Fuel Cell Design Research Articles

Fabrication of Single Chamber Microbial Fuel Cell (SMFC) Using Soil as a Substrate

This paper presents a Single-chamber Microbial Fuel Cell (SMFC) design by utilizing soil as a substrate with two sets of electrode combinations, which are graphite-activated carbon and copper-zinc of different sizes. It was found that graphite and activated carbon produced greater power density compared to copper and zinc. Moreover, it was observed that the graphite-activated carbon cloth electrode with a bigger surface area of 51cm2, resulted in a higher power density of 904mW/m2. To further improve the voltage production of this model, four SMFCs were stacked in series and connected to a DC-DC boost converter to increase the voltage to 1.482 V for the copper-zinc electrode and 1.722 V for the graphite-activated carbon electrode, respectively, which was sufficient to light up an LED light.

Production of a monolithic fuel cell stack with high power density

The transportation sector is undergoing a technology shift from internal combustion engines to electric motors powered by secondary Li-based batteries. However, the limited range and long charging times of Li-ion batteries still hinder widespread adoption. This aspect is particularly true in the case of heavy freight and long-range transportation, where solid oxide fuel cells (SOFCs) offer an attractive alternative as they can provide high-efficiency and flexible fuel choices. However, the SOFC technology is mainly used for stationary applications owing to the high operating temperature, low volumetric power density and specific power, and poor robustness towards thermal cycling and mechanical vibrations of conventional ceramic-based cells. Here, we present a metal-based monolithic fuel cell design to overcome these issues. Cost-effective and scalable manufacturing processes are employed for fabrication, and only a single heat treatment is required, as opposed to multiple thermal treatments in conventional SOFC production. The design is optimised through three-dimensional multiphysics modelling, nanoparticle infiltration, and corrosion-mitigating treatments. The monolithic fuel cell stack shows a power density of 5.6 kW/L, thus, demonstrating the potential of SOFC technology for transport applications.

Inventor of the Year

Siemens Mobility honors the outstanding achievements of one young female inventor whose patented fuel cell design promises to make hydrogen trains more efficient and affordable

Towards cost-effective soil microbial fuel cell designs

Soil microbial fuel cell (SMFC) is a carbon-neutral energy harvesting technology that exploits the use of electroactive bacteria naturally present in soil to directly generate electricity from organic compounds. Given the simplicity of the system design, SMFCs have great potential to be used for decentralised solutions, especially in areas where access to conventional energy sources is limited. Yet, the high cost to power ratio severely limits the translation of this technology into the market. With the aim of reducing the capital cost, in this study we explore the effect of decreasing the amounts of current collector (CC) on the performance. The results demonstrate that increasing the amount of current collector per surface area of the electrode is not a feasible way of enhancing power densities, as to increase the performance by 20% and 35%, the amount of current collector would have to be increased by 150% and 300%, respectively. This highlights the importance of economic evaluations when optimising the design of a SMFC.

Recent advances in tuning redox properties of electron transfer centers in metalloenzymes catalyzing oxygen reduction reaction and H2 oxidation important for fuel cells design.

Current fuel-cell catalysts for oxygen reduction reaction (ORR) and H2 oxidation use precious metals and, for ORR, require high overpotentials. In contrast, metalloenzymes perform their respective reaction at low overpotentials using earth-abundant metals, making metalloenzymes ideal candidates for inspiring electrocatalytic design. Critical to the success of these enzymes are redox-active metal centers surrounding the enzyme active sites that ensure fast electron transfer (ET) to or away from the active site, by tuning the catalytic potential of the reaction as observed in multicopper oxidases but also in dictating the catalytic bias of the reaction as realized in hydrogenases. This review summarizes recent advances in studying these ET centers in multicopper oxidases and heme-copper oxidases that perform ORR and hydrogenases in carrying out H2 oxidation. Insights gained from understanding how the reduction potential of the ET centers effects reactivity at the active site in both the enzymes and their models are provided.

