Air-breathing Direct Methanol Fuel Cell Research Articles

Experimental analysis on the influence of cathode current-collector open ratio on the performance of an air breathing direct methanol fuel cell (AB-DMFC) with the addition of alkali solution

Experimental analysis on the influence of cathode current-collector open ratio on the performance of an air breathing direct methanol fuel cell (AB-DMFC) with the addition of alkali solution

Evolution of oxygen reduction property by the role of CeO2 in CeO2/MnO2 cathode catalyst for passive direct methanol fuel cells

The oxygen reduction reaction (ORR) efficiency of direct methanol fuel cell (DMFC) is of great significance. In this work, MnO2 supported on CeO2-QDs (CeO2-QDs@MnO2) and CeO2-QDs supported on MnO2 (MnO2@CeO2-QDs) composite with different loading method were synthesized to investigate the role of CeO2 for ORR, according to the excellent oxygen adsorption and oxygen ion conductivity of CeO2 quantum dots (CeO2-QDs). A passive DMFC was assembled by CeO2-QDs@MnO2 or MnO2@CeO2-QDs as cathodic catalyst and PtRu/C as anodic catalyst. The maximum power densities for CeO2-QDs@MnO2 and MnO2@CeO2-QDs-based DMFCs were 9.4 and 7.8 mW·cm−2, while 8.5 and 7.0 mW·cm−2 for air-breathing DMFCs, respectively. CeO2-QDs@MnO2 showed a more superior ORR activity and stability in the high discharge currents especially for air-breathing DMFCs. The temporary storage and timely replenishment mechanism of oxygen in CeO2-QDs@MnO2 catalyst could significantly enhance the ORR efficiency at cathode. This work developed a new thought about the loading method of CeO2 on the ORR catalytic activity for CeO2/MnO2 catalysts.

A new water management system for air-breathing direct methanol fuel cell using superhydrophilic capillary network and evaporation wings

Oxygen starvation caused by water flooding in cathode is a key performance bottleneck for air-breathing direct methanol fuel cell (DMFC). To solve this problem, we present a new water management system consists of superhydrophilic capillary network and evaporation wings in this work. The cathode flow field (CFF) with water management system (WMCFF) is obtained by fabricating capillary network on titanium substrates with micromachining techniques. A pair of evaporating wings made of carbon papers are used to collect water from the capillary network and further evaporate them into the air quickly. Results show that, before a long-term discharge test, the initial peak power density (Pmax) of WMCFF-DMFC is 38.9% higher than that of the conventional cathode flow field DMFC (CCFF-DMFC). After 2 and 4 h discharge, the performance gaps between the two DMFCs become larger, and the Pmax of WMCFF-DMFC increases by 55.6% and 74.3% compared with that of the CCFF-DMFC, respectively. Moreover, the corresponding Pmax decline rate in the WMCFF-DMFC is only about 12% and 27% of that in the CCFF-DMFC. This suggests that the new water management system can effectively prevent water flooding in cathode and significantly improve the performance and stability of the air-breathing DMFCs.

Design and fabrication of a quick-fit architecture air breathing direct methanol fuel cell

An air breathing direct methanol fuel cell (AB-DMFC) with a unique architecture was designed and fabricated to hold cell components together firmly, avoid fuel leakage and limit cell resistance. Pt and PtRu catalysts prepared by pulse electrodeposition on Ti mesh-based electrodes were employed and compared to traditional carbon-based electrodes. Results showed that Ti mesh can be a suitable catalyst support without the need for a gas diffusion layer (GDL) at the anode, while the absence of a GDL at the cathode drastically reduces cell performance, which can be attributed to the diffusion limitation of oxygen to the cathode. Among the various Ti mesh-based cell configurations explored, the optimum configuration was found with PtRu on an 80 mesh (47% open ratio) Ti anode and a Pt/C coated GDL with 40 mesh (71% open ratio) Ti as a cathode. The single cell AB-DMFC architecture was extended to 2-cell and 6-cell mini-stacks. The 6-cell stack, offering an OCV of 2.9 V and a maximum power of 60 mW using 2 M methanol and ambient air, was used to run a small portable device.

