Electrochemical Reaction Of Hydrogen Research Articles

Mesoporous Palladium Catalyst for Efficient Electrochemical Semi‐Hydrogenation of Alkynes

AbstractDeveloping robust electrocatalysts for efficient semi‐hydrogenation of alkynes to markedly important alkenes is highly desirable in both research and industry areas. In this work, it is reported that robust palladium mesoporous nanospheres (Pd MSs) with electron‐rich active sites perform perfectly as cathode electrocatalyst for electrochemical semi‐hydrogenation of alkynes in water. In comparison to its counterparts, Pd MSs hold remarkable conversion (97%), superior selectivity (98%), good operation stability in selective semi‐hydrogenation of p‐aminophenylene. High performance is assigned to electron‐rich Pd sites within mesopores that not only favor the formation of active H* but also accelerate the desorption of p‐aminostyrene. Meanwhile, Pd MSs are also highly efficient in selective semi‐hydrogenation of various terminal alkynes with different substituents. It is thus expected that robust Pd MSs can be demonstrated as an alternative catalyst design paradigm for other electrochemical hydrogenation reactions.

Electrocatalytic hydrogenation of acetonitrile to ethylamine in acid

Electrochemical hydrogenation of acetonitrile based on well-developed proton exchange membrane electrolyzers holds great promise for practical production of ethylamine. However, the local acidic condition of proton exchange membrane results in severe competitive proton reduction reaction and poor selection toward acetonitrile hydrogenation. Herein, we conduct a systematic study to screen various metallic catalysts and discover Pd/C exhibits a 43.8% ethylamine Faradaic efficiency at the current density of 200 mA cm−2 with a specific production rate of 2912.5 mmol g−1 h−1, which is about an order of magnitude higher than the other screened metal catalysts. Operando characterizations indicate the in-situ formed PdHx is the active centers for catalytic reaction and the adsorption strength of the *MeCH2NH2 intermediate dictates the catalytic selectivity. More importantly, the theoretical analysis reveals a classic d-band mediated volcano curve to describe the relation between the electronic structures of catalysts and activity, which could provide valuable insights for designing more effective catalysts for electrochemical hydrogenation reactions and beyond.

Navigating through Complexity: Optimizing Cathodes for Organic Electrohydrogenation through Coherent Workflows

AbstractElectrochemical hydrogenation reactions offer a green and sustainable production pathway for both bulk and fine chemicals employed in the modern chemical industry. However, optimizing such systems can be tremendously challenging due to the number of variables that potentially influence the overall performance. The tailored and scalable electrode fabrication via catalytic inks can be especially difficult due to the complex interplay of material and process variables during the formulation of the inks and their deposition on suitable substrates. As a result, the significance of each variable must be systematically investigated to reveal the high‐impact and low‐impact variables, enabling rapid progression towards finding optimal conditions and parameters. In this work, we present an adaptable, coherent workflow to proficiently optimize electrode fabrication for electrochemical hydrogenation reactions with well‐adjustable experimental effort. Using the hydrogenation of phenylacetylene as a model reaction in a scalable zero‐gap reactor, we demonstrate the influence of deposition techniques, substrates, and catalyst loadings as well as the interactions of binders and additives on the electrochemical performance. Future works can greatly benefit from this coherent workflow as it enables direct comparability between datasets and functional, multidimensional optimization, hastening the rate at which new material systems are understood, reach maturity, and become industrially relevant.

Proton Relay for the Rate Enhancement of Electrochemical Hydrogen Reactions at Heterogeneous Interfaces.

Proton transfer is critically important to many electrocatalytic reactions, and directed proton delivery could open new avenues for the design of electrocatalysts. However, although this approach has been successful in molecular electrocatalysis, proton transfer has not received the same attention in heterogeneous electrocatalyst design. Here, we report that a metal oxide proton relay can be built within heterogeneous electrocatalyst architectures and improves the kinetics of electrochemical hydrogen evolution and oxidation reactions. The volcano-type relationship between activity enhancement and pKa of amine additives confirms this improvement; we observe maximum rate enhancement when the pKa of a proton relay matches the pH of the electrolyte solution. Density-functional-theory-based reactivity studies reveal a decreased proton transfer energy barrier with a metal oxide proton relay. These findings demonstrate the possibility of controlling the proton delivery and enhancing the reaction kinetics by tuning the chemical properties and structures at heterogeneous interfaces.

