Proton Exchange Membrane Technology Research Articles

Water transport across the membrane of a direct toluene electro-hydrogenation electrolyzer: Experiments and modelling

Toluene/methylcyclohexane is a promising liquid organic hydride for hydrogen storage and transport under ambient conditions. Direct toluene electro-hydrogenation electrolyzers, utilizing proton exchange membrane technology, offer benefits in reducing the reversible decomposition voltage and eliminating theoretical heat losses associated with conventional hydrogenation methods. Nevertheless, water transport across the membrane can inhibit the supply of toluene to reaction sites at the cathode. This study investigates water transport across the Nafion™ 117 membrane of an in-house electrolyzer cell, employing sulfuric acid and toluene solutions as the anode and cathode reactant, respectively, and operating at current densities from 0.1 to 0.8 A/cm2. The experiments show that the cathode toluene concentration has a negligible effect on drag water, while water flux increases with electric current and decreases with higher anode sulfuric acid concentrations. The modelling approach assumes electro-osmosis and diffusion mechanisms govern water transport. Simulations predict a linear decrease in the electro-osmotic drag coefficient from 2.3 to 1.6 as the sulfuric acid concentration rises from 0.1 to 1.5 mol/L, while the back diffusion flux increases linearly up to 2 mg/(min·cm2). These findings closely align with experimental data and previous literature, despite the high complexity of water transport in polymer electrolyte membranes.

Photovoltaic Energy Generation in Hungary: Potentials of Green Hydrogen Production by PEM Technology

The dynamic spread of photovoltaic power plants in the global energy industry facilitates cost-effective and clean electricity generation. However, the intermittent nature of solar energy poses an increasing challenge from a system management point of view due to the fast-growing capacities. As a consequence, energy storage systems are increasingly important in this area, as they allow the efficient and flexible storage of excess electricity generated in the electricity system. Among various energy storage systems, the power-to-gas technology is becoming more and more important in the integration of weather-dependent renewable energy sources, as it can now provide an effective solution for increasing grid stability and scheduling efficiency, as well as enabling wide variety of application possibilities in the economy, for example in transport, industry or heating systems. The aim of the present research was to determine the potential amount of green hydrogen that can be produced by using the proton-exchange membrane technology, taking into account the climatic conditions in Hungary and the energy production potentials of photovoltaic power plants of given capacities. This is not only novel but also of practical use, as it provides important information about the integration of photovoltaic power plants and the power-to-gas technology to the actors of energy systems and the energy market and the decision-makers concerned. In addition to the vital economic aspects of the research, supporting the decisions of potential investors, it also contains important insights for market-related technological developments.

Evaluación de Electrolizadores Alcalinos y PEM para Producción de Hidrógeno Verde de Fuentes Hidroeléctricas en el Ecuador

Introducción The yearly increase in energy demand has encouraged the scientific community to find new sources of energy production without affecting the environment. Renewable technologies have become extremely popular due to the low greenhouse emissions and availability of natural energy sources (wind, sun, water, earth, tides, etc.), However, because of the intermittent energy generation from renewable sources, it is complex to rely on these technologies to guarantee the energy supply. Therefore, over the last decade, hydrogen has become increasingly studied as an energy carrier to replace current energy production technologies based on fossil fuels. Hydrogen can be easily coupled with other energy sources, increasing the efficiency of the systems. Nevertheless, hydrogen cannot be found in nature on its own and needs to be produced, currently, the most efficient method for green hydrogen generation is based on the electrolysis of water, this electrochemical process relies on the availability of water and the efficiency and correct selection of the electrolyser. Thus, this research evaluates the Alkaline and Proton Exchange Membrane (PEM) electrolysers for green hydrogen generation using water from hydroelectric power plants in Ecuador. Objetivos Evaluate Alkaline and PEM electrolysers for green hydrogen generation from hydroelectric power in Ecuador Método The methodology consists of a literature review of different brands of alkaline and PEM electrolysers selecting the ones with the highest efficiencies. For the analysis of data and information processing, quantitative methods were used. Finally, a sample of 9 hydroelectric plants was obtained for the study (Molino, Mazar, Agoyán, San Francisco, Pucará, La Península, Illuchi N 1, Illuchi N 2, Marcel Laniado). Principales resultados Different electrolyser manufacturers were analysed: Nel ASA producer of alkaline as well as PEM electrolysers, among them several models were evaluated NEL A 300, NEL A 485, NEL A 1000, NEL A 3880 with alkaline technology, and NEL MC 250, NEL M 5000 with PEM technology. H-TECH Electronic Co.Ltd with its model H-TEC HCS 10 using PEM technology. SIEMENS Energy, with its electrolyser technology PEM Silyzer 300 and McPhy with Mclyzer alkaline technology. All models were evaluated with the data from the 9 hydroelectric plants. Using technical data from the selected electrolysers and availability factor (90 %) from the hydroelectric plants, the potential of hydrogen production per year was calculated. The NEL A 3880 model with a system factor of 94% and a power of 14.7 MW displays the highest hydrogen production for alkaline technology, while the NEL MC 250, with an efficiency of 79% and 1 MW of power using PEM technology shows the highest hydrogen generation, these results are achieved for the Agoyan hydroelectric plant. Conclusiones The alkaline electrolysers show a better hydrogen generation capacity, achieving a total of 300 x 10e6 Kg of H2 per year with the NEL A 3880 model, in comparison with the PEM electrolyser technology that accounts for a maximum hydrogen production of 214 x 10e6 Kg of H2 per year. These results from the evaluation of the electrolysers show that it is feasible to establish a system for green hydrogen production based on hydroelectric power plants in Ecuador. The authors acknowledge the financial support received from the Universidad Técnica de Ambato and Dirección de Investigación y Desarrollo (DIDE) through the research project number PFICM28 “ANÁLISIS DE FACTIBILIDAD DE GENERACIÓN DE HIDRÓGENO VERDE MEDIANTE FUENTES DE ENERGÍA HIDROELÉCTRICA EN EL ECUADOR”.

