YSZ传导膜H_2S固体氧化物燃料电池

研究了Y2O3稳定的ZrO2(YSZ)氧离子传导膜H2S固体氧化物燃料电池性能。掺杂NiS、电解质、Ag粉和淀粉制备了双金属复合MoS2阳极催化剂,掺杂电解质、Ag粉和淀粉制备了复合NiO阴极催化剂,用扫描电镜对YSZ和膜电极组装(MEA)进行了表征,比较了不同电极催化剂的性能和极化过程,考察了不同温度对电池性能的影响。结果表明,双金属复合MoS2/NiS阳极催化剂在H2S环境下比Pt和单金属MoS2催化剂稳定,复合NiO阴极催化剂比Pt性能好,在电极催化剂中加入Ag可显著提高电极的导电性;与Pt电极相比,复合MoS2阳极和复合NiO阴极催化剂的过电位较小,阳极的极化比阴极侧小;温度升高,电池的电流密度与功率密度增加,电化学性能变好。在750℃、800℃、850℃和900℃及101.13 kPa时,结构为H2S、(复合MoS2阳极催化剂)/YSZ氧离子传导膜/(复合NiO阴极催化剂)、空气的燃料电池最大功率密度分别为30 mW/cm2、70 mW/cm2、155 mW/cm2及295 mW/cm2、最大电流密度分别为120 mA/cm2、240 mA/cm2、560 mA/cm2和890 mA/cm2。     

Insights into the distribution of water in a self-humidifying H2/O2 proton-exchange membrane fuel cell using 1H NMR microscopy

Proton ((1)H) NMR microscopy is used to investigate in-situ the distribution of water throughout a self-humidifying proton-exchange membrane fuel cell, PEMFC, operating at ambient temperature and pressure on dry H(2)(g) and O(2)(g). The results provide the first experimental images of the in-plane distribution of water within the PEM of a membrane electrode assembly in an operating fuel cell. The effect of gas flow configuration on the distribution of water in the PEM and cathode flow field is investigated, revealing that the counter-flow configurations yield a more uniform distribution of water throughout the PEM. The maximum power output from the PEMFC, while operating under conditions of constant external load, occurs when H(2)O(l) is first visible in the (1)H NMR image of the cathode flow field, and subsequently declines as this H(2)O(l) continues to accumulate. The (1)H NMR microscopy experiments are in qualitative agreement with predictions from several theoretical modeling studies (e.g., Pasaogullari, U.; Wang, C. Y. J. Electrochem. Soc. 2005, 152, A380-A390), suggesting that combined theoretical and experimental approaches will constitute a powerful tool for PEMFC design, diagnosis, and optimization.     

Hydrogen isotope separation with an alkaline membrane fuel cell

The separation of deuterium from a hydrogen–deuterium mixture was carried out using an alkaline membrane fuel cell (AMFC) with a Pt catalyst. This novel use of an AMFC to separate deuterium from a mixture of H₂ and D₂ was demonstrated by the production of deuterium-enriched water during power generation by the AMFC. The deuterium separation factor increased with output current (i) to a maximum value of 1.64 attained at i = 30 mA cm^− 2.     

Steady-state dc and impedance investigations of H2/O2 alkaline membrane fuel cells with commercial Pt/C, Ag/C, and Au/C cathodes

The performances of H(2)/O(2) metal-cation-free alkaline anion-exchange membrane (AAEM) fuel cells operated with commercially available Au/C and Ag/C cathodes are reported for the first time. Of major significance, the power density obtained with 4 mg cm(-2) Ag/C (60% mass) cathodes was comparable to that obtained with 0.5 mg cm(-2) Pt/C (20% mass) electrodes, whereas the performance when using the same Ag/C cathode in a Nafion-based acidic membrane electrode assembly (MEA) was poor. These initial studies demonstrate that the oxygen reduction electrokinetics are improved when operating Pt/C cathodes at high pH in AAEM-based fuel cells as compared with operation at low pH (in Nafion-based proton-exchange membrane fuel cells). The results of in situ alternating current impedance spectroscopy were core to the assignment of the source of the limited performances of the AAEM-based fuel cells as being the limited supply of water molecules to the cathode reaction sites. Minimizing the thickness of the AAEM improved the performances by facilitating back-transport of water molecules from the anode (where they are generated) to the cathode. The urgent need for development of electrode architectures that are specifically designed for use in AAEM-based fuel cells is highlighted.     

