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Inside Collection (Course):

Course by: Mary McHale. E-mail the author

# Hydrogen and Fuel Cells

Module by: Mary McHale. E-mail the author

## Hydrogen and Fuel Cells Experiment

### Objective

• Build a fuel cell in order to appreciate practically a range of important chemical and physical principles, such as galvanic cells, energy conversion, energy quality, combustion reactions, water electrolysis and bio-fuels.
• Crituique the design in order to improve the efficiency of the fuel cell and to accomplish it practically

• Pre-lab (10%)
• Lab Report (80%)
• TA points (10%)

## Caution!!! Plastic can burn.

To get good results, very careful measurements are required. Be sure to wear suitable eye protection.

Materials:

• 2X 50-60mL disposable hypodermic syringes without needles and pistons.
• 3X pieces of nickel net (2 cut to cover the flanges of the syringe cylinders approximately 2cm X 10cm + 1 extra piece) The net should be a very fine mesh.
• 2X machine screws with nuts and waters (all brass)
• 2X 20cm pieces of insulated 1mm copper wire with ~1.5cm insulation removed from each end
• Heating plate
• Aluminum plate 4-6mm thick with 7-8mm hole drilled through center
• Baking paper
• Screwdriver, drill, spanner, flat bit, scissors, wooden board and small saw
• tape
• Lab stand with clamps
• 600mL beakers
• 1.5V electric motor
• Red LED
• digital mulitimeter
• balloons
• electrical leads with alligator clips
• 1M sodium hydroxide solution
• 4M nitric acid
• ethanol
• methanol
• Palladium chloride solution (very expensive and should be recycled)
• NaBH4
• Oxygen gas
• Hydrogen gas

Building an electrode (each group should build 2)

• Cut a piece of nickel mesh to cover the flange of the syringe cylinder completely
• Place an aluminum plate on a heating plate. Place the baking paper on the Al plate and the nickel net on the paper.
• Heat the plate to a temperature that will melt the plastic but not burn it.
• 4. Place the flange of the syringe on the nickel net on the heating plate. Press down firmly so that the nickel net is melted onto the flange. Make sure that the net is sealed tight to the whole of the flange surface, but take care not to melt so much plastic that the cylinder hold itself is covered with molten plastic.
• Remove the syringe and net form the eating plate and allow to cool.
• At one of the sides of the flange drill a hole through the flange using the electric drill. Place a piece of wood beneath to prevent drilling into the lab bench. (see picture) Push the machine screw through the hole and fasten using a washer and nut. (see picture)
• Mount a piece of insulated copper wire around the machine screw by twisting an end into a loop with a flat bit and fastening it with the nut. Tighten it so that good electrical contact is established between the wire and the nickel net. Use tape to attach the wire to the syringe cylinder.
• Cut off excess nickel net around the flange.
• Clean the nickel net by immersing the electrode in 4M nitric acid for at least five minutes. Also clean the extra piece of nickel net in this manner. This much be carried out in the fume hood since poisonous flumes may evolve. Rinse thoroughly with water.
• Place the nickel net of the electrode in a solution of palladium chloride for 30 minutes and then gently rinse with water. Be sure to put the extra piece of nickel net in the palladium chloride solution as well. The electrode is now ready. You should have something that resembles the picture.

Figure 1: Drilling holes in flange.

Figure 2: Wire connection assembly.

Figure 3: Final assembled cell

Building the cell

• First cut top off of one of the syringes. This will be the electrode you introduce the liquid/solid fuel.
• Place your two electrodes into a 600mL beaker containing 1M NaOH solution. The nickel meshing should be completely submerged in solution.
• Fill a balloon with oxygen gas (from gas cylinder) and connect using rubber hosing to the syringe that was not cut. The oxygen may bubble slowly through the syringe.
• Roll up the extra piece of nickel mesh and place into the cut syringe.
• Add ~20mg of NaBH4 to the syringe with the extra piece of nickel mesh. If time permits you may test other fuels later.

Figure 4: Functional cell layout.

Testing the cell

• Measure the voltage generated by your cell by taking a digital multimeter and setting it to DC voltage. Connect one probe to each wire of the cell. The reading may continue to grow for a while and then stabilize. Record this stable voltage. It should read between 0.8V-1V.
• Measure the current your cell sources by keeping the probes connected and switching to current mode. This reading should be between 30mA-50mA.

