insight on the applications of conventional and alternative plasticisers in various areas, as well as to address the working mechanism of plasticisers within polymer films. Most importantly, this paper highlights recent developments incorporating plasticisers in proton exchange membranes and the future potential of these materials. The outlook presented here demonstrates that some of the challenges faced during the fabrication of ion exchange membranes, which are alternatives to Nafion membranes, can be overcome.

Nitrogen-doped carbon materials have great potential as metal-free catalysts in a variety of applications, including batteries, supercapacitors and fuel cells. In this paper, nitrogen-doped graphene (NG) catalysts were synthesized via thermal annealing with varying ratios of graphite oxide and melamine precursors. The NG catalysts were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The prepared NG catalysts were folded transparent films with wrinkles. The nitrogen content of the NG catalysts calculated from XPS varied from approximately 4.18%–7.40%. NG1 displayed the highest performance, with a remarkable reduction peak of 0.39 mA cm−2 at −0.21 V vs. Ag/AgCl in alkaline media. A direct correlation between total nitrogen content and catalytic activity was not observed, but catalytic activity was dependent on the nature of the nitrogen configurations. XPS analysis revealed that the high catalytic activity of NG1 is attributable to the configuration of the graphitic N-type nitrogen.

This research involves the rare utilisation of the kapok fibre (Ceiba pentandra) as a raw material for the fabrication of cellulose nanocrystal (CNC) and self-assembled CNC membranes. The isolation of CNC from Ceiba pentandra began with the extraction of cellulose via the chemical alkali extraction by using 5wt% NaOH, followed by the typical acidified bleaching method and, finally, the CNC production through acid hydrolysis with 60wt% H2SO4 at the optimum time of 60min. The prepared CNC was then employed for the preparation of self-assembled membrane through the water suspension casting evaporation technique. The obtained CNC membrane was characterised in terms of its composition, crystallinity, thermal stability, as well as, structural and morphological features with the use of several techniques including FTIR, XRD, AFM, TEM, FESEM, and TGA. The FESEM and AFM analyses had illustrated the achievement of a self-assembled CNC membrane with a smooth surface and a well-distributed nano-porous structure, with the porosity of 52.82±7.79%. In addition, the findings proved that the self-assembled CNC membrane displayed good adsorption capability indicated by the recorded efficiency of 79% and 85% for 10mg/L and 5mg/L of methylene blue in an aqueous solution, respectively.

The effect of adding silica (SiO2) to a mixed-salt solid acid composite, CsH2PO4/NaH2PO4, was studied via conductivity measurements, thermal analyses and X-ray diffraction. The conductivity value of the composites ranged from 1.1 × 10−4 S cm−1 to 7.6 × 10−3 S cm−1 for temperatures from 210 °C to 250 °C, respectively. Adding NaH2PO4 to the composite reduced the conductivity value at 230 °C due to the decomposition of NaH2PO4, which initiated at 210 °C. Dehydration of CsH2PO4 was evident at 230 °C and 270 °C, while the superprotonic phase transition was not observed. Dehydration was detected for NaH2PO4 at temperatures above 210 °C, but a thermally stable composite was produced by mixing it with CsH2PO4 and SiO2. An X-ray diffraction analysis confirmed the existence of solid acid solutions for the composites consisting of NaH2PO4:CsH2PO4 and SiO2:CsH2PO4 in molar ratios of 1:10 to 3:10. The presence of SiO2 partially obstructed the dehydration of the composite, as the diffraction intensity of the dehydration by-product Cs2H2P2O7 decreased at the end of the thermal treatment.

Carbon powder in the gas diffusion layer (GDL) contained in the membrane electrode assembly (MEA) has an important role in the flow of electrons and reactant gas. Meanwhile, the method of making the electrode is one of the many studies conducted to determine the most appropriate method to use. Comparative study of the performance of proton exchange membrane fuel cell (PEMFC) electrodes with different carbon powder content (vulcan XC-72) in the GDL and methods of manufacture of the electrode between casting and spraying method has been carried out. The spraying method consists of one layer and three layer of catalyst layer (CL). The content of carbon powder in the GDL as much as 3 mg cm - 2 has a better performance compared to 1.5 mg cm - 2 with an increase of 177.78% current density at 0.6 V. Meanwhile, the manufacture of CL with three-layer spraying method has better performance compared with one-layer spraying and casting method. Key words: casting method, spraying method, catalyst layer (CL), GDL. Abstrak (Indonesian): Serbuk karbon pada lapisan difusi gas (LDG) yang menyusun elektroda membran memiliki peran penting dalam mengatur aliran elektron dan gas reaktan. Pada sisi lain metoda pembuatan elektroda adalah salah satu dari banyak studi yang dilakukan untuk menentukan metoda yang paling sesuai yang dapat dikerjakan. Telah dikerjakan studi komparatif kinerja membran penukar proton pada elektroda sel bahan bakar dengan kandungan serbuk karbon (vulcan XC-72) dalam LDG yang bervariasi dan studi komparasi metoda pembuatan elektroda secara tuang dan semprot. Metoda semprot dikerjakan dalam dua variasi yakni pembuatan lapisan katalis (LK) satu dan tiga lapisan. Kandungan serbuk karbon dalam LDG hingga 3 mg cm -2 memiliki kinerja lebih baik dibanding 1,5 mg cm -2 dengan peningkatan kerapatan arus 17,78% pada 0,6 V. Pembuatan LK dengan metoda semprot tiga lapisan memperlihatkan kinerja terbaik dibanding metoda semprot satu lapisan dan metoda tuang. Kata kunci: metode casting, metode spraying, layer katalis, GDL

Organic solar cells are photovoltaic cells and a type of green energy source with great potential application due to low production costs and mechanical flexibility. This study focused on t...

