Performance Of Direct Methanol Fuel Cell Research Articles

Performance evaluation of the incorporation of different wire meshes in between perforated current collectors and membrane electrode assembly on the Passive Direct methanol fuel cell

Passive Direct methanol fuel cells (DMFC) are more suitable for charging small capacity electronic devices. In passive DMFC, the fuel and oxidant are supplied by diffusion and natural convection process on the anode and cathode sides respectively. Current collectors (CC) play a vital importance in fuel cell performance. This paper presents the combined impact of perforated and wire mesh current collectors (WMCC) on passive DMFC performance. Three types of open ratios of perforated current collectors (PCC), such as 45.40%, 55.40% and 63.40% and two types of wire mesh current collectors with open ratios of 38.70% and 45.40% were chosen for the experimental work. A combination of Taguchi-L9 rule is considered. A combination of three PCC and two WMCC on both anode and cathode was used. Methanol concentration was varied from 1 mol·L −1 –5 mol·L −1 for nine combinations of PCC and WMCC. From the experimental results, it is noticed that the combination of PCC and WMCC with an open ratio of 55.40% and 38.70% incorporated passive DMFC produced peak power density at 5 mol·L −1 of methanol concentration. The passive DMFC performance was evaluated in terms of maximum power density and maximum current density. The combined current collectors of PCC and WMCC open ratios of 55.40% + 38.70% have more stable voltage than single PCC of open ratio 63.40% at 4 mol·L −1 of methanol concentration. This paper presents the combined impact of perforated and wire mesh current collectors (WMCC) on passive DMFC performance. Three types of open ratios of perforated current collectors (PCC) such as 45.40%, 55.40% and 63.40% and two types of wire mesh current collectors with open ratios of 38.70% and 45.40% were chosen for the experimental work.

Analysis on Geometry of Fluid Flow Manifold in Direct Methanol Fuel Cell

Fuel cells are the devices that convert chemical energy into electrical energy through an electrochemical reaction. Direct Methanol Fuel cell (DMFC) is a proton exchange membrane fuel cells in which methanol is used as fuel. Its high energy density makes it suitable for fuel cells. Even though carbon dioxide is produced, there is no production of sulfur or nitrogen oxides. The problems usually occurred while working with DMFC are methanol crossover, condensation of methanol, water management and carbon dioxide release. In that the uneven flow distribution, accumulation of carbon dioxide bubbles in the fuel cell are the major issues in DMFC. To prevent these issues, this work focuses on the theoretical and experimental studies on development of fuel cells with special importance to geometry of the manifold. This paper provides the optimal solution for preventing uneven flow distribution that is the usage of squoval shaped manifold which is the combination of both square and circle. Performance of DMFC with squoval shape manifold is evaluated experimentally and is compared with square shape manifold and rectangle shape manifold geometry design.

Analysis on Geometry of Fluid Flow Manifold in Direct Methanol Fuel Cell

Fuel cells are the devices that convert chemical energy into electrical energy through an electrochemical reaction. Direct Methanol Fuel cell (DMFC) is a proton exchange membrane fuel cells in which methanol is used as fuel. Its high energy density makes it suitable for fuel cells. Even though carbon dioxide is produced, there is no production of sulfur or nitrogen oxides. The problems usually occurred while working with DMFC are methanol crossover, condensation of methanol, water management and carbon dioxide release. In that the uneven flow distribution, accumulation of carbon dioxide bubbles in the fuel cell are the major issues in DMFC. To prevent these issues, this work focuses on the theoretical and experimental studies on development of fuel cells with special importance to geometry of the manifold. This paper provides the optimal solution for preventing uneven flow distribution that is the usage of squoval shaped manifold which is the combination of both square and circle. Performance of DMFC with squoval shape manifold is evaluated experimentally and is compared with square shape manifold and rectangle shape manifold geometry design.

