Performance of a hybrid direct ethylene glycol fuel cell

In this work, a hybrid fuel cell is developed and tested, which is composed of an alkaline anode, an acid cathode, and a cation exchange membrane. In this fuel cell, ethylene glycol and hydrogen peroxide serve as fuel and oxidant, respectively. Theoretically, this fuel cell exhibits a theoretical voltage reaching 2.47 V, whereas it is experimentally demonstrated that the hybrid fuel cell delivers an open‐circuit voltage of 1.41 V at 60°C. More impressively, this fuel cell yields a peak power density of 80.9 mW cm^?2 (115.3 mW cm^?2 at 80°C). Comparing to an open‐circuit voltage of 0.86 V and a peak power density of 67 mW cm^?2 previously achieved by a direct ethylene glycol fuel cell operating with oxygen, this hybrid direct ethylene glycol fuel cell boosts the open‐circuit voltage by 62.1% and the peak power density by 20.8%. This significant improvement is mainly attributed not only to the high‐voltage output of this hybrid system design but also to the faster kinetics rendered by the reduction reaction of hydrogen peroxide.     

Performance of a direct ethylene glycol fuel cell with an anion-exchange membrane

This paper reports on the development and performance test of an alkaline direct ethylene glycol fuel cell. The fuel cell consists of an anion-exchange membrane with non-platinum electrocatalysts at both the anode and cathode. It is demonstrated that this type of fuel cell with relatively cheap membranes and catalysts can result in a maximum power density of 67 mW cm⁻² at 60 °C, which represents the highest performance that has so far been reported in the open literature. The high performance is mainly attributed to the increased kinetics of both the ethylene glycol oxidation reaction and oxygen reduction reaction rendered by the alkaline medium with the anion-exchange membrane.     

An alkaline direct ethylene glycol fuel cell with an alkali-doped polybenzimidazole membrane

An alkaline direct ethylene glycol fuel cell (DEGFC) with an alkali-doped polybenzimidazole membrane (APM) is developed and tested. It is demonstrated that the use of APMs enables the present fuel cell to operate at high temperatures. The fuel cell results in the peak power densities of 80 mW cm⁻² at 60 °C and 112 mW cm⁻² at 90 °C, respectively. The power output at 60 °C is found to be 67% higher than that by DEGFCs with proton exchange membranes, which is mainly attributed to the superior electrochemical kinetics of both ethylene glycol oxidation and oxygen reduction reactions in alkaline media.     

High-performance high-entropy quinary-alloys as anode catalysts for direct ethylene glycol fuel cells

Noble metals are the most commonly used electrocatalysts, but due to the high-cost and scarcity, improving their utilization has become a hot topic. As the Pt-based high-entropy alloy (HEA) can greatly increase the activity of catalyst and increase the utilization of noble metal, herein, a HEA with promising performance in ethylene glycol oxidation reaction (EGOR) is developed. The EGOR results show that, the onset potential of PtPdAuNiCo/C is 0.55 V, which is 20 mV lower than Pt/C (0.57 V) reference. Besides, the PtPdAuNiCo/C exhibits a high activity of 0.482 A mg^?1_PtPdAu, which is 2.18 times of Pt/C (0.221 A mg^?1_Pt) reference. And the current retention rate of PtPdAuNiCo/C (81.3%) is also higher than Pt/C (73.0%) reference in 500-cycle stability test. When as-obtained PtPdAuNiCo/C assembled into a direct ethylene glycol fuel cell, it exhibits a high-power density of 8.38 mW cm^?2. It is 1.40 times than that of Pt/C (6.00 mW cm^?2) reference. This work would be a good reference to HEA materials application on electrocatalysis in future.     

