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Since the advent of the wheel, man's interest in energy conservation has stoked the imaginations of leading scientists and inspired inventions both practical and bizarre. The Industrial Revolution in the nineteenth century and the popularity of the automobile, the television and the home computer demonstrated a proclivity for convenience and a penchant for the creature comforts afforded by technology. These advances have necessitated the need to identify affordable energy sources capable of powering our ever increasing technology dependent lives, without relying on fossil fuels and other non-renewable resources. Over the last half-century, the most promising alternative power source has been the fuel cell.

A breakthrough in rechargeable fuel cells, the metal-air cell derives its energy from a solid state fuel, which provides a relatively inexhaustible power source. The density of the metal fuel source combined with its electrochemical properties and availability make this variety of fuel cell inexpensive, environmentally friendly and highly versatile. The simple structure of the metal-air cell can be adapted to almost any size for use in almost any application. A significant advantage of the aluminum air cell is that it can be mechanically recharged in seconds and the cathode reaction uses oxygen, a readily available cost-free gas from the atmosphere

As a renewable and sustainable source of energy, aluminum-air based fuel cells offer tremendous advantages in many applications. The aluminum-air fuel cell's high-energy output results from the characteristic energy density of aluminum and the fact that three electrons are released for every atom of aluminum reacted (1 mole electrons released per 9 g aluminum compared to 1 mole electrons released per 32.7 g Zn used). Recent developments in aluminum-air chemistry are expected to enable widespread application of aluminum-air fuel cells in a number of applications with power requirements from 1 watt to 250 kilo-watts and higher.
Development efforts of aluminum-air cells have faced significant chemistry challenges: activation of the aluminum anode, controlling the aluminum oxidation reaction, preventing fouling of the reaction anode surface, providing a cathode which is active enough to keep pace with the aluminum anode and controlling hydrogen generated through the corrosion side-reaction (a common problem in this industry). Through careful construction of the anode, cathode and electrolyte solution, Aluminum-Power has solved these problems and, in its cell designs for portable electronic devices, is achieving energy densities of 800 Wh/kg with nominal current densities of 70 mA/cm2, maximum current densities of 150 mA/cm2, and peak current densities of 250 mA/cm2 at standard operating conditions.

Unlike other carriers of energy such as gasoline, natural gas or hydrogen, aluminum has tremendous advantages including high energy density, light-weight, stability in a wide range of temperatures. In addition, aluminum is not volatile, not explosive and requires no special transport or storage containers. Perhaps most importantly, the aluminum-air fuel cell has no emissions. The overall reaction by-product, principally aluminum-hydroxide, is environmentally benign and recyclable. Given the high efficiency of the aluminum-air system, recycling makes both economic and environmental sense.

Deconstruction of the Alumium Air Fuell Cell

Power is generated through an electrochemical reaction between the Aluminum, once placed in an alkaline solution, and oxygen from the air. As the Aluminum oxidizes in the Alkaline solution, electricity is produced.

Anode Reaction
The anode dissociation of aluminum occurs at the negative electrode according to the equations :

Al + 4OH- => AlO2- + 2H2O + 3e- and/or Al + 4OH- => Al (OH)4- + 3e-

Cathode Reaction
The cathode reduction of the oxygen occurs at the positive electrode (gas diffusion cathode) according to the equation: O2 + 2H2O + 4e- <=> 4OH-

Complete Reaction
The final reaction can be represented as a summation of the equations for the current formation process:

4Al + 3O2 + 6H2O => 4Al(OH)3, and for the corrosion reaction: 2Al + 6H2O => 2Al(OH)3 + 3H2

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