Electrochemical Hydrogenation of Organic Compounds: A Sustainable Approach

AbstractConventional methods for hydrogenation of organic compounds generally use corrosive catalysts and reagents, along with extreme conditions like high temperatures and pressures. Quenching of corrosive materials does not deter its negative impact on the environment, nor is one safe when it comes to working with high temperature and pressure. Electrochemical hydrogenation (ECH) has proven to be safe and green since most of the efficient reactions are conducted at ambient pressure and temperature, minimizing, and sometimes even negating the use of toxic catalysts and corrosive reagents as compared to conventional methods. This review therefore provides different strategies used for ECH in the past, modification of different electrodes, half reactions taken up for efficient energy usage and catalysts used for different hydrogenation reactions. It presents the advances in electrochemical hydrogenation reactions of organic compounds, starting from simple aliphatic compounds to complex polyaromatics and heterocyclic aromatic compounds.

Developing electrochemical hydrogenation towards industrial application.

Electrochemical hydrogenation reactions gained significant attention as a sustainable and efficient alternative to conventional thermocatalytic hydrogenations. This tutorial review provides a comprehensive overview of the basic principles, the practical application, and recent advances of electrochemical hydrogenation reactions, with a particular emphasis on the translation of these reactions from lab-scale to industrial applications. Giving an overview on the vast amount of conceivable organic substrates and tested catalysts, we highlight the challenges associated with upscaling electrochemical hydrogenations, such as mass transfer limitations and reactor design. Strategies and techniques for addressing these challenges are discussed, including the development of novel catalysts and the implementation of scalable and innovative cell concepts. We furthermore present an outlook on current challenges, future prospects, and research directions for achieving widespread industrial implementation of electrochemical hydrogenation reactions. This work aims to provide beginners as well as experienced electrochemists with a starting point into the potential future transformation of electrochemical hydrogenations from a laboratory curiosity to a viable technology for sustainable chemical synthesis on an industrial scale.

Recent Progress in Electrochemical Upgrading of Bio-Oil Model Compounds and Bio-Oils to Renewable Fuels and Platform Chemicals.

Sustainable production of renewable carbon-based fuels and chemicals remains a necessary but immense challenge in the fight against climate change. Bio-oil derived from lignocellulosic biomass requires energy-intense upgrading to produce usable fuels or chemicals. Traditional upgrading methods such as hydrodeoxygenation (HDO) require high temperatures (200−400 °C) and 200 bar of external hydrogen. Electrochemical hydrogenation (ECH), on the other hand, operates at low temperatures (<80 °C), ambient pressure, and does not require an external hydrogen source. These environmental and economically favorable conditions make ECH a promising alternative to conventional thermochemical upgrading processes. ECH combines renewable electricity with biomass conversion and harnesses intermediately generated electricity to produce drop-in biofuels. This review aims to summarize recent studies on bio-oil upgrading using ECH focusing on the development of novel catalytic materials and factors impacting ECH efficiency and products. Here, electrode design, reaction temperature, applied overpotential, and electrolytes are analyzed for their impacts on overall ECH performance. We find that through careful reaction optimization and electrode design, ECH reactions can be tailored to be efficient and selective for the production of renewable fuels and chemicals. Preliminary economic and environmental assessments have shown that ECH can be viable alternative to convention upgrading technologies with the potential to reduce CO2 emissions by 3 times compared to thermochemical upgrading. While the field of electrochemical upgrading of bio-oil has additional challenges before commercialization, this review finds ECH a promising avenue to produce renewable carbon-based drop-in biofuels. Finally, based on the analyses presented in this review, directions for future research areas and optimization are suggested.