Status of the development of a direct methanol fuel cell

In the past, most papers on direct methanol fuel cells (DMFC) reported about systems using pure oxygen instead of air supplied to the cathode. The status of the work on DMFC at Siemens was characterized by more than 200 mW/cm² at a cell voltage of 0.5 V under oxygen operation (4–5 bar abs.) at high temperatures (140°C). High oxygen pressure operation at high temperatures is only useful in special market niches. Low air pressure up to 1.5 bar abs. and therefore low operation temperatures in the range of 80–110°C are necessary technical features and economic requirements for widespread application of the DMFC. Today, our system produces 50 mW/cm² under air operation at low over pressure and at 80°C, while the cell voltage again amounts to 0.5 V. These measurements were carried out in single cells between 3 and 60 cm². First results for a cell design with an electrode area of 550 cm², which is appropriate for assembling a DMFC-stack, are shown. In the new cell it was possible to achieve the same power densities as in the experimental cells at low air over pressure. Also a three-celled stack based on this design revealed nearly the same performance. At 80°C a power output of 77 W at a stack voltage of 1.4 V can be obtained in the air mode. The low pressure air operation results in a lower performance which must be compensated by future improvements of the activity of the anode catalyst and by an adequate membrane with a low methanol and water permeation, which would be a great progress for the DMFC.     

Micro-electro-mechanical systems (MEMS)-based micro-scale direct methanol fuel cell development

This paper describes a high-power density, silicon-based micro-scale direct methanol fuel cell (DMFC), under development at Carnegie Mellon. Major issues in the DMFC design include the water management and energy-efficient micro fluidic sub-systems. The air flow and the methanol circulation are both at a natural draft, while a passive liquid–gas separator removes CO₂ from the methanol chamber. An effective approach for maximizing the DMFC energy density, pumping the excess water back to the anode, is illustrated.     

Electro-oxidation of ethylene glycol on PtCo metal synergy for direct ethylene glycol fuel cells: Reduced graphene oxide imparting a notable surface of action

Slow electro-oxidation reaction and low power output are two major limiting factors in successful commercialization of fuel cell technology. An efficient and stable electro-catalyst with effectual metal combination supported on a durable matrix may provide a viable solution to overcome these issues. The direct ethylene glycol fuel cell consisting of bimetallic anode catalysts are expected to lead out the high-power output issues. In the present paper, we emphasized on the synthesis of a high performing CO poisoning resistant Pt based binary anode catalysts for the electro-oxidation of ethylene glycol (EG) using a chemical reduction route. The electrocatalysts consists of PtCo alloy nanoparticles with different composition of Pt and Co, supported on reduced graphene oxide (rGO). Physical characterizations revealed the formation of bi-metallic catalysts within the size ranges from 2 nm to 3 nm. Electrochemical analysis revealed that Pt_xCo_y/rGO electrocatalyst with x: y molar ratio of 1:9 imparts the highest peak current and power density as compared to commercially available Pt/C and PtCo/C anode catalysts for ethylene glycol electro-oxidation. The power density (81.1 mW/cm²) obtained using Pt_xCo_y/rGO with x:y molar ratio of 1:9 metal catalyst in DEGFC is more than other synthesized catalysts at an operating temperature of 100 °C and the operating pressure of 1 bar with 2 M ethylene glycol as anode fuel and anode and cathode platinum metal loading of 2 mg/cm².     

Progress and perspectives in micro direct methanol fuel cell

Micro Direct Methanol Fuel cells (μDMFC) are of considerable interest for both academic laboratories and industries to commercialize, since the energy demand has been increased. Although intensive researches are conducted to understand μDMFC, many challenges still remain to be solved to exploit them for real commercial applications. The pros and cons of various substrate materials used and various designs fabricated so far for fuel delivery are highlighted. One of the existing problems is membrane swelling, which has been reduced by the polymer modification recently. The removal of evolved CO₂ gas in the anode and reduction of water flooding in the cathode are accomplished through the advanced materials fabrication is discussed. The important parameters such as fuel, water, air and thermal managements to increase cell performance by material manipulation and design are outlined in this review. A handful of companies are trying μDMFC technology toward real commercial strides. We have also presented an update of the achievements so far by these companies.     