One of the obstacles to the commercialisation of fuel cells is the high cost of noble metals, such as platinum, that are used as electrocatalysts. Silver-incorporated nitrogen-doped reduced graphene oxide (Ag/N-rGO) has been synthesised through the simple annealing of metal salts with graphene oxide and melamine. The presence of silver and nitrogen atoms in Ag/N-rGO was confirmed by X-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS) analysis. Both the XPS and EDS results showed a higher Ag loading on the N-rGO surface compared with the rGO surface. Transmission electron microscopy (TEM) images revealed a wide size distribution of Ag particles loaded on the N-rGO surface. Electrochemical results indicate that N-rGO is a better support for Ag than rGO. Cyclic voltammetry (CV) and linear sweep voltammetry (LSV) results indicate that Ag/N-rGO is a potential ORR catalyst candidate in alkaline as it exhibited an onset potential of −0.15 V vs. Ag/AgCl and a limiting diffusion current density of −4.38 mA cm −2 with four electron pathways. In addition, Ag/N-rGO also showed better methanol tolerance than Pt/C.

The aim of this review was to analyze/investigate the synthesis, properties, and applications of polyvinyl alcohol–halloysite nanotubes (PVA–HNT), and their nanocomposites. Different polymers with versatile properties are attractive because of their introduction and potential uses in many fields. Synthetic polymers, such as PVA, natural polymers like alginate, starch, chitosan, or any material with these components have prominent status as important and degradable materials with biocompatibility properties. These materials have been developed in the 1980s and are remarkable because of their recyclability and consideration of the natural continuation of their physical and chemical properties. The fabrication of PVA–HNT nanocomposites can be a potential way to address some of PVA’s limitations. Such nanocomposites have excellent mechanical properties and thermal stability. PVA–HNT nanocomposites have been reported earlier, but without proper HNT individualization and PVA modifications. The properties of PVA–HNT for medicinal and biomedical use are attracting an increasing amount of attention for medical applications, such as wound dressings, drug delivery, targeted-tissue transportation systems, and soft biomaterial implants. The demand for alternative polymeric medical devices has also increased substantially around the world. This paper reviews individualized HNT addition along with crosslinking of PVA for various biomedical applications that have been previously reported in literature, thereby showing the attainability, modification of characteristics, and goals underlying the blending process with PVA.

The performance characteristics of proton exchange membrane fuel cells (PEMFCs) can be affected by a degradation of the membrane-electrode-assembly (MEA). In this paper, the performance degradation of MEA in a single cell PEMFC was examined at 80 °C and a backpressure of 10 psi after 100 h of operational time using open circuit voltage (OCV) conditions. A control experiment was conducted by testing the MEA at ambient temperature without backpressure. Both electrochemical impedance spectroscopy (EIS) and an OCV analysis showed that both the conductivity and the performance of the cell operating at 80 °C were less than the control values after 100 h of operation. In contrast, an application of 10 psi of backpressure improved the cell conductivity and can maintain OCV in compare with ambient and 80 °C conditions. Characterizations of the pre- and post-operation of the MEA (cathode, anode and membrane) by scanning electron microscope-energy-dispersive X-ray spectroscopy (SEM-EDX), transmission electron microscopy (TEM) and X-ray diffraction (XRD) showed that the MEA performance degradation at 80 °C after 100 h resulted mainly from carbon corrosion combined with Pt agglomeration and dissolution, producing a PtS compound with reduced activity at both the cathode and the anode and also drying and cracking of the membrane.

Vanadium pentoxide nanoparticles were synthesized using a solvo-thermal method and were characterized via X-ray powder diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). The ozonation of palm oil was performed by using vanadium pentoxide nanoparticles as catalysts to synthesize ethyl malonate. This procedure presented several advantages, such as simple operation for a precise ozonation, excellent yield, short reaction times and reusability because of the recyclability of palm oil. Ethyl malonate was synthesized via the one-step ozonolysis of palm oil and was spectroscopically characterized using gas chromatography-mass spectroscopy (GC-MS).

