We have performed first-principles density functional theory calculations to investigate how subsurface 3d transition metals M (M = Ni, Co, Fe, Ti, or V) affect the energetics and mechanisms of oxygen reduction reaction (ORR) on the outermost Pt mono-surface layer of Pt/M (111) surfaces. We found that the alteration of the ORR mechanism pathway can explain the activity enhancement for ORR on the Pt/M (111) surfaces.

Oxygen reduction in SOFC cathodes has long been the rate determining step in SOFC operations, mixed ionic-electronic conductors (MIECs) and/or forming composite between cathode and electrolyte materials have been common strategies in order to aid the cathode kinetics. We demonstrate here a viable synthesis route to impregnate mesopores with high loading of platinum towards a mesoscale bicontinuous material that composed of channels of a fast ionic conductor, i.e. gadolinium doped ceria (GDC) intertwined with channels of a good electronic conductor, i.e. Pt. This highly structural composite material holds the promise of a high performing cathode in SOFC.

The manufacture of composite materials can improve the properties of proton-conducting polymers as membranes in PEM fuel cells. We have investigated composite membranes obtained by dispersion of nanodiamond particles in a sulfonated PolyEtherEtherKetone (SPEEK) matrix. SPEEK is a major proton-conducting aromatic polymer. Nanodiamond has been studied for various applications and can be functionalized with different surface groups. For use in proton-conducting membranes, surface functionalization with proton-donating groups is a promising approach. In this preliminary work, we have studied the properties of membranes made using pristine nanodiamond from diverse origins for a first assessment of the potential properties. The composites were analysed by various techniques, including Thermogravimetric Analysis, water vapor uptake and mechanical tensile tests.

In last years, the carbon nanotubes have been studied as an advanced metal catalyst support for proton exchange membrane fuel cell. This study focuses on the sonochemical treatment of multi walled carbon nanotubes (MWCNTs) as a platinum supporting material for proton exchange membrane fuel cell (PEMFC) by mixture of sulfuric acid and nitric acid and mixture of sulfuric acid and hydrogen peroxide. X-ray diffraction (XRD) and Infrared (IR) spectroscopy were used to characterize the surface of sonochemically treated MWCNT and nanostructured electrocatalyst Pt/MWCNT. According to the experimental results of this work, the surface of MWCNT can be more successfully functionalized with hydroxyl and carboxyl groups after sonochemical treatment by mixture of sulfuric acid and nitric acid. The particle size of prepared Pt -electrocatalyst on MWCNT was determined 3.4 nm by XRD.

We report the preparation and characterization of binary blend films of poly(vinylidene fluoride) (PVDF) and poly(1- ethyl-3-vinylimidazolium trifluoromethylsulfonylimide) (PVIm+TFSI-) derived from ionic liquid imidazolium monomers and doped with TFSI- salt. The potential utility of such materials in capacitive electronic devices and in proton exchange membrane fuel cells is of particular interest. Thin PVDF/ PVIm+TFSI- films were fabricated from solutions of dimethly formamide (DMF) by doctor blading. The nature of the PVDF crystalline polymorph and degree of crystallinity were evaluated as a function of the volume fraction of imidazolium polymer and thermal treatment. The morphology, thermal and mechanical characteristics and crystallinity of PVDF, in semicrystalline blend films was studied by wide angle X-ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetry, and dynamic mechanical analysis. In these materials, conditions such as choice of solvent, drying conditions, and thermal treatment affect the crystal phase, crystallite size, and degree of crystallinity of PVDF as well as the distribution of the minor component, the vinylimidazolium polymer. The polar beta phase of PVDF crystals dominates in as-cast films, while the non-polar alpha phase is observed after cooling from the melt. PVDF imparts mechanical strength and chemical stability to the composite films, and because of its high crystal melting point (Tm > 160 °C), serves to improve the high temperature stability of resulting films.