A H2/O2 enzymatic fuel cell as a sustainable power for a wireless device

We report the first example of an H₂/O₂ enzymatic fuel cell able to power a wireless transmission system. Oxygen-tolerant hydrogenase from Aquifex aeolicus and bilirubin oxidase from Myrothecium verrucaria were incorporated from diluted solutions in carbon felt-based material, allowing mediatorless catalytic currents more than 1 mA to be reached. The enzymatic fuel cell open circuit voltage was 1.12 V, and short circuit current was 767 μA. It delivered a maximum power of 410 μW, sufficient to power the electronic device that measured in real time the anodic/cathodic compartments and room temperatures, the voltage of the capacitor and voltage output of the enzymatic fuel cell itself. Notably, data were sent every 25 s during 7 hours of continuous operation which constitute the highest performances ever reported for a realistic environmental application fully powered with an enzymatic fuel cell.     

High performance miniature glucose/O2 fuel cell based on porous silicon anion exchange membrane

Mesoporous silicon membranes are functionalized with ammonium groups and evaluated as high efficient anion exchange membrane in a miniaturized alkaline glucose fuel cell setup. N-Trimethoxysilylpropyl-N,N,N-trimethylammonium chloride is grafted onto the pore walls of porous silicon resulting in the anionic conductivity enhancement. The functionalization process is followed by FTIR spectroscopy where the optimized parameter could be determined. The ionic conductivity is measured using impedance spectroscopy and gives 5.6 mS cm^− 1. These modified mesoporous silicon membranes are integrated in a specially designed miniature alkaline (pH 13) glucose/air fuel cell prototype using a conventional platinum-carbon anode and a cobalt phthalocyanine-carbon nanotube cathode. The enhanced anion conductivity of these membranes leads to peak power densities of 7 ± 0.12 mW cm^− 2 at “air breathing” conditions at room temperature.     

Electrocatalysts and membrane for direct ethanol-oxygen fuel cell with alkaline electrolyte

Results of studies of anodic (RuNi/C) and cathodic (PtCo/C; CoN₄/C) catalysts, polybenzimidazole membrane, and membrane-electrode assemblies on their basis for alkaline ethanol-oxygen fuel cell are presented. It is shown that the anodic catalyst RuNi/C optimized in its composition (Ru: Ni = 68: 32 in atomic percent) and the metal mass on carbonaceous support (15–20%) is sufficiently effective with respect to ethanol oxidation; it is well superior to commercial Pt/C- and RuPt/C-catalysts when calculated per unit mass of the precious metal. The effect of electrolyte composition, electrode potential, and temperature on the CO₂ yield is studied by chromatographic analysis of the ethanol oxidation products. It is shown that the highest CO₂ yield (the process involves the C-C bond break) is achieved at low electrolysis overvoltage and elevated temperature. The mean number of electrons given up by C₂H₅OH molecule approaches 10 at temperatures over 60°C. The studied cathodic catalysts form the following series of their specific activity in the oxygen reduction reaction: (20 wt % Pt) E-TEK ≥ (7.3 wt % Pt) PtCo/C > CoN₄/C; however, in the presence of alcohol the activity series is reversed. On this reason fuel cell cathodes were prepared by using synthesized CoN₄/C-catalyst. For the alkali-doped polybenzimidazole membrane the conductivity and ethanol crossover were determined. A membrane-electrode assembly for platinum-free alkaline ethanol-oxygen fuel cell is designed. It comprised anodic (RuNi/C) and cathodic (CoN₄/C) catalysts and polybenzimidazole membrane. The period of service of the fuel cell exceeded 100 h at a voltage of 0.5 V and current of 100 mA/cm².     

Direct ethanol oxidation fuel cell with anionite membrane and alkaline electrolyte

A number of cathode catalysts were synthesized from nitrogen-containing organic complexes on XC-72R carbon black for an alkaline electrolyte. The catalysts were studied by the rotating disc electrode (RDE) technique. The polyacrilonitrile (PAN), phthalocyanine (Pc), and cobalt tetra(methoxyphenyl)porphyrin (CoTMPP) systems showed the highest activity. The slope of the oxygen polarization curves in the first region in 1 M KOH was 35–40 mV; this corresponds to concentration polarization in an alkaline solution in the O₂-HO₂⁻ system. A cyclic voltammetry study demonstrated that the catalytic systems with the highest corrosion stability were Pc + Co + Fe/XC-72R and CoTMPP/XC-72R pyropolymer. The activity of the catalysts decreased by 20–25% compared with the initial current densities on average. An ethanol-oxygen fuel cell with a Fumasep FAA anionite membrane and nonplatinum catalysts was tested. The maximum power density was 32 mW/cm² at 40°C. The stability test of the fuel cell showed that the materials used for the membrane-electrode assembly allowed more than 100 h of continuous operation with constant working characteristics.     