Graphene quantum dot reinforced hyperbranched polyamide proton exchange membrane for direct methanol fuel cell

The hyperbranched macromolecule (HBM) polyamide proton exchange membrane with uniform 3D matrix topology is beneficial to the enhancement of proton conductivity. In order to extend the application of HBM in direct methanol fuel cell (DMFC), graphene oxide (GO) and graphene quantum dot (GQD) are incorporated into HBM to enhance the proton/methanol selectivity of the membrane. The functional groups on GO and GQD surface would interact with –SO3H groups in HBM by the hydrogen-bond interaction and participate in the proton conductive channel construction. And the GO and GQD in the composite can effectively prevent the permeation of methanol molecules. Most important, the HBM membrane filled by GQD (GQD-HBM) can effectively avoid large scale phase separation which occurs in HBM membrane filled by GO (GO-HBM) due to the greater size of GO. Proton conductivity of GQD-HBM (0.30 S/cm) is 17% improved compared with the pristine HBM while methanol permeability is significantly reduced by ca. 50% due to the physical barrier of GQD. The proton/methanol selectivity is therefore enhanced by more than 80% and the DMFC performance is also significantly enhanced.

Effect of Nafion loading and the novel flow field designs on innovative anode electrocatalyst for improved Direct Methanol Fuel cells performance

Efficiency of a Direct methanol fuel cells (DMFCs) not just merely depends on the catalyst, but also on the flow channels, physical/electrochemical kinetics, Membrane Electrode Assembly (MEA) preparation and other operating parameters. This article is focused on the influence of novel flow field design and the effect of Nafion loading during MEA preparation on the performance of DMFC. A novel Pt/NiTiO3 was used as the anode electrocatalyst in the DMFC. The results show a 27.8% & 5.1% increment in cell performance due to changes in Nafion loading and flow field designs, respectively. A Nafion loading of 0.5 mg/cm2 and the sinuous flow field gave the highest performance. Thus, Pt-NiTiO3/C performed to be an encouraging anode catalyst with the new sinuous flow field.

Evaluation of Quaternized polyvinyl alcohol/graphene oxide‐based membrane towards improving the performance of air‐breathing passive direct methanol fuel cells

Graphene oxide (GO) nanosheets are introduced to a Quaternized polyvinyl alcohol (QPVA) polymer matrix to obtain an anion exchange membranes (AEMs) for application of fuel cells. QPVA/GO nanocomposite membranes provide desirable properties such as low fuel uptake and permeability, excellent ionic conductivity, and cell performance, all of which are favorable for AEMs based on our previous works. Passive direct methanol fuel cells (DMFCs) are recognized as suitable technologies for use in portable devices. Nevertheless, the commercialization of DMFCs remains restricted due to a number of issues related to the conventional membrane; one of these issues is high fuel crossover problems due to high fuel uptake and permeability of Nafion membrane. This study aimed to expand the potential applications of QPVA/GO nanocomposite membranes in air-breathing passive DMFCs. The ionic conductivity, methanol uptakes (MUs), and permeabilities of self-synthesis QPVA/GO nanocomposites are examined to evaluate the ability to operate in methanol atmosphere. At 30°C, the ionic conductivity of the membranes reached 1.74 × 10−2 S cm−1. The MUs and permeabilities were as low as 35% and 7.6 × 10−7 cm2 s−1, respectively. The performance of air-breathing passive DMFCs bearing QPVA/GO nanocomposite membrane is much higher compared to conventional membranes. The maximum power density of air-breathing passive DMFCs was achieved 27.2 mW cm−2 under the optimum condition of 2 M methanol + 4 M KOH at 70°C. Single-cells could be sustained for 1000 hours. This article is the first to optimize and highlight the performance air-breathing passive DMFCs by using a QPVA-based membrane.