Rhenium-Based Electrocatalysts for Water Splitting

Due to the contamination and global warming problems, it is necessary to search for alternative environmentally friendly energy sources. In this area, hydrogen is a promising alternative. Hydrogen is even more promising, when it is obtained through water electrolysis operated with renewable energy sources. Among the possible devices to perform electrolysis, proton exchange membrane (PEM) electrolyzers appear as the most promising commercial systems for hydrogen production in the coming years. However, their massification is affected by the noble metals used as electrocatalysts in their electrodes, with high commercial value: Pt at the cathode where the hydrogen evolution reaction occurs (HER) and Ru/Ir at the anode where the oxygen evolution reaction (OER) happens. Therefore, to take full advantage of the PEM technology for green H2 production and build up a mature PEM market, it is imperative to search for more abundant, cheaper, and stable catalysts, reaching the highest possible activities at the lowest overpotential with the longest stability under the harsh acidic conditions of a PEM. In the search for new electrocatalysts and considering the predictions of a Trasatti volcano plot, rhenium appears to be a promising candidate for HER in acidic media. At the same time, recent studies provide evidence of its potential as an OER catalyst. However, some of these reports have focused on chemical and photochemical water splitting and have not always considered acidic media. This review summarizes rhenium-based electrocatalysts for water splitting under acidic conditions: i.e., potential candidates as cathode materials. In the various sections, we review the mechanism concepts of electrocatalysis, evaluation methods, and the different rhenium-based materials applied for the HER in acidic media. As rhenium is less common for the OER, we included a section about its use in chemical and photochemical water oxidation and as an electrocatalyst under basic conditions. Finally, concluding remarks and perspectives are given about rhenium for water splitting.

Energy management strategy for integration of fuel cell-electrolyzer technologies in microgrid

Proton exchange membrane technology is proven for stationary application but one of crucial aspect of this technology is its durability which is subjected to the operating conditions i.e. load transients, switch ON/OFF events and idling conditions. Such operating conditions may lead to premature failure of electrolyzer (ELY) and fuel cell (FC). However, transient load variation and rapid switch ON/OFF are unavoidable conditions in microgrid due to erratic variation in the photovoltaic source power during cloudy condition and load transients. Therefore, it is challenging to develop a control (energy management) strategy which can ensure the smooth operation of FC and ELY and achieve the others multi-objectives such as balance in demand and supply, higher energy efficiency, reliability and resiliency. The smooth operations of FC and ELY can be achieved by controlling the rate of change of power during transient operating conditions. Present study is dedicated to energy management system (EMS) of hydrogen storage based microgrid. In present study, photovoltaic (PV) generator is used as primary generator while battery and hydrogen (metal hydride) units are used as energy storage mediums. Different control strategies i.e. model predictive control (MPC), hysteresis band control strategy (HBCS), equivalent consumption and minimization strategy (ECMS) and state machine (SM) are used in proposed EMS. The operating cost of system is found to be 8.79, 8.88, 29.54 and 14.73 USD while efficiency is obtained 79.0%, 80.5%,77.4% and 80.0% in HBCS, MPC, ECMS and SM modes, respectively.