Advanced parametric model for analysis of the influence of channel cross section dimensions and clamping pressure on current density distribution in PEMFC

The design of the flow field and the channel cross section of a bipolar plate as well as the intrusion effect of gas diffusion layers due to clamping pressure can significantly influence the performance of a fuel cell. The land and channel areas at a channel cross section can have different boundary conditions due to compression, intrusion of gas diffusion layers and transport phenomena. Todayapplication engineers are faced with the challenge of finding advantageous overall solutions from this plurality of multi-criteria parameters. In this thesis, a model approach is presented which combines a fully parametric analytical-empirical intrusion model with a 1D fuel cell model. This allows the calculation of current density distributions at the channel cross section, taking into account clamping pressure, channel parameters and operating conditions. Depending on the operating points considered, the results show that the maximum current densities occur in different areas of the channel cross section. In addition, with regard to the clamping pressure current density optima can be determined. Using this model approach, in an early development process application engineers will be able to compare hundreds of variants in a reasonable short time and thus determine advantageous fuel cell designs.

Numerical study on the influence of waveform channel and related design parameters on the cold start of proton exchange membrane fuel cell

In order to enable the proton exchange membrane fuel cell to be used under outdoor conditions, research on the cold start of the fuel cell is essential. In this paper, numerical simulation is used to study the influence of fuel cell cathode channel geometry and porosity on the fuel cell cold start process. By analyzing the internal parameters of the fuel cell at different times, including current density, ice volume fraction, temperature and water content, the optimal fuel cell design was obtained. From a comprehensive comparison, although the current density and temperature rise of the ordinary wave channel fuel cell with higher porosity increase slowly at the beginning of the cold start, the decline process and icing process of it are also relatively slow. Therefore, a fuel cell with an ordinary wave channel and a higher porosity may perform better at cold start. This research contributes to the application and commercialization of fuel cells in a wider range of practical conditions.

DFT Study of NiO@Graphene Composite for Electrochemical Oxidation of Urea in Alkaline Electrolyte

The continuous increase in the energy demand needs to pursuit a clean and renewable energy source because non-renewable energy sources such as traditional fossil fuels are limited and lead to global warming. It is necessary to bridge the gap between academia and industry with extensive research and their practical applications. Although hydrogen and oxygen evolution reactions (HER and OER respectively) have been considered as revolutionary fuel cell designs that utilize water-splitting technology, they suffer from efficiency drawbacks and can be realized in a limited pristine fresh water and with the use of noble metal catalysts. Urea oxidation reaction (UOR) is a fundamental step in fulfilling the need for practical green energy because they do not need high-voltage supply and also do not release both O2 and H2 gases simultaneously, encountered during water splitting. Furthermore, urea is an abundant component of human and animal waste, which can result in the production of problematic ammonia under normal degradation or standard hydrolysis practices. More importantly, the UOR process could provide an opportunity for waste disposal and green hydrogen production.In a typical UOR, urea in an alkali electrolyte is oxidized to the production of N2 and CO2 at the anode and H2 on the cathode from water electrolysis. This process is depicted in equations 1-3, respectively.Anode: CO(NH2)2 + 6OH- → N2 + 5H2O + CO2 + 6e- (1)Cathode: 6H2O + 6e- → 3H2 + 6OH- (2)Overall: CO(NH2)2 + H2O → N2 + H2 + CO2 (3)The UOR process is slow and inefficient under normal conditions due to the 6-electron transfer process from anode to cathode. Thus, it is necessary to modify the working electrode using a catalyst. Nickel-based materials are considered as one of the most promising groups of materials for catalysis in UOR owing to their low-cost, easy synthesis route, and abundant in nature. To improve the conductivity of Ni-based materials while maintaining the compounds’ catalytic performance, several effective strategies were applied, including the introduction of conductive support, element doping, high valence Ni-based materials, and defect engineering. Many of these effective strategies were developed to realize the commercial implementation of Ni-catalyst driven UOR. Nevertheless, the in-depth theoretical-fundamental understanding on the UOR were not studied due to its complicated multi-step gas adsorption and desorption.Moreover, one major theoretical drawback found by density functional theory calculation is the rate-limiting intermediate step of CO2 desorption during the reaction on the anode. In our previous work, we investigated the use of nano-NiO supported on eggshell membrane-derived carbon for a Ni-catalyzed UOR, and the periodic heterojunction model was selected to illustrate the impact of between the porous carbon and NiO nanoparticles. NiO also possesses many merits, including easy-to-obtain, low-cost, and exchangeable valence states. Meanwhile, graphene was employed as the alternative porous carbon for simulations. It is important to add theoretical simulation to understand the UOR process using different models, especially for the existence of single-atom model due to attractive findings. The in-depth mechanism of UOR the NiO@Graphene is still not clear. Consequently, it is useful to employ the single-atom model to investigate the role of NiO@Graphene in the UOR process.In this work, a single-atom model was built to understand the relationship of NiO@Graphene composite and its urea oxidation behavior. The single-atom model, which differs from the previous theoretical model, was applied to illustrate the influence of between graphene and NiO nanoparticles. Meanwhile, this work also served as an important theoretical supplement for the previous research. Prior to the investigation of UOR, the adsorption of hydroxyl group and urea on the NiO@Graphene was compared. Then, the adsorption of urea and CO2 on NiO and NiOOH with graphene was calculated and compared. The electron density difference map was also used to study the electron transfer of NiO@Graphene composite. Figure 1