Performance of H2/O2 fuel cell using membrane electrolyte of phosphotungstic acid-modified 3-glycidoxypropyl-trimethoxysilanes

Proton-conducting membranes based on phosphotungstic acid (PWA) and 3-glycidoxypropyl-trimethoxysilane (GPTMS) was investigated as the electrolyte for low temperature H₂/O₂ fuel cell. Parameters determining the conductivity and elastic modulus of the membranes were characterized by thermogravimetry/differential thermal analysis and infrared spectroscopic measurements. The composite containing 5% of PWA exhibited an elastic modulus below 100 MPa at room temperature and a high proton conductivity of 1.0 × 10⁻² S/cm at 80 °C and 100% RH. Low elastic modulus of the membrane was found to be useful for both the reduction of the membrane thickness and the better contact with the electrodes. The performance of the membrane electrode assemblies (MEA) was systematically studied as an effect of preparation conditions. A maximum power density of 45 mW/cm² and the current density of 175 mA/cm² at 0.2 V were achieved at 90 °C and 100% RH for the membrane of 5PWA·95GPTMS composition and 0.2 mm thickness.     

In situ observations of water production and distribution in an operating H2/O2 PEM fuel cell assembly using 1H NMR microscopy

Proton NMR imaging was used to investigate in situ the distribution of water in a polymer electrolyte membrane fuel cell operating on H2 and O2. In a single experiment, water was monitored in the gas flow channels, the membrane electrode assembly, and in the membrane surrounding the catalysts. Radial gradient diffusion removes water from the catalysts into the surrounding membrane. This research demonstrates the strength of 1H NMR microscopy as an aid for designing fuel cells to optimize water management.     

Decomposition pathways of an alkaline fuel cell membrane material component via evolved gas analysis

Petroleum samples were analyzed by TG between 25–600°C. Mass loss was observed up to 500°C. The volatile fraction of petroleum samples in the range of 25–150°C were recovered by bubbling the outgoing gaseous products of the TG experiments in dichloromethane. Each volatile fraction obtained was analyzed by HRGC-MS for identification and quantification of the major components. Following this procedure the classification of the petroleum samples were done according to the obtained mass losses between 25–150°C (which varied from 1.76 to 21.89%) and according to their normal paraffin, aromatic and naphthene contents.     

Optical constants of HNO3/H2O and H2SO4/HNO3/H2O at low temperatures in the infrared region

The complex index of refraction of liquid HNO3/H2O and H2SO4/HNO3/H2O has been obtained at different temperatures and acid concentrations. FT-IR specular reflectance spectra were obtained for 30, 54, and 64 wt % aqueous HNO3 and for four different H2SO4/HNO3/H2O mixtures in the temperature region from 293 to 183 K. The complex index of refraction was obtained from the reflectance spectra with the Kramers-Kronig transformation. The optical constants of the binary and ternary mixtures vary with the acid concentration and the temperature. The results demonstrate that vibrational bands originating from the sulfate species are more sensitive to changes in temperature than the bands originating from vibrations in the nitrate species; only minor changes in the nitrate vibrational bands are observed as the temperature decreases below 248 K.     

Synthetic architectures of TiO2/H2Ti5O11.H2O, ZnO/H2Ti5O11.H2O, ZnO/TiO2/H2Ti5O11.H2O, and ZnO/TiO2 nanocomposites

Although synthetic investigations of inorganic nanomaterials had been carried out extensively over the past decade, few of them have been devoted to fabrication of complex nanostructures that comprise multicomponents/phases (i.e., composite nanobuilding blocks), especially in the area of structural/morphological architecture. In this work, nanobelts of a protonated pentatitanate (H(2)Ti(5)O(11).H(2)O) were synthesized hydrothermally for the first time. Two technologically important transition-metal-oxides TiO(2) and ZnO were then grown respectively or sequentially onto the surface of the as-prepared nanobelts in aqueous mediums. With a main emphasis on organizational manipulation, the present investigation examines general issues of morphological complexity, synthetic interconvertibility, and material combinability related to fabrication of inorganic nanocomposites. Using this model material system, we demonstrate that complex binary and tertiary composite building blocks of TiO(2)/H(2)Ti(5)O(11).H(2)O, ZnO/H(2)Ti(5)O(11).H(2)O, ZnO/TiO(2)/H(2)Ti(5)O(11).H(2)O, and ZnO/TiO(2) can be architected stepwise in solution. Structural features of these nanocomposites have also been addressed.     

