A review on direct methanol fuel cells–In the perspective of energy and sustainability

To overcome the high cost of the catalyst in Direct Methanol Fuel Cell (DMFC) technology, research is moving towards the reduction in the Pt loading in the electrodes by increasing the electrochemical surface area. To date, the state of the art of catalyst supports is dominated by mesoporous carbon. It shows high conductivity but suffer from stability issues especially on long term operation. As shown in the literature, titanium nitride (TiN) has a metal-like conductivity with an outstanding chemical stability [1], and moreover, it is reported to be functional towards the oxidation of adsorbate CO on platinum active sites [2]. In this contribution, we report about TiN catalysts support with self-assembled, hierarchical mesoporous nanostructure, grown by Pulsed Laser Deposition. This approach controls the gas dynamics of the nanoclusters-inseminated supersonic jet to differentiate the resulting impaction deposition, affecting the growth of the film. Platinum is deposited by means of pulsed electrodeposition and it shows a peculiar lamellar structure, most likely due to the strong electric field on the nanostructures. Electrochemical and physical characterization are performed, showing performances towards both methanol oxidation and oxygen reduction, and revealing information about the interaction between catalyst, scaffold and reactants. We demonstrate that it is possible to obtain a catalyst support with large surface area whose morphology can be controlled at the nanoscale. Such as a support could be ideal for the highest platinum utilization, and for the metal loading reduction, since it has similar effects with respect to the metallic Ru in commercial DMFC catalysts with a much lower cost. Stability at high potential is also investigated, and so is the possibility to use the same material as a cathode exploiting the stability of the TiN. These results show the potential of a PVD based technique that opens the doors of the nanoscale to the fabrication of high performing electrodes whose morphological and electrical properties are easily tuned. This approach holds promises for a consistent reduction in the metal loading in DMFC technology. [1] M. Wittmer, B.Studer and H.Melchior, Journal of Applied Physics, 52, 5722 (1981) [2] M. Roca-Ayats, G. Garcia, J.L. Galante, M.A. Peña and M.V. Martinez-Huerta, Journal of Physical Chemistry C 117, 20769-20777 (2013) Figure 1

A facile methodology to fabricate graphene aerogel (GA), and its application in a direct methanol fuel cell (DMFC), is demonstrated for the first time. A new GADMFC design is proposed by using GA to replace two main components within the DMFC—the gas‐diffusion layer and the flow field plate. The results indicate a 24.95 mW cm−2 maximum power density of air polarization is obtained at 25 °C. The membrane electrolyte assembly has a 63.8% mass reduction compared to an ordinary one, which induced 3 times higher mass power density. Benefiting from its excellent organic solvent absorbency, the methanol crossover effect is dramatically suppressed while using 12 m methanol, therefore, a higher concentration or even pure methanol can be refilled into the fuel cell. Due to the excellent fuel‐storage function of the GA, the methanol cartridge and complicated fuel circulation system in the DMFC can be eliminated, which can reduce the manufacturing cost for DMFCs. It is expected this research will promote the application of GA in fuel‐cell applications, as well as shed light on the novel fuel‐cell technology to address future energy challenges.

In this work, it is shown that a novel tubular-shaped, passive Direct Methanol Fuel Cell (DMFC) can produce up to 2 times the instantaneous volumetric power density of a planar DMFC. First a numerical model was developed to determine the benefits of a tubular geometry and design characteristics for a passive tubular-shaped DMFC. Secondly, a tubular-shaped DMFC frame was designed, built, and tested to improve upon existing tubular DMFC literature and compare against an identical planar-shaped DMFC. From the numerical model, it was determined that increasing the ambient temperature from 20 to 40 °C increases the peak power density produced by the fuel cell during operation with 1 and 2 M methanol solutions. During operation with 3 M methanol the increased methanol crossover and oxygen depletion along the Cathode Transport Layer (CTL) reduce the power from the tubular DMFC. It was also determined that the thickness of the CTL must be greater than 1 mm for 1 M operation, greater than 5 mm for 2 M operation, and greater than 10 mm for 3 M methanol operation to prevent oxygen limitations along the CTL. From the experimental work, a tubular-shaped DMFC was built that presented an 870% improvement in power density from the previous best, passive, tubular-shaped DMFC found in the literature. The tubular DMFC produced 24.9 mW cm−2 while the planar DMFC produced 23.0 mW cm−2 with a Nafion® 115 membrane and 3 M methanol. The tubular DMFC experienced slightly higher methanol crossover than the planar DMFC, potentially due to a higher static fluid pressure in the Anode Fuel Reservoir (AFR), which is caused by the vertical orientation of the tubular fuel reservoir.