Development of Membrane Electrode Assemblies for State-of-the-Art Anion Exchange and Proton Exchange Membrane Electrolysis

Proton exchange membrane (PEM) electrolysis and anion exchange membrane (AEM) electrolysis are both able to directly produce high purity hydrogen from electricity and water. Key benefits of electrolysis using polymer membrane separators include a quick response rate, enabling load following, and ability to operate with high differential pressure. Operation under differential pressure allows for simultaneous electrolysis and electrochemical compression, simplifying overall system design. The development and stack integration of new, high performance electrolysis materials must include consideration of operating range and durability under differential pressure to maintain the technologic benefits. PEM electrolyzers are commercially available on the megawatt scale and produce hydrogen fuel that is increasingly cost competitive with fossil fuel in select parts of the world. Better utilization of low cost electricity from renewable energy (wind and solar) is one route to additional hydrogen cost reductions, for which a wide current operating range is beneficial. Thinner membranes, more active catalysts, and better electrode design enable high currents at acceptable cell efficiencies. Performance and durability data will be presented on state-of-the-art PEM electrolyzer materials operating under differential pressure. AEM electrolyzers are not currently commercially available, but promise membrane, catalyst, and balance of stack cost reductions. To begin to compete with PEM technology, performance and durability need to be improved. This work focuses on membrane stability under differential cell pressure and material integration into high performance AEM electrolyzers.

(Invited) High Conductivity, Stable Anion Conducting Membranes Based on Poly(norbornene)

Alkaline exchange membranes (AEM) fuel cells and electrolyzers are potentially cost-saving alternatives to traditional proton exchange membrane (PEM) devices. Recently, anion conducting polymer membranes have achieved ionic conductivity and chemical stability comparable to Nafion, the current state of the art in PEM technology. Phase segregation is an effective way to achieving high hydroxide mobility. An all-carbon backbone with light cross-linking and a long, alkyl tether for the cation head-group are effective means of achieving chemical stability and limiting unwanted water hydration. In this study, a series of tetrablock copolymers containing an all-hydrocarbon backbone and tethered quaternary ammonium groups were synthesized based on vinyl addition polymerization of norbornene. Several variations of block copolymer AEMs with different ion exchange capacities (IEC) were made by adjusting the ratio of hydrophilic to hydrophobic blocks. Correlations were found between the ionic conductivity and mechanical properties to the polymer structure, channel size, and degree of phase separation. Furthermore, it was found that light crosslinking of the membranes allows for high IEC materials to be used while maintaining acceptable water uptake. The crosslinked AEMs have demonstrated record-high hydroxide conductivities (198 mS/cm) for a chemically stable polymer. The chemical degradation at 80oC in 1 M KOH was <1% degradation in 1,200 hours. The AEMs were also used to construct MEAs for alkaline fuel cells.

Thermoeconomic modeling of a completely autonomous, zero-emission photovoltaic system with hydrogen storage for residential applications

Abstract In this study a completely autonomous, zero-emission photovoltaic (PV)-based system is modeled for residential applications. Apart from the PV subsystem, an electrolyzer-hydrogen storage-fuel cell subsystem is integrated to the system to fully fulfill a varying load profile throughout the year. The fuel cell and electrolyzer components are based on proton exchange membrane technology. The model allows quantification of energy and power flows, such as power input from the PV subsystem, conversion of electricity to hydrogen, and re-production of electricity. The system components are sized to satisfy demand, which is varied through a case study conducted to investigate system performance at different capacities. The economic performance of the proposed system is assessed with a detailed cost model. The proposed system (base case) results in a unit cost of electricity at 0.216 EUR/kWh for a system capacity of 100 households, which is moderately higher than the current cost of electricity in Cyprus. A parametric study including those economic parameters with a high degree of uncertainty is conducted to investigate the sensitivity and future potential of the system. The results show that the unit cost of electricity for the proposed system can be reduced below the current cost, making the system competitive, if electrolyzer/fuel cell lifetime is increased, while the specific costs of the electrolyzer and the PV are reduced.

Environment–Climate–Energy: Quo Vadis, Industry?

Steel is a crucial material for energy transition and low-carbon economy. Since it will never be possible to produce steel without energy, we must change from coal (coke) to other carbon-free energy sources in order to reduce or prevent CO2 emissions in the long term. voestalpine is working consistently on the further development of the processes towards the stepwise de-carbonization of steel production. Specifically, the company plans to make a gradual shift from the use of coal via bridging technologies to the potential use of hydrogen in the steel production over the next 20 years. The current European flagship project H2FUTURE brings together energy suppliers, the steel industry, technology providers, and research partners. The facility at the Linz site of voestalpine will produce ‘green’ hydrogen by electrolyzing water via PEM (proton exchange membrane) technology. Based on the results of the project, voestalpine is planning to take its R&D activities further to examining hydrogen plasma in steel production.