Non-Fourier Heat Conduction and Thermal-Stress Analysis of a Spherical Ice Particle Subjected to Thermal Shock in PEM Fuel Cell at Quick Cold Start-Up

Quick start at low temperature is one of the key bottleneck technologies that restrict the large-scale commercialization of proton exchange membrane (PEM) fuel cell vehicles. Ice and devices in battery systems based on thermal deicing are inevitably subjected to thermal shock. In order to study this problem, a non-Fourier heat conduction model is established to study the temperature response of a spherical ice particle subjected to thermal shock with different boundary conditions on the surface. Furthermore, distribution of thermal stress in the particle is obtained using the calculated temperature field, and the effect of thermal relaxation time and boundary conditions on the temperature response as well as the thermal stress field are also analyzed. The results, which are significantly different from that obtained using Fourier law of heat conduction, show that the mechanical stresses and the serious expansion of the ice particle may lead to the severe deformation of the devices connected to the ice during the cold start-up, imposing a great challenge in controlling structural reliability of PEM fuel cells. The numerical results are expected to provide a scientific theoretical basis for PEM fuel cell design and low-temperature start-up control.

Online voltage consistency prediction of proton exchange membrane fuel cells using a machine learning method

Widely acknowledged by experts, the inconsistency between the cells of the proton exchange membrane fuel cell stack during operation is an important cause of the fuel cell life decay. Existing studies mainly focus on qualitative analysis of the effects of operating parameters on fuel cell stack consistency. However, there is currently almost no quantitative research on predicting the voltage consistency through operating parameters with machine learning methods. To solve this problem, a three-dimensional model of proton exchange membrane fuel cell stack with five single cells is established in this paper. The Computational Fluid Dynamic (CFD) method is used to provide the source data for prediction model. After predicting the voltage consistency with several machine learning methods and comparing the accuracy through simulation data, the integrated regression method based on Gradient Boosting Decision Tree (GBDT) gets the highest score (0.896) and is proposed for quickly predicting the consistency of cell voltage through operating parameters. After verifying the GBDT method with the experimental data from the fuel cell stack of SUNRISE POWER, in which the accuracy score is 0.910, the universality and accuracy of the method is confirmed. The influencing sensitivity of each operating parameter is evaluated and the current density has the greatest influence on the predicted value, which accounts for 0.40. The prediction of voltage consistency under different combination of operating parameters can guide the optimization of structural parameters in the process of the fuel cell design and operating parameters in the process of fuel cell control.

