Portable Fuel Cell Applications Research Articles

Phosphorus oxide promoted solid state hydrolysis of sodium borohydride for efficient onsite hydrogen production

The hydrolysis of solid sodium borohydride (NaBH4) as a hydrogen source for portable fuel cells offers the advantages of excellent safety and convenient storage, making it the optimal alternative to NaBH4 solutions. However, the hydrolysis process is relatively slow and requires the addition of a catalyst to enhance its efficiency. Recent studies have demonstrated that introducing H+ can effectively promote the hydrolysis of NaBH4. In this study, therefore, selects solid acid anhydride, phosphorus pentoxide (P2O5), as a promoter for the hydrolysis of NaBH4. By controlling the ratio of H+ to H− in the NaBH4–P2O5 system, the conditions for hydrogen production via NaBH4 hydrolysis are optimized. Subsequently, to cater to the requirements of portable fuel cell applications, the optimal NaBH4–P2O5 hydrogen production system is selected, with hydrogen generation rate being controlled by regulating water flow speed. In order to enhance the practical applicability of NaBH4–P2O5, the scale-up of hydrogen production from this system is also undertaken. Finally, to validate the practicality of this reaction system, integration with a proton exchange membrane fuel cell (PEMFC) toy car using the NaBH4–P2O5 hydrogen generation system is performed. The results indicate that a NaBH4 conversation exceeding 90 % can be achieved when the ratio of H+ to H− is approximately 0.14, and within the range of H+/H− ratios from 0.05 to 0.14, the maximum hydrogen density reached 6 %. Furthermore, it was found that adjusting the water flow rate only impacts the rate of hydrogen production without significantly affecting the NaBH4 conversion, which consistently surpassed 90 %. Similar high NaBH4 conversion, above 90 %, were also attained in the scaled-up experiments of the NaBH4–P2O5 system. When implemented in a 5W PEMFC, this hydrogen production system delivered an output power of approximately 1.76 W, thereby affirming its operational feasibility and effectiveness.

Thermal management of polymer electrolyte membrane fuel cell with stearyl alcohol and fans combined

In this experimental work, the potential of utilizing the Phase change material (PCM) for the passive thermal management of Polymer Electrolyte Membrane Fuel cell (PEMFC) is explored. The development of a passive thermal management system for the fuel cell is essential to reduce the parasitic power consumed by the thermal management system. Stearyl alcohol as PCM which has a melting point of 59°C and an enthalpy of 260 J/g will be best suited for the portable fuel cell application operating around 60°C. Stearyl Alcohol kept inside the cooling plate as passive thermal management is studied and also utilized to improve the thermal management of an edge air cooling system. The power density applied to the Fuel cell thermal management system (FCTMS) is varied from 0.1 to 0.45 W/cm2 by a DC power supply. The FCTMS is tested in four modes of operation no cooling, with PCM, cooing with fan, and fan combined with PCM. The FCTMS with PCM can hold the temperature of the cooling plate below 60°C till the power density of 0.30 W/cm2 which is 20% higher compared to the FCTMS under no cooling. Further, the combination of PCM with air cooling improved its maximum power density applied by 14 % compared to the air cooling system.

KINETIC STUDIES OF HYDROLYSIS REACTION OF NaBH4 WITH γ-Al2O3 NANOPARTICLES AS CATALYST PROMOTER AND CoCl2 AS CATALYST

Abstract Solid-state hydrogen storage is of considerable concern as a potential hydrogen source for portable fuel cell applications. This study mainly focuses on kinetics of NaBH4/Al2O3 nanoparticles (20 nm)/H2O system with CoCl2 as catalyst and the factors that affect the hydrogen generation rate (HGR). It is observed that the reaction rate increases considerably with increase in NaBH4, Al2O3 nanoparticle (20 nm), CoCl2 and NaOH concentrations and the respective reaction orders are calculated. Hydrogen generation rate is also investigated at different temperatures (303, 313, 323 and 333 K) for constant NaBH4 (1.25 moles/L), NaOH (1.4 moles/L), CoCl2 (0.02 moles/L) and Al2O3 (0.09 moles/L) concentrations. Kinetics of the NaBH4 hydrolysis reaction increases with γ-Al2O3 nanoparticles and the calculated activation energy is 29 kJ/moles. This study also reports that a combined dual-solid-fuel system is highly efficient in terms of hydrogen storage capacities compared with a single hydride based system. Maximum hydrogen generation efficiency, observed at a mass ratio of 0.09: 0.7 (Al2O3/NaBH4), is 99.34%.