A dual electrolyte H2/O2 planar membraneless microchannel fuel cell system with open circuit potentials in excess of 1.4 V

A dual electrolyte H2/O2 fuel cell system employing a planar microfluidic membraneless fuel cell has been investigated and compared to single electrolyte H2/O2 systems under analogous conditions. The fuel is H2 dissolved in 0.1 M KOH (pH 13), and the oxidant is O2 dissolved in 0.1 M H2SO4 (pH 0.9), comprising a system with a calculated thermodynamic potential of 1.943 V (when 1 M H2 and O2 concentrations are assumed). This value is well above the calculated thermodynamic maximum of 1.229 V for an acid, or alkaline, single electrolyte H2/O2 fuel cell. Experimentally, open-circuit potentials in excess of 1.4 V have been achieved with the dual electrolyte system. This is a 500 mV increase in the open circuit potentials observed for single electrolyte H2/O2 systems also studied. The dual electrolyte fuel cell system shows power generation of 0.6 mW/cm2 from a single device, which is nearly 0.25 mW/cm2)greater than the values obtained for single electrolyte H2/O2 fuel cell systems studied. Microchannels of varying dimensions have been employed to study both the single and dual electrolyte H2/O2 systems. Channel thickness variation and the flow rate dependences of power generation are also addressed.     

Determination of long-range intermolecular interaction energies using RPA/moment function methods. Application to H2O,H2O2 and H2O/H2O2 mixtures

The fully expanded expression for the Boltzmann-averaged pairwise intermolecular interaction energy of two molecules of arbitrary symmetry in the long-range (interaction < kT) limit has recently been determined explicitly as a series in r⁻ⁿ (r is the intermolecular separation) for n < 11. The resultant expression contains only multipolar products (point moment functions: PMFs) and energy terms which are characteristic of the ground state and excitation properties of the isolated molecules. These quantities are determined for H₂O and H₂O₂ using the single particle-hole RPA method, and the interaction energy contributions determined by direct state summation. Static electric dipole polarizabilities are determined as a by-product of the procedure, and are shown to agree closely with finite field results using a comparable basis. For the chiral H₂O₂/H₂O₂ system, the r⁻⁶ and r⁻⁹ discrimination energies are also calculated, suggesting that the r⁻⁹ contributions could well exceed the r⁻⁶ discriminatory terms for separations less than 20 au.     

Flow reactor studies and kinetic modeling of the H2/O2/NOX and CO/H2O/O2/NOX reactions

Flow reactor experiments were performed over wide ranges of pressure (0.5–14.0 atm) and temperature (750–1100 K) to study H₂/O₂ and CO/H₂O/O₂ kinetics in the presence of trace quantities of NO and NO₂. The promoting and inhibiting effects of NO reported previously at near atmospheric pressures extend throughout the range of pressures explored in the present study. At conditions where the recombination reaction H + O₂ (+M) = HO₂ (+M) is favored over the competing branching reaction, low concentrations of NO promote H₂ and CO oxidation by converting HO₂ to OH. In high concentrations, NO can also inhibit oxidative processes by catalyzing the recombination of radicals. The experimental data show that the overall effects of NO addition on fuel consumption and conversion of NO to NO₂ depend strongly on pressure and stoichiometry. The addition of NO₂ was also found to promote H₂ and CO oxidation but only at conditions where the reacting mixture first promoted the conversion of NO₂ to NO. Experimentally measured profiles of H₂, CO, CO₂, NO, NO₂, O₂, H₂O, and temperature were used to constrain the development of a detailed kinetic mechanism consistent with the previously studied H₂/O₂, CO/H₂O/O₂, H₂/NO₂, and CO/H₂O/N₂O systems. Model predictions generated using the reaction mechanism presented here are in good agreement with the experimental data over the entire range of conditions explored. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 705–724, 1999     

A feasibility analysis for alkaline membrane direct methanol fuel cell: thermodynamic disadvantages versus kinetic advantages

As the proton exchange membrane direct methanol fuel cell (PEMDMFC) faces sustaining obstacles, alkaline membrane direct methanol fuel cell (AMDMFC) is attracting increasing attention. Although some advantages may be expected, the feasibility of AMDMFC does not seem well verified. In this paper, thermodynamic disadvantages and kinetic advantages of AMDMFC are elucidated. In thermodynamic aspect, a large voltage loss due to the pH difference across the membrane is predicted by theoretical calculation; in kinetic aspect, besides the well-known superiority of alkaline media for oxygen reduction, experimental data show much higher anodic performance in carbonate/bicarbonate than in acid. In-situ FTIR measurements indicate that methanol can be fully oxidized to carbon dioxide in carbonate/bicarbonate as in sulfuric acid. Taking into account all the foreseeable advantageous and disadvantageous factors, AMDMFC is worth study, and an alkaline membrane stable at elevated temperatures is the prerequisite for a successful AMDMFC.