High power direct methanol fuel cell with a porous carbon nanofiber anode layer

The sensors can be developed based on ampherometric principle using Direct Methanol Fuel Cell (DMFC) technology. The synthesis of cost effective electrocatalyst materials for improved oxygen reduction reaction (ORR) and preparing electrodes by using suitable methods to reduce the cost of the sensing electrode is the major objective of the present work. Pt-Sn alloy exhibits high sensitivity in ORR among other Pt alloys and hence will be used as the ORR catalysts. For various concentration of methanol at different temperature, the current density of the chemically synthesised and characterized Pt-Sn/C was analysed. The accuracy will be determined by the detection of electric current or changes in electric current to design the sensor. To analyse the sensor accuracy, we have used passive mode design protocol in COMSOL Multiphysics. From the constructed cell of 1.0 cm cell area, we can optimize the overall power density and hence the sensitivity of the sensor by the modification of the cell parameters and interfacing it with Darcy’s law of fluidic flow through porous electrode medium. The micro electro mechanical systems (MEMS) technology was used for the design and fabrication of sensor with the electrochemical inputs from a standard DMFC single cell arrangement. The cell structure has been fabricated using a 3D printing technology and the output of the cell was optimized for ampherometric detection. The sensor with microfludic interconnects were fabricated by MEMS technology. The sensor response characteristics were studied and will be presented.

Direct methanol fuel cells (DMFCs) provide an avenue for developing high (specific) energy density, portable power sources. While the overall energy efficiencies that have been reported for DFMCs are rather modest (e.g., approximately 15-20%), interest in the technology stems from the specific energy methanol (6.1 kWhr/kg) which still enables very large system energy densities to be achieved (1, 2). Despite this key benefit, the size and cost of the DMFC technology remain key technical hurdles.To date, many if not most efforts to develop DMFC technologies have used membrane electrolyte assemblies (MEAs) which utilize proton exchange membrane (PEM) electrolyte materials. These acidic PEM materials tend to be quite robust ; however, their use has relegated the DMFC systems to use of relatively large balance of plant (BoP) components for active water/fuel management (3, 4) and expensive platinum based catalyst materials (5). In this talk, we review an approach which is intended to address the size of the BoP required for active water/fuel management as well as enable the removal of some of the platinum based catalysts. This approach uses a bi-cell, or pseudo-bipolar, configuration which has been previously shown to be well suited to portable power applications (6). The novelty of this approach is the combination of a first acidic MEA using PEM electrolyte materials and a second alkaline MEA using anion exchange membrane (AEM) electrolyte materials. This configuration naturally balances the water stoichiometry of the methanol oxidation and oxygen reduction reactions between the adjacent acid and alkaline MEAs, significantly improving the water balance within the system. The integration of alkaline AEM materials has the additional benefit of opening doors for alternatives to platinum based catalysts.A multi-phase, multi-component transport model is used as the basis of this work, which is intended to demonstrate the technical feasibility of the approach for miniaturizing portable DMFC system. A previous study by Kim et al. has shown the compatibility of the materials (7). In this talk, focus will be placed on comparing standard and hybrid configurations and the relative water/fuel management requirements. Additional attention will be placed on the treatment of direct oxidation of methanol in an alkaline MEA and the effect of MEA properties. 1. D. Chu and R. Jiang, Electrochim Acta 51(26), 5829 (2006).2. R. Jiang, C. Rong and D. Chu, J Power Sources 126(1-2), 119 (2004).3. R. Jiang and D. Chu, J Electrochem Soc 155(8), B798 (2008).4. R. Jiang and D. Chu, J Electrochem Soc 155(8), B804 (2008).5. S. Wasmus and A. Kuver, J Electroanal Chem 461(1-2), 14 (1999).6. R. Jiang and D. Chu, J Power Sources 93(1-2), 25 (2001).7. H. Kim, M. Unlu, J. F. Zhou, I. Anestis-Richard and P. A. Kohl, J Power Sources 195(21), 7289 (2010).