Progress and major BARRIERS of nanocatalyst development in direct methanol fuel cell: A review

Direct methanol fuel cells (DMFC), among the most suited and prospective alternatives for portable electronics, have lately been treated with nanotechnology. DMFCs may be able to remedy the energy security issue by having low operating temperatures, high conversion efficiencies, and minimal emission levels. Though, slow reaction kinetics are a significant restriction of DMFC, lowering efficiency and energy output. Nowadays, research is more focused on fundamental studies that are studying the factors that can improve the capacity and activity of catalysts. In DMFC, among the most widely explored catalysts are platinum and ruthenium which are enhanced in nature by the presence of supporting materials such as nanocarbons and metal oxides. As a result, this research sheds light on nanocatalyst development for DMFCs based on Platinum noble metal. To summarize, this research focuses on the structure of nanocatalysts, as well as support materials for nanocatalysts that can be 3D, 2D, 1D, or 0D. The support material described is made up of CNT, CNF, and CNW, which are the most extensively used because they improve the performance of catalysts in DMFCs. In addition, cost estimations for fuel cell technology are emphasized to show the technology's status and requirements. Finally, challenges to nanocatalyst development have been recognized, as well as future prospects, as recommendations for more innovative future research.     

Nanocatalyst for direct methanol fuel cell (DMFC)

Nanotechnology has recently been applied to direct methanol fuel cells (DMFC), one of the most suitable and promising options for portable devices. With characteristics such as low working temperature, high energy-conversion efficiency and low emission of pollutants, DMFCs may help solve the future energy crisis. However, a significant limitation to DMFC includes slow reaction kinetics, which reduces performance and power output. Recently, research has focused on increasing the performance and activity of catalysts. Catalysts composed of small, metallic particles, such as platinum and ruthenium, supported on nanocarbons or metal oxides are widely used in DMFC. Thus, this paper presents an overview of the development of nanocatalysts for DMFC. Particularly, this review focuses on nanocatalyst structure, catalyst support, and challenges in the synthesis of nanocatalyst. This paper also presents computational approaches for theoretical modeling of nanomaterials such as carbon nanotubes (CNT) through molecular dynamic techniques.     

Study of fuel efficiency in a direct borohydride fuel cell

In this study, direct borohydride fuel cells (DBFCs) potentialities are evaluated. These emerging systems make it possible to reach maximum powers of about 200 mW cm⁻² at room temperature and ambient air (natural convection) with high concentrated borohydride solutions. On the other hand, a part of borohydride hydrolyses during cell operating which leads to hydrogen formation and fuel loss: the practical capacity represents about only 18% of the theoretical one. In order to improve fuel efficiency, thiourea is tested as an inhibitor of the catalytic hydrolysis associated with BH₄⁻ electro-oxidation on Pt. The practical capacity is drastically improved: it represents about 64% of the theoretical one. Against, electrochemical performances (I–E curves) are affected by the presence of thiourea.     

Design,simulation and experimental characterization of a high-power density fuel cell

This research proposes a novel design of a millimeter-sized air-breathing proton exchange membrane fuel cell (AB-PEMFC). The producing method of the air-breathing PEMFC consisted of the sequential deposition of the elements in layers: 1) endplate of a flat polymer, 2) fuel flow channel with gas diffusion layers (GDL), 3) silicone seal with embedded micro Pt (platinum) wires, 4) membrane electrode assembly (MEA) with high platinum load, 5) GDL with micro Pt wires. Performance tests were done using an AB-PEMFC and the stack of two mono cells under different conditions. The results obtained by the computational fluid dynamics (CFD) allowed analyzing the current collector (CC) position. The performance results show 110 W L^?1 for the cell power density and 2200 W kg^?1 for the specific power density.     

