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Summary of saturated salt solutions used for the samples conditioning at different relative humidity (RH).
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In this communication we present a detailed study of Nafion™ composite membranes containing different amounts of nanosized sulfated titania particles, synthesized through an optimized one-step synthesis procedure. Functional membrane properties, such as ionic exchange capacity and water uptake (WU) ability will be described and discussed, together...
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... membranes have been obtained by equilibrating the samples in a close container in presence of different saturated salt solutions, at least for 24 h (for higher conditioning time no weight difference was observed). The used salts are listed in the Table 1. RH values were taken from [33]. ...Context 2
... were performed at RH = 11, 33 and 100%. Prior to the AFM tests, membranes were fully conditioned for 30 days in a closed vessel at 11%, 33% and 100% RH ( Table 1). The AFM study was carried out in tapping intermittent contact mode (TM). ...Context 3
... were stored in close container in presence of different saturated salt solutions, at least for 24 h. The used salts are listed in Table 1. Before each measurement, samples were taken from the storage container and quickly moved to a sealed measuring chamber, in which the same salt solution was present in order to keep the desired RH condition also during the spectra acquisition. ...Context 4
... enhanced electrode/electrolyte interfacial properties, as well as the lower ohmic resistance associated with M5, explain its better behavior showed above in terms of cell performance. Since the thickness of the two membranes is comparable (see data shown in Table 1) and electrode active area is the same, the reduction of the ohmic resistance can be easily attributed to the larger conductivity value observed for the M5 membrane compared to Nafion™ at low humidity (RH = 30%). Turning to the different charge transfer resistance, one may speculate about a possible improved interfacial properties between membrane and electrode in the presence of the S-TiO2 filler. ...Context 5
... enhanced electrode/electrolyte interfacial properties, as well as the lower ohmic resistance associated with M5, explain its better behavior showed above in terms of cell performance. Since the thickness of the two membranes is comparable (see data shown in Table 1) and electrode active area is the same, the reduction of the ohmic resistance can be easily attributed to the larger conductivity value observed for the M5 membrane compared to Nafion™ at low humidity (RH = 30%). Turning to the different charge transfer resistance, one may speculate about a possible improved interfacial properties between membrane and electrode in the presence of the S-TiO 2 filler. ...Context 6
... enhanced electrode/electrolyte interfacial properties, as well as the lower ohmic resistance associated with M5, explain its better behavior showed above in terms of cell performance. Since the thickness of the two membranes is comparable (see data shown in Table 1) and electrode active area is the same, the reduction of the ohmic resistance can be easily attributed to the larger conductivity value observed for the M5 membrane compared to Nafion™ at low humidity (RH = 30%). Turning to the different charge transfer resistance, one may speculate about a possible improved interfacial properties between membrane and electrode in the presence of the S-TiO2 filler. ...Citations
... Sulfonated compounds embedded as fillers for PFSA composites are of greatest interest in order to increase the number of ionogenic sulfonic acid groups in the membrane involved in the proton exchange mechanism [39][40][41][42]. Sulfonated nanodiamonds, if they have been prepared, are excellent candidates for this purpose. ...
Aquivion®-type perfluorosulfonic acid membranes with a polytetrafluoroethylene backbone and short side chains with sulfonic acid groups at the ends have great prospects for operating in hydrogen fuel cells. To improve the conducting properties of membranes, various types of nanofillers can be used. We prepared compositional Aquivion®-type membranes with embedded detonation nanodiamond particles. Nanodiamonds were chemically modified with sulfonic acid groups to increase the entire amount of ionogenic groups involved in the proton conductivity mechanism in compositional membranes. We demonstrated the rise of proton conductivity at 0.5–2 wt.% of sulfonated nanodiamonds in membranes, which was accompanied by good mechanical properties. The basic structural elements, conducting channels in membranes, were not destroyed in the presence of nanodiamonds, as follows from small-angle neutron scattering data. The prepared compositional membranes can be used in hydrogen fuel cells to achieve improved performance.
... PEMFC research and development (R&D) activities are oriented today towards achieving higher efficiency and durability along with identifying low materials and manufacturing costs [8]. Recent PEMFC published research focused on identifying new component materials [9][10][11][12][13][14][15][16][17][18][19][20], novel designs [21][22][23][24][25][26][27], new manufacturing methods [28][29][30][31][32][33][34][35][36][37], improved balance of plant [38][39][40][41] and on developing theoretical models and experimental diagnostics [42][43][44][45][46][47][48][49][50][51][52][53] that improve our understanding of fuel cells operation. Along with fundamental research, manufacturing R&D is needed to prepare advanced manufacturing and assembly technologies that are necessary for low-cost, high volume fuel cell powerplant production. ...