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.

Performance evaluation of an air breathing–direct methanol fuel cell with different cathode current collectors with liquid electrolyte layer

AbstractDevelopment of possible technologies for the generation of green energy is the focus of research worldwide. Fuel cells are a promising option in this regard. Out of the various categories of fuel cells, air breathing–direct methanol fuel cells (AB‐DMFCs) are finding a prominent place as an electric power source for charging of compact electronic devices. In AB‐DMFC, the design and construction of the cathode current collector is very crucial, since the cathode current collector performs important functions in the fuel cell operation such as collecting the electrons, facilitating the flow of oxygen for the cathode reaction and evacuating the water bubbles formed at the cathode side. An ideal current collector improves the cell performance multifold. The present paper deals about the performance of an AB‐DMFC fitted with three different cathode current collector designs, viz., a wire mesh current collector (WMCC) made of SS316L, WMCC with a supporting plate (SP) and a perforated current collector (PCC) with an open ratio of 45.40%. A single serpentine flow channel engraved on a graphite plate was used as the anode flow channel plate. Experimental investigations are carried out to examine the impact of the cathode current collector design on the performance of AB‐DMFC and also by varying the operating parameters of methanol flow rate and concentration. The next stage of the experiments are carried out with the addition of a liquid electrolyte layer (LE), which is kept between two half Membrane Electrode Assemblies. Experimental results reveal that the LE layer enhances the fuel cell performance compared to conventional AB‐DMFC.

Investigation of In Situ Thermal Behavior of a Passive Direct Methanol Fuel cell Using Infra‐Red Thermography

AbstractIn a passive direct methanol fuel cell, the cell temperature is linked to the heat generated during operation. It is important to study about cell temperature to understand cell performance, and dynamic behavior. In the present study, experiments on passive and air breathing direct methanol fuel cells (DMFC) of a 25 cm2 effective cell area are conducted using printed circuit board (PCB) to investigate the surface temperature distribution. A non‐intrusive infra‐red thermography is used to record in situ surface temperature and it is observed that the maximum temperature recorded for a passive DMFC (PDMFC) is 42 °C compared to 34 °C for air breathing direct methanol fuel cell (ABDMFC) at steady state condition. Temperature distribution reveals that maximum temperature near the top middle portion of the PCB. Subsequently, PDMFC recorded maximum power density of 3.9 mW cm−2 compared to 2.8mW cm−2 for ABDMFC. Based on the PCB rib orientation for 5M feed concentration, vertical rib recorded 46 °C whereas 44 °C for horizontal rib. For ABDMFC, the response to load change is 22 s due to CO2 removal when compared to 4–5 min for PDMFC. It is concluded that the methanol concentration governs the heat generated in a PDMFC and lead to cell temperature distribution, depending on the cell fixture design under average ambient condition of 30 °C and 50% relative humidity.

Compact Direct Methanol Fuel Cell: Design Approach Using Commercial Micropumps

Direct methanol fuel cells (DMFC) are typically supplied under pressure or capillary action with a solution of methanol in water optimized for the best specific power and power density at an operating temperature of about 60 °C. Methanol and water consumption at the anode together with water and methanol losses through membrane due to crossover create an imbalance over time so the fuel concentration at the anode drifts from the optimal ratio. In the present study, we demonstrate a DMFC with a means for continuous adjustment of water and methanol content in the anode fuel mixture of an air-breathing DMFC to maintain the optimal concentration for maximum and continuous power. Two types of piezoelectric micropumps were programmed to deliver the two liquids at the designated rate to maintain optimal concentration at the anode during discharge. The micropumps operate over a wide range of temperature, can be easily reprogrammed and can operate in any orientation. A study of performance at different current densities showed that at 100 mA/cm2, the self-contained, free convection, air-breathing cell delivers 31.6 mW/cm2 of electrode surface with thermal equilibrium reached at 52 °C. The micropumps and controllers consume only 2.6% of this power during 43 h of continuous unattended operation. Methanol utilization is 1.83 Wh cm−3.