Identifiability Analysis of Degradation Model Parameters from Transient CO2 Release in Low-Temperature PEM Fuel Cell under Various AST Protocols

The detrimental effects of the catalyst degradation on the overall envisaged lifetime of low-temperature proton-exchange membrane fuel cells (LT-PEMFCs) represent a significant challenge towards further lowering platinum loadings and simultaneously achieving a long cycle life. The elaborated physically based modeling of the degradation processes is thus an invaluable step in elucidating causal interaction between fuel cell design, its operating conditions, and degradation phenomena. However, many parameters need to be determined based on experimental data to ensure plausible simulation results of the catalyst degradation models, which proves to be challenging with the in situ measurements. To fill this knowledge gap, this paper demonstrates the application of a mechanistically based PEMFC modeling framework, comprising real-time capable fuel cell performance, and platinum and carbon support degradation models, to model transient CO2 release rates in the LT-PEMFCs with the consistent calibration of reaction rate parameters under multiple different accelerated stress tests at once. The results confirm the credibility of the physical and chemical modeling basis of the proposed modeling framework, as well as its prediction and extrapolation capabilities. This is confirmed by an increase of only 29% of root mean square deviations values when using a model calibrated on all three data sets at once in comparison to a model calibrated on only one data set. Furthermore, the unique identifiability and interconnection of individual model calibration parameters are determined via Fisher information matrix analysis. This analysis enables optimal reduction of the set of calibration parameters, which results in the speed up of both the calibration process and the general simulation time while retaining the full extrapolation capabilities of the framework.

A novel fuel cell design for operando energy-dispersive x-ray absorption measurements

A polymer electrolyte fuel cell has been designed to allow operando x-ray absorption spectroscopy (XAS) measurements of catalysts. The cell has been developed to operate under standard fuel cell conditions, with elevated temperatures and humidification of the gas-phase reactants, both of which greatly impact the catalyst utilisation. X-ray windows in the endplates of the cell facilitate collection of XAS spectra during fuel cell operation while maintaining good compression in the area of measurement. Results of polarisation curves and cyclic voltammograms showed that the operando cell performs well as a fuel cell, while also providing XAS data of suitable quality for robust XANES analysis. The cell has produced comparable XAS results when performing a cyclic voltammogram to an established in situ cell when measuring the Pt LIII edge. Similar trends of Pt oxidation, and reduction of the formed Pt oxide, have been presented with a time resolution of 5 s for each spectrum, paving the way for time-resolved spectral measurements of fuel cell catalysts in a fully-operating fuel cell.

The role of input gas species to the cathode in the oxygen-ion conducting and proton conducting solid oxide fuel cells and their applications: Comparative 4E analysis

Most of the gas species in the air entering the fuel cell through the cathode electrode is nitrogen. Nitrogen recognizes as the only reactant inside the fuel cell stack that remains unchanged during its internal chemical and electrochemical processes. Owing to this specific behavior of nitrogen, this study investigates the performance of two types of solid oxide fuel cells with different electrolytes (oxygen-ion conducting and proton conducting) and their electricity generation applications under the influence of changes in nitrogen ratio of the air entering the cathode electrode. Also, the role of simultaneous changes in nitrogen ratio with two main fuel cell design parameters, precisely, current density and fuel utilization factor, on the performance of the fuel cell is scrutinized. Moreover, this study compares the performance of two different electrolytes in the fuel cell structure and their application under identical conditions from thermodynamic, economic, and environmental prespectives. According to the results, with increasing input nitrogen ratio, the voltage output of each cell, energy and exergy efficiencies, electricity generation rate, and exergoeconomic factor of the applications decrease, while the unit cost of electricity and carbon dioxide emission increase. The sensitivity of the reduction in performance is higher in nitrogen ratios above 0.7.