A superhydrophobic bromomethylated poly(phenylene oxide) as a multifunctional polymer filler in SPEEK membrane towards neat methanol operation of direct methanol fuel cells

Development of novel proton exchange membrane (PEM) with the aim toward neat methanol operation of direct methanol fuel cell (DMFC) has attracted increasing attention. Proton exchange membrane technology with remarkably low methanol permeability has been considered as one of the most facile ways to approach this target. Here, sulfonated poly(ether ether ketone) (SPEEK) membrane was modified by blending with superhydrophobic bromomethylated poly(phenylene oxide) (BPPO). The fabricated SPEEK/BPPO membranes possess obviously low methanol permeability, which is attributed to the formed interrupted methanol transport channels arising from the combined properties of the hydrophobic BPPO polymeric backbone, the formed spherical BPPO obstacles and the cross-linking networks derived from the Friedel-Craft reaction between bromobenzyl groups and nucleophilic phenyl rings. Therefore, the SPEEK/BPPO membrane DMFC demonstrates a much higher cell performance both at low methanol concentration and high methanol concentration than the Nafion 117 DMFC. In particular, the actual value of the maximum power density at high methanol concentration of 20M suggests that the SPEEK/BPPO membranes can be considered as a desirable candidate for potential application in high methanol concentration DMFCs.

Coproducing Value-Added Chemicals and Hydrogen with Electrocatalytic Glycerol Oxidation Technology: Experimental and Techno-Economic Investigations

The electrocatalytic oxidation technology of biomass-derived oxygenates such as glycerol presents a promising method of coproducing renewable chemicals and hydrogen in an electrochemical reactor system that uses oxidation chemistry and existing proton exchange membrane technology to electrocatalytically convert oxygenates into value-added chemicals and hydrogen. In this paper, we first demonstrate the techno-economic feasibility of the electrocatalytic glycerol oxidation technology with our experimental investigations. Simple and direct conversion of glycerol into glyceraldehyde (GAD), glyceric acid (GLA), and hydroxypyruvic acid (HPA) by anodic oxidation in an electrocatalytic batch reactor over Pt/C catalysts was performed with only water as a stoichiometric chemical oxidant. We also conducted conventional catalytic (non-electrocatalytic) glycerol oxidation using a catalytic batch reactor with pressurized oxygen as the oxidant to compare conventional catalytic performances to that of the electrocatalyti...

Electrochemical Activation of Single-Walled Carbon Nanotubes with Pseudo-Atomic-Scale Platinum for the Hydrogen Evolution Reaction

The development of effective and inexpensive hydrogen evolution reaction (HER) electrocatalysts for future renewable energy systems is highly desired. Platinum-based materials are the most active electrocatalysts for catalyzing HER, but reducing the use of Pt is required because of the high price and scarcity of Pt. Here, we achieve pseudo-atomic-scale dispersion of Pt, i.e. individual atoms or subnanometer clusters, on the sidewalls of single-walled carbon nanotubes (SWNTs) with a simple and readily upscalable electroplating deposition method. These SWNTs activated with an ultralow amount of Pt exhibit activity similar to that of commercial Pt/C with a notably higher (∼66–333-fold) Pt loading for catalyzing the HER under the acidic conditions required in proton exchange membrane technology. These catalysts resemble pseudo-atomic-scale Pt systems which are mainly composed of a few to tens of Pt atoms dispersed on the sidewalls of the SWNTs. The Pt loading is only 0.19–0.75 atom % at the electrode surface,...

Comparing Low- and High-Temperature Electrochemical Process Pathways for Converting H2o and CO2 into Synthetic Natural Ga

The conversion of water and carbon dioxide into useful products such as synthetic natural gas using renewably supplied electrical energy can offer several advantages for stabilizing the electric grid and increasing the security of energy supply chains. In addition to providing increased grid operational flexibility for dealing with intermittent renewable electrical energy supplies, infrastructure changes such as hydrogen pipelines could conceivably be avoided in situations where natural gas pipelines and CO2 sources coincide. The natural gas distribution infrastructure is well developed in many countries, enabling the fuel to be transported long distances and easily delivered throughout cities. Using the existing pipeline to transport renewably generated synthetic natural gas (SNG) can further enhance the value of the product via offering grid services such as load leveling. While the price of natural gas is near record lows in the United States, many other countries are working to develop SNG as an alternative fuel for transportation and residential/commercial heating markets, especially in Europe and for island nations. This study presents pathway studies of low- and high-temperature electrolysis integrated with an SNG plant design and evaluates their performance for producing SNG by reacting renewably generated hydrogen with carbon dioxide. The carbon dioxide feedstock is assumed to be captured and scrubbed from either an existing coal fired power plant at the city-gate or from sequestered CO2, where the SNG plant is co-located. In the first pathway, water is split using either low-temperature alkaline or proton exchange membrane technology. In a second path, the co-electrolysis of steam and CO2 is done in-situ using high temperature (600°C) solid oxide cell technology. Historically, methanation has been a common practice for eliminating carbon monoxide and carbon dioxide in various chemical processes such as ammonia production and natural gas purification; for these processes, only small amounts (1-3% molar basis) of carbon oxides need to be converted to methane. A “bulk” methanation process is unique due to the high concentration of carbon oxides and hydrogen. In addition, the carbon dioxide is the only carbon source, and the reaction characteristics of carbon dioxide are much different than carbon monoxide. In process paths involving low-temperature electrolyzers, a methanation plant is required. In this study, thermodynamic and kinetic considerations of the methanation reaction are explored to model and simulate a system of reactors for the conversion of hydrogen and carbon dioxide to SNG. Multiple reactor stages are used to increase temperature control of the reactor and drain water to promote the forward direction of the methanation reaction. Heat recuperation and recovery using organic Rankine cycle units for electricity generation utilizes the heat produced from the methanation reaction. Bulk recycle is used to increase the overall reactant conversion while allowing a satisfactorily high methane content SNG product. A hydrogen membrane separates hydrogen for recycle to increase the Wobbe index of the product SNG by increasing the methane content to nearly 93% by volume. In both pathways, the product SNG has a minimum Wobbe index of 47.5 MJ/m3 which is acceptable for natural gas pipeline transport and end-use appliances in existing infrastructures. The overall plant efficiencies of both pathways are compared as well as the expected price of the product SNG using the H2A tool.