Enhanced Water Management and Fuel Efficiency of a Fully Passive Direct Methanol Fuel Cell With Super-Hydrophilic/ -Hydrophobic Cathode Porous Flow-Field

Water management is a critical issue for a direct methanol fuel cell (DMFC). This study focuses primarily on the use of a super-hydrophilic or super-hydrophobic cathode porous flow field to improve the water management of a passive air-breathing DMFC. The flow field layer was made of an in-house copper-fiber sintered felt (CFSF) which owns good stability and conductivity. Results indicate that the super-hydrophilic flow field performs better at a lower methanol concentration since it facilitates water removal when the water balance coefficient (WBC) is high. In the case of high-concentration operation, the use of a super-hydrophobic pattern is more able to reduce methanol crossover (MCO) and increase fuel efficiency since it helps maintain a lower WBC due to its ability in enhancing water back flow from the cathode to the anode. The effects of methanol concentration and the porosity of the CFSF are also discussed in this work. The cell based on the super-hydrophobic pattern with a porosity of 60% attains the best performance with a maximum power density of 18.4 mW cm−2 and a maximum limiting current density of 140 mA cm−2 at 4 M.

Investigation of Methanol Crossover and Water Flux in an Air-Breathing Direct Methanol Fuel Cell

Investigation of Methanol Crossover and Water Flux in an Air-Breathing Direct Methanol Fuel Cell

Study on a Vapor-Feed Air-Breathing Direct Methanol Fuel Cell Assisted by a Catalytic Combustor

Feeding vaporized methanol to the direct methanol fuel cell (DMFC) helps reduce the effects of methanol crossover (MCO) and facilitates the use of high-concentration or neat methanol so as to enhance the energy density of the fuel cell system. This paper reports a novel system design coupling a catalytic combustor with a vapor-feed air-breathing DMFC. The combustor functions as an assistant heat provider to help transform the liquid methanol into vapor phase. The feasibility of this method is experimentally validated. Compared with the traditional electric heating mode, the operation based on this catalytic combustor results in a higher cell performance. Results indicate that the values of methanol concentration and methanol vapor chamber (MVC) temperature both have direct effects on the cell performance, which should be well optimized. As for the operation of the catalytic combustor, it is necessary to optimize the number of capillary wicks and also catalyst loading. In order to fast trigger the combustion reaction, an optimal oxygen feed rate (OFR) must be used. The required amount of oxygen to sustain the reaction can be far lower than that for methanol ignition in the starting stage.

Efficient water recirculation for portable direct methanol fuel cells using electroosmotic pumps

We present an efficient water recirculation method for air-breathing direct methanol fuel cells (DMFC) by utilizing so-called electroosmotic (EO) pumps. The fuel management system includes three EO pumps for the delivery of methanol solution, pure methanol, and pure water, respectively. Water recirculates from the fuel cell back to the fuel supply stream with the aid of these pump systems. We characterized the performance of the air-breathing DMFC for 2 M and 4 M methanol solutions using a syringe pump and EO pumps, respectively. The DMFC performance is similar for both types of pumps as long as the EO pump operates with the applied voltage of 6 V or higher. The maximum net power density (fuel cell power generation minus pump power consumption) was 50 mW cm−2 for 2 M methanol solution and the applied pump potential of 8 V. The minimum parasitic power ratio (pump power consumption divided by fuel cell power generation) was merely 2.1% for 4 M methanol solution and the applied pump potential of 6 V. We successfully demonstrated that the air-breathing DMFC integrated with the EO pumps operated in a stable condition in 1-h galvanostatic measurement.