Conceptual Design of Fuel Cell Based Hybrid Unmanned Air Vehicle

Unmanned air vehicles (UAVs) are used successfully in many different fields mainly various military and civilian applications. Recently electric powered UAVs have become more preferable due to their better accessibility, cost, transportation and silence. However, the batteries used in electric UAVs still do not have enough energy density for long endurance flights. Due to the difficulty of using piston and gas turbine engines in small-sized UAVs, hydrogen fuel cells are seen as one of the considerable options to increase endurance and range. In this study, conceptual design of hybrid UAV including fuel cell, solar unit and battery is presented. Small, light and high endurance UAV was designed using aerodynamic calculations and minimum power requirement for cruise flight was determined. 100 W fuel cell produced by Horizon Fuel Cell Technologies and 3S, 5 Ah of battery were used for main power supplies, moreover solar cells to charge the battery were designed to mount on the surface of the wings. Also, a new power management system is designed for switching between the energy sources. As a result of this work, it is determined that fuel cells and solar units are the significant options which can increase the endurance of UAV up to 8 times depending on the design, solar flux, hydrogen capacity etc.

Bipolar‐Interface Hydrogen Fuel Cells: A Review and Perspective on Future High‐Performance, Low Platinum‐Group Metal Content Designs

AbstractThis Review elucidates the state‐of‐the‐art, challenges, and future prospects for bipolar‐interface‐based fuel cells (BPIFCs), focusing on hydrogen‐based systems. On the one side, it provides a summary of state‐of‐the‐art design strategies for BPIFCs from different fields of application. On the other hand, it identifies the two most pivotal areas for a future understanding that particularly refer to the changed mass transport situations introduced by the bipolar fuel cell design, that is, the water management and the bipolar interface layer itself. All operation‐relevant components such as the gas diffusion layers, catalyst layers, and membrane designs are discussed within the framework of these two main areas. As non‐platinum‐group metal (PGM) oxygen reduction is one of the key benefits of bipolar hydrogen fuel cells, a particular focus is put on this configuration. Several additional challenges that exclusively originate from non‐PGM‐based catalyst layers and possible mitigation approaches are discussed. One key insight is that these thick layers could take over the role of microporous layers in the future. Finally, we emphasize that there is a strong lack in both theoretical and experimental approaches that improve our understanding of the underlying processes in bipolar fuel cell designs.

Preparation and characterization of the SPEEK/PVA/Silica hybrid membrane for direct methanol fuel cell (DMFC)

The SPEEK-PVA-Silica hybrid membranes are prepared by solution casting method. The physical, chemical and electrical properties of the polymer membranes are studied by FESEM, FTIR, XRD, DSC, TGA, DMA, water and methanol uptake capacity, Ion Exchange Capacity (IEC), Degree of Sulfonation (DS), hydration number (λ), void volume fraction (%), methanol permeability and proton conductivity. The void volume fraction and density of the polymer membrane increases with increase in the silica content of the membrane which decreases glass transition temperature. At 30 °C, the maximum proton conductivity is found for SPS-3 membrane (3.8 × 10–2 S/cm) which is much higher than recast SPEEK membrane (2.9 × 10–2 S/cm). The proton conductivity of the polymer membrane is dominated by free water facilitated vehicular mechanism. The improvement of the conductivity of the proton in the silica filled polymer membrane at medium to higher temperature is due to the strong interaction between the silica and water resulting in a reduction in the loss of evaporation of water as well as an improvement in the bound water content of the polymer channel, which is regulated by the Grotthuss mechanism. The reduction of methanol permeability and increment in membrane selectivity clearly confirms that the silica filled polymer have excellent methanol blocking capacity which is beneficial for direct methanol fuel cell design.

Design and Simulation of Air-Breathing Micro Direct Methanol Fuel Cells with Different Anode Flow Fields.

The design of the anode flow field is critical for yielding better performance of micro direct methanol fuel cells (µDMFCs). In this work, the effect of different flow fields on cell performance was investigated by the simulation method. Compared with grid, parallel and double-serpentine flow fields, a single-serpentine flow field can better improve the mass transfer efficiency of methanol and the emission efficiency of the carbon dioxide by-product. The opening ratio and channel length also have important effects on the cell performance. The cells were manufactured using silicon-based micro-electro-mechanical system (MEMS) technologies and tested to verify the simulation results. The experimental results show that the single-serpentine flow field represents a higher peak power density (16.83 mWcm−2) than other flow fields. Moreover, the results show that an open ratio of 47.3% and a channel length of 63.5 mm are the optimal parameters for the single-serpentine flow field.