Novel sulphonated poly (vinyl chloride)/poly (2-acrylamido-2-methylpropane sulphonic acid) blends-based polyelectrolyte membranes for direct methanol fuel cells

Proton-conducting and methanol barrier properties of the proton exchange membrane (PEM), as well as the high cost of direct methanol fuel cell (DMFC) components, are the key determinants of the performance and commercialization of DMFCs. Therefore, this study aimed to develop cost- and performance-effective membranes based on sulphonated poly (vinyl chloride) (SPVC)/poly (2-acrylamido-2-methyl-1-propane sulphonic acid) (PAMPS) blends. Such membranes have been simply prepared by blending SPVC and PAMPS solutions, followed by solvent evaporation via casting. Interaction of SPVC with PAMPS was confirmed by different characterization techniques such as Fourier Transform Infra-red (FTIR) and Raman scattering spectroscopy in which the two characteristic absorption bands of sulfonic groups appeared at 1093 and 1219 cm−1 additionally, strong peaks at around 1656 cm−1 attributed to vibration of amide groups of PAMPS portion in the polymer blend. Furthermore, the interaction of SPVC with PAMPS improves the thermal properties along with ion exchange capacity in turn decreasing the methanol permeability through the membrane in comparison with the SPVC membrane. The IEC of PVC and Nafion 117 membranes were 1.25, 0.91 meq/g; respectively. And the maximum water uptake of PVC and Nafion 117 membranes were 75 and 65.44%; respectively. Methanol permeability value of 7.7 × 10−7 cm2/s which was noticeably lower than the corresponding value recorded for Nafion® (3.39 × 10−6 cm2/s). Therefore, these fabricated membranes can be considered a low-cost efficient candidate for use in DMFC, especially for its capability to resolve the methanol cross-over issue.

High‐Performance Direct Methanol Fuel Cells with PGM‐Free Cathode

Direct methanol fuel cells (DMFCs) hold great promise for applications ranging from portable power for electronics to transportation. However, apart from the high costs, current Pt‐based cathodes in DMFCs suffer significantly from performance loss due to severe methanol crossover from anode to cathode. The migrated methanol in cathodes tends to contaminate Pt active sites through yielding a mixed potential region resulting from oxygen reduction reaction and methanol oxidation reaction. Therefore, highly methanol‐tolerant cathodes must be developed before DMFC technologies become viable. The newly developed MOF‐based Fe‐N‐C cathode exhibits high methanol tolerance and exceeds the performance of current Pt cathodes, as evidenced by both rotating disk electrode and DMFC tests. In addition to the highly oxygen-reduction active atomically dispersed FeN4 sites, the unique morphology of MOF-derived carbon in Fe‐N‐C cathodes provides a more unique porous structure. DMFC tests with various methanol concentrations are systematically studied using the best performing Fe‐N‐C catalyst. At feed concentrations greater than 2.0 M, the obtained DMFC performance from the Fe‐N‐C cathode is found to start exceeding that of a Pt/C cathode. This work will open a new avenue to use PGM-free cathode for advanced DMFC technologies with increased performance and at significantly reduced cost.

Comparison of single-cell testing, short-stack testing and mathematical modeling methods for a direct methanol fuel cell

In this paper, a comparison between direct methanol fuel cell (DMFC) measurements performed on a single cell and a short-stack, and the results of a mathematical model for a DMFC, is presented. The testing of a short-stack, which consists of 5 cells with an active area of 315 cm2, was performed at various current densities, permeation current densities, and cathode flow rates (CFR) in order to determine the voltage outputs of each cell. Methanol concentration and stack temperature results obtained from short-stack testing were then integrated into the single cell test and single cell mathematical model as the input parameters. For the mathematical modelling, transport equations originating from methanol, water, and oxygen were coupled with the electrochemical relations. Therefore, a comparison between these three methods is made in order to gain a deeper understanding of the effects of the operating parameters on DMFC performance. This study showed that the model could describe experimental results well when lower methanol concentrations (under 1.2 M) and temperature (under 60 °C) values are used as input parameters. The results also show very good agreement at lower methanol permeation rates and therefore lower temperatures. It is found that the voltage output for a given current density is higher for the theoretical model than that of the experimental studies; and the differences in the results can be up to 0.04 V for a cell.