Borohydride in ionic liquids for tailored hydrogen release

H2 as an environmentally benign energy carrier could answer the world's continuously increasing demand for sustainable energy sources, especially in portable fuel cell applications. Thereby, H2 storage is the key issue. In the present work, we developed a liquid H2 storage material based on BH4− and ionic liquids for tailored H2 release under ambient conditions using various catalysts as releasing agents. Thereto, we synthesized four BH4− ionic liquids via ionic exchange. The most promising BH4− based ionic liquids are 1-Ethyl-3-methylimidazolium BH4− and 1-Propyl-3-methylimidazolium BH4−, containing up to 3 wt% releasable hydrogen and the latter being liquid at standard temperature. The hydrolysis of 1-Ethyl-3-methylimidazolium BH4− with various supported metal catalysts (Pt/C, Pt/CNT, Ru/CNT, Pd/CNT, 5 wt% metal) and H2O (8, 16, 24 eq.) was assayed. The highest yield was obtained with 24 eq. H2O and Pt/CNT. The catalysts were characterized via X-ray photoelectron spectroscopy and transmission electron microscopy/energy-dispersive X-ray spectroscopy. To calculate the catalyst activities, the dispersion and size distribution of the metal particles were determined. Recycling of Pt/CNT showed a reasonable stability of the catalyst activity over four recycling runs. In order to avoid spontaneous crystallization of 1-Ethyl-3-methylimidazolium BH4− as a storage material, 1-Propyl-3-methylimidazolium BH4− was introduced. The hydrolysis yield was significantly increased by the use of acidic catalysts, such as HCl and Amberlyst 36. Further enhancement of the H2 yield was achieved by adopting a semi batch process, continuously adding 1 M HCl to 1-Propyl-3-methylimidazolium BH4−. The H2 release correlated approximately linearly with the acid addition rate, excluding liquid-liquid mass transfer limitations during the hydrolysis. Based on 11B NMR analysis, a reaction mechanism of the hydrolysis of BH4− ionic liquid with HCl as catalyst is proposed.

Catalytic reforming of dimethyl ether in microchannels

The steam reforming and oxidative steam reforming of dimethyl ether (DME) were tested at 573–773 K over a CuZn/ZrO2 catalyst in microreactors with three different types of channels: ceramic square channels with side lengths of 900 and 400 μm, and silicon microchannels of 2 μm of diameter. The channels were first coated with ZrOCl2 (ceramic channels) or Zr(i-PrO)4 (silicon microchannels) and calcined at 773 K for 2 h to obtain a homogeneous and well-adhered ZrO2 layer, as determined by SEM, and then Cu and Zn (Cu:Zn = 1:1 M, 20 wt% total metal) were co-impregnated. Operation at highly reduced residence time (10−3 s) while achieving hydrogen yields similar to those recorded over the ceramic channels was possible for the silicon microchannels due to the three orders of magnitude increased contact area. In addition, the amount of catalyst used for coating the silicon microchannels was two orders of magnitude lower with respect to the conventional ceramic channels. Outstanding specific hydrogen production rates of 0.9 LN of H2 per min and cm3 of reactor volume were achieved as well as stable operation for 80 h, which demonstrates the feasibility of using on-site, on-demand hydrogen generation from DME for portable fuel cell applications.

Hydrolysis of Mg(BH4)2 and its coordination compounds as a way to obtain hydrogen

Three ligand-stabilized Mg(BH4)2–based complexes have been synthesized and evaluated as potential hydrogen storage media for portable fuel cell applications. The new borohydrides: Mg(BH4)2 × 0.5Et2O and Mg(BH4)2 × diglyme (diglyme – CH3O(CH2)2O(CH2)2OCH3) have been synthesized and examined by X-ray single crystal diffraction method. Hydrolysis reactions of the compounds liberate hydrogen in quantities ranging from 46 to 96% of the theoretical yield. The hydrolysis of Mg(BH4)2 and other borohydrides is also accompanied by the diborane formation. The amount of liberated diborane depends on the Mg-coordination environment. To explain this fact quantum-chemical calculations have been performed. It is shown that formation of Mg-O-Mg-bridges enables the side process of diborane generation. It means that the size and denticity of the ligand directly affects the amount of released diborane. In general, the larger the ligand and the higher its denticity, the smaller is amount of diborane produced. The new compound Mg(BH4)2 × diglyme decomposes without diborane formation that allows one to be considered as a new promising chemical hydrogen storage compound for the practical usage.

