Direct hydrazine fuel cells

For a direct hydrazine fuel cell, anion conductive aromatic multi-block copolymers, PAES with quaternized ammonio-substituted fluorene groups have been described [118]. The ammonio groups can be selectively introduced onto the fluorene-containing units. 

Another notable electrocatalytic reaction where surface oxides take part is the electrooxidation of hydrazine (N2H4). The use of hydrazine as a fuel in the direct hydrazine fuel cell has attracted research interest because the hydrazine/02 fuel cell exhibits a high open circuit potential of 1.61 V (as opposed to 1.23 V in H2/O2 fuel cell) and its theoretical energy-conversion efficiency (AG/AH) is 100 % (as opposed to 83 % in H2/O2 fuel cell) [85]. The electrooxidation of hydrazine occurs via a 4-electron oxidatirm process yielding molecular N2 [86] ... 

Asazawa K, Yamada K, Tanaka H, Oka A, Taniguchi M, Kobayashi T (2007) A platinum-free zero-carbon-emission easy fuelling direct hydrazine fuel cell for vehicles. Angew Chem Int Ed Engl 46 8024-8027... 

Serov A, Kwak C (2010) Direct hydrazine fuel cells a review. Appl Catal B Environ 98 1-9. doi 10.1016/j.apcatb.2010.05.005... 

Yamada, K., Asazawa, K., Yasuda, K., loroi, T., Tanaka, H., Miyazaki, Y., Kobayashi, T. (2003) Investigation of PEM type direct hydrazine fuel cell. Journal of Power Sources, 115, 236-242. 

Fuel cells using directly liquid fuels are advantageous in this aspect. Methanol, formaldehyde (water solution), formic acid (water solution) and hydrazine are among fuels relatively easy to oxidize electrochemically. Alcohol and hydrocarbon with larger molecular weight are much harder to oxidize completely to C02- Other qualifications to be considered are price, availability, safety, energy density and ease of handling. 

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. 

Fuel cells are electrochemical devices in which fuels (e.g., hydrogen, carbon monoxide, hydrocarbons, and alkali metals), oxidants, and reaction products move into and out of a system of electrodes separated by an electrolyte. The reduction-oxidation reactions that take place generate a direct current while the materials are supplied to the cell. A number of transportation and other applications for this technology are being explored, partly because of the environmental benefits the reaction products have over those of fossil fuels. M86 fuel, a mixture of anhydrous and methyl hydrazines, is used in fuel cells including those used to generate electricity for some aircraft hydraulics systems. These fuel tanks are leak-tight, double-walled aluminium pressure vessels that contain up to 42 litres of M86. 

Fabio H. B. Lima was bom in Brazil in 1978. He graduated in Chemistry at University of Sao Paulo, Sao Carlos, in 2001. He obtained his Ph.D. in Physical Chemistry in the same institution, in 2006, with a stage at the Brookhaven National Laboratory. He spent 12 months as a postdoctoral fellow at the Chemistry Institute of Sao Carlos (IQSC) between 2006 and 2008. He is currently interested in synthesis and electrocatalysis for reactions involved in electrochemical energy conversion devices such as regenerative fuel cells (H2/O2 and HCOOH/CO2), rechargeable metal-air batteries, direct hydrazine, borohydride and ethanol fuel cells. Publication of scientific research includes 36 articles in journals, 3 chapters in books and more than 50 scientific summaries in collective books and proceedings. 

However, hydrazine is extremely toxic and dangerously unstable. Due to these serious problems, it is not recommended that hydrazine be used as an H2 source or directly oxidized at the fuel cell anode for the general public to use. 

Zhang F, Zhang H, Ren J, Qu C (2010) PTFE based composite anion exchange membranes thermally induced in situ polymerization and direct hydrazine hydrate fuel cell application. J Mater Chem 20 8139-8146. doi 10.1039/c0jm0131 Ik... 

Union Carbide Corp. (UCC) developed AFCs for terrestrial mobile applications starting in the late 1950s, lasting until the early 1970s. UCC systems used liquid caustic electrolytes the electrodes were either pitch-bonded carbon plates or plastic-bonded carbon electrodes with a nickel current collector. UCC also built fuel cell systems for the U.S. Army and the U.S. Navy, an alkaline direct hydrazine powered motorcycle, and the Electrovan of General Motors. Finally, Professor Karl V. Kordesch built his Austin A-40 car, fitted with UCC fuel cells with lead acid batteries as hybrid. It was demonstrated on public roads for three years. The years of research and development are very well summarized in reference (5) Brennstofflyatterien. 

Direct systems where fuels, such as hydrogen, methanol and hydrazine, can react directly in the fuel cell... 

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