Hydrogen alkaline fuel cell

The air-hydrogen alkaline fuel cell of Kordesch s Austin produced a tepid 6 kilowatts in conjunction with a bank of ordinary 12-volt lead-acid batteries (for acceleration and hill climbing). The fuel cell s electrodes, donated by Union Carbide, had been used earlier in another ground-breaking fuel cell vehicle, General Motors Electrovan, a six-passenger van that had been converted with Kordesch s help in 1967. 

A fuel cell is a voltaic cell in which a fuel, usually hydrogen, is oxidized at the anode. At the cathode, oxygen is reduced. The reaction taking place in the alkaline fuel cells used in the space program since the 1960s is... 

Bidault, F., Brett, D.J.L., Middleton, P.H., Abson, N. and Brandon, N.P. (2010) Animproved cathode for alkaline fuel cells. International Journal of Hydrogen Energy, 35, 1783-1788. 

The space shuttle uses a fuel cell as a source of energy. This cell depends on the oxidation of hydrogen by oxygen to form water. The fuel cell operates under basic conditions, so it is sometimes referred to as an alkaline fuel cell. Figure 11.31, on the next page, shows the design of the cell. The half-reactions and the overall reaction are as follows. 

Alkaline Fuel Cell (AFC) The electrolyte in this fuel cell is concentrated (85 wt%) KOH in fuel cells operated at high temperature ( 250°C), or less concentrated (35-50 wt%) KOH for lower temperature (<120°C) operation. The electrolyte is retained in a matrix (usually asbestos), and a wide range of electrocatalysts can be used (e.g., Ni, Ag, metal oxides, spinels, and noble metals). The fuel supply is limited to non-reactive constituents except for hydrogen. CO is a poison, and CO2 will react with the KOH to form K2CO3, thus altering the electrolyte. Even the small amount of CO2 in air must be considered with the alkaline cell. 

In the early 1970s, K. Kordesch modified a 1961 Austin A-40 two-door, four-passenger sedan to an air-hydrogen fuel cell attery hybrid car (23). This vehicle used a 6-kW alkaline fuel cell in conjunction with lead acid batteries, and operated on hydrogen carried in compressed gas cylinders mounted on the roof The car was operated on public roads for three years and about 21,000 km. 

The Alkaline Fuel Cell (AFC) was one of the first modern fuel cells to be developed, beginning in 1960. The application at that time was to provide on-board electric power for the Apollo space vehicle. Desirable attributes of the AFC include its excellent performance on hydrogen (H2) and oxygen (O2) compared to other candidate fuel cells due to its active O2 electrode kinetics and its flexibility to use a wide range of electrocatalysts, an attribute which provides development flexibility. 

Fuel cells operate in a manner reverse to that of electrolysis, discussed in Chapter 2, combining fuel to make electricity. The basic design consists of two electrodes separated by an electrolyte. The oldest type of fuel cell is the alkaline fuel cell where an alkaline electrolyte like potassium hydroxide is used. The hydrogen enters through the anode compartment and oxygen through the cathode compartment. The hydrogen is ionized by the catalytic activity of the anode material and electrons are released into the external circuit. The protons react with the hydroxyl ions in the electrolyte to form water. The reaction can be written as ... 

Austria is one of Europe s early pioneers of fuel cell development. As early as the 1970s, Professor K. Kordesch of the University of Graz constructed a vehicle equipped with an alkaline fuel cell supplied with pressurised hydrogen. Austrian MFC work has primarily been "horizontal" across a number of broad R D activities. 

In alkaline fuel cells (AFCs), the electrolyte is 34-46% KOH, immobilized on a porous support, and the operating temperature is 60-120 °C. Because the environment is alkaline, Raney nickel (a finely divided form of nickel) can be used in place of expensive platinum. However, the alkali will be neutralized by any CO2 in the hydrogen fuel, so AFCs are not suitable for operation with reformed hydrocarbons but can be fueled with alcohols or hydrazine. AFCs were used successfully on the Apollo space missions. 

Justi et al. (75) had already introduced Raney-nickel anodes for anodic hydrogen oxidation in alkaline fuel cells in the early sixties. At that time they used sintered electrodes composed of Raney-nickel particles, which are, however, too heavy and too expensive to be of use for commercial cells as too high loadings of the relatively expensive nickel are needed. Today... 

As the synergistic hydrogen production process using natural gas and nuclear heat is efficient and economic, and also the subsequent electro-chemical conversion of hydrogen into electricity in an alkaline fuel cell is efficient, electricity generation by combining these two processes have the following possibilities ... 

Hori, M. (2007a), Electricity Generation in Fuel Cell Using Nuclear-fossil Synergistic Hydrogen -Evaluation of a System with Sodium Reactor Heated Natural Gas Membrane Reformer and Alkaline Fuel Cell , 2007 Fall Meeting of Atomic Energy Society of Japan, Japan, September (in Japanese). 

One of the first fuel cell designs was low-temperature alkaline fuel cells (AFCs) used in the U.S. space program. They served to produce both water and electricity on the spacecraft. Some of their disadvantages are that they are subject to carbon monoxide poisoning, are expensive, and have short operating lives. The AFC electrodes are made of porous carbon plates laced with a catalyst. The electrolyte is potassium hydroxide. At the cathode, oxygen forms hydroxide ions, which are recycled back to the anode. At the anode, hydrogen gas combines with the hydroxide ions to produce water vapor and electrons that are forced out of the anode to produce electric current. 

It was not until 1959 that the first working hydrogen-oxygen fuel cell was developed. Modern cells employ an alkaline electrolyte, so the electrode reactions differ from the one shown above by the addition of OH- to both sides of the equations (note that the net reaction is the same) ... 

Historically, and in space, alkaline fuel cells are run on pure H2 and 02. There is as yet no massive terrestrial source of hydrogen (e.g., from photovoltaics and the... 

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