Aluminum Oxygen Galvanic Cell

Aluminum Oxygen Galvanic Cell

Description

The spontaneous chemical reaction between aluminum metal and dioxygen is conducted so as to obtain the available chemical energy released in the form of electrical energy. This is a particularly interesting example of the importance of materials science.

Set

When connected to an electric load, aluminum reacts with oxygen to produce oxide. When the external circuit is cut (i.e., very high resistance such as an open switch), the reaction ceases; the aluminum does not react directly with oxygen in the surrounding air. The engineering involves both the aluminum alloy used and the special air cathode with a porous, non-wettable layer that permits oxygen diffusion and a porous, catalytic, partially wettable conductive layer.
The overall equation for the cell is:
- 4 Al + 6 H₂O + 3 O₂ --> 4 Al(OH)₃

Procedure

Assemble the cell according to the manufacturer's instructions. Typically cells will contain these sorts of parts: a plastic spacer; an aluminum alloy anode; electrolyte (such as a paper towel or cloth wick saturated with the electrolyte solution); an air cathode (the partially wettable side touches the pad of electrolyte; the "dry" side touches a plastic grid that permits oxygen access to the other side of the cathode); a plastic grid to permit oxygen access; and a plastic spacer to separate the cells into compartments.
Electrical contact between the air cathode of one cell and the aluminum anode of an adjacent cell is maintained by folding the air cathode and making direct contact.
Connect the assembled cell to a suitable load such as a group of light emitting diodes connected in parallel.
Connect the battery to a suitable DC voltmeter. Measure and record the voltage.

Handout Makeup

Name ___________________________ Class ________

Teacher__________________________

DoChem 117 Aluminum Oxygen Galvanic Cell

Watch the slides and movies.

Describe the galvanic cell.
How are two galvanic cells connected in the apparatus displayed?

Teachers Guide

Purpose

To illustrate a galvanic cell.

Materials

commercial apparatus (such as that supplied by Alupower, Inc., 6 Claremont Rd., Bernardsville, New Jersey 07924)

Lab Hint

Purchase the apparatus from a supply house.

Time

Teacher preparation: 20 minutes

Presentation: 10 minutes

Hazards

There are no unusual hazards associated with this experiment.

Precautions

Follow routine laboratory precautions.

Disposal

All of the materials used in this experiment are saved or disposed of with ordinary trash.

Applications

The aluminum cell has a wide variety of practical applications, particularly where high power, low mass batteries are required.

Background

Aluminum is a plentiful, reactive element. The chemical reaction of aluminum with oxygen is spontaneous. Due to the formation of a 'protective' oxide coating, aluminum objects survive for long periods in the environment. Aluminum has a low molar mass; 9 grams of aluminum present the opportunity for harnessing one mole of electrons. Several of these features speak in favor of using aluminum for the construction of cells and batteries provided that the direct reaction and oxide coating problems can be dealt with.
As the result of clever engineering, the Aluminum Company of Canada has devised a galvanic cell in which aluminum reacts with oxygen. Ordinary salt water may serve as the electrolyte.
When connected to an electric load, aluminum reacts with oxygen to produce oxide. When the external circuit is cut (i.e., very high resistance such as an open switch), the reaction ceases; the aluminum does not react directly with oxygen in the surrounding air. The engineering involves both the aluminum alloy used and the special air cathode with a porous, non-wettable layer that permits oxygen diffusion and a porous, catalytic, partially wettable conductive layer.
The overall equation for the cell is:
- 4 Al + 6 H₂O + 3 O₂ --> 4 Al(OH)₃

Makeup Ans.

Describe the galvanic cell.

A plastic spacer holds layers in place. An aluminum alloy acts as the anode. The anode make electrical contact with the cathode through a wet paper or cloth. The cathode is a special catalytic material with two layers which facilitates air contact and current flow.
The cathode of one cell is bent over the spacer to contact the anode of the next cell directly.

Key Words

cathode
anode
galvanic cell