A single robot-based manufacturing system for unattended machining and inspection of graphite bipolar flow field plates for proton exchange membrane fuel cells is designed and integrated for demonstration and validation. Unlike most robotic manufacturing systems where an industrial robot is used for tending an automated tool such as a computer numerical control machine, in the present system the industrial robot performs all manufacturing operations, including machining the flow fields on both sides of the plates, changing the tools, handling the plates, vacuuming the plates and the workholding device of graphite dust, flipping the plates, air blowing them and performing machine vision inspection for quality control. The toolpath for robotic machining the flow fields and the manifolds are generated offline using Roboguide simulation software. The manufacturing system uses an integrated machine vision inspection process as a diagnostic tool for in-line checking the presence of machined features and in-line verification of feature dimensions. Besides the considerably lower capital cost compared to other automated manufacturing systems resulted from the elimination of the automated machine tool, the proposed robotic cell has the advantage of better managing the abrasive graphite dust resulted in the manufacturing process. The limitations of the proposed robotic cell are assessed and recommendations for further development are considered. The manufacturing system is demonstrated as part of a larger endeavour of bringing to readiness advanced manufacturing technologies for renewable energy devices and responds the high priority needs identified by the U.S. Department of Energy for fuel cells manufacturing research and development.
... Such composites using functionalized nanofillers should improve the functional characteristics of membrane materials-proton conductivity, water retention at elevated temperatures, mechanical strength, and their performance in membrane electrode assemblies (MEA). Thus, opportunities have opened up for the creation of new materials with unique properties that the original polymer material could not possess [33][34][35]. ...
Compositional proton-conducting membranes based on perfluorinated Aquivion®-type copolymers modified by detonation nanodiamonds (DND) with positively charged surfaces were prepared to improve the performance of hydrogen fuel cells. Small-angle neutron scattering (SANS) experiments demonstrated the fine structure in such membranes filled with DND (0–5 wt.%), where the conducting channels typical for Aquivion® membranes are mostly preserved while DND particles (4–5 nm in size) decorated the polymer domains on a submicron scale, according to scanning electron microscopy (SEM) data. With the increase in DND content (0, 0.5, and 2.6 wt.%) the thermogravimetric analysis, potentiometry, potentiodynamic, and potentiotatic curves showed a stabilizing effect of the DNDs on the operational characteristics of the membranes. Membrane–electrode assemblies (MEA), working in the O2/H2 system with the membranes of different compositions, demonstrated improved functional properties of the modified membranes, such as larger operational stability, lower proton resistance, and higher current densities at elevated temperatures in the extended temperature range (22–120 °C) compared to pure membranes without additives.
... As summarized in Table 2, the composite membrane shows a lower ∆H value and a higher transition temperature compared to plain Nafion, suggesting the hydration degree of M-HSA is lower than that of pristine Nafion. This finding can be explained as follows: it can be due to a non-optimized distribution of the filler within the Nafion matrix, which obstructs the mobility of the chain segments and restricts the release of water [36,37], or it can be related to preferential filler-to-polymer interactions, preventing a direct coordination of water with the polymer hydrophilic groups. The latter is also supported by TGA results, where strong interactions of the acidic HSA filler with Nafion side chains were already supposed. ...
A series of sulfated aluminum oxides (S-Al 2 O 3 ), investigated as an electrolyte additive in Nafion membranes, was synthesized via three different methods: (i) sol–gel sulfation starting from an aluminum alkoxide precursor, (ii) room temperature sulfation of fumed aluminum oxide, and (iii) hydrothermal sulfation of fumed aluminum oxide. Through the characterization of the synthesized S-Al 2 O 3 by means of X-ray diffraction (XRD), thermogravimetric analysis (TGA), and infrared (IR) spectroscopy, a higher sulfation rate was found to be achieved via a hydrothermal sulfation, and the coordination state of sulfate groups was identified as monodentate. By using this hydrothermally synthesized S-Al 2 O 3 as additive, a composite Nafion-based membrane was realized and compared to plain Nafion, by means of thermal analyses and fuel cell tests. Although higher hydration degree was found for the undoped membrane by differential scanning calorimetry (DSC), improved retention of fuel cell performance upon the increase of operation temperature was observed by using the composite electrolyte, confirming the stabilizing effect of the acidic inorganic additive.
... The development of proton-conducting membrane technologies in recent years has been associated with the possibilities of targeted synthesizing of ordered composite structures by introducing organic and inorganic nanoparticles into polymer matrices to improve the functional properties of the membranes [3][4][5][6][7] and achieve higher conductive and strength characteristics than those of the original polymers [8][9][10]. The synthesis of hybrid membranes based on perfluorinated proton-conducting membranes exhibiting a unique combination of electrochemical and physicomechanical properties and chemical and thermal stability for use in FCs is of particular interest. ...
... Among all samples, the composite membrane M5 (containing 5 wt.% of the CaTiO3−δ additive) shows a higher ΔH value than both M10 (10 wt.% of CaTiO3−δ) and, to a lower extent, N (plain Nafion) samples. The addition of CaTiO3−δ particles caused an increase in the water content, even though the M10 sample, having the highest concentration of additive, displayed the lowest water affinity, possibly due to phase segregation and a non-optimized distribution of the inorganic additive [23,24], which can prevent the motions of the segments among the fluorocarbon backbone to restrict the water release. The TGA curves obtained for the three membranes are shown in Figure 2 (panel a). ...