Physicochemical Properties and Low Relative Humidity Fuel Cell Performance of Pt/ECSTM Catalysts

The maturity of the current polymer electrolyte membrane fuel cells (PEMFCs) has been product of the considerable scientific and industrial effort devoted to developing highly efficient and reliable versions of this technology, resulting in its increased application in the transportation and energy generation sectors. Fuel cells are one of the most advantageous solutions for clean energy applications due to their near-zero-emission, high efficiency, low maintenance cost, and high energy density. PEMFCs produce electricity through the electrochemical reaction of hydrogen and oxygen (or air) taking place in the Membrane Electrode Assembly (MEA) by converting chemical energy of the hydrogen oxidation and oxygen reduction into electrical energy with water as a byproduct. However, producing oxygen reduction reaction (ORR) catalysts with high performance at scale is still a challenge that needs to be tackled to enable an increment in energy generation of this technology. Additionally, tunability of the materials at the core of this technology is essential to meet the demands of the specific application and operating conditions. Here we investigate commercially available ORR catalysts based on platinum nanoparticles (Pt-NPs) supported on nitrogen-functionalized carbon (Engineered Carbon SupportsTM, ECSTM) produced by Pajarito Powder, LLC at scale. The ORR performance of three MEAs made with different Pt/ECS catalysts, by IRD Fuel Cells, LLC was studied under low relative humidity conditions, exhibiting competitive performance, and reaching current densities between 1.8 and 1.3 A/cm2 at 0.6 V, at extremely low loading of Pt – 0.1 mgPt cm-2. The physicochemical properties of these Pt/ECS catalysts alongside their Pt-free ECSTM analogue carbon support materials were comprehensively studied. For this purpose, several characterization techniques were used, such: X-ray diffraction, Raman spectroscopy, and transmission electron microscopy (TEM) to investigate structural and morphological properties, X-ray photoelectron spectroscopy to determine the surface composition and chemical properties, thermogravimetric analysis to evaluate thermal oxidation properties, and nitrogen sorption to determine the surface area and porosity, of the materials. This thorough characterization enabled us to determine that the best performing catalyst in the conditions used in this work have the highest surface area and the highest concentration of surface dopants (nitrogen and oxygen). Although, catalyst supported on lower surface area carbon, but with higher graphitic content, also exhibited competitive performance that can be exploited in applications where more corrosion-resistant carbon is needed. Finally, based on the highly competitive MEA performance for the three Pt/ECS catalysts supported on these carbons, our work demonstrates that these carbon supports (developed by Pajarito Powder, LLC) with engineered morphology and composition fabricated through VariPoreTM synthetic technology can result in tunable properties suitable for a targeted application. We can conclude that these commercially available materials can be adapted through modification of the versatile synthesis platform to tune the physiochemical properties of carbons for other applications and conditions.

Synthesis and Characterization of Platinum on Carbon Nanoparticles Selectively Coated with Titanium Nitride (TiN)

The serious impact that high emissions of pollutants, derived from fossil fuel-based energy power generation, have on climate change resulted in the growing demand for cleaner and more efficient power sources. From the currently available green technologies, Proton Exchange Membrane Fuel Cell (PEMFC) offers the prospect of zero-emissions power production by using the electrochemical reactions of hydrogen and oxygen to generate electrical energy. Platinum (Pt)/Platinum alloy nanoparticles distributed on a carbon (C) catalyst support are the most efficient catalyst materials due to their high activity, even though the scarcity of Pt makes it expensive for widespread fuel cell application and commercialization. Furthermore, the carbon support is prone to corrosion and subsequent degradation when operating in typical PEMFC environment. This phenomenon can induce the loss of Pt nanoparticles (NPs) active surface area due to its detaching from the support, Pt NPs growth and Pt NPs agglomeration, which leads to premature performance losses in a PEMFC. Here we propose a novel way to prevent the carbon corrosion by depositing a corrosion-resistant layer of titanium nitride (TiN) on platinum on carbon (Pt/C) catalyst (in powder state). The goal of fabricating such designed catalysts is to selectively coat the carbon support with TiN, while the Pt catalyst centers are left uncoated and accessible for reagents reactions (oxygen O and H+ protons). Another attractive property of this TiN coating is its electronic conductivity, which is enough to enable the free movement of electrons from the current collector toward the catalytic centers. The deposition of the approximately 1.5 nm thick layer of TiN was carried out employing hollow-cathode plasma-assisted atomic layer deposition (HCPA-ALD) while using tetrakis(dimethylamino)titanium (IV) (TDMAT) and Ar/N2 plasma as the metal precursor and nitrogen co-reactant, respectively, at 150°C. To maintain the Pt NPs protected from TiN deposition on its surfaces during HCPA-ALD, its surface was selectively coated with a thin film of oleylamine, a polymer that would only absorb onto Pt NPs, which is later removed from the catalyst and TiN system (after the ALD process is over), by heat treatment. Here we will mainly focus on the TiN deposition process and the subsequent Transmission Electron Microscopy (TEM) characterization performed on these nanoparticles, which allows us to prove the successful formation of homogenous coatings and architecture characteristics of these nanoparticles after oleylamine application and TiN deposition. Our preliminary results have shown that highly conformal TiN can be successfully grown onto Pt/C powder nanoparticles by using HCPA-ALD with a custom-made agitator mechanism. The second phase of this research will be focused on the electrochemical responses of the TiN coated catalysts and the effect TiN coating has on its catalytic response, as well as inspecting the degradation mechanisms this novel catalyst system experiences after potential cycling.