(Invited) The Role of Electrolysis in a Renewable Energy Economy

The United Nations Framework Convention on Climate Change (COP21) in Paris last year has underlined the urgency of a fast and consequent transformation of the various energy systems from a fossil based energy feedstock towards renewable energies like photovoltaics, wind- and hydropower, in order to drastically decrease the greenhouse gas emissions (GHG). Such a transformation requires a thorough restructuring of the energy systems with all energy carriers and consumer sectors including its intersectoral dependencies, grid structures and energy storage needs. At Fraunhofer ISE we performed time-resolved studies on how to reach the main goal of the German energy transformation to decrease its GHG emissions by at least 80% until 2050 and thus, to widely decarbonize all energy related sectors. Potential transformation pathways based on various scenarios were studied and the required costs were modelled for each scenario. The results of this modelling made very obvious that the ambitious GHG reduction targets can only be fulfilled by a strong rise in electricity generation by fluctuating renewable energies and on the other hand by the installation of large plants for producing synthetic energy carriers from renewable energies. The most versatile energy carrier for such large amounts of energy is hydrogen produced from water electrolysis. Hydrogen can be stored in large amounts in gas tube fields or salt caverns and can be used directly either in fuel cell cars and buses as a fuel or in stationary combined heat and power fuel cell systems. Furthermore the hydrogen can be used in order to hydrogenate CO2 and thus to generate green liquid fuels such as oxymehylenether (OME) or other chemicals in order to replace oil based products. The conversion of electricity into hydrogen is called Power-to-Gas, the further processing of the hydrogen and CO2 towards liquid energy carriers and chemicals is called Power-to-Liquid. With the advent of various Power-to-Gas demonstration projects it becomes clear how important this technology will be in the future energy system. Distributed water electrolyzers in the Megawatt power range will stabilize the grid frequency and voltage or will deliver other ancillary services and thus, will contribute to the secondary balancing market. Alkaline water electrolyzers are applied for more than 100 years in industrial applications and are nowadays complemented by proton exchange membrane (PEM) electrolysers in order to cover the needs for a highly dynamic load in the grid. However, main challenges of the PEM technology are high costs associated with expensive materials and the durability of cells and stacks. With ongoing technological development it is expected that PEM electrolysis systems become a competitive alternative to alkaline systems in the next years. In this talk, the technological base of water electrolyzers will be described and the related performance data, life-time expectation and cost reduction potential will be discussed. Furthermore the impact of distributed water electrolyzers in the Megawatt power range as part of an increasingly renewable energy system in terms of Power-to-Gas modelling scenarios will be given. Figure 1

Cross-Linked Phosphoric Acid Doped PBI Membranes and Their Performance on Operation As Automotive Range Extender

One of the promising application areas for high temperature proton exchange membrane technology is as a range extender in a battery electric vehicle. Unlike low temperature PEM fuel cells dependent on perfluorosulfonic acid type membranes, HT-PEM fuel cells need no humidification, the conductivity of the membrane having much lower dependence on degree of hydration, and their use therefore eliminates water management issues. The operation conditions of a fuel cell for range extender application differ from those when the PEMFC stack is used for the power train. Thus the stack is subjected less to transients and operates in semi-continuous mode, but with stop/start events corresponding to the normal start up and shut down of vehicle operation. HT-PEM membranes are based upon polybenzimidazole (PBI) polymers that are doped with (generally) phosphoric acid. This acid "doping" may be achieved by immersion of a polymer membrane in acid, or by methods involving the preparation of the PBI polymer in polyphosphoric acid followed by membrane casting and a controlled hydrolysis step, or the dissolution of PBI in a polyphosphoric acid/phosphoric acid followed by membrane casting, in a thermoreversible sol-gel transition. The last two approaches lead to very high acid contents, easily exceeding 20 molecules H3PO4/PBI repeat unit, and the resulting membrane is soft with poor mechanical properties. Polymer cross-linking is a recognized means for improving membrane strength. To date, in the case of PBI, acid doping has been carried out on the cross-linked membrane, resulting in low phosphoric acid uptake. We have developed an approach that allows the covalent cross-linking of PBI by introduction of a molecular cross-linking species at the polymer dissolution stage, following by membrane casting and thermal curing to give the cross-linked membrane. Since this approach provides mechanical stabilization to an acid-swollen membrane containing a high content of acid, it is a means leading to highly proton conducting membranes of satisfactory mechanical properties. A range of synthesis parameters including the amount of cross-linking, temperature for thermal curing etc., have been examined and, most recently, we have provided experimental evidence for cross-linking with the help of X-ray photoelectron and nuclear magnetic resonance spectroscopies. Membrane electrode assemblies (MEAs) have been developed using the novel cross-linked acid doped PBI membranes, and fuel cell test protocols relevant to range extender application, based upon load cycling at 160 °C, have been applied. The results demonstrate that the novel MEAs comprising cross-linked PBI have lower voltage decay on load cycling than is observed using commercial MEAs, reaching >1000 h operation without the voltage dipping below the end-of-life criterion. The research leading to these results has received funding from the European Community’s Seventh Framework Programme for the Fuel Cells and Hydrogen Joint Undertaking under grant agreement ARTEMIS no. 303482.