... Among all samples, the composite membrane M5 (containing 5 wt.% of the CaTiO 3−δ additive) shows a higher ∆H value than both M10 (10 wt.% of CaTiO 3−δ ) and, to a lower extent, N (plain Nafion) samples. The addition of CaTiO 3−δ particles caused an increase in the water content, even though the M10 sample, having the highest concentration of additive, displayed the lowest water affinity, possibly due to phase segregation and a non-optimized distribution of the inorganic additive [23,24], which can prevent the motions of the segments among the fluorocarbon backbone to restrict the water release. ...
... Among all samples, the composite membrane M5 (containing 5 wt.% of the CaTiO3−δ additive) shows a higher ΔH value than both M10 (10 wt.% of CaTiO3−δ) and, to a lower extent, N (plain Nafion) samples. The addition of CaTiO3−δ particles caused an increase in the water content, even though the M10 sample, having the highest concentration of additive, displayed the lowest water affinity, possibly due to phase segregation and a non-optimized distribution of the inorganic additive [23,24], which can prevent the motions of the segments among the fluorocarbon backbone to restrict the water release. ...
A composite membrane based on a Nafion polymer matrix incorporating a non-stoichiometric calcium titanium oxide (CaTiO3−δ) additive was synthesized and characterized by means of thermal analysis, dynamic mechanical analysis, and broadband dielectric spectroscopy at different filler contents; namely two concentrations of 5 and 10 wt.% of the CaTiO3−δ additive, with respect to the dry Nafion content, were considered. The membrane with the lower amount of additive displayed the highest water affinity and the highest conductivity, indicating that a too-high dose of additive can be detrimental for these particular properties. The mechanical properties of the composite membranes are similar to those of the plain Nafion membrane and are even slightly improved by the filler addition. These findings indicate that perovskite oxides can be useful as a water-retention and reinforcing additive in low-humidity proton-exchange membranes.
... These are important parameters because they provide a direct measure of the hydration level and of the number of available protons. Based on these parameters it possible to derived the value of λ [29]; the results are reported in Figure 4. The figure shows the composite membranes M2 and M5 exhibiting higher water content with respect to both plain Nafion and M7 sample, as also suggested by the DSC results. ...
... However, the M5 sample has the highest IEC value among all the composite membranes. This critical effect of the filler content was already observed [29], with the intermediate additive concentration (5 wt %) being the optimal choice. Such effect can be explained considering a uniform distribution of the filler amount within the polymer matrix, establishing positive interactions in terms of proton exchangeability. ...
... These are important parameters because they provide a direct measure of the hydration level and of the number of available protons. Based on these parameters it possible to derived the value of λ[29]; the results are reported inFigure 4. The figure shows the composite Differential scanning calorimetry (DSC) curves of the membranes. ...
Nafion composite membranes, containing different amounts of mesoporous sulfated titanium oxide (TiO2-SO4) were prepared by solvent-casting and tested in proton exchange membrane fuel cells (PEMFCs), operating at very low humidification levels. The TiO2-SO4 additive was originally synthesized by a sol-gel method and characterized through x-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and ion exchange capacity (IEC). Peculiar properties of the composite membranes, such as the thermal transitions and ion exchange capacity, were investigated and here discussed. When used as an electrolyte in the fuel cell, the composite membrane guaranteed an improvement with respect to bare Nafion systems at 30% relative humidity and 110 °C, exhibiting higher power and current densities.
Sulfated titania (TiO2‐SO4²⁻) is a unique and versatile catalytic material which is non‐toxic, non‐corrosive, non‐pollutant and easily separable in nature. Sulfated titania can engage in various organic reactions, as it contains both Lewis acid and Bronsted acid sites. A wide number of organic reactions in the presence of sulfated titania have been reported, most of which displays excellent conversion and selectivity for the syntheses of desired products with significant applications. This review endeavors to give an overview of the research highlights solicitous with sulfated titania. Even though it is arduous to cover all the research articles in the literature, various milestones in the route towards highly functionalized sulfated titania are explored. It is hoped that this review article will trigger the attention of researchers over sulfated titania for the advancement of new eco‐compatible approaches in organic chemistry.
Recently demonstrated robotic assembling technologies for fuel cell stacks used fuel cell components manually pre-arranged in stacks (presenters). Identifying the original orientation of fuel cell components and loading them in presenters for a subsequent automated assembly process is a difficult, repetitive work cycle which if done manually, deceives the advantages offered by either the automated fabrication technologies for fuel cell components or by the robotic assembly processes. We present for the first time a robotic technology which enables the integration of automated fabrication processes for fuel cell components with a robotic assembly process of fuel cell stacks into a fully automated fuel cell manufacturing line. This task uses a Yaskawa Motoman SDA5F dual arm robot with integrated machine vision system. The process is used to identify and grasp randomly placed, slightly asymmetric fuel cell components, to reorient them all in the same position and stack them in presenters in preparation for a subsequent robotic assembly process. The process was demonstrated as part of a larger endeavor of bringing to readiness advanced manufacturing technologies for alternative energy systems, and responds the high priority needs identified by the U.S. Department of Energy for fuel cells manufacturing research and development.