Inorganic Nanocatalysts for Hydrogenation Reactions Contributable to a Sustainable Material Supply

Hydrogenation reactions using non-fossil-based hydrogen sources upgrade ubiquitous molecules to useful chemicals with low environmental load and can be promoted on nanoscale inorganic catalysts (nanocatalysts). This review discusses determining factors that enhance the catalytic activity and selectivity of thermal and electrochemical hydrogenation reactions using nanocatalysts, of which the reactivity is dependent on their electronic states, atomic arrangements and surface structures.

Process model for multilayer slide coating of polymer electrolyte membrane fuel cells

Slide coating is a precision method suitable for depositing multiple liquid-film layers simultaneously. Originally developed in the photographic film industry, it has been deployed for manufacturing of other products that benefit from multilayer coatings. One emerging application is the manufacture of polymer electrolyte membrane fuel cells (PEMFCs), which are used to produce electricity through electrochemical reactions of hydrogen and oxygen gas. The membrane-electrode assembly (MEA), in which key electrochemical reactions occur, consists of three layers that are typically deposited separately in serial fashion and then laminated together to form the three-layer MEA, i.e., three sequential steps of coat and dry. Adapting the process to simultaneous, multilayer slide coating of all three layers will save equipment cost and space while minimizing possible exposure to contaminants during transition between the steps. We are developing a three-layer slide coating model to aid the manufacturing process design of PEMFC. The model accounts for rheology of each layer, which typically exhibit shear thinning behavior. Model predictions are used to investigate simultaneous coatability of catalyst inks and to determine the best layer-by-layer ink selection.

Application of Electrospun Nanofibers for Fabrication of Versatile and Highly Efficient Electrochemical Devices: A Review.

Electrochemical devices convert chemical reactions into electrical energy or, vice versa, electricity into a chemical reaction. While batteries, fuel cells, supercapacitors, solar cells, and sensors belong to the galvanic cells based on the first reaction, electrolytic cells are based on the reversed process and used to decompose chemical compounds by electrolysis. Especially fuel cells, using an electrochemical reaction of hydrogen with an oxidizing agent to produce electricity, and electrolytic cells, e.g., used to split water into hydrogen and oxygen, are of high interest in the ongoing search for production and storage of renewable energies. This review sheds light on recent developments in the area of electrospun electrochemical devices, new materials, techniques, and applications. Starting with a brief introduction into electrospinning, recent research dealing with electrolytic cells, batteries, fuel cells, supercapacitors, electrochemical solar cells, and electrochemical sensors is presented. The paper concentrates on the advantages of electrospun nanofiber mats for these applications which are mostly based on their high specific surface area and the possibility to tailor morphology and material properties during the spinning and post-treatment processes. It is shown that several research areas dealing with electrospun parts of electrochemical devices have already reached a broad state-of-the-art, while other research areas have large space for future investigations.