Design and Implementation of Hydrogen Fuel Cell as a Means of Alternative Energy

The demand for electrical energy is on the increase particularly in a developing economy such as Nigeria, where the government has not been able to provide adequate and uninterruptible power supply to her fast growing population. More research is needed to bring electricityto the door step of the people by diverting attention into other sourcesof energy which can stand as viable alternative to the conventional sources of energy. This research is aimed at employing the potentials of water electrolysisto produce hydrogen fuel cell which can be used to power electrical appliances, among other applications. Step-by-step procedures where observed in using locally available materials to construct a containment of hydrogen fuel cell with an electrolyte and two electrodes separated apart into two equal halves of a transparent box made of Perspex. A light bulb (resistive load) was connected across the output terminals, and voltage/current variation s with respect to time was measured using appropriate instruments in order to deduce charging, discharging power and efficiency of the fuel cell. Graphs of measured values were plotted to determine their characteristics including the current/voltage (I-V) characteristics curve of the hydrogen fuel cell. Results of measured values and characteristic curves show that hydrogen fuel cell capable of powering electricalloads was produced, and the current density is dependent on the surface area surrounding the electrodes. That is, the wider the surface area around electrodes the higher the electrical energy generated.

Direct carbon fuel cell design for continuous operation

The design of a direct carbon fuel cell (DCFC) for continuous operation was successfully executed and is presented in this study. Petroleum coke, an abundant carbon source in Canada, was used as a fuel and pneumatically supplied to the anode side of the cell. The open circuit voltage (OCV) of the cell reached 1.1 V and generated a power density of 28 mW/cm2 at 700 °C and 85 mW/cm2 at 850 °C. After about 180 h of operation the cell's performance declined, due to loss of electrolyte. In the next design, a cell was fabricated with an electrolyte circulation loop. This cell generated a lower power density than the first cell assembly but its OCV drop during 180 h operation was significantly improved. These are the first molten carbonate DCFC results demonstrating continuous carbon supply and electrolyte recirculation with potential for ash and impurities removal.

Biochar-Terracotta Conductive Composites: New Design for Bioelectrochemical Systems

Research in the field of bioelectrochemical systems is addressing the need to improve components and reduce their costs in the perspective of their large-scale application. In this view, innovative solid separators of electrodes, made of biochar and terracotta, are investigated. Biochar-based composites are produced from giant cane (Arundo Donax L.). Two different types of composite are used in this experiment: composite A, produced by pyrolysis of crushed chipping of A.donax L. mixed clay; and composite B, produced by pyrolysis of already-pyrolyzed giant cane (biochar) mixed with clay. Electrical resistivity, electrical capacity, porosity, water retention, and water leaching of the two composites types (A and B) with 1, 5, 10, 15, 20, and 30 mass percentages of carbon (w/w) are characterized and compared. Less than 1 kΩ cm of electrical resistance is obtained for composite A with a carbon content greater than 10%, while physical and electrical performances of composite B do not significantly change. SEM micrographs and 3D microcomputed tomography of different composite materials are provided, demonstrating a different matrix structure of carbon in the terracotta matrix. The possibility of suitably decreasing electric resistance and increasing water retention/leaching of composite A opens the way for a new class of resistive materials that can be simultaneously used as electrolytic separators and as external electric circuits, allowing a compact microbial fuel cell design. A proof of concept of such an MFC design was provided for different tested composites. Although all the anolytes become anaerobic, only the MFCs equipped with the composite A30% were able to produce power, reaching the maximum power peak in correspondence to resistance of about 1 kΩ. The low, but significant, produced power (about 40 mW m−2, cathode area) confirm that the proposed solution is particularly suitable for nutrient recovery and environment pollution bioremediation, where energy harvesting is not requested.