This paper presents a comparison study on thermal performance conic cut twist tape inserts in laminar flow of nanofluids through a constant heat fluxed tube. Three tape configurations, namely, quadrant cut twisted tape (QCT), parabolic half cut twisted tape (PCT), and triangular cut twisted (VCT) of twist ratioy= 2.93 and cut depthde= 0.5 cm were used with 1% and 2% volume concentration of SiO2/water and TiO2/water nanofluids. Typical twist tape with twist ratio ofy= 2.93 was used for comparison. The results show that the heat transfer was enhanced by increasing of Reynolds number and nanoparticles concentration of nanofluid. The results have also revealed that the use of twist tape enhanced the heat transfer coefficient significantly and maximum heat transfer enhancement was achieved by the presence of triangular cut twist tape insert with 2% volume concentration of SiO2nanofluid. Over the range investigated, the maximum thermal performance factor of 5.13 is found with the simultaneous use of the SiO2nanofluid at 2% volume concentration VCT at Reynolds number of 220. Furthermore, new empirical correlations for Nusselt number, friction factor, and thermal performance factor are developed and reported.

Direct methanol fuel cell (DMFC) durability tests were conducted in three different operational modes: continuous operation with constant load (LT1), on–off operation with constant load (LT2) and on–off operation with variable load (LT3). Porous carbon nanofiber (CNF) anode layers were employed in three sets of single passive DMFCs; each membrane electrode assembly (MEA) was run continuously in durability testing for 3000 h. The objective of this study is to investigate the degradation mechanisms in an MEA with a porous CNF anode layer under different modes of operation. The polarization curves of single passive DMFCs before and after durability tests were compared. The degradation of DMFC performance under the cyclic LT1 mode was much more severe than that of LT2 and LT3 operation. The loss of maximum power density after degradation tests was 49.5%, 28.4% and 43.7% for LT1, LT2 and LT3, respectively. TEM, SEM and EDS mapping were used to investigate the causes of degradation. The lower power loss for LT2 was mainly attributed to the reversible degradation caused by poor water discharge, which thus reduced the air supply. Catalyst agglomeration was especially observed in LT1 and LT3 and is related to carbon corrosion due to possible fuel starvation. The loss of active catalyst area was a major cause of performance degradation in LT1 and LT3. In addition to this, the dissolution and migration of Ru catalyst from the anode to cathode was identified and correlated with degraded cell performance. In the DMFC, the carbon nanofiber anode catalyst support exhibited higher performance stability with less catalyst agglomeration than the cathode catalyst support, carbon black. This study helps understand and elucidate the failure mechanism of MEAs, which could thus help to increase the lifetime of DMFCs.

A combination between the nanostructured photocatalyst and cellulose-based materials promotes a new functionality of cellulose towards the development of new bio-hybrid materials for various applications especially in water treatment and renewable energy. The excellent compatibility and association between nanostructured photocatalyst and cellulose-based materials was induced by bio-combability and high hydrophilicity of the cellulose components. The electron rich hydroxyl group of celluloses helps to promote superior interaction with photocatalyst. The formation of bio-hybrid nanostructured are attaining huge interest nowadays due to the synergistic properties of individual cellulose-based material and photocatalyst nanoparticles. Therefore, in this review we introduce some cellulose-based material and discusses its compatibility with nanostructured photocatalyst in terms of physical and chemical properties. In addition, we gather information and evidence on the fabrication techniques of cellulose-based hybrid nanostructured photocatalyst and its recent application in the field of water treatment and renewable energy.

Metal-free nitrogen-doped carbon nanotube (NCNT) catalysts were synthesised via chemical vapour deposition with ethylenediamine and iron phthalocyanine. The electrochemically active NCNT was studied via thin-film rotating-ring disk voltamogram analysis to elucidate the optimum loading of catalysts for oxygen reduction reaction (ORR) in 0.1 M KOH electrolyte. In this study, the activity and stability of NCNT at elevated temperature were investigated. The current limiting plateau was achieved with loading above 500 μg/cm 2 on glassy carbon tip with insignificant change in onset potential (c.a. +0.9 V vs RHE). The highest electron transfer number of 3.90 was obtained and it was found comparable to n = 3.95 on 130 μg/cm 2 Pt/C catalysts. The subjection to cell's temperature from 298 K to 343 K showed improved activity and was found stable above 323 K.

Malonic acid ester was synthesized via the one-step ozonolysis of palm olein. Malonic acid ester was spectroscopically characterized using gas chromatography mass spectroscopy (GC-MS). Tungsten oxide nanoparticles were used as the catalyst, which was characterized via X-ray powder diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). Tungsten oxide provided several advantages as a catalyst for the esterification malonic acid such as simple operation for a precise ozonation method, an excellent yield of approximately 10%, short reaction times of 2 h, and reusability due to its recyclability.

The efficiency of Schiff base derived from 4-aminoantipyrine, namely 2-(1,5-dimethyl-4-(2-methylbenzylidene)amino)-2-phenyl-1H-pyrazol-3(2H)-ylidene) hydrazinecarbothioamide as a corrosion inhibitor on mild steel in 1.0 M H2SO4 was investigated using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PD) and electrochemical frequently modulation (EFM) in addition to the adsorption isotherm, corrosion kinetic parameters and scanning electron microscopy (SEM). The results showed that this inhibitor behaved as a good corrosion inhibitor, even at low concentration, with a mean efficiency of 93% and, also, a reduction of the inhibition efficiency as the solution temperature increases. A polarization technique and EIS were tested for different concentrations and different temperatures to reveal that this compound is adsorbed on the mild steel, therefore blocking the active sites, and the adsorption follows the Langmuir adsorption isotherm model. The excellent inhibition effectiveness of 2-(1,5-dimethyl-4-(2-methylbenzylidene)amino)-2-phenyl-1H-pyrazol-3(2H)-ylidene)hydrazinecarbothioamide was also verified by scanning electron microscope (SEM).