A New Complex Design for Air-Breathing Polymer Electrolyte Membrane Fuel Cells Aided by Rapid Prototyping

One of the most difficult issues to fabricate a fuel cell with a complex design is the manufacturing method. To solve this difficulty, the authors applied an innovative method of fuel cell fabrication, i.e., rapid prototyping technology. The rapid prototyping technology can both fabricate the complex design and shorten the fabrication time. In this paper, the authors used a 3D software (CATIA) on the fuel cell design and utilized the rapid prototyping to accelerate the prototype development of complex stack designs and to verify the practicability of the new fabrication for fuel cells. The honeycomb shape methanol reservoir and cathode structure design of a direct methanol fuel cell (DMFC) and the complex flow distributor design of a monopolar air-breathing proton exchange membrane fuel cell (PEMFC) stack, which were almost impossibly manufactured by traditional manufacturing, were made in this study. The performance of the traditional air-pumping DMFC and that of an air-breathing DMFC were compared in this study. The feasibility of a complex pseudobipolar design DMFC stack was also verified. For the miniature air-breathing PEMFC made by rapid prototyping with ABS material, its performance is close to the state-of-the-art compared to previous published literatures (Hsieh et al. 2006, “Study of Operational Parameters on the Performance of Micro PEMFCs With Different Flow Fields,” Energy Convers. Manage., 47, pp. 1868–1878; Schmitz, A., Wagner, S., Hahn, R., Uzun, H., and Hebling, C., 2004, “Stability of Planar PEMFC in Printed Circuit Board Technology,” J. Power Sources, 127, pp. 197–205; Hottinen, T., Mikkola, M., and Lund, P., 2004, “Evaluation of Planar Free-Breathing Polymer Electrolyte Membrane Fuel Cell Design,” J. Power Sources, 129, pp. 68–72). A new solution to manufacture complex fuel cell design, rapid prototyping, has been first applied to the fabrication of complicated flow channels in ABS materials and directly used in both DMFC and PEMFC in this paper. Its feasibility was verified and its promising performance was also proved.

Effect of carbon black additive in Pt black cathode catalyst layer on direct methanol fuel cell performance

Vulcan XC-72R, Ketjen Black EC 300J and Black Pearls 2000 carbon blacks were used as the additive in Pt black cathode catalyst layer to investigate the effect on direct methanol fuel cell (DMFC) performance. The carbon blacks, Pt black catalyst and catalyst inks were characterized by N 2 adsorption and scanning transmission electron microscopy (STEM) with Energy dispersive X-ray (EDX) spectroscopy. The cathode catalyst layers without and with carbon black additive were characterized by scanning electron microscopy, EDX, cyclic voltammetry and current-voltage curve measurements. Compared with Vulcan XC-72R and Black Pearls 2000, Ketjen Black EC 300J was more beneficial to increase the electrochemical surface area and DMFC performance of the cathode catalyst layer. The cathode catalyst layer with Ketjen Black EC 300J additive was kept intimately binding with the Nafion membrane after 360 h stability test of air-breathing DMFC.

Optimization of Membrane Electrode Assembly in Air-Breathing Direct Methanol Fuel Cell

Optimization of Membrane Electrode Assembly in Air-Breathing Direct Methanol Fuel Cell

Proton exchange membrane using partially sulfonated polystyrene- b-poly(dimethylsiloxane) for direct methanol fuel cell

A diblock copolymer ionomer containing a rubbery poly(dimethylsiloxane) block has been developed as a proton exchange membrane for direct methanol fuel cell (DMFC). The partially sulfonated polystyrene- b-poly(dimethylsiloxane) (sPS- b-PDMS) membrane with 38% sulfonation degree exhibited 3 times lower methanol permeability and 2.6 times higher membrane selectivity (proton conductivity/methanol permeability) compared to Nafion ® 115 at 25 °C. Coexistence of microphase domains and ionic clusters was confirmed from the morphological studies by small-angle X-ray scattering and tapping-mode atomic force microscopy. Gas chromatographic analysis revealed that water/methanol selectivity of sPS- b-PDMS was 20 times higher than that of Nafion ® 115. Such a high water/methanol selectivity can be attributed to the existence of PDMS microdomains minimizing methanol permeation through hydrophilic ion channels. sPS- b-PDMS membranes were fabricated into membrane electrode assembly (MEA), and air-breathing DMFC test for these MEAs showed a better performance compared to the MEA composed of Nafion ® 115.