Ruthenium nanoparticles immobilized on surfactant-directed polypyrrole as an effective and reusable catalyst for hydrogen generation

An effective catalyst with high activity and stability is required to produce hydrogen from the hydrolysis of sodium borohydride (NaBH4) for the portable fuel cell applications. In this study, the synthesis of highly effective, stable and reusable polypyrrole (PPy) supported ruthenium nanoparticles (NPs) is presented. PPy powders with porous structure were prepared by the chemical oxidative polymerization, followed by the deposition of Ru NPs using the wet impregnation—reduction method. Due to the synergistic effect of Ru NPs with PPy, the as-synthesized catalyst exerts good catalytic activity, with the hydrogen release rate of 22.74 ± 0.84 L min−1 g Ru −1 and activation energy of 39.08 ± 1.69 kJ mol−1, which is lower than most of the reported activation energy values. This novel Ru/PPy catalyst is a promising candidate for small portable hydrogen generators by NaBH4 hydrolysis. Structural, morphological and textural properties of the catalysts were investigated by analytical techniques. Moreover, the effects of reaction temperature, NaOH and NaBH4 concentrations on catalytic activity were also investigated.

Pt/C Spontaneously Decorated with Citrate As a Catalyst for Formic Acid Electro-Oxidation

Efficient direct electro-oxidation of liquid fuels, such as methanol and formic acid for low-temperature portable fuel cell applications, remains a challenge limiting commercialization. The major performance detractors are: (1) the formation of strongly adsorbed reaction intermediates, (2) fuel crossover through the membrane depolarizing the cathode, and (3) mass transport for fast fuel delivery into the anode catalyst layer and gaseous product removal. Direct formic acid fuel cells (DFAFCs) have the advantage over direct methanol fuel cells in that it is possible for formic acid to be electro-oxidized via a direct non-strongly adsorbed reaction intermediate pathway.[1] In addition to being less susceptible to fuel crossover due to electrostatic repulsion of the polarized formic acid dipole by the negatively charged sulfonic groups in the proton exchange membrane (PEM).[2] However, the catalyst selection is pivotal for enhanced performance. Previous research from our group has shown highly active carbon-supported platinum (Pt/C) catalyst layers spontaneously decorated with bismuth exhibiting low overpotential for formic acid electro-oxidation, shown in Fig 1. This enhancement of catalytic ability has been attributed to promotion of the direct oxidation pathway by the ‘third-body’ as well as an electronic effect to promote CH-down adsorption of formic acid on the unoccupied Pt/C surface.[3] However, adsorbed Bi is unstable under oxidizable potentials, as demonstrated in our previous studies, Figure 2.[4] Pore-former was incorporated into the catalyst layer to increase formic acid mass transport. During open potential acid wash removal of the pore-former the Bi was lost from the Pt surface and performance was also lost. Research by Antaño-López et al. has shown that the spontaneous adsorption of citrate, a common nanoparticle capping agent, suppresses the formation of platinum oxide.[5] This implies that citrate is a stable surface adsorbate in the oxide region. It is predicted that citrate will exhibit a similar ‘third-body’ effect as Bi with an optimal surface coverage fraction yet to be determined due to the chelation effect of citrate that Bi does not exhibit.