Effect of Cr on the hydrogen storage and electronic properties of BCC alloys: Experimental and first-principles study

Inventing an effective method to store large amounts of hydrogen at room temperature is one of the key challenges in developing a hydrogen-based economy. Metal hydrides have attracted attention owing to their promising hydrogen storage capabilities. We have systematically studied the structural and electronic properties of mechanically synthesized Ti0.5V1.5-xCrx (0 ≤ x ≤ 0.3) alloys and investigated the influence of the addition of Cr atoms on the hydrogen storage properties of vanadium-rich body-centered-cubic (V-BCC) alloys. X-ray diffraction (XRD) results indicate that all alloys are composed of BCC main phase, with the lattice parameters exhibiting no change following chemical modification. The kinetic measurements have revealed that Cr-containing alloys exhibit improved hydrogen uptake. X-ray photoelectron spectroscopy (XPS) measurements have shown that the addition of Cr has a significant effect on the anti-oxidation properties of V-BCC alloys, increasing their chemical activity and thus enhancing the hydrogen storage properties. Moreover, XPS results elucidate the role of activation of the studied materials. Additionally, the electrochemical properties of the negative electrodes (as part of Ni-MHx secondary batteries) made of Ti0.5V1.4-xNi0.1Crx (0 ≤ x ≤ 0.3) system have been studied by cyclic charge-discharge and demonstrate that doping of the V-BCC alloys with Cr can significantly improve the cycle-life stability of anode that exhibits similar discharge performance up to 50 cycles. First principles simulations are used to analyse the changes in the electronic density of states close to the Fermi level, as a function of Cr concentration, as well as binding energies and structural changes upon hydrogen absorption. Furthermore, ab initio studies confirmed that H absorption is favoured with increasing Cr-content. Our study highlights the importance of the addition of Cr to V-BCC alloys on both solid-gas and electrochemical hydrogenation reactions.

Synthesis and Characterizations of Y-Doped BaCeO&lt;sub&gt;3&lt;/sub&gt; Ceramic for Use as Electrolyte in Solid Oxide Fuel Cell

Fuel cell is an electrochemical cell which converts chemical energy into electricity via electrochemical reaction of hydrogen and oxygen gases. It is also an alternative energy with environmental friendly. Generally, the fuel cell consists of many parts. Electrolyte is an important part for fuel cell because it has high ion conductivity which leads to increase electrical conductivity of the fuel cell. In case solid oxide fuel cell, barium cerate-based ceramics have been much attention due to their good properties for the fuel cell. In this work, the BaCe1-xYxO3-δ(x= 0.20) ceramic was synthesized by a solid state reaction in order to study their mechanical and electrical properties. The ceramic was sintered at high temperature of 1500°C with various soaking times. The crystalline phase structure was investigated by X-ray diffraction (XRD). The surface morphologies was observed by a scanning electron microscope (SEM). The impedance properties was measured by LCR meter. The obtained results suggestes that the ceramic sinter at 1500°C with 15 h dewell time shows the best properties as compared to other ceramics.

Counting surface redox sites in carbon-supported electrocatalysts by cathodic stripping of O deposited from N2O

Methods of determining in situ the electrochemically active surface area of bulk noble metal electrodes (e.g., underpotential deposition of a strongly interacting sorbent followed by columbic stripping) may not be appropriate for certain base metals supported on electroactive supports, such as carbon, because of the difficulty of finding a metal-specific titrant and because the support itself can contribute a very large background current. For example, the coulometric stripping of metal-selective sorbates, like carbon monoxide, works for the in situ characterization of certain electrode-supported metals (e.g. Pt, Pd) if applied carefully, but not for base metals, like Cu that do not strongly adsorb the titrant. Moreover, in scoping studies, we found that underpotential deposition of Tl on carbon-supported Cu failed to be selective for the copper. Here we present the use of gentle oxidation of the metal domains using N2O as the oxidant, followed by cathodic stripping of the surface oxide. The method compares approximately with XRD line broadening for characterizing ∼10 nm particles of Cu supported on graphite felt. More significantly, we show that the method usefully normalizes the rates of two electrochemical hydrogenation reactions: conversion of nitrobenzene to aniline and conversion of benzaldehyde to benzyl alcohol.