Novel approach to membraneless direct methanol fuel cells using advanced 3D anodes

A conventional membrane electrode assembly (MEA) for a direct methanol fuel cell (DMFC) consists of a polymer electrolyte membrane (PEM) compressed between an anode and cathode electrode. Limitations with this conventional design include: cost, fuel crossover, membrane degradation or contamination, ohmic losses and reduced active triple phase boundary (TPB) sites for catalyst located away from the electrode/membrane interface. In this work, ex situ and in situ characterization of a novel electrode assembly based on a membraneless architecture and advanced 3D anodes was investigated. The approach was shown to be fuel independent and scaleable to a conventional bi-polar fuel cell arrangement. The membraneless configuration exhibits comparable performance to a conventional ambient (25 °C, 1 atm) air-breathing DMFC. However, it has the additional advantages of a simplified design, the elimination of the membrane (a significant component expense) and enhanced fuel and catalyst utilization through the extension of the active catalyst zone.

Methanol oxidation by pEDOT-pSS/PtRu in DMFC

Direct methanol fuel cells (DMFCs) are attracting more and more attention because of their operating temperature and easy fuel management. While carbons are the most widely used supports for both metal catalysts, i.e. PtRu for methanol oxidation and Pt for oxygen reduction, conducting polymers also can act as suitable supports for catalyst particles because of their conductive and stable three-dimensional structure. We thus chemically synthesized poly(3,4-ethylenedioxythiophene)-polystyrene-4-sulfonate (pEDOT-pSS) with different (3,4-ethylenedioxythiophene):styrene-4-sulfonate (EDOT:SS) molar ratios and prepared the electrocatalytic systems pEDOT-pSS/PtRu and pEDOT-pSS/Pt, the former by both electrochemical and chemical deposition of PtRu and the latter by chemical deposition of Pt. The results of the electrocatalytic activity tests of the pEDOT-pSS/PtRu composite electrodes performed in 0.1 M H 2SO 4–0.5 M CH 3OH liquid solution and in passive, air-breathing DMFC configuration with Nafion ® 115 protonic membrane and 1 M CH 3OH are reported and discussed.

MEA design for low water crossover in air-breathing DMFC

The water crossover behavior in air-breathing direct methanol fuel cell (DMFC) was studied with varying structural variables of membrane electrode assembly (MEA), such as existence of microporous layer (MPL) in cathode diffusion layer, hydrophobicity of cathode backing layer, and membrane thickness. Water crossover from anode to cathode was lowered by the introduction of MPL to cathode backing layer, the reduction of hydrophobicity of cathode backing layer, and the reduction of membrane thickness. To account for the observed water crossover behavior, water back flow caused by the hydraulic pressure difference between the cathode and anode was considered. It was also found that the methanol crossover was lowered with the reduction of water crossover. The MEA designed for low water crossover revealed improved stability under continuous operation.

Cathode structure optimization for air-breathing DMFC by application of pore-forming agents

The cathode catalyst layer in an air-breathing, direct methanol fuel cell (DMFC) has been improved by addition of pore-forming materials, such as ammonium carbonate and ammonium hydrocarbonate. These construct an effective electrode pore structure. During fabrication of the membrane electrode assembly (MEA), these pore-formers decompose, increase the BET surface area of the electrodes, and form additional porosity. Ammonium carbonate predominantly produces macropores, while ammonium hydrocarbonate is effective for mesopores. This results in an increase in electrochemical active area and catalyst utilization. The higher open-circuit voltage with MEAs prepared with pore-forming material indicates improved air transfer through the cathode. The power density is increased by 30–40% with the employment of the pore-forming materials.