Direct Methanol Fuel Cells

Direct Methanol Fuel Cells

Nonrenewable energy sources accounted for roughly 80% of total energy consumption [1]. Solar energy, wind energy, geothermal energy, hydropower, and fuel cells (FCs) have all recently been described as renewable energy sources. In commercial uses, renewable energy has experienced meteorological and logistical obstacles. Because of advantages such as simple fabrication/operation conditions, eco-friendly, high energy conversion efficiency, and long-term durability, FCs technologies are considered one of the most important renewable energy sources for many applications such as portable devices, cars, and electricity plants [2–5]. Methanol can be utilized in direct methanol fuel cells (DMFC) to produce clean energy that can be used in smart electronic gadgets or small automobiles in this regard [6]. However, before DMFC can be used commercially, the slow oxidation kinetics and catalyst toxicity [7] must be resolved. Therefore, the development of direct methanol fuel cells (DMFCs) is one of the most promising technologies for the applications of these devices in stationary power supplies and electric vehicles [8]. Apart from the future of mobile devices such as mobile chargers, phones, computers, and many other applications, this energy is environmentally benign because no gases are emitted and the waste is simply clean water. The biggest issue that this technique may encounter is its high cost due to the usage of noble metal catalysts (platinum (Pt) and ruthenium (Ru)) [9]. Methanol is oxidized via a multi-electron process and several products and/or intermediates can be formed, depending on the electrolyte and the nature of the electrode. Electrode materials are important parameters in the electrochemical oxidation of methanol, where high efficient electrocatalysts are needed. Several metal oxides such as Fe2O3, CeO2, MoOx, Co3O4, NiO, and CuO has been used in various applications, such as catalysis, water splitting photocatalysis, solar cells and gas sensing, besides their uses to enhance the electrocatalytic activity for methanol oxidation [10-11].This paper describes the preparation of graphene quantum dot-doped polyaniline embedded copper metal-organic frameworks composite catalysts for investigating methanol oxidation in alkaline solutions. The electrode surface was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and electrochemical impedance spectroscopy (EIS). After physicochemical characterizations of graphene quantum dot-doped polyaniline embedded copper metal-organic frameworks composite modified carbon ceramic electrode (Cu- MOF/GQDs-PAN/CCE), its electrocatalytic and stability characterizations toward methanol oxidation in alkaline media were investigated in detail by cyclic voltammetry and chronoamperometry. Results showed that, the electrocatalytic activity of the Cu- MOF/GQDs-PAN/CCE electrode is much higher than those of unmodified electrode under similar experimental conditions, showing the possibility of attaining good electrocatalytic anodes for fuel cells. Kinetic parameters such as the electron transfer coefficient (α) and the number of electrons involved in the rate determining step (nα) for the oxidation of methanol were determined utilizing cyclic voltammetry (CV). Keywords: Graphene quantum dot, Polyaniline, Metal-organic frameworks, electrocatalyst, MethanolReferences[1] S.K. Kamarudin, F. Ahmad, W.R.W. Daud, Overview on application of direct methanol fuel cell (DMFC) for portable electronic devices, Int. J. Hydrog. Energy 34 (2009) 6902–6916.[2] L. Carrette, K.A. Friedrich, U. Stimming, Fuel cells: principles, types, fuels and applications, ChemPhysChem 1 (2000) 162–193.[3] A.B. Stambouli, Fuel cells: The expectations for an environmental-friendly and sustainable source of energy, Renew. Sustain. Energy Rev. 15 (9) (2011) 4507– 4520.[4] P. Joghee, J.N. Malik, S. Pylypenko, R. O’Hayre, A review on direct methanol fuel cells – In the perspective of energy and sustainability, MRS Energy Sustain. 2 (2015), https://doi.org/10.1557/mre.2015.4.[5] D. Hassen, M.A. Shenashen, S.A. El-Safty, M.M. Selim, H. Isago, A. Elmarakbi, H. Yamaguchi, Nitrogen-doped carbon-embedded TiO2 nanofibers as promising oxygen reduction reaction electrocatalysts, J. Power Sources 330 (2016) 292– 303.[6] M. Mansor, S.N. Timmiati, K.L. Lim, W.Y. Wong, S.K. Kamarudin, N.H. Nazirah Kamarudin, Recent progress of anode catalysts and their support materials for methanol electrooxidation reaction, Int. J. Hydrogen Energy 44 (29) (2019) 14744–14769, https://doi.org/10.1016/j.ijhydene.2019.04.100.[7] Z. Mousavi, A. Benvidi, S. Jahanbani, M. Mazloum-Ardakani, R. Vafazadeh, H. R. Zare, Investigation of electrochemical oxidation of methanol at a carbon paste electrode modified with Ni(II)-BS complex and reduced graphene oxide nano sheets, Electroanalysis 28 (12) (2016) 2985–2992, https://doi.org/10.1002/ elan.201501183.[8] S. Wasmus, A. Küver, Methanol oxidation and direct methanol fuel cells: a selective review, J. Electroanal. Chem. 461 (1-2) (1999) 14–31.[9] M. Liu, R. Zhang, W. Chen, Graphene-Supported Nanoelectrocatalysts for Fuel Cells: Synthesis, Properties, and Applications, Chem. Rev. 114 (2014) 5117– 5160.[10] N. Spinner, W.E. Mustain, Electrochim. Acta 56 (2011) 5656.[11] M.S. Risbud, S. Baxter, M. Skyllas-Kazacos, Open Fuels Energy Sci. J. 5 (2012) 9.