Current State of the Art in Water Electrolysis Performance Based on Anion Exchange Membranes

Hydrogen represents a major chemical feedstock worldwide, and is currently manufactured primarily from fossil fuel-based sources. Obtaining hydrogen from non-fossil sources is thus an important part of the overall strategy to reduce greenhouse gas emissions, including the potential tie to transportation infrastructure. Large scale renewable hydrogen production is also a key part of the global energy storage strategy, to capture peak solar and wind and convert energy that would otherwise be stranded to a deployable source. Water electrolysis is the only technology currently mature enough to meet the scale requirements in the near term for renewable hydrogen. However, manufacturing and material cost need to be decreased to meet the economic requirements of these applications. Commercial options for water electrolysis are currently limited to liquid KOH electrolyte based systems, and proton exchange membrane (PEM)-based systems. Both have advantages and disadvantages. Anion exchange membrane (AEM) technology represents a potential hybrid approach which leverages the advantages of both legacy systems. However, the key obstacle in the AEM systems is the robustness of the polymers, both in the ionomer and membrane form. The ionomer is subject to chemical degradation leading to loss of integrity of the electrocatalyst layer, while the membrane can lose mechanical strength due to both thermal damage during processing and chemical attack of the polymer backbone during operation, leading to pinhole failures. The membrane can also lose efficiency through loss of active sites, either through carbonation of the hydroxide conducting sites, or chemical degradation. These membrane and ionomer materials are much less mature than the PEM analogs, and fundamental understanding is still being developed around polymer design and degradation methods. Proton OnSite has developed cell designs and manufacturing processes which improve the robustness of the existing AEM materials, and have also collaborated with several membrane partners to develop improved materials. Most recently, the Illinois Institute of Technology (IIT) performed mechanistic studies to determine potential membrane degradation pathways, while both IIT and Sandia provided materials for cell testing. In this talk, results of these studies will be discussed, as well as resulting performance in commercial stack hardware. Proton has currently achieved stable operation of the AEM cell for over 1700 hours, with over 1000 hours at 500 mA/cm2, and has scaled the technology to a 1 L/min prototype AEM generator. Comparison to state of the art in PEM technology and the ultimate outlook for each technology will also be discussed.