Hydrogen production using Al-Sn alloys prepared by rapid solidification

Air pollution produced by the direct burning of fossil fuels is a serious problem. Therefore, there is a vital demand for renewable and clean fuel replacements for future energy source. Hydrogen, which exhibits high calorific value and is a clean burning product, could be the first choice in the future, as it is a good-looking fuel for fuel cells where the electric energy is directly gotten by the electrochemical reactions of hydrogen and oxygen. Rapidly solidified Al100-x-Snx alloy X= (0, 25, 55, 75 all in wt.%) was prepared using melt spinning technique at 800 ºC. The structural and microstructural evolutions of the phases have been studied using X-ray powder diffraction (XRD) and the Rietveld method. Al45Sn55 alloy shows the best volume of hydrogen generation which is (531 ml), this alloy has the highest number of grains (1096) than other prepared alloys in its surface which examined through a Scanning electron microscope (SEM) and analyzed using an SPM data visualization and analysis tool (Gwyddion 2.32). Differential thermal analysis (DTA) was used for calculating melting temperature for all prepared alloys. Melting temperature reduced from 933.47 K for Al pure to 500.95 K in Al45Sn55 alloy. Temperature dependence of resistivity had been performed for all prepared alloys. Electrical properties of prepared alloys show the decrease in volume of the unit cell V with increasing VEC, which means that the volume of the first Brillouin zone increases by increasing VEC since they are inversely proportional to each other.

Automated SOFC Design Exploration

Fuel cells are a clean alternative to internal combustion engines and many experts consider them to be the future of ground-transportation. Solid oxide fuel cells are already heavily used in Japan for clean energy grid storage applications. Unlike combustion of hydrogen and oxygen that only generates heat, electrochemical reactions of hydrogen and oxygen may be separated to harness ion and electron transport for high efficiency energy conversion. We present computer automated engineering of fuel cell stack design to maximize power production and minimize energy losses. Validated cell models are applied to 3-D stack simulations, where optimization algorithms obtain better designs, faster. Each simulation conserves flow, energy, species, and charge transport using efficient sparse segregated solvers. Automated workflows and state-of-the-art search algorithms allow for fast design space exploration of fuel cell material properties, dimensions, and boundary conditions. Bibliography [1] O. R. J. G. a. J. M. V. Costa-Nunes, "Comparison of the performance of Cu–CeO 2–YSZ and Ni–YSZ composite SOFC anodes with H 2, CO, and syngas," Journal of power sources, vol. 141, no. 2, pp. 241-249, 2005. [2] F. Scholz, "Thermodynamics of electrochemical reactions," Electroanalytical Methods. Springer Berlin Heidelberg, pp. 11-31, 2010. [3] A. D. S. B. B. a. J. G. P. Le, "Validation of a Solid Oxide Fuel Cell Model on the International Energy Agency Benchmark Case with Hydrogen Fuel," Fuel Cells, vol. 15, no. 1, pp. 27-41, 2015. [4] S. G. Bratsch, "Standard electrode potentials and temperature coefficients in water at 298.15 K," Journal of Physical and Chemical Reference Data , vol. 18, no. 1, pp. 1-21, 1989. Figure 1: In solid oxide fuel cells, hydrogen fuel diffusing through the porous anode (left) reacts with oxygen ions traveling across the electrolyte membrane separator (middle) and produce electrons conducting through the solid porous cathode (right). Power is generated by flow of electrons from anode through an external circuit to the cathode (top), where they recombine with oxygen, in the air feed diffusing through the porous cathode, to repopulate membrane oxygen ions. Figure 1

