Direct ammonia fuel cell

Bridging the temperature gap with proton-conducting ceramics Direct ammonia fuel cells... 

Ganley J (2006), Intermediate temperature direct ammonia fuel cell , presentation at Ammonia Fuel III, Denver, CO. 

Suzuki S, Muroyama H, Matsui T, Eguchi K (2012) Fundamental studies on direct ammonia fuel cell employing anion exchange membrane. 

DIRECT AMMONIA FUEL CELL WITH AN ANION-EXCHANGE MEMBRANE... 

As membrane material for their direct ammonia-oxygen fuel cells, Lan and Tao used a blend of the anion-exchange resin Amberlite IRA 400 (hydroxide form) and poly(vinyl alcohol). As cathode material, Mn02 deposited on carbon materials was used. In different cell versions the anodes were prepared from Pt-Ru-C and from chrom-decorated nanosized nickel (size about 6 nm). Experiments with such cells at room temperature showed maximal power densities in the range 12 to 16 mW/cm. In some cases the power densities for ammonia-fed cells were higher than those for hydrogen-fed cells. The authors note that the development of direct ammonia fuel cells with alkaline membranes and inexpensive catalysts is still at an early stage. 

Therefore, when ammonia is introduced into such a cell, it is completely converted to nitrogen and hydrogen at the nickel-containing anode, the hydrogen then undergoing electrochemical oxidation. This direct ammonia fuel cell is actually a direct internal ammonia-reforming fuel ceU. 

Vidal-lglesias, F.J., Solla-Gullon, J., Montiel, V., Feliu, J.M. and Aldaz, A. (2007) Screening of electrocatalysts for direct ammonia fuel cell ammonia oxidation on PtMe (Me Ir. Rh, Pd. Ru) and preferentially oriented Pt(lOO)... 

The hydrogen economy can rather be attained by a so-called ammonia economy , where ammonia (NH3) is used as a hydrogen carrier for its easier delivery and storage characteristics. Especially, if such developments currently underway on production and application of NH3 as the electrochemical synthesis of NH3 from nitrogen and water and the direct NH3 fuel cells have made progress, the ammonia economy becomes feasible. 

As a constituent of synthesis gas, hydrogen is a precursor for ammonia, methanol, Oxo alcohols, and hydrocarbons from Fischer Tropsch processes. The direct use of hydrogen as a clean fuel for automobiles and buses is currently being evaluated compared to fuel cell vehicles that use hydrocarbon fuels which are converted through on-board reformers to a hydrogen-rich gas. Direct use of H2 provides greater efficiency and environmental benefits. ... 

Most fuel cells being developed consume either hydrogen or fuels that have been preprocessed into a suitable hydrogen-rich form. Some fuel cells can directly consume sufficiently reactive fuels such as methane, methanol, carbon monoxide, or ammonia, or can process such fuels internally. Different types of fuel cells are most appropriately characterized by the electrolyte that they use to transport the electric charge and by the temperature at which they operate. This classification is presented in Table 7.4. 

Apart from hydrocarbons and gasoline, other possible fuels include hydrazine, ammonia, and methanol, to mention just a few. Fuel cells powered by direct conversion of liquid methanol have promise as a possible alternative to batteries for portable electronic devices (cf. below). These considerations already indicate that fuel cells are not stand-alone devices, but need many supporting accessories, which consume current produced by the cell and thus lower the overall electrical efficiencies. The schematic of the major components of a so-called fuel cell system is shown in Figure 22. Fuel cell systems require sophisticated control systems to provide accurate metering of the fuel and air and to exhaust the reaction products. Important operational factors include stoichiometry of the reactants, pressure balance across the separator membrane, and freedom from impurities that shorten life (i.e., poison the catalysts). Depending on the application, a power-conditioning unit may be added to convert the direct current from the fuel cell into alternating current. 

C. G. Vayenas and R. D. Farr, Science 208, 593 (1980), describe a solid electrolyte fuel cell in which ammonia is the fuel and is catalyt-ically converted at 1000 K with oxygen (or air) to nitric oxide. The idea is that the energy released in this step in industrial nitric acid production (Section 9.4) could be recovered directly as electricity. 

This section discusses the production of methanol and ammonia from wood. Methanol is a clean-burning material that may find widespread future use as an automotive fuel (directly or for conversion to gasoline by the Mobil process) as a fuel for industrial or utility boilers, gas turbines, or fuel cells as a chemical intermediate or as a biological feedstock for protein. 

Direct ammonia feed to a SOEC has been demonstrated several times (Wojcik et al., 2003 Fournier et al., 2006 Ma et al., 2006). Whether hydrogen atoms are fed as H2 or as an equivalent amount of NH3 there is little or no difference in the fuel cell output (Wojcik et al., 2003). The SOFC actually benefits from... 

Fournier G G M, Gumming 1W, HeUgardt K (2006), High performance direct ammonia solid oxide fuel cell , J. Power Sources, 162(1), 198-206. 

Ma Q, Peng R, Tian L, Meng G (2006) Direct utilization of ammonia in intermediate-temperature sohd oxide fuel cells , Electrochem. Commun., 8, 1791-1795. 

The endothermic reaction is favored by high temperature and low pressure and is accelerated by the presence of nickel or iron catalysts. NH3 can be burned directly in combustion engines or used in solid oxide fuel cells without preprocessing [238]. In alkaline and PEM fuel cells, the ammonia has first to be decomposed according to the above reaction. For the PEM cell, even trace amounts of ammonia left in the gas after decomposition must be removed [239]. 

The Mg(NH3)6Cl2 complex shows a considerably high hydrogen content of 9.1mass% - in the form of ammonia. The desorbed ammonia could be used directly as a fuel for a solid oxide fuel cell without further reaction. With alkaline or low temperature (PEM) fuel cells, the ammonia must be decomposed (see above). 

Lan R, Tao S (2010) Direct ammonia alkaline anion-exchange membrane fuel cells. Electrochem Solid State Lett 13(8) B83-B86. doi 10.1149/L3428469... 

The studies show that direct electrochemical oxidation of urea (or ammonia) could be used to recover energy from urine. However, the energy recovery from one person s urine is rather low (less than 1 W p for a urea fuel cell, [3]). This process might only be economically interesting at places with high urine production [3]. 

With a properly designed fuel processing system, SOFC can use many available fuel types. Operating at temperatures above 600°C, SOFC can reform methane (the main component of natural gas) directly on the cell anode or operate on CO-containing gas or even on ammonia. 

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