Electrocatalyst for Direct Alcohol Fuel Cells

Direct alcohol fuel cells (DAFC) offer a number of advantages compared to other fuel cell solutions or batteries. So the liquid fuel allows for easy handling and high energy storage densities. At the same time, the system design can be kept simple and thus offers a certain robustness. Direct methanol fuel cells converting (DMFC) using low temperature proton exchange membrane technology have achieved a high level of maturity and have already entered some special markets like battery chargers for portable applications and recreational vehicles, back-up power systems or material handling vehicles. Two facts are currently hindering a wider use DMFC, high costs due to the high usage of platinum based catalysts and the reluctance of many potential users to employ methanol as fuel. In this contribution catalyst developments with respect to two different concepts to address these issues will be presented. The first is the use of alkaline anion exchange membrane fuel cells in order to avoid or reduce the use of platinum. The second concept is the use of ethanol as alternative non-toxic fuel with even higher energy density. Because of the less corrosive effect of the alkaline environment less noble metals can be used as catalysts. In particular palladium has shown high activity for the oxidation of alcohols under these conditions [1]. In order to further enhance both, the activity of the catalysts and the CO2 current efficiencies Pd binary [2] and ternary alloys were investigated. As will be shown, the addition of nickel or silver as second metal is able to enhance the catalytic activity of palladium for the methanol as well as the ethylene glycol oxidation reaction. Thereby, the addition of silver also enhances the CCE of the methanol oxidation reaction, whereas the addition of nickel enhances the CCE of the ethylene glycol oxidation reaction. In both cases the addition of tin or ruthenium as third element to form ternary catalysts causes a further significant increase of the performance; so the combination of palladium and nickel with either tin or ruthenium leads to high CCEs and high faradic currents for the ethylene glycol oxidation at significantly lower potentials. Fig. 1: CCE of the methanol oxidation at PdxM/C catalysts (upper) and the ethylene glycol oxidation at PdxMyNiy/C catalysts (lower). As has been reported, the alkaline environment is not suitable to enhance the complete oxidation of ethanol. In contrary, the high availability of OH fosters the formation of acetic acid or acetate which are dead end products. In order to enhance the catalytic activity of platinum based catalysts in an acidic environment the addition of tin is known to be useful [3]. However, no positive effect with respect to the complete oxidation of ethanol has been reported so far. On the other hand side positive results on the addition of rhodium on the CCE of the ethanol oxidation have been reported by different groups [4, 5]. In this contribution results of a study of the effect of rhodium and/or tin addition to platinum electrodes on the ethanol oxidation in acidic environment at ambient temperature will be reported. It will be shown that the addition of either metal causes an enhancement of the catalytic activity. Furthermore it will be shown that the addition of rhodium is able to increase the CCE of the ethanol oxidation even at ambient temperature. Using a recently developed set-up for DEMS like measurements under HT-PEMFC relevant conditions [6], the ethanol oxidation at Pt/C and PtRh/C catalysts was also studied in the vapour phase at 150 °C. It will be shown that CCE under these conditions is much higher exceeding 65% for both catalysts. The particular effect of the addition of rhodium under these conditions was found to be that it mitigates the self-poisoning of the catalysts by ethanol which allows for achieving high CCEs also for technical relevant ethanol concentration of 5 mol l-1. [1] D. Bayer, C. Cremers, H. Baltruschat, J. Tubke, ECS Transactions, 41 (2011) 1669-1680. [2] T. Jurzinsky, C. Cremers, K. Pinkwart, J. Tübke, ECS Transactions, 58 (2013) 633-636. [3] C. Lamy, S. Rousseau, E.M. Belgsir, C. Coutanceau, J.M. Leger, Proc. 54th Annual ISE Meeting, Sao Pedro, BRAZIL, Sep 01-05, 2003. [4] F.H.B. Lima, E.R. Gonzalez, Electrochimica Acta, 53 (2008) 2963-2971. [5] A. Kowal, M. Li, M. Shao, K. Sasaki, M.B. Vukmirovic, J. Zhang, N.S. Marinkovic, P. Liu, A.I. Frenkel, R.R. Adzic, Nature Materials, 8 (2009) 325-330. [6] C. Niether, M.S. Rau, C. Cremers, D.J. Jones, K. Pinkwart, J. Tübke, Journal of Electroanalytical Chemistry, 747 (2015) 97-103. Figure 1

(Industrial Electrochemistry & Electrochemical Engineering Division New Electrochemical Technology (NET) Award) Development of Large Scale Commercial PEM Electrolysis