(Invited) Development of Alkaline- and Bipolar-Membranes for Hybrid Fuel Cell Applications

The development of technologies which offer efficient and scalable energy conversion and storage is a challenge of considerable importance. Potential applications range from the integration of renewable energy supplies into the domestic power grid to reducing the logistic burden of supplying energy to our military and defense forces. Electrochemical processes are a natural fit for addressing many of these problems; however, system limitations and technical issues confound development efforts. Cost, reliability, scalability, and ease of integration are often among the leading challenges for established domestic technologies, whereas size, weight, storage/transportability, and environmental considerations are of utmost importance for defense applications. Research and development efforts for electrochemical energy conversion and storage technologies are driven by materials requirements. Materials in these electrochemical systems typically have demanding functional requirements (e.g., conductivity, catalyst activity, selectivity, mechanical strength, etc.), which must be met under aggressive operating conditions (e.g., acidic or basic electrolytes, the presence of strong solvents and/or contaminants, highly oxidizing and reducing electrode processes, high temperatures, etc.). All of these functional requirements must be met with expectations for little-to-no degradation during operation and cycling (e.g., loss in active catalyst area, poisoning or chemical degradation, corrosion, fatigue, crack formation, etc.). In many cases the individual constituent materials cannot meet the complex and intertwined functional, environmental, and stability requirements alone, which has driven research and development efforts towards the use of heterogeneous materials. Our own research and development efforts focus on hybrid acidic- and alkaline-membranes for portable fuel cell applications [1-2]. Proton exchange membrane (PEM) electrolytes are relatively well established. Alkaline anion exchange membrane (AEM) electrolytes have more recently come to prevalence. AEMs have been ushered into the fuel cell community based on the prospect of developing cheaper and more compact systems via reductions in noble-metal catalyst content, membrane and packaging materials costs, and water and fuel management requirements [3]. However, development efforts have been hindered by challenges with materials performance and stability [3-5], penalties for anodic processes including hydrogen oxidation [6], and thermodynamic and resistive losses associated with the presence of carbon dioxide [7-8], among others. These challenges have led us to explore the development of hybrid-membrane approaches, such as the bipolar membrane which was shown by Unlu et al [9]. We believe that this type of approach can mitigate some of the catalyst and water/fuel management challenges. However, a suitable AEM and acid-alkaline membrane interface are needed for such an approach. This has led us to study the modification of the underlying AEM materials as well as the introduction of heterogeneity through processing (e.g., via electrospinning processes popularized for fuel cells in the PEM community [10]). In this modeling and theory focused talk, we address the introduction of heterogeneity into membrane electrolyte materials, its influence on key material properties, and the corresponding impact of its integration to bipolar membrane fuel cells. Acknowledgement: The authors gratefully acknowledge the support of the U.S. Department of the Army, Army Materiel Command, and U.S. Army Research Development and Engineering Command.

Advances in stationary and portable fuel cell applications

The reliance on fossil fuels is one of the most challenging problems that need to be dealt with vigorously in recent times. This is because using them is not sustainable and leads to serious environmental issues, such as: air pollution and global warming. This condition affects economic security and development. An alternative to fossil fuel is highly possible which will be more environmentally friendly, sustainable and efficient as well. Among all the different technologies associated with renewable energy, fuel cell technologies represent one of the most promising technological advancement to curb the situation.In this paper, an overview of the technology and its advantages and disadvantages compared with competitive technologies was revealed. The application of different fuel cell types in the stationary and portable sectors was covered. Furthermore, recent challenges and promising developments of current fuel cell technologies in different studied applications were reviewed. Some possible solutions to the challenges were named in this paper for both the portable and stationary fuel cell applications. The paper further seeks to expose the world to the current progress made in the fuel cell industry up to date and possible areas that needs intensified research and modifications to make the fuel cell industry more vibrant and buoyant.