Three anode electrodes containing Pt–Ru Black as a catalyst were fabricated with a porous layer made with different carbon materials: carbon black (CB), carbon nanofiber (CNF) and a combination of both carbon materials (CB + CNF). The carbon-based porous layer was coated onto a carbon cloth with PTFE pre-treatment for delivering hydrophobic properties and applied in direct methanol fuel cells (DMFCs). Characterisation of electrochemical properties for three different anode electrodes was performed with cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) at room temperature in a half-cell configuration. The evolution of the surface morphology of diffusion layer and electrodes was characterised by using variable-pressure scanning electron microscopy (VP-SEM). The electrochemical results indicate that electrode with CNF layer showed the highest current densities compared to CB and CB + CNF with the same catalyst loading. VP-SEM measurements show the network formation within the structure, which could facilitate the methanol mass transfer and improve the catalyst efficiency. The electrodes were applied to a single-cell DMFC, and the cell performance was experimentally investigated under passive operating mode and room temperature. A maximum power density of 23.0 mW cm −2 at a current density of 88.0 mA cm −2 with a 3 M dilute methanol solution was achieved. The results show that the electrodes with a CNF layer could improve the performance of DMFC as compared with commercially used CB and prove it’s potentially application in DMFC technology especially for portable power source applications due to several advantages as followings: operating at low concentration of methanol, operating at room temperature, low catalyst loading in anode and cathode, cheaper, less hazardous and no parasitic load.

A diverse sulfonated polybenzimidazole copolymer (SPBI) as proton exchange membrane was synthesiszed via one-step high temperature polymerization method with 3,3-diaminobenzidine (DABD), 5-sulfoisophthalic acid (SIPA), 4,4-sulfonyldibenzoic acid (SDBA) and biphenyl-4,4-dicarboxylic acid (BDCA). The SPBI membrane was prepared through a direct hot-casting and in situ phase inversion technique. Characterization tests were carried out on the membranes including surface morphology, distribution of elements on the membrane, determination of functional groups, thermal stability, ion exchange capacity, water uptake rate and proton conductivity. The as-synthesized SPBI membrane displayed a smooth surface via scanning electron microscopy (SEM) analysis which is thermally stable up to 443 °C. The SPBI membrane showed higher water uptake rate (WUR) and proton conductivity though it had lower ion exchange capacity (IEC) value compared to recast Nafion membrane. The proton conductivity of the SPBI membrane with IEC of 0.60 mmol/g was 4.50 × 10-2 S/cm at 90 °C. This study shows that the SPBI membrane has great potential in polymer exchange membrane fuel cell (PEMFC) applications.

Palladium–silica nanofibres (Pd–SiO 2 fibre) were adopted as an additive to Nafion recast membranes in order to reduce methanol crossover and improve the cell performance. The performance of a membrane electrode assembly (MEA) with fabricated composite membrane was evaluated through a passive air-breathing single cell direct methanol fuel cell (DMFC). The limiting crossover current density was measured to determine the methanol permeation in the DMFC. The effects of membrane annealing temperature and casting solvent of composite membrane on the cell performance were investigated and are discussed here. Compared to recast Nafion with the same thickness (150 μm), the Pd–SiO 2 fibre/Nafion composite membrane exhibited higher performance and lower methanol permeability. A maximum power density of 10.4 mW cm −2 was obtained with a 2 M methanol feed, outperforming the much thicker commercial Nafion 117 with a power density of 7.95 mW cm −2 under the same operating conditions. The experimental results showed that the Pd–SiO 2 fibre as inorganic fillers for Nafion could effectively reduce methanol crossover and improve the membrane performance in DMFC applications.

CFD simulation of heat transfer and friction factor characteristics in a circular tube fitted with twisted tape inserts in laminar flow and constant heat flux is conducted using FLUENT version 6.3.26. Plain and alternate axis twisted tape inserts with twist ratios (y = 2.93, 3.91, 4.89) and alternative angles (β = 30°, 60°, 90°) have been used for the simulation. The simulated results are matched with the literature correlations for a plain tube with a discrepancy of less than ±8% for Nusselt number and ±6.25% for friction factor. The results also revealed that the heat transfer in terms of the Nusselt number increased with increases of Reynolds number, alternative angles, and decreases of twist ratio. Among the various twist ratios and alternative angles, the twist ratio of y = 2.93 and alternative angle β = 90° offered a maximum heat transfer enhancement. © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res, 43(4): 384–396, 2014; Published online 3 October 2013 in Wiley Online Library (wileyonlinelibrary.com/journal/htj). DOI 10.1002/htj.21089

The aim of this research was to study the effect of the membrane electrode assembly fabrication factors on the performance of a passive micro direct methanol fuel cell by studying the hot pressing parameters. The MEA was prepared with a Nafion 117 membrane and porous electrodes having an active area of 1 cm 2 with Pt and Pt/Ru catalysts of 8 mg cm −2 loading at the cathode side and anode side, respectively. The Design of Experiment work was performed with the Response Surface Method using the Central Composite Design. The One-factor-at-a-time method was used to select the significant level of factors for the DOE method, which are temperature in the range of 100–135 °C and pressure in the range of 6.0–16.0 kgf cm −2 . The results show that the proposed mathematical model in the Response Surface Method can be used adequately for prediction and optimization within the factor levels investigated. The combined optimum hot pressing parameters that gave the highest performance of 7.23 mW cm −2 predicted in this study are temperature 130 °C and pressure 6 kgf cm −2 .