Valveless piezoelectric micropump for fuel delivery in direct methanol fuel cell (DMFC) devices

Fuel cells are being considered as an important technology that can be used for various power applications. For portable electronic devices such as laptops, digital cameras, cell phone, etc., the direct methanol fuel cell (DMFC) is a very promising candidate as a power source. Compared with conventional batteries, DMFC can provide a higher power density with a long-lasting life and recharging which is almost instant. However, many issues related to the design, fabrication and operation of miniaturized DMFC power systems still remain unsolved. Fuel delivery is one of the key issues that will determine the performance of the DMFC. To maintain a desired performance, an efficient fuel delivery system is required to provide an adequate amount of fuel for consumption and remove carbon dioxide generated from fuel cell devices at the same time. In this paper, a novel fuel delivery system combined with a miniaturized DMFC is presented. The core component of this system is a piezoelectric valveless micropump that can convert the reciprocating movement of a diaphragm activated by a piezoelectric actuator into a pumping effect. Nozzle/diffuser elements are used to direct the flow from inlet to outlet. As for DMFC devices, the micropump system needs to meet some specific requirements: low energy consumption but a sufficient fuel flow rate. Based on theoretical analysis, the effect of piezoelectric materials properties, driving voltage, driving frequency, nozzle/diffuser dimension, and other factors on the performance of the whole fuel cell system will be discussed. As a result, a viable design of a micropump system for fuel delivery can be achieved and some simulation results will be presented as well.     

Investigations of direct methanol fuel cell (DMFC) fading mechanisms

In this report, we present the microscopic investigations on various fading mechanisms of a direct methanol fuel cell (DMFC). High energy X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), energy dispersive X-ray spectroscopy (EDX), and Raman spectroscopic analysis were applied to a membrane-electrode-assembly (MEA) before and after fuel cell operation to figure out the various factors causing its fading. High energy XRD analysis of the fresh and faded MEA revealed that the agglomeration of the catalyst particles in the cathode layer of the faded MEA was more significant than in the anode layer of the faded MEA. The XAS analysis demonstrated that the alloying extent of Pt (J_Pt) and Ru (J_Ru) in the anode catalyst was increased and decreased, respectively, from the fresh to the faded MEA, indicating that the Ru environment in the anode catalyst was significantly changed after the fuel cell operation. Based on the X-ray absorption edge jump measurements at the Ru K-edge on the anode catalyst of the fresh and the faded MEA it was found that Ru was dissolved from the Pt-Ru catalyst after the fuel cell operation. Both the Ru K-edge XAS and EDX analysis on the cathode catalyst layer of the faded MEA confirms the presence of Ru environment in the cathode catalyst due to the Ru crossover from the anode to the cathode side. The changes in the membrane and the gas diffusion layer (GDL) after the fuel cell operation were observed from the Raman spectroscopy analysis.     

Non-linear optimization of passive direct methanol fuel cell (DMFC)

The cost associated with a direct methanol fuel cell (DMFC) is the main drawback of its commercialization. To address this issue, the main objective of this study is to minimize the cost of micro DMFCs for portable applications. The model was coupled with a non-linear constrained optimization to determine an optimum design of the DMFC with respect to the design and geometrical parameters of the anode and cathode, including methanol concentration, power density, catalyst loading, etc. Optimization was performed using Matlab to minimize the difference between the power input required and the power optimum via Non-Linear Programming (NLP). The optimum characteristics of DMFC were solved by using an NLP simulation. The outputs were verified by both experimental and modeling results. These dynamic optimization results provided an optimum design parameters for the physical properties of DMFC required to generate the portable application. Lastly, a cost analysis was also considered in this study.     

Parametric study on direct ethanol fuel cell (DEFC) performance and fuel crossover