Studies on Influence of Cell Temperature in Direct Methanol Fuel Cell Operation

Directmethanol fuel cells (DMFCs) offer one of the most promising alternatives for the replacement of fossil fuels. A DMFC that had an active Membrane Electrode Assembly (MEA) area of 45 cm2, a squoval-shaped manifold hole design, and a Pt-Ru/C catalyst combination at the anode was taken for analysis in simulation and real-time experimentation. A mathematical model was developed using dynamic equations of a DMFC. Simulation of a DMFC model using MATLAB software was carried out to identify the most influencing process variables, namely cell temperature, methanol flow rate and methanol concentration during a DMFC operation. Simulation results were recorded and analyzed. It was observed from the results that the cell temperature was the most influencing process variable in the DMFC operation, more so than the methanol flow rate and the methanol concentration. In the DMFC, real-time experimentation was carried out at different cell temperatures to find out the optimum temperature at which maximum power density was obtained. The results obtained in simulation and the experiment were compared and it was concluded that the temperature was the most influencing process variable and 333K was the optimum operating temperature required to achieve the most productive performance in power density of the DMFC.

Barrier properties of sulfonated polysulfone/layered double hydroxides nanocomposite membrane for direct methanol fuel cell operating at high methanol concentrations

High performing and cost effective nanocomposite membranes for DMFC application are synthesized by incorporating hygroscopic layered double hydroxides (LDH) particles into sulfonated polysulfone (sPSU). A significant improvement in the dimensional stability as well as in the water and methanol molecular dynamics of the sPSU_LDH composite membrane is observed in comparison with both pristine sPSU and Nafion 212. The strong electrostatic interaction occurring between positively charged LDH platelets and negatively charged polymer chains of sPSU alters the microstructure of the ionic domains, allowing an effective reduction of the methanol permeability whilst improving the proton conductivity. The methanol crossover measurements confirmed that sPSU_LDH membranes are able to withstand high methanol concentration without significant aftermath on the chemical stability of the electrolyte. The features enable the single DMFC assembled with the sPSU_LDH nanocomposite to achieve the remarkable power density of 150 mW cm−2 at 80 °C in 5 M methanol solution.

A review of quaternized polyvinyl alcohol as an alternative polymeric membrane in DMFCs and DEFCs

Direct methanol fuel cells (DMFCs) and direct ethanol fuel cells (DEFCs) have emerged as alternative power generators for portable devices and household appliances because of their easy and fast production of electricity, as well as high energy conversion to provide high-power density. However, several critical factors limit the commercialization of DMFCs and DEFCs, particularly issues related to polymer electrolyte membranes, including the high-cost production of Nafion membranes and cell degradation caused by high fuel crossover and dehydration. This review paper provides an overview of the current status and challenges in quaternized polyvinyl alcohol (QPVA)-based membranes as an alternative polymer electrolyte membrane for DMFCs and DEFCs. The main advantages of using QPVA-based membranes in fuel cells are reduced cost production of membrane, fuel-crossover minimization, and competitive conductivity with Nafion membrane. The effects of modifying the QPVA-based membrane, especially on conductivity properties, fuel crossover, uptake condition, mechanical, thermal, and chemical properties, and single-cell performance are comprehensively discussed. The best performances of DMFCs and DEFCs with utilizing QPVA-based membrane are reported as 272 and 144 mW cm−2, respectively. This paper is the first to highlight the current status and challenges of QPVA-based membranes for DMFCs and DEFCs applications.

Coupled computational fluid dynamics-response surface methodology to optimize direct methanol fuel cell performance for greener energy generation

Optimization of operational parameters is vital for improving the performance of direct methanol fuel cells. To investigate the effects of these parameters on the power density, the experiments were performed using an experimental setup to yield the highest performance. In this regard, response surface methodology (RSM) was applied to select the proper combination of operating variables such as cell temperature, methanol concentration, and oxygen flow rate. Furthermore, a computational fluid dynamics (CFD) model of DMFC flow field plates, including two parallel-serpentine channels with circular bends were conducted using the finite element method at the optimum operating conditions, which obtained by applying RSM. The developed model solves the conservation of charge, mass, momentum, and species (methanol, water, and oxygen) transport equations. The performance tests based on RSM gave the optimum operating conditions as a cell temperature of 70 °C, methanol concentration of 1 M, and an oxygen flow rate of 300 ml/min. The mathematical model in the optimal operating conditions showed that the polarization curve obtained from the modeling study is in good agreement with the experimental data. Also, the concentration distributions of methanol and oxygen at the optimum operating conditions were predicted by the CFD model.