The emergence of fuel cell technology has created a new tool for the generation of clean, high efficiency alternative energy for humans. The research and development of new catalysts to replace the expensive and rare platinum (Pt) to reduce the overall cost of fuel cells is ongoing in this area. Nitrogen-doped carbon and its composites possess great potential for fuel cell catalyst applications especially at the oxygen reduction cathode. It is proposed that the reaction mechanisms of nitrogen-doped carbon catalysts for oxygen reduction involve adsorption of oxygen at the partially polarised carbon atoms adjacent to the nitrogen dopants, different from the mechanism at platinum catalysts, which utilise d-bands filling at oxygen adsorption sites. Nitrogen doping in both carbon nanostructures and its composites with active metals or ceramics are reviewed. Nitrogen-doped carbon without composite metals, displays high catalytic activity in alkaline fuel cells and exhibits significant activity in proton exchange membrane fuel cells and direct methanol fuel cells. Pt-based catalysts with nitrogen-doped carbon supports show enhanced catalytic activity towards oxygen reduction, attributed to the enhanced anchoring of Pt to the support that results in better dispersion and stability of the electrodes. For nitrogen-doped carbon composites with non-noble metals (Fe, Co, etc), enhanced activity is seen in both proton exchange and alkaline fuel cells. There are many ongoing debates about the nature of nitrogen-carbon bond in catalysis. Pyrrole- and pyridinic-type nitrogen generally considered to be responsible for the catalytic sites in acidic and alkaline media, respectively. In recent years, significant efforts have been made towards increasing the stability of nitrogen-doped carbon catalysts in acidic media through the formation of composites with ceramic or metal oxide materials. This article reviews the progress in the area of this new class of catalysts and their composites for greater enhancement of oxygen reduction activity and stability in various fuel cell applications.

The characterization of electrodes and performance tests for membrane electrode assemblies (MEAs) with varying Pt content have been carried out. The electrodes were made using a spraying method. The physical properties of the electrodes (i.e., surface structure, content and distribution of catalysts) were characterized using scanning electron microscope–energy-dispersive X-ray spectroscopy (SEM–EDX), and MEA performance tests were performed through a fuel cell test station with varying catalyst content, fuel cell temperature and with applied back pressure. The physical characterization of the electrode indicated that the Pt catalyst was uniformly dispersed on both the surface and cross section of the catalyst layer (CL), with a Pt loading between 7.5 and 21.5 wt%. The current–voltage performances generally increased with Pt content. Similarly, the use of back pressure and increasing the fuel cell operation temperature improved MEA performance.

One of the major challenges for direct methanol fuel cells is the problem of methanol crossover. With the aim of solving this problem without adverse effects on the membrane conductivity, Nafion/Palladium–silica nanofiber (N/Pd–SiO 2 ) composite membranes with various fiber loadings were prepared by a solution casting method. The silica-supported palladium nanofibers had diameters ranging from 100 nm to 200 nm and were synthesized by a facile electro-spinning method. The thermal properties, ionic exchange capacities, water uptake, proton conductivities, methanol permeabilities, chemical structures, and micro-structural morphologies were determined for the prepared membranes. It was found that the transport properties of the membranes were affected by the fiber loading. All of the composite membranes showed higher water uptake and ion exchange capacities compared to commercial Nafion 117 and proved to be thermally stable for use as proton exchange membranes. The composite membranes with optimum fiber content (3 wt%) showed an improved proton conductivity of 0.1292 S cm −1 and a reduced methanol permeability of 8.36 × 10 −7 cm 2 s −1 . In single cell tests, it was observed that, the maximum power density measured with composite membrane is higher than those of commercial Nafion 117.

The optical properties of a ZnO photocatalyst were enhanced with various dopant concentrations of Fe(3+). Doped ZnO nanoparticles were synthesized via a sol-gel method without the use of capping agents or surfactants and was then characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and ultraviolet-visible (UV-Vis) spectroscopy. The results showed that ZnO has a wurtzite, hexagonal structure and that the Fe(3+) ions were well incorporated into the ZnO crystal lattice. As the Fe(3+) concentration increased from 0.25 wt.% to 1 wt.%, the crystal size decreased in comparison with the undoped ZnO. The spectral absorption shifts of the visible light region (red shift) and the band gap decreases for each Fe-ZnO sample were investigated. The photocatalytic activities of the ZnO and Fe-ZnO samples were evaluated based on the degradation of 2-chlorophenol in aqueous solution under solar radiation. The samples with a small concentration of Fe(3+) ions showed enhanced photocatalytic activity with an optimal maximum performance at 0.5 wt.%. The results indicated that toxicity removal of 2-chlorophenol at same line of degradation efficiency. Small crystallite size and low band gap were attributed to high activities of Fe-ZnO samples under various concentrations of Fe(3+) ions compared to undoped ZnO.