Optimized Direct Formic Acid Fuel Cells Anodes

Efficient direct electro-oxidation of liquid fuels, such as methanol and formic acid for portable fuel cell applications, remains a challenge limiting commercialization. The major performance detractors are (1) the formation of strongly adsorbed reaction intermediates, (2) fuel crossover through the membrane depolarizing the cathode, and (3) mass transport for fast fuel delivery into the anode catalyst layer and gaseous product removal. Direct formic acid fuel cells (DFAFCs) have the advantage over direct methanol fuel cells in that it is possible for formic acid to be electro-oxidized via a direct non-strongly adsorbed reaction intermediate pathway.[1] In addition to being less susceptible to fuel crossover due to anionic repulsion of the polarized formic acid dipole by the anionicly charged sulfonic groups in the proton exchange membrane (PEM).[2] However, catalyst selection is pivotal for enhanced performance as show by the low onset of formic acid electro-oxidation in Fig 1 for bismuth decorated Pt/C catalyst layer. The bismuth at 54wt% coverage promotes the direct electro-oxidation pathway by the ‘third-body’ effect and adsorption in the CH-down orientation. Fig 1. Anodic linear sweep voltammetry (40°C) with 5M formic acid (2.5 ml min-1) at 10 mV sec-1 for catalyst layers of PtRu alloyed and Pt/C-Bi (54% of a monolayer). The next component of anode catalyst layer optimization is selective structuring. This will be done in two ways (i) ionomer content and (ii) catalyst layer porosity. Ionomer content (NafionTM) in the catalyst layer has thus far been probed from 20wt% - 40 wt%. Optimal performance ca. 32wt% NafionTM. It has been shown that DFAFC performance is strongly impacted by catalyst layer porosity via either swelling of the catalyst layer[3] or using a pore former to create larger pore structures in the catalyst layer[4]. The pore-forming templating agent selected for these initial studies was micron-sized lithium carbonate (Li2CO3), due to facile removal upon acid treatment.[5] Acknowledgements: We gratefully acknowledge support of this work by the NSF-funded TN_SCORE program, NSF EPS-1004083, under Thrust 2 and the Center for Manufacturing Research at Tennessee Tech University.

Ultrafast hydrogen generation from the hydrolysis of ammonia borane catalyzed by highly efficient bimetallic RuNi nanoparticles stabilized on Ti3C2X2 (X = OH and/or F)

Graphene-like transition metal carbide [Ti3C2X2 (X = OH and/or F)]-supported RuNi bimetallic nanoparticles (NPs) were synthesized from the co-reduction of ruthenium chloride and nickel chloride with Ti3C2X2 as a stabilizer and carrier. Ti3C2X2-supported RuNi NPs were well dispersed in aqueous solution. The as-synthesized composites were applied as catalysts in the hydrolysis of ammonia borane (AB), which is a promising solid-state hydrogen storage material for portable fuel cell application. Results indicated that the RuNi/Ti3C2X2 catalyst was highly active for the hydrolysis of AB at room temperature, with the highest turnover frequency number of 824.7 mol H2·(mol Ru·min)−1. The activation energy for the hydrolysis of AB in the aqueous phase reached 25.7 kJ/mol, which was lower than most of the reported values.

Hydrogen supply system employing direct decomposition of solid-state NaBH4

Under the overarching aim to develop an onboard hydrogen generation system for portable fuel cell application, a hydrogen supply system that exploits the direct decomposition of solid-state NaBH4 was designed and integrated into a model fuel cell for evaluation of the system performance. The operation characteristics were evaluated based on measurement of the hydrogen yield and performance parameters including the HCl concentration and HCl/NaBH4 reaction ratio. A hydrogen yield of 95% was obtained at hydrogen supply rates higher than 650 ml/min. The gravimetric hydrogen density was highest when a 4.0 N HCl solution was used, given that the HCl/NaBH4 reaction ratio was lowest at this HCl concentration. The system performance was not affected by concentration fluctuations due to aging of the HCl solution. A stable hydrogen supply rate was achieved by optimization of the operating conditions such as the reactor pressure. The hydrogen supply system stably operated a 100 W fuel cell under various load conditions.

Applied hydrogen storage research and development: A perspective from the U.S. Department of Energy

To enable the wide-spread commercialization of hydrogen fuel cell technologies, the U.S. Department of Energy, through the Office of Energy Efficiency and Renewable Energy’s Fuel Cell Technology Office, maintains a comprehensive portfolio of R&D activities to develop advanced hydrogen storage technologies. The primary focus of the Hydrogen Storage Program is development of technologies to meet the challenging onboard storage requirements for hydrogen fuel cell electric vehicles (FCEVs) to meet vehicle performance that consumers have come to expect. Performance targets have also been established for materials handling equipment (e.g., forklifts) and low-power, portable fuel cell applications. With the imminent release of commercial FCEVs by automobile manufacturers in regional markets, a dual strategy is being pursued to (a) lower the cost and improve performance of high-pressure compressed hydrogen storage systems while (b) continuing efforts on advanced storage technologies that have potential to surpass the performance of ambient compressed hydrogen storage.