Proton Energy Systems (d/b/a Proton OnSite) was founded in 1996, based on the premise that hydrogen generation from proton exchange membrane (PEM)-based electrolysis cells could be made cost competitive versus existing solutions. From small scale laboratory generators, Proton has successfully scaled up products over several design generations. A key advance has been the development of Proton’s C Series, a 30 Nm3/hr or 65 kg/day hydrogen generator based on PEM technology. A building block of this size is more suited for many applications, including common industrial markets and fueling infrastructure for small fleets of cars. This presentation will describe the evolution of Proton’s electrolyzer technology, including improvements in cell stack technology, balance-of-plant scale up, and the strong product platform we have built leading to our next product scale-up effort, for megawatt scale electrolysis applications. Market drivers and applications for various unit capacities, especially the C Series, will also be discussed. Electrolysis based on PEM technology was initially used in space and underwater for life support applications. Reliability is therefore a key characteristic of these systems. Proton has demonstrated over 50,000 hours of continuous operation in house, and has over 2000 systems fielded across product lines, with excellent reliability and up time. An advantage of the PEM systems in general is the ability to generate and electrochemically compress hydrogen at differential pressure, enabling low pressure on the oxygen side of the cell and inexpensive plastic components. The non-corrosive electrolyte also enables low maintenance cost and simpler balance-of-plant. Commercial applications for on-site hydrogen generation are driven by factors such as the desire for low hydrogen inventory, high purity hydrogen requirements, and lack of easily accessible hydrogen delivery infrastructure. Proton’s initial systems were designed to replace helium as the carrier gas in gas chromatographs, or as the lifting gas in weather balloons. The H Series, the precursor to the C Series, was developed specifically to address the electric generator cooling market. Hydrogen is utilized as a cooling fluid for the windings of over 16,000 power plant generators worldwide due to its high heat capacity and low density. Many of these plants are in areas with no reliable hydrogen delivery infrastructure. By 2006, Proton had established a robust cell design leveraging many of the design principles used today. The C Series was developed to serve larger power plants as well as the next level of fueling demonstrations, including small fleets of fuel cell vehicles and fuel cell buses. In addition, it is an appropriate size for heat treating and semiconductor applications. The cell stack, the core technology for the electrochemical system, was originally developed as a replacement for the existing electrolysis stack design for oxygen generation on board submarines. Proton was selected as the preferred developer based on our water electrolysis cell technology knowledge and expertise, leading to the development of a new, larger active area cell stack, including new flow field materials for the hydrogen side of the cell and a thinner cell configuration. This design effort was completed in 18 months, from early 2008 to 2009. Proton is currently under contract to manufacture cell stacks for several submarine platforms. This new cell architecture was then modified for the commercial application, and used as the basis for designing the new C Series system configuration. On the systems side, funding from the U.S. Army / TARDEC led to the development of key balance-of-plant subsystems, such as the implementation of a new gas/water management system, as well as a new high efficiency power supply configuration to drive the cell stacks. Internal investment from Proton paid for the development of system controls, manufacturing processes, and all of the quality documentation and third party agency certification testing required to release this platform as a commercial product. This development effort also spanned about 18 months, from 2009 to early 2011. Currently, Proton is working to translate many of the material advancements from PEM fuel cells to PEM electrolysis cells. While some changes will require modification, there are significant cost savings and efficiency improvements still possible, which Proton has demonstrated to have feasibility. In addition, Proton is performing another scale up effort to launch a megawatt scale product, representing another order of magnitude increase in hydrogen output. These systems will be designed based on requirements for emerging energy markets such as renewable energy capture and biogas methanization, and will also be discussed in this talk. Figure 1

Fuel cell mobile lighting: A fuel cell market transformation project

We report the results of a project aimed to introduce proton exchange membrane (PEM) hydrogen fuel cell technology into aviation ground support equipment (GSE) and rental construction equipment. The purpose of the project was to design, build, field-test and then commercialize fuel cell equipment that is superior to its diesel counterpart. The commercializing of this hydrogen-based technology will help to start the process of displacing diesel fuel use in aviation GSE and in mobile construction equipment. We describe a hydrogen fuel cell mobile lighting tower (H2LT) that combines hydrogen stored as a high pressure gas, PEM fuel cell technology, and advanced lighting into a single unit with uses in aviation and construction. We assembled a project team of 15 institutional partners combining new technology expertise (hydrogen, fuel cells), equipment mass manufacturing capability (mobile light towers, lighting) and influential end-users to field test the H2LT in real-world use in diverse environments. Seed funding provided by Boeing enabled additional funding from the U.S. Department of Energy (DOE) and a preponderance of in-kind contributions from the industrial partners. Prototype units were constructed and field tested in the entertainment industry, at the San Francisco International Airport, at the NASA Kennedy Space Center, with the California Department of Transportation (Caltrans), and with the Connecticut Department of Transportation. The goals of these approximately year-long field tests were to assess operation of the H2LT technology in a wide variety of potentially corrosive environments (cold, wet, hot, humid, salty air) performing a wide variety of tasks, to reduce diesel emissions at these locations, and to help promote hydrogen PEM technology in new influential markets. The H2LT proved to be exceptionally durable in these diverse environments, demonstrating the compatibility of PEM fuel cells and high-pressure hydrogen storage with the construction equipment application. Results from the field tests are discussed, including system performance (efficiency, duration, durability) and the efficacy of refueling the system by different methods (H2 stations, mobile refueling). The H2LT system is compared directly to a comparable diesel-fueled light tower with regard to size, performance and emissions savings. Overall, end users were pleased with the performance of the H2LT, noting the lack of emissions and exceptionally low noise level. Recommendations for improvement were also collected and will be discussed. Two types of lighting used on the H2LT (plasma, LED) were characterized by U.C. Davis in collaboration with Caltrans. LED lighting was found to be the most energy efficient and robust lighting technology for the highly mobile H2LT application. The technical “lessons-learned” are reviewed, along with the plans for commercialization of the H2LT technology by Multiquip Inc. Finally, the benefits to the industrial participants of the project organization are described.

Advances in Proton Exchange Membrane Technology

Significant advances in low humidity and high temperature operation of proton exchange membrane fuel cells have been achieved by using a novel polymeric composite membrane based on Nafion® perfluorosulfonic acid (PFSA) copolymer. A fundamental understanding of the microstructure of currently used ePTFE reinforced Nafion® perfluorosulfonic acid (PFSA) copolymer and how the microstructure limits the high temperature and low humidity performance is discussed. Fuel cell performance data and mechanical stability data of the new composite membrane are also presented in this paper.