Simple sol-gel route was used to synthesis the TiO2 nanoparticles and examined by X-ray diffraction (XRD). The small particle size and uniform morphology of the TiO2 were found at different calcination temperatures. The kinetic study of phase changes from the anatase to rutile using the X-ray diffraction data with Avrami equation was investigated. The transformation of anatase to rutile was started after 500 °C and above by decreasing of XRD peaks intensity of anatase with rutile increased. The activation energy of the rutile phase was found lower which indicated that uniform shape and morphology of TiO2 nanoparticles. At same time, changes of activation energy value depended on the experimental conditions was observed.

Nanohybrids, based on a modified natural rubber,Epoxidized Natural Rubber (ENR-50), and organomodified montmorillonite (MMT) containing alkyl ammonium, were prepared by solvent casting technique. Morphology and non-isothermal degradation of ENR-50 and various ENR/MMT nanohybrids were characterized by POM, SEM and TG-DTG. In the hybrid materials,an increase MMT loading in the ENR-50 increased the maximum decomposition temperature (Tmax) of thermal profiles. Kissinger and Ozawa plots deduced a trend of the decomposition activation energy, Ed, which is related to the agglomeration and heat transfer ability of MMT. A mechanism comprising of the degradation of ENR-50 via scission of epoxy-isoprene chains to shorter chains, ring opening reaction and the possible interactions of modified nanoclay and ENR-50 is discussed.

Tremendous efforts are being made to produce polymer electrolyte membrane (PEM) for fuel cell using advanced materials in order to replace Nafion due to the high costs and its complicated synthesis procedures. One of the efforts include an extensive research on natural polymer to produce biopolymer based electrolyte membranes with desirable properties such as high proton conductivity, as well as good chemical and thermal stabilities. The examples of biopolymer that have been used are polysaccharide (e.g. cellulose, starch and glycogen), chitin and chitosan. This paper presents an overview of the types of biopolymer used to produce a PEM, comprised also their chemical and physical properties, and its performances in fuel cell applications.

The experimental conditions for the synthesis of ZnO nanoparticles to produce minimal size were optimized using the D-optimal design. The influence of process parameters involves molar ratio of the starting materials, pH and the calcination temperature on the particle size were evaluated using the polynomial regression. The optimum conditions revealed by the model for obtaining a minimum particle size of ZnO were predicted to have a molar ratio of 1.76, pH of 1.50 and calcination at 402.2 °C. The obtainable particle size upon applying the model is 22.9 nm in compare to experimental result of 18 ± 2 nm was obtained.

In this study, the photocatalytic degradation of toxic pollutant (2-chlorophenol) in the presence of ZnO nanoparticles (ZnO NPs) was investigated under solar radiation. The three main factors, namely pH of solution, solar intensity and calcination temperature, were selected in order to examine their effects on the efficiency of the degradation process. The response surface methodology (RSM) technique based on D-optimal design was applied to optimise the process. ANOVA analysis showed that solar intensity and calcination temperature were the two significant factors for degradation efficiency. The optimum conditions in the model were solar intensity at 19.8 W/m2, calcination temperature at 404 °C and pH of 6.0. The maximum degradation efficiency was predicted to be 90.5% which was in good agreement with the actual experimental value of 93.5%. The fit of the D-optimal design correlated very well with the experimental results with higher values of R 2 and R 2 adj correlation coefficients of 0.9847 and 0.9676, respectively. The intermediate mechanism behaviour of the 2-chlorophenol degradation process was determined by gas chromatography-mass spectrometry (GC-MS). The results confirmed that 2-chlorophenol was converted to acetic acid, a non-toxic compound. The authors wish to thank the Research Centre for Sustainable Process Technology (CESPRO), Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia for supporting this study under project PKT-6/2012, iconic-2014-004 and NPRP grant no. [5-1425-2-607] from the Qatar National Research Fund (a member of Qatar Foundation). Muneer M. Ba-Abbad is also grateful to the Hadhramout University of Science & Technology, Yemen for financial support of his PhD. Scopus

Background/Objectives: Nanotechnology has been stated in Malaysia New Economic Model and widely used in much application. The article focuses on nanoparticle formation using liquid pulsed-laser ablation technique. Methods: There are two methods have been used to produce the metal nanoparticles namely breakdown and build up method. In this article, the pulse laser ablation (build up method) has been used to generate the metal nanoparticles whereby the metal target is immersed in ultra-pure water. The Al alloy metal nanoparticles were studied using two laser parameters namely laser exposure time and laser power. Findings: The above mentioned method identified can generate the metal nanoparticles. The longer laser exposure time with higher power contribute higher weight loss of the Al metal. The new incoming black dots were detected on the surface of Al alloy metal samples that were shot by a laser beam. It was contributed to the formation of instabilities plasma on the metal surface towards Al nanostructures ejection. The average weight of a mass loss of Al alloy increases with the exposure time of laser shot was increases. It was shown that average of mass loss of Al metal alloy increased dramatically from the 30 second to 60 second at laser power of 1 watt. However, the higher ablation condition of 3 watt for 180s forms the bigger particle size of 900 nm and more. Conclusion/Application: At the condition of 3 watts for 30s, smaller particles size ranging of 76-1281 nm has been formed. The higher power and exposure time subsequently increase the size and homogeneity.