Electrochemical and Physical Characterization of Ru Activated Carbon Supported Electrodes in Alkaline Solution

Polymer electrolyte fuel cells (PEMFC) are promising energy sources for stationary and portable fuel cell applications [1-3]. However, the slow oxygen reduction reaction (ORR) on different catalysts is one of the most limiting factors in the energy conversion efficiency of PEMFC. Improved cathode catalysts could have a dramatic impact on the fuel cell efficiency. Therefore platinum-ruthenium and other alloys deposited onto various carbon supports have been studied to find materials with higher ORR activity [2, 4-6].The following work examines the impact of ruthenium nanoparticles (20 wt%), deposited onto various carbon supports prepared from α-WC and Vulcan, on ORR kinetics in 0.1 M KOH aqueous solution. Experiments show that there is an important contribution of the nanoparticles to the electroreduction process of O2. Scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), high resolution transmission electron microscopy (HRTEM) and low temperature N2 adsorption experiments were carried out to characterize the structure of the prepared materials.EDX studies show that Ru nanoclusters have been deposited into/onto carbon support quite uniformly. A comparison of the N2 adsorption data (table) and SEM images show that ruthenium forms mesoporous clusters on the surface of the supporting material (figure). SEM images show also that small ruthenium nanoparticles were uniformly observed on the support material, which means that deposition doesn’t take place quite homogenously.Electrochemical measurements were carried out in a three-electrode electrochemical cell. Electrochemical characteristics for various Ru-modified micromesoporous carbons have been established by cyclic voltammetry (CV) and rotating disc electrode (RDE) methods. RDE data were measured at rotation rates from 0 to 3000 rpm (v=10 mV∙s-1) and in the region of potentials from +0.17 to -0.50 V vs. Hg|HgO|0.1 M KOH. CVs were measured at potential scan rates (v mV/s) 5, 10, 20, 30, 50, 70, 100, 150 and 200, in both Ar and O2 saturated solutions. The solutions were saturated with Ar or O2, respectively, between measuring of each voltammogram. A glassy carbon disk electrode (GCDE) was used as a catalyst support for electrochemical measurements. Catalyst ink was prepared by suspending the catalyst powders in isopropanol, Milli-Q+ water and Nafion dispersion solution (Aldrich) mixture (5 wt%) and pipetted onto GCDE.It was established that the ORR activity for 20%Ru-C(WC) is higher but comparable to 20%Ru-Vulcan. Ru-metal loadings play a dominant role in the kinetics of the ORR on both electrodes in alkaline solution. After correction for Ar saturated supporting electrolyte current densities, very nice diffusion current plateaus have been observed at E < -0.28 V vs. Hg|HgO|0.1 M KOH for 20%Ru-C(WC) and 20%Ru-Vulcan systems. CV data demonstrate that 20%Ru-C(WC) exhibits higher capacitance values than 20%Ru-Vulcan, which is in a good agreement with N2 adsorption data. Acknowledgements: This work was supported by the Estonian target research project SF0180002s08, the Estonian Centre of Excellence in Science Project TK117T "High-technology Materials for Sustainable Development", the Estonian Energy Technology Program project SLOKT10209T, the Materials Technology project SLOKT12180T.

On-line estimation of inlet and outlet composition in catalytic partial oxidation

An estimation strategy is presented for determining inlet and outlet composition of catalytic partial oxidation (CPOX) of methane over rhodium catalyst using simple, fast measurements: temperature, and thermal conductivity. A 1-D high fidelity simulation model for CPOX studied in Ref. [1] for a portable fuel cell application is developed and enhanced for transient experiments. Process dynamics are analysed to demonstrate how solid temperatures along the axes of the reactor reflect the endothermic/exothermic interplay of reactions during a process upset. Model reduction is then used to obtain a low complexity model suitable for use in a moving horizon estimator with update rates faster than 0.02 s. System theoretic observability analysis is then conducted to predict the suitability of different measurement designs and the best locations for temperature measurements for estimating both inlet and outlet gas mole fractions for all species. Finally, a Moving Horizon estimator is implemented and simulation experiments are conducted to verify the accuracy of the estimator.