A parametric study was carried out to investigate the effect of fuel concentration (0.5 M–3.0 M), operating temperature (ambient temperature to 85 °C), flow rate of ethanol (0.5–5.0 mL min⁻¹) and air (100–600 mL min⁻¹) on the direct ethanol fuel cell (DEFC) performance. The operations were conducted in three operational modes, namely, passive, semi passive, and active modes, and power generation were measured. Ethanol crossover was indicated by the carbon dioxide (CO₂) concentration present at the cathode outlet and measured by using a CO₂ analyzer. Results indicated that DEFC performance increased with the increase of ethanol concentration, and ethanol and oxidant flow rate increased with temperature until DEFC reaches the optimum conditions, i.e., concentration and flow rate. Meanwhile, the DEFC performance significantly and proportionally increased with operation temperature and reached values of up to 8.70 mW cm⁻² and 85 °C at stable conditions. Furthermore, fuel crossover, that is, ethanol flux, increased in proportion to the ethanol concentration, i.e., 3.71 × 10⁻⁴ g m⁻² s⁻¹ and 8.79 × 10⁻⁴ g m⁻² s⁻¹ for 0.5 M and 3.0 M ethanol concentration, respectively. At different modes of operation, the active DEFC system exhibited the highest performance, followed by the semi passive and passive DEFC system. These results indicated that optimizing ethanol, oxidant flow rate and temperature would enhance the mass transport in anodes and cathodes, and hence improve the electrochemical reactions and DEFC performance.     

Poly(ethylene glycol) modified activated carbon for high performance proton exchange membrane fuel cells

A high water retention membrane is developed by co-assembling poly(ethylene glycol) (PEG) grafted activated carbon (AC-PEG) with Nafion. The AC-PEG is prepared via a sol–gel process. The use of PEG as a transporting medium in AC-PEG shows a largely improved water retention ability, a higher proton conductivity and a reduced swelling ratio, making it well suited for proton exchange membrane fuel cells (PEMFCs). Further, the composite membranes show improved mechanical properties at high temperature, thus ensuring the structural stability of membranes during the fuel cell operation. Compositional optimized AC-PEG/Nafion composite membrane (15 wt% compared to Nafion) demonstrates a better performance than the commercially available counterpart, Nafion 212, in fuel cell measurements. To identify the key factor of the improved performance, current interrupt technique is used to quantitatively verify the changes of resistance under different relative humidity environment.     

Response of a direct methanol fuel cell to fuel change

Methanol and ethanol have recently received much attention as liquid fuels particularly as alternative ‘energy-vectors’ for the future. In this sense, to find a direct alcohol fuel cell that able to interchange the fuel without losing performances in an appreciable way would represent an evident advantage in the field of portable applications. In this work, the response of a in-house direct methanol fuel cell (DMFC) to the change of fuel from methanol to ethanol and its behaviour at different ambient temperature values have been investigated. A corrosion study on materials suitable to fabricate the bipolar plates has been carried out and either 316- or 2205-duplex stainless steels have proved to be adequate for using in direct alcohol fuel cells. Polarization curves have been measured at different ambient temperature values, controlled by an experimental setup devised for this purpose. Data have been fitted to a model taking into account the temperature effect. For both fuels, methanol and ethanol, a linear dependence of adjustable parameters with temperature is obtained. Fuel cell performance comparison in terms of open circuit voltage, kinetic and resistance is established.     

A development of direct hydrazine/hydrogen peroxide fuel cell

A direct hydrazine fuel cell using H₂O₂ as the oxidizer has been developed. The N₂H₄/H₂O₂ fuel cell is assembled by using Ni-Pt/C composite catalyst as the anode catalyst, Au/C as the cathode catalyst, and Nafion membrane as the electrolyte. Both anolyte and catholyte show significant influences on cell voltage and cell performance. The open-circuit voltage of the N₂H₄/H₂O₂ fuel cell reaches up to 1.75 V when using alkaline N₂H₄ solution as the anolyte and acidic H₂O₂ solution as the catholyte. A maximum power density of 1.02 W cm⁻² has been achieved at operation temperature of 80 °C. The number of electrons exchanged in the H₂O₂ reduction reaction on Au/C catalyst is 2.     

Sulfonated poly(ether ether ketone)/ethylene glycol/polyhedral oligosilsesquioxane hybrid membranes for fuel cell applications

The paper describes the preparation of hybrid membranes using a trisilanol phenyl polyhedral oligosilsesquioxane (TSP POSS) as filler, ethylene glycol (EG) as cross-linker and sulfonated poly(ether ether ketone) [SPEEK] (DS ∼65%) as polymer matrix.