Parametric Studies of Direct Methanol Fuel Cell under Different Modes of Operation

Direct methanol fuel cell (DMFC) performance tests were carried out in different modes of operation, namely, passive, active (air as oxidant) and active (oxygen as oxidant). Few parameters including methanol concentration (2 M, 4 M, 6 M, and 8 M) and methanol flow rate (1-4 mL min-1) were considered to investigate their effects on the DMFC performance. Fuel consumption was indicated by refractive index tests. Results showed that the performance of DMFC increased with the increase of methanol concentration and flow rate, until they reach certain values, i.e., 4-6 M and 2 mL min-1. Furthermore, for all parameters, the active mode with oxygen yielded the highest power density, followed by the active mode with air and passive DMFC system. The active mode with oxygen yielded the power density which peaks at 10.41 mW cm-2 during 6 M of methanol concentration and 2 mL min-1 rate of flowing methanol, followed by active mode with air at the cathode with 8.39 mW cm-2 and passive mode with 5.39 mW cm-2 respectively. It also records a better fuel consumption efficiency among all modes. These results indicate that investigating the level of fuel concentration and flow rate can lead to enhancement of mass transport and diffusion thus generating better performance of DMFC system.

40SiO2–40P2O5–20ZrO2 sol-gel infiltrated sSEBS membranes with improved methanol crossover and cell performance for direct methanol fuel cell applications

Membranes commonly used in direct methanol fuel cell (DMFC) are expensive and show a great permeability to methanol which reduces fuel utilization and leads to mixed potential at the cathode. In this work, sulfonated styrene-ethylene-butylene-styrene (sSEBS) modified membranes with zirconia silica phosphate sol-gel phase are developed and studied in order to evaluate their potential use in DMFC applications. The synthesized hybrid membranes and sSEBS are subjected to an exhaustive physicochemical characterization by liquid uptake, ion exchange capacity, atomic force microscopy, X-ray photoelectron spectroscopy and dynamic mechanical and thermogravimetric analyses. Likewise, the potential use of the prepared membranes in DMFC is evaluated by means of electrochemical characterizations in single cell, determining the limiting methanol crossover current densities, proton conductivities and DMFC performances. The hybrid membranes show lower water and methanol uptakes, higher stiffness, water retention capability, upper power density and lower methanol crossover than sSEBS and Nafion 112.

Methanol tolerant Pd-Based carbon supported catalysts as cathode materials for direct methanol fuel cells

Alcohol crossover and the sluggish oxygen reduction reaction (ORR) at the cathode are the main practical drawbacks of direct methanol fuel cells (DMFCs). The current work attempts to disclose and compare several strategies to study the factors affecting the performance of DMFCs. With this end in view, kinetic and mechanistic parameters of several carbon-supported palladium–based electrocatalysts towards the ORR in 0.5 M H2SO4 and in 0.5 M H2SO4 + X M CH3OH (X = 0.5–3.0), were investigated applying rotating-ring disc electrode (RRDE) technique. Several procedures were employed and compared to scrutinize the data acquired during ORR in presence and absence of CH3OH. Furthermore, the first derivative method as practical way to determine the methanol tolerance is reported. It was found that PdFeIr/C exhibits the highest catalytic performance for the ORR in the absence and the presence of methanol, in comparison to PdIr/C, PdFe/C and Pd/C electrocatalysts.