Numerical Analysis of Ammonia-Fueled Planar Solid Oxide Fuel Cells

Ammonia is receiving attention as a hydrogen carrier because of a number of advantages over other hydrogen carriers, such as greater hydrogen content, easy liquefaction and no carbon emission. Mass production process of ammonia has also been established and well-known as the Haber-Bosch process. Among the energy systems operated with hydrogen and hydrogen-containing fuels, solid oxide fuel cells (SOFCs) are one of the candidates that can be operated with ammonia-based fuels because they can decompose ammonia on their Ni-based anodes and produce hydrogen inside the systems; this can simplify the whole system configuration and realize cost reduction. In addition, the excess heat generation from the electrochemical reaction can be effectively utilized for the ammonia decomposition reaction. Because the ammonia decomposition reaction is endothermic, temperature distribution on the cells is likely to be altered compared with the hydrogen-fueled SOFCs. Also, charge-transfer current distribution will be affected by the temperature distribution. To understand unique characteristics of ammonia-fueled SOFCs and to propose their appropriate operation conditions, numerical analysis is indispensable because of the difficulty in the direct measurement of physicochemical properties inside the cells. However, there are not many studies found in open literature where the characteristics of ammonia-fueled SOFCs are analyzed in detail by numerical analysis. In this study, a numerical model of ammonia-fueled planar SOFCs has been developed. The model consists of a planar SOFC cell and fuel/air supply channels. Mass, momentum, energy and charge conservation equations are considered and coupled with the electrochemical reaction of hydrogen and the ammonia decomposition reaction. The ammonia decomposition rate per unit Ni-pore contact area in the Ni-YSZ anodes was developed in the authors’ group and implemented in the numerical model. Distributions of the physicochemical properties, such as gas concentration, temperature and charge-transfer current, are analyzed and compared between the ammonia-fueled SOFCs and the hydrogen-fueled SOFCs. It was found that in the ammonia-fueled SOFCs the cell temperature first decreased in the upstream region by the endothermic decomposition reaction and then gradually increased towards the downstream, whereas in the hydrogen-fueled SOFCs the cell temperature monotonically increased in the flow direction. Also the peak in the charge-transfer current distribution was shifted towards the downstream in the ammonia-fueled SOFCs because of the altered temperature distribution.

연료전지 철도차량 적용을 위한 인터리브드 다상 승압형 컨버터 제어

Fuel cell power generation system, unlike conventional energy sources, converts chemical energy into electrical energy through electrochemical reaction of hydrogen and oxygen. This paper presents the control of interleaved multi-phase boost converter as the feasibility study on small-scale prototype electric railway vehicle application using fuel cell generation system. PSIM simulation program is to be used to implement the modeling of the electrical fuelcell as well as traction motor control with interleaved multi-phase boost converter. Comparing the input current ripple rate, two-phase interleaved boost converter is less than the boost converter. But the more multi-phase not less proportional to the ripple factor. we confirmed that the amplitude of the input current ripple rate of converter depend on duty ratio.

Impact of Liquid Water on Oxygen Transport Resistance in a PEMFC Cathode Via Limiting Current Methods and Concurrent Synchrotron X-Ray Radiography

The accumulation of liquid water formed by the electrochemical reaction of hydrogen and oxygen in a polymer electrolyte membrane (PEM) fuel cell causes a gas diffusion layer (GDL) to become effectively less porous and more tortuous. To achieve designs directed for water and gas transport in PEMFC diffusion media, a nuanced understanding of the nature and extent of GDL water as an impedance to oxygen flux is required. In this work, a limiting current approach was used to measure the mass transport resistance in a custom PEM fuel cell. Using a small active area at high stoichiometric ratios, it was assumed that the concentration of gases was constant along the length of the reactant flow channels, creating a uniform concentration gradient across the entire diffusion medium. If the fuel cells are then operated at the limiting current density, where cell potential approaches zero, it can also be assumed that all the reactants are being consumed and the concentration of reactants at the reaction site is effectively zero. Consequently, oxygen transport resistance in these conditions can be inferred directly from the limiting current density using the following equation, where RT is the transport resistance in s/cm, c0 is the oxygen concentration at the reactant channel and iL is the limiting current: RT = 4Fc0/iL Previously, through a thorough set of limiting current experiments at a range of operating conditions, Baker et al.1 showed that the carbon-fiber diffusion medium is the dominant contributor to oxygen transport resistance. Owejan et al.2 combined limiting current methods with in situ neutron radiography to demonstrate a strong qualitative correlation between GDL saturation and oxygen transport resistance. Synchrotron radiography has been established as a powerful tool for visualizing water distribution in PEMFC diffusion media3. In this work, synchrotron X-ray radiographs were obtained with a pixel size of 6.5 µm with a spatial resolution of 10 μm. GDL materials were imaged in operando at limiting current over a range of relative humidities (set in the inlet cathode gas stream). Figure 1 (a) is an example radiograph of a cell operating at limiting current density processed according to the Beer-Lambert law5,6. A distinct in-plane variation in liquid water distributions is visible between regions over ribs and regions over channels (Figure 1 (b)). This work exploits the high spatial resolution for capturing liquid water accumulation trends, information which is essential for building towards a direct, quantitative empirical relation between oxygen transport resistance and GDL saturation.