In order to develop a novel proton conductive membrane for proton exchange membrane fuel cell (PEMFC), a poly(vinyl di-fluoride) (PVDF) matrix was irradiated with swift heavy ions (SHI) to obtain radically active cylindrical latent tracks in the polymer film. Styrene was then radiografted and further sulfonated into these irradiated cylindrical regions, leading to sulfonated polystyrene (PVDF-g-PSSA) domains within PVDF. The role of the grafting degree and fluence of irradiation of the PVDF matrix on PVDF-g-PSSA membranes properties (chemical composition, ion exchange capacity) was investigated. Then, a membrane-electrode assembly (MEA) was prepared and fuel cell tests have been performed. Our results clearly show that PVDF-g-PSSA membranes with a grafting degree of about 140%, obtained after irradiation at a fluence of 1010 ions/cm2, exhibit good conductivity values but their durability is limited to about 70 h. Decreasing the fluence leads to membranes with lower grafting yield but with fuel cell performances closer to those of 140% grafted PVDF-g-PSSA membrane and improved mechanical properties. Then, ion track grafting technique is a promising technique to obtain PEM with a good trade-off between proton conductivity and mechanical properties.

Layered LnBa(Co,Me)2O5+δ (Ln = Nd, Sm, Ho and Y; Me = Fe, Ni, Cu) with double perovskite structure were synthesized by the solid-state reaction and glycerin-nitrate technique and characterized by X-ray diffraction, thermogravimetric analysis, iodometric titration and dilatometry. Homogeneity ranges for the solid solutions were determined. The oxygen content in LnBa(Co,Me)2O5+δ decreases with decreasing rare-earth cation size. Partial substitution of cobalt by iron increases oxygen content while introduction of copper decrease it. The average thermal expansion coefficients were calculated. Chemical compatibility of studied perovskites with Ce0.8Sm0.2O2 and Zr0.85Y0.15O2 solid electrolytes has been studied.

Samples of carbon fiber were prepared from polyacrylonitrile (PAN)-based precursors, covering a range of electrical resistivity from 0.9 to 1,000 mΩ cm corresponding to a range of carbonization heat treatment temperatures (HTT) estimated to be between 700 and 2600°C. Experimental gas diffusion media (GDM) were made from these fibers using conventional phenolic resin/carbon fiber construction, prepared at two different carbonization temperatures (950 and 2150°C). GDM thermal and electrical properties displayed similar trends with respect to fiber and paper HTT. Unexpectedly, GDM bending and shear moduli increased with fiber resistivity, possibly due to shortening of the lower resistivity fiber types during GDM production. Results showed that high HTT of either the carbon fiber or the paper was sufficient to enable average (“wet” and “dry”) 5-cm2 fuel cell performance comparable to current state-of-the-art GDM. A proprietary GDM wet-laid production model predicts a potential cost reduction of about 2% at 20 million m2 annual production by reducing the paper HTT.

Reduction in the operating temperature of solid oxide fuel cells (SOFCs) allows for the use of ferritic stainless steels as the interconnect material. However, cathode poisoning due to volatilization of chromium from the oxide scale formed on these alloys requires the use of a ceramic coating on the alloy. The reaction layer formed between the coating and the alloy affects the performance of the fuel cell, so the composition and properties of this layer must be considered in selecting the alloy and coating compositions. In this paper, the factors relevant to selection of the alloy/coating materials and the effect of the alloy-coating interaction on these factors are discussed.

Thermal stability, hydration and mechanical properties of thermally cross-linked Sulfonated Aromatic Polymers (SAP) with high ionic exchange capacity (IEC) were measured and compared to untreated samples. The formation of cross-linking greatly stabilizes SAP in terms of thermal, mechanical, and hydrolytic degradation: they can resist in water even at a temperature of 145 °C with improved mechanical properties. Acid-base titration and FTIR spectra consistently indicate that SAP microstructure stabilization is related to cross-linking of the polymer chains by SO2 bridges, which is promoted by temperature.