An advanced, efficient and highly durable of reduced graphene oxide/platinum nanoparticles nanocomposite electrocatalyst fabricated via one-step method of the hydrothermal-assisted formic acid process for the electrocatalytic oxidation reaction of methanol

The high-quality of reduced graphene oxide (rGO) supported platinum nanoparticles (PtNPs) was synthesized by a simple, efficient, rapid, clean, surfactant-free, and single-step of hydrothermal-assisted formic acid process. The as-synthesized rGO/PtNPs catalyst was extensively characterized in which demonstrated that the PtNPs have successfully anchored on the surface of rGO with the small average particle size of 4 nm. The evaluation of electrocatalytic activity and durability performance of the as-synthesized rGO/PtNPs nanocomposite catalyst towards methanol oxidation reaction (MOR) as well as the determination of electrochemical surface area (ECSA) were carried out by cyclic voltammogram and chronoamperometry. Besides, the as-prepared rGO/PtNPs nanocomposite catalyst has further proved the remarkably higher electrocatalytic property which exhibited superior maximum forward peak current density (64.04 mA/cm2) toward MOR in acidic media compared with Vulcan XC72/PtNPs (47.54 mA/cm2) and rGO/PdNPs (6.21 mA/cm2) catalysts owing to homogenous distribution and synergic effects of PtNPs with rGO as well as improved electron transfer by rGO. Moreover, the rGO/PtNPs nanocomposite catalyst still achieve the high current density even after 2900 s of continuous catalyst at 0.6 V. This study provides new insights into the production of superior electrocatalytic activity and durability of anode catalyst through a facile, low cost and clean synthesis approach for the enhancement of direct methanol fuel cell performance.

Effect of Calcium Hydroxy Phosphate as a Crystallinity Enhancer in Nafion Membrane for Direct Methanol Fuel Cell

Nafion is a widely used membrane in direct methanol fuel cell (DMFC). Many advantages of Nafion including good chemical stability, good thermal resistance, and high proton conductivity. However, Nafion has high methanol crossover which remarkably reduces the performance of DMFC and results in waste of fuel. Therefore, in this work, calcium hydroxy phosphate (CHP) was incorporated into Nafion to increase its crystallinity. The properties of Nafion/CHP such as crystallinity, water uptake, ion exchange capacity, methanol crossover, and solubility were studied. SEM/EDS with elemental mapping was used to observe the dispersion of CHP within the membrane. It was clearly shown that by incorporating 1.0 wt% and 2.5 wt% of CHP into the membrane, methanol crossover at 30 C was reduced from 125.6 x 10-6 cm2s-1 to 2.58 x 10-6 cm2s-1 and 65.58 x 10-6 cm2s-1. The reduction of methanol crossover of CHP/Nafion composite membrane at higher weight was lesser than that of the composite at lower weight due to the agglomeration of CHP.

Enhanced water management via the optimization of cathode microporous layer using 3D graphene frameworks for direct methanol fuel cell

Water management is one of the key roles in determining the output performance of a passive direct methanol fuel cell (DMFC). By decreasing the size of hydrophobic pores inside the cathode microporous layer (MPL), a high hydraulic pressure can be built up inside the cathode catalyst layer, which enhances the water recovery from cathode to anode and thus improves the cathode mass transfer. To achieve this, three-dimensional graphene frameworks are adopted to construct cathode MPL for the first time, whose intrinsic pore structure and characteristics contribute to an enhanced water management. Experimental results show that the performance and stability of the as-prepared DMFC are significantly improved. To illustrate the mechanism of the improvement, the in-situ measurements of polarization and methanol crossover are conducted, which reveals a greatly lowered water transport coefficient, along with a reduced in-situ methanol crossover rate. Since the role of polytetrafluoroethylene (PTFE) is weakened in the novel design of MPL, a further optimization via reducing PTFE content is realized, leading to a total increase of 43% of the output performance. The significant elevation of both the performance and stability of DMFC can expand its potential as a green energy source in practical applications.

Sulfonated poly(ether sulfone) based sulfonated molybdenum sulfide composite membranes: proton transport properties and direct methanol fuel cell performance

Composite membranes of sulfonated poly(ether sulfone) (sPES) are prepared in combination with sulfonated molybdenum sulfide (s-MoS2) as an alternative polymer electrolyte for direct methanol fuel cells (DMFC).