Proton exchange membrane fuel cells (PEMFC) comprise a diverse range of fuel cell thought to have future commercial application and transportation. The introduction of nitrogen into carbon nanostructures has created new pathways for the development of non-noble metal electro-catalysts in fuel cells. This review provides insight into the role of nitrogen inclusion into the carbon nanotubes (CNT) and the possible mechanisms involved in oxygen reduction reaction (ORR) activity. The doping effects of nitrogen into CNT on the surface morphology, electronic structures and electrochemical activity are discussed. Catalyst nanoparticles distribution, chemical composition and the incorporation of a binder play crucial roles in the generation of good catalytic activity and high stability in organic electro-catalysts. Synthesize methods for making nitrogen-containing carbon nanostructures and the resultant oxygen reduction reactivity are compared. Finally, stability issues of the N-CNT electrocatalysts are discussed.

Quaternary metal oxide of Ba2NiTi5O13was synthesized by using two-step sol-gel method. Excess of titanium dioxide obtained from the first step of sol-gel synthesis, were subsequently reacted in second step of sol-gel synthesis in order to produce Ba2NiTi5O13monoclinic phase. Calcination temperature of 900 °C for as long as 8 hours was needed for obtaining pure phase of Ba2NiTi5O13. Homogenous micron sized particles of Ba2NiTi5O13with average size of 0.10 μm and narrow distribution were observed using Scanning Electron Microscopy (SEM). Besides, porous structures can also be seen distributed across the surface of the particles of Ba2NiTi5O13particles. Characterization of monoclinic phase of Ba2NiTi5O13was described based on the investigations of X-Ray Diffraction (XRD), Fourier Transform Infrared (FTIR) and Thermo Gravimetric Analysis (TGA).

The organic material named 4-amino-5-phenyl-4H-1, 2, 4-trizole-3-thiol (APTT) was studied as inhibitor for mild steel corrosion in 1.0 M HCl at 30 °C. The effects of turbulent flow on the inhibition process were characterized using open circuit potential (OCP), potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). Turbulent flow condition experiments were simulated by Rotating Cylinder Electrode (RCE). Results obtained from changes of open circuit potential (OCP) with immersion time, potentiodynamic polarization, and impedance measurements all are in good agreement and indicated that the formation and the development of the inhibitor film were flow rate dependence. The scanning electron micrograph confirmed film structure is dependence of flow condition.

Electrode performance is the most important part in proton exchange membrane fuel cell system because all electrochemical processes and chemical conversions into energy occur via electrode interface. However the main problem in widespread proton exchange membrane fuel cells (PEMFCs) applications is the cost of the catalyst and life time of electrode, due to different parameters effects. Intense research imply in reducing the cost with increase the activity of catalyst in additional to other parameters (components) to make electrode for PEM more efficient with reasonable cost. This paper review recent research for the most parameters affecting performance of (Pt/C and Pt/C/M ) electrode for proton exchange membrane fuel cells (PEMFCs) such as Catalyst oxidation (degradation), and life time of the electrode using Pt/C, gas diffusion layer (GDL) thickness, and loading of PTFE in the diffusion layer, Nafion@ solution in the catalyst layer, methods of fabrication of electrode as spraying, casting, and electro deposition methods. Then the link between these parameters to achieve high performance and avoid the electrode degradation by optimized these parameters.

Catalysis is the major process involved in fuel cell technology to generate electricity which is known renewable. Generally, fuel cell electrodes utilize platinum supported carbon to catalyze the reactions at both cathode and anode. However, cheaper substitution materials such as nitrogen-doped carbon catalyst have attracted greater attention in recent year due to its significant catalytic activity at cathode in fuel cell. Nitrogen-doped CNT (N-CNT) is believed to allow oxygen reduction reaction (ORR) at cathode to take place which play a role as n-type dopant for electrical conductivity. The objective of this paper is to understand the mechanism of oxygen adsorption on N-CNT using the density-functional theory (DFT). N-CNT with two configurations involve sp2 and sp3 hybridized nitrogen are studied and compared in order to find the most thermodynamically stable N-CNT for sustainable ORR activity in fuel cell. The structural stability is studied through the binding energies of each configurations and the metallic behavior is examined through the energy gaps from the HOMO-LUMO studies. Finally, the adsorption energies and deformation energies of oxygen on N-CNT is discussed. Results revealed that sp3 hybridized N-CNT gives the most stable structure with compatible oxygen adsorption ability.