Electronic structure calculations were performed to study the effects local hydration, neighboring side chain connectivity, and protogenic group separation have in facilitating proton dissociation and transfer in fragments of 3M ionomers under conditions of low hydration. Two different types of ionomers, each consisting of a poly(tetrafluoroethylene) (PTFE) backbone, were considered: (1) perfluorosulfonic acid (PFSA) ionomeric fragments containing two pendant side chains (–O(CF2)4SO3H) of distinct separation along the PTFE backbone to model different equivalent weight ionomers and (2) single side chain fragments of three bis(sulfonyl imide)- based fragments with multiple and distinct acid groups per side chain having structural and chemical differences mediating protogenic group separation (side chains: –O(CF2)4SO2(NH)- SO2C6H4SO3H) with the sulfonic acid group located in either the meta or the ortho position on the phenyl ring and –O(CF2)4SO2(NH)SO2(CF2)3SO3H). Fully optimized structures of these fragments with and without the addition of water molecules at the B3LYP/6-311G** level revealed that both side chain connectivity and protogenic group separation, along with local hydration, are key contributors to proton dissociation and the energetics of proton transfer in these materials. Specifically, cooperative interaction between protogenic groups through hydrogen bonding and electron withdrawing –CF2– groups are critical for first proton dissociation and the state of the dissociated proton at low levels of hydration. However, the close proximity of protogenic groups in the ortho bis acid precluded second proton dissociation at low hydration as the relatively fixed protogenic group separation promoted interactions between water molecules, while the labile side chains in the PFSA ionomers allowed for greater freedom in the hydrogen bond network formed. Potential energy profiles for proton transfer were determined at the B3LYP/6-31G** level. The energetic penalty associated with proton transfer was found to be strongly dependent on the surrounding hydrogen bond network and the state of the dissociated proton(s), as well as, the separation between protogenic groups.

The various perovskite ceramic electrolytic membranes, (Ba,Sr)(Zr,Ce,Nb,In,Sn)O3 modified by incorporation of Ln/RE elements, are widely investigated due to their high industrial potential for H2 production and CO2 conversion. One of the most important criteria to classify such ceramic as a good membrane is its high mechanical and chemical stability over thousands hours in severe operating conditions: high temperature and (high water) vapour pressure cycling. It is well known that the Ba- and Sr-based materials can easily form the mixed carbonates, hydroxides, hydrates, hydroxycarbonates, … The presence of undesirable phases, even limited to traces, on the ceramic surface, and/or at the grain boundary, may lead directly to the premature degradation. Since such mixed, hydrated, poorly crystallized phases cannot be detected by diffraction experiments, we have performed thermogravimetric analysis as well as IR and Raman spectroscopic study. The comparison of vibrational and TGA signatures characteristic of complex secondary phases i.e. (Sr/ Ba)(OH)x(CO3)y, nH2O and of proton conducting perovskite reveals that the ignorance of a second phase presence can lead to wrong conclusion concerning the bulk proton nature and understanding of associated conductivity mechanisms.

A multi-component, multiple-relaxation-time (MRT) lattice Boltzmann (LB) model has been employed to study transport processes in the nanostructured cathode catalyst layer of a prototype proton exchange membrane (PEM) fuel cell. The electrode consists of an array of ordered and aligned nanorods that are continuously coated with platinum (Pt). The effect of spacing between the nanorods was studied. Simulation results showed that smaller spacing in nanorods leads to lower utilization of the Pt catalyst due to O2 mass transport limitations. Results from the LB model were found to be in good agreement with the continuum model using the finite element method (FEM) with the same boundary conditions until the systems reached the O2 mass transport limited regions, where the solutions diverged.

Hybrid inorganic-organic proton-conducting membranes are prepared by a standard solvent casting procedure. Nafion® is used as the host polymer and [(ZrO2)·(Ta2O5)0.119] “core-shell” nanoparticles (d ~ 10-50 nm) are incorporated as the nanofiller. This filler is characterized by a “core” of ZrO2 nanoparticles covered by a Ta2O5 “shell”. The mechanical properties of the resulting hybrid membranes determined by dynamic mechanical analysis are better than those of pristine Nafion. The elastic modulus of the hybrid membranes with a filler content greater than 5 wt% is at least 1 MPa up to 200°C, while pristine Nafion undergoes an irreversible elongation at 160°C. The hybrid membranes are characterized by promising conductivities above 115°C (7.5×10-2 S·cm-1 for 9 wt% nanofiller vs. 3.3×10-2 S·cm-1 for pristine Nafion), as determined by broadband electric spectroscopy. The single fuel cell performance at low levels of hydration of the best-performing hybrid membrane (9 wt% nanofiller) is better than that of pristine recast Nafion. The maximum power densities yielded by the MEAs fabricated with pristine Nafion and the hybrid membrane are 0.026 and 0.108 W·cm-2, respectively, at 85°C, aH2O = 0.13, a reagent back pressure = 1 bar and using pure oxygen as the oxidant.