Syngas production by catalytic partial oxidation of methane over (La0.7A0.3)BO3 (A = Ba, Ca, Mg, Sr, and B = Cr or Fe) perovskite oxides for portable fuel cell applications

Hydrogen is a clean energy carrier for the future. More efficient, economic and small-scale syngas production has therefore important implications not only on the future sustainable hydrogen-based economy but also on the distributed energy generation technologies such as fuel cells. In this paper, a new concept for syngas production is presented with the use of redox stable lanthanum chromite and lanthanum ferrite perovskites with A-site doping of Ba, Ca, Mg and Sr as the pure atomic oxygen source for the catalytic partial oxidation of methane. In this process, catalytic partial oxidation reaction of methane occurs with the lattice oxygen of perovskites, forming H2 and CO syngas. The oxygen vacancies due to the release of lattice oxygen ions are regenerated by passing air over the reduced nonstoichiometric perovskites. Studies by XRD, temperature-programmed reduction (TPR) and activity measurements showed the enhanced effects of alkaline element A-site dopants on reaction activity of both LaCrO3 and LaFeO3 oxides. In both series, Sr and Ca doping promotes significantly the activity towards the syngas production most likely due to the significantly increased mobility of the lattice oxygen in perovskite oxide structures. The active oxygen species and performance of the LaACrO3 and LaAFeO3 perovskite oxides with respect to the catalytic partial oxidation of methane are discussed.

Development of a continuous hydrogen generator fueled by ammonia borane for portable fuel cell applications

Thermally-induced dehydrogenation from a mixture of ammonia borane (AB) and a chemical promoter, tetraethyleneglycol dimethylether (T4EGDE) (AB:T4EGDE = 79:21, wt%) has been demonstrated as an efficient method for hydrogen production at 85–145 °C. We further build on these prior results to create a continuous H2 generator fueled by solid AB beads. The as-developed H2 generator releases ca. 2 equiv of hydrogen autothermally during operation by utilizing excess heat produced from AB dehydrogenation without any external heater. A purifying system equipped with acidic filter materials is further utilized to remove gaseous byproducts other than hydrogen. The H2 generator shows a rapid H2-release rate up to 3.3 l(H2) min−1 with fast load-following capability. The as-developed H2 generator is ultimately integrated with a commercial 200 We polymer electrolyte membrane fuel cell (PEMFC) to test its capability.

Hydrogen generation from hydrolysis of aluminum/graphite composites with a core–shell structure

Hydrogen generated by hydrolysis of metal aluminum with water is promising for portable fuel cell applications. However aluminum would not react with water to yield hydrogen at ordinary conditions due to the passive oxide film formed on its surface. In the present investigation, the aluminum/graphite composite were prepared by a ball milling process in an attempt to improve the reactivity of aluminum, using sphere-shape aluminum particles and laminate graphite as the initial materials and 2 wt% NaCl as the milling-assisted agent. The TEM observation showed that the Al particles are covered by graphite to form a core–shell structure. Such a Al/graphite composite material exhibited a pronounced hydrolysis reactivity with tap water to generate hydrogen while Al alone did not react with water. The presence of graphite could lower the hydrogen generation reaction temperature below 45 °C. Increasing the reaction temperature could obtain an increased hydrogen generation rate and the maximum hydrogen generation rate of 40 cm3 min−1 g−1 Al was obtained when the reaction temperature was increased to 75 °C. Prolonging milling time could also improve the Al hydrolysis reactivity in the composite particularly at a relatively low temperature. The XRD results identified that the hydrolysis byproducts are bayerite (Al(OH)3) and boehmite (AlOOH). The microstructure-related hydrolysis reaction mechanism was finally proposed.

Energy from hydrogen. Hydrogen from renewable fuels for portable applications

Molecular hydrogen is an environmentally clean source of energy, but it is not available on Earth. Steam reforming of bio-derived compounds represents a valuable route for the generation of molecular hydrogen and has the advantage that it is CO2-neutral and it requires a limited amount of additional infrastructure for implementation. At present, suitable catalysts for selective bio-alcohol and dimethyl ether reforming into hydrogen and carbon dioxide are being developed, but their use on structured wall reactors for practical application is still under way. Among them, aerogel-based coated structures appear very promising due to their very high mass transfer rates and their ability to disperse highly active metal nanoparticles. The performance of these systems improves considerably by using microreaction technologies. Microreactors based on silicon micromonoliths together with integrated downstream carbon monoxide selective oxidation hold a promising futurefor the effective on-site and on-demand generation of hydrogen from renewable fuels in portable fuel cell applications.