The solar photocatalytic degradation of 2,4-dicholrophenol in aqueous solution was carried out direct solar radiation without any collector. A slurry reactor with TiO2 nanoparticles catalyst was used. The catalyst sample was prepared by sol-gel method from titanium tetra-isopropoxide as raw material and calcinated at 400°C. The photocatalytic activity of TiO2 nanoparticles were evaluated by photocatalytic degradation of initial concentration (50 mgl-1) 2,4-dicholrophenol under solar irradiation. The average solar intensity of ultra violet (UV) was recorded as 23 Wm-2. HPLC was used for monitoring the concentration of 2,4-dicholrophenol in solution at different time intervals during the experiment. The degradation efficiency of 2,4-dicholrophenol removal was 93.8% at pH solution of 6, irradiated for 1 h and using optimum amount of catalyst 2gl-1 .

Polymer electrolyte membrane based on Nafion and zirconium oxide (ZrO2) was developed via film casting method. The content of ZrO2 (1.0, 2.0, and 3.0 wt.%) was incorporated with Nafion solution to prepare Nafion-ZrO2 composite membranes. Recast Nafion membrane was used as reference material. All of the prepared membranes have been subjected to both physical and chemical characterizations such as Fourier transform infra-red (FT-IR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) analysis, water uptake rate (WUR) and conductivity measurements. The Nafion-ZrO2 composite membranes were found to possess high thermal stability (Tg= 188 - 192°C) and conductivity (0.30 – 0.93 S cm-1). This study demonstrates the possibility of developing Nafion-ZrO2 composite membrane as promising polymer electrolyte membrane for fuel cell operated at medium temperature and low humidity.

The relatively inexpensive SiO2 layer was studied as the silicon etch mask in a KOH etching process for the fabrication of a flow field pattern that consists of channels as well as through-holes on the substrate of a fuel cell. The SiO2 layer was grown in a wet thermal oxidation process to obtain a thickness of up to 6.5 μm and the growth was predicted using the Deal–Grove model. The flow fields on the cathode and anode sides were done using a wet etch process with KOH as etchant. Etching time was utilized to control the depth of the required pattern and the pattern shape was found to have an influence over the etch rate. With constant monitoring of the conditions and parameters used throughout the micro-fabrication process, the thick SiO2 layer was found to be a reliable masking material for a long KOH etching.

The corrosion of aluminum alloy (6262) in artificial sea water under flow condition was evaluated using electrochemical impedance spectroscopy (EIS) and potentiodynamic methods. The flow condition experiments were simulated using rotating cylinder electrode (RCE). Results showed that the increasing of the flow velocity enhances the corrosion kinetic of the system and changes the corrosion mechanism. Limiting current density was increased with increasing in the flow velocity. This behavior was due to the presence of a mixed control on the corrosion process related with the formation and stabilization of corrosion product layers on the electrode surface.

The corrosion inhibition of Al-Alloy (Al2024) in 0.5 M nitric acid solution at 30 °C was achieved using 4-4-dimethyloxazolidine-2-thione (DMT) as a corrosion inhibitor. The electrochemical performance of the DMT was studied by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization measurements, and scanning electron microscopic study (SEM). The results indicated that DMT acts as an inhibitor for Al2024 in 0.5 M nitric acid. Polarization curves indicated that DMT was a mixed-type inhibitor. Inhibition efficiencies were observed to be increased with an increase in DMT concentration and attains approximately to 93.4% at 2 mM of DMT in 0.5 M nitric acid. The adsorption of DMT model on Al2024 surface obeyed in accordance with Langmuir adsorption isotherm model. The value of the free energy of adsorption ΔG ads indicated that the adsorption of DMT molecule was a spontaneous process and was typical of physical and chemical adsorption.

The corrosion inhibition of mild steel in a 2.5 M H2SO4 solution by 4-amino-5-phenyl-4H-1, 2, 4-trizole-3-thiol (APTT) was studied at different temperatures, utilising open circuit potential, potentiodynamic and impedance measurements. The results indicate that APTT performed as an excellent mixed-type inhibitor for mild steel corrosion in a 2.5 M H2SO4 solution and that the inhibition efficiencies increased with the inhibitor concentration but decreased proportionally with temperature. The kinetic and thermodynamic parameters for adsorption of APTT on the mild steel surface were calculated. A chemisorption mechanism of APTT molecules on the mild steel surface was proposed based on the thermodynamic adsorption parameters.

Electrochemical polarization and electrochemical impedance spectroscopy (EIS) were involved to study the corrosion inhibition of aluminum alloy 2024 in 2.5M H2SO4 solution by 4-amino-5-phenyl-4H-1, 2, 4-triazole-3-thiol (APTT) at 30 ○C. Potentiodynamic polarization results were comparable with those obtained by impedance measurements. Results showed that APTT performed as inhibitor for aluminum alloy 2024 corrosion in 2.5M H2SO4 solution and it attains an efficiency of more than 32% at 4×10- 4 M at 30 ○C . The inhibition efficiency increases with an increase in the concentration of APTT. Polarization curves show that APTT is a mix-type inhibitor. Changes in impedance parameters (charge transfer resistance, Rct, and double layer capacitance, Cdl) were indicative of adsorption of APTT on the aluminum alloy 2024 surface, leading to the formation of protective films