Promising application of MXene-based materials in direct methanol fuel cells: A review

1 - Introduction to direct methanol fuel cells

>> A lightweight 200W direct methanol fuel cell (DMFC) stack is designed and fabricated to powera small scale Unmanned Aerial Vehicle (UAV). The DMFC stack consists of 33-cells in which membrane-electrodeassemblies (MEAs) having an active area of 88 cm 2 are sandwiched with lightweight composite bipolar plates.The total stack weight is around 3.485 kg and stack performance is tested under various methanol feed concentrations. The DMFC stack delivers a maximum power of 248 W at 13.2 V and 71.3℃ under methanol feed concentrationof 1.2 M. In addition, the voltage of individual cell in the 33-cell stack is measured at various current levelsto ensure the stability of DMFC stack operations. The cell voltage distribution data exhibit the maximum cell voltage deviation of 28 mV at 15 A and hence the uniformity of cell voltages is acceptable. These results clearlydemonstrate that DMFC technology becomes a potential candidate for small-scale UAV applications. Key words : Direct methanol fuel cell, DMFC(직접메탄올연료전지), Unmanned aerial vehicle, UAV(무인비행기),Fuel cell stack(연료전지 스택), Methanol crossover(메탄올 크로스오버)

Direct methanol fuel cell (DMFC) is promising energy source for portable and automotive applications, mainly due to their low operating temperature, direct use of liquid fuel, and simple structure without the stringent need for a reformer [1-3]. Carbon black, nanometer-size carbon particles, is commercially used as the catalyst support in fuel cell owing to its high surface area, porosity, electric conductivity, low density, and low cost. In the previous work, we have used various carbon nanomaterials as a catalyst support for DMFC [4]. In this study, we measured the powder conductivity of carbon nanomaterials including carbon nanocoil (CNC), carbon nanoballoon (CNB), Vulcan XC-72R (Vulcan), and vapor-grown carbon fiber (VGCF-H). Under compression of these materials, it is shown that the electrical conductivity of carbon nanomaterials did not only depend on its intrinsic morphological properties, which determine the degree of packing of the material and hence the change in density, but also on such extrinsic factors as the applied pressure and the ambient humidity. In addition, this study investigates the effects of the conductivity and structure of the carbon nanomaterials used in the anode catalyst layer (CL) on the performance of DMFC using transmission and scanning electron microscopies, polarization technique, and electrochemical impedance spectroscopy (EIS). CNCs were synthesized using an automatic chemical vapor deposition system with a consecutive substrate transfer mechanism. The fiber diameter of the CNCs is ~300 nm, the coil diameter is ~1000 nm, and the coil length is ~10 μm. Arc black (AcB) was synthesized using the twin-torch arc discharge apparatus developed in our laboratory. CNB was obtained by heating AcB in a Tammann oven in Ar gas at 2600 ºC for 2 h. Commercially available Vulcan (Cabot Corp., Boston, MA, USA) and VGCF-H (SHOWA DENKO K. K., Tokyo, Japan) were used as the Vulcan and VGCF-H samples, respectively. CNB and Vulcan were composed of spherical with a particle diameter of ~50 nm. The fiber diameters of the VGCF-H were ~15 nm, and their length was ~3 μm. Powder conductivity of each sample was measured by a source meter, with an applied voltage of 0.1 V at room temperature. 300 mg of the sample was set in acrylic pipe. Subsequently the sample was compressed between the brass pistons. The compressive force was varied from 0.01 to 1.0 MPa. Nafion®115 membrane (Dupont) was used as electrolyte membrane. The anode and cathode catalysts used were 30-wt.% PtRu/CNC, /CNB, /Vulcan, and /VGCF-H and 50-wt.% Pt/C (Tanaka Kikinzoku International K.K), respectively. The membrane electrode assembly (MEA) was mounted into the DMFC cell (Japan Automobile Research Institute). In this performance testing, 0.5 M (M = moldm-3) methanol solution were supplied to the anode at a flow rate of 0.1 mLs-1, and dry air was supplied to the cathode at a flow rate of 5 mLs-1. The DMFC was operated 60 ºC and its polarization characteristics and EIS were measured using a fuel cell impedance meter (Kikusui Electronics Corp., KFM2030). The carbon nanomaterials and the surface morphologies of the anode catalyst layer were examined by TEM (JEM-2100F, JEOL, Tokyo, Japan) and SEM (S-4500 II and SU8000, Hitachi, Tokyo, Japan), respectively. The density of the carbon nanomaterials by compressive forces depends on the rearrangement and fragmentation of agglomerates [5]. In addition, the powder conductivity during compaction is mainly governed by the increase of particle contact area. From the measurement results of the powder compression electrical conductivity, CNB showed comparable powder conductivity to Vulcan. Moreover, VGCF-H showed the highest conductivity. The figure shows the cell polarization and power density of the DMFCs with different carbon nanomaterials in the anode CL. The DMFC performance exhibited the highest power density (15.3 mW cm-2) when CNC was used as the catalyst support in the anode CL, while that using CNB showed the lowest power density (8.1 mW cm-2). Therefore, the DMFC performance was not correlated with the results obtained by the measurement of the powder compression electrical conductivity. From the results of the EIS measurement and SEM images, it is suggested that the interface state of the catalyst supports was also an important factor in the DMFC performance.

The objective of this study focuses on the characterization of polyetheretherketone (PEEK) membranes for direct methanol fuel cells (DMFC) application. The PEEK membrane was modified with sulfonation and charged surface modifying macromolecule (cSMM) using MDI, DEG and HBS in NMP solvent. The characterized of membrane were done using Scanning Electron Microscopy (SEM), water uptake, contact angle, thermal stability, methanol permeability, proton conductivity and DMFC test. DMFC tests were performed at room temperature to obtain polarization curves that show voltages and power density of each variable. The results showed that the cSMM methode of the polymer increases water uptake, thermal stability, methanol permeability and proton conductivity. In terms of morphology, it was found that cSMM method can be applied for membrane modification for DMFC application. In terms of the DMFC tests of the membranes, SPEEK without modification proved to have the best performance in stability because of its low methanol permeability. In contrast, the best performance was achieved by the SPEEK/cSMM (with modification) in highest voltage and power density because of its high proton conductivity.

High performance batteries currently used in laptop computers, cell phones, and other portable electronic devices have been making small improvements for decades. Nevertheless, such power supplies have inherent limitations which restrict the advancement of the technical capability of these electronic devices. For instance, the designer must strike a balance between compactness and run time. As batteries age, run time typically drop significantly, so the designer must oversize the battery system initially, thus adding weight and increasing the cost. Overall efficiency is also an issue, as losses occur during generation of electricity at the power plant, in transmission, in charging, in slow discharge during storage, and finally in conversion of stored chemical energy into electrical energy at time of use. Direct methanol fuel cells (DMFCs) are an emerging technology which has the potential to improve on several of these limitations. In the DMFC, methanol/water mixtures react and produce hydrogen ions and electrons electrochemically. The electrons flow through the load circuit, while the ions diffuse through a membrane electrolyte, completing the reduction reaction at the cathode in the presence of oxygen from air. This paper aims to compare the DMFC systems against conventional batteries in respect of energy capacity degradation, gravimetric and volumetric energy densities. It is concluded that, although the initial mass and volume of a DMFC system dominate the gravimetric and volumetric energy densities profile respectively for a short operation time, the methanol conversion efficiency becomes the dominant factor as the operation time increases. Depending on the initial system mass and volume and conversion efficiency, commercially available DMFC systems can offer weight advantages over current battery technology for operation times longer than 10 hours and volume advantages for the operation time longer than 50 hours. Near-term advances in these break-even times are expected to be an order of magnitude, given the relatively rapid development rate of the DMFC. Additionally, although the energy capacity of both the DMFC system and the battery degrades with operation time, the degradation for the battery is typically higher, especially for long time of service. For these reasons, DMFC systems appear to be highly promising for portable electronic devices.