Powering an LED

• One fuel cell does not generate enough voltage to power anything of interest. Just like you would connect 2 or 4 AA batteries in series to power a portable CD player, it is necessary to connect multiple fuel cells to generate larger voltages.
• Pair up with another group and connect the positive terminal of one cell to the negative terminal of the other cell using the wires with alligator clips. Now connect the unwired positive terminal to the positive (longer lead) of the red LED. The unwired negative terminal should be connected to the negative (short lead) of the red LED. At this point the LED should be lit. If you do not see any light, you should use the multimeter to check the voltage generated by the two cells in series and verify that it is greater that 1.5V. If you do not measure any voltage verify that you have wired everything correctly.

Figure 5: Powering an LED circuit.

Powering a small motor

• While two cells in series generate the proper voltage to operate the motor, they cannot source enough current to run a motor longer than a few seconds. By putting cells in parallel more current can be obtained.
• You will need two sets of two cells in series as described in the “Powering an LED” section (4 groups are needed for this part).
• Take the positive connection from each series cell and connect to one terminal of the electric motor. Take the negative connection from each series cell and connect to the other terminal on the electric motor. At this point the motor shaft should begin to turn. If not, check the wiring and verify that you are applying at least 1.5V. It is also possible that 2 parallel cells will not generate enough current. Additional cells can be added in parallel to generate more current.

Figure 6: Powering a motor circuit.

### Pre-Lab: (Total 10 Points)

Name(Print then sign): ___________________________________________________

Lab Day: ___________________Section: ________TA__________________________

This assignment must be completed individually and turned in to your TA at the beginning of lab. You will not be allowed to begin the lab until you have completed this assignment.

1.Fill in the blanks:

Fuel cells are used for direction conversion of the energy of combustion reactions to ______________. A fuel cell is a ______________ in which electricity is generated by a combustion reaction. A fuel cell provides a ______________ voltage that can be used to power motors, lights or any number of electrical appliances.

2.T or F At the anode, oxidation of the fuel takes place.

3.T or F The fuel cell emissions will be nothing but water vapor.

4.T or F The efficiency of fuel cells, chemical-to-electric energy conversion, is approximately 40%.

Review of series and parallel circuits:

In a series circuit, the electrons in the current have to pass through all the components, which are arranged in a line. Consider a typical series circuit in which there are three resistors of value R1, R2, and R3.

There are two key points about a series circuit:

• The current throughout the circuit is the same.
• The voltages add up to the battery voltage.

Therefore:

VT = V1 + V2 + V3

From Ohm’s Law:

• VT = IRT;
• V1 = IR1;
• V2 = IR2;
• V3 = IR3

Þ IRT = IR1 + IR2 + IR3

Therefore:

RTot = R1 + R2 + R3

5.In the circuit below, the current is 100 mA.

(a) What is the current in each resistor?

(b) What is the voltage across each resistor?

(c) What is the total resistance?

(d) What is the battery voltage?

Parallel circuits have their components in parallel branches so that an individual electron can go through one of the branches but not the others.  The current splits into the available number of branches.

In this case, the current will split into three.   For a parallel circuit:

• The voltage across each branch is the same.
• The currents in each branch add up to the total current.

From this:

Itot = I1 + I2 + I3

From Ohm’s Law:  I T = V ; I1 = V; I2 = V; I3 = V

RT R1 R2 R3

Þ V = V + V + V

RT R1 R2 R3

Þ 1/RTot = 1/R­1 + 1/R2 + 1/R3

6.This question refers to the circuit below.

(a) What is the total resistance of the circuit?

(b) What is the current through each resistor?

(c) What is the total current?

For resistors in both series and parallel, follow these guidelines:

• Work out the total resistance of the parallel combination.
• Work out the total resistance of the circuit by adding your answer in the previous step to the values of the series resistors.

7.What is the single resistor equivalent of this circuit?

### Report (80 points)

Note: In preparing this report you are free to use references and consult with others. However, you may not copy from other students’ work (including your laboratory partner) or misrepresent your own data (see honor code).

The following tables and questions should be answered in your written report. Please put the information in the relevant section of your report (i.e. observations and results, discussion)

What would happen if zinc screws were used instead of brass?

What is the purpose of the palladium coating on the anode?

What is the purpose of the palladium coating on the cathode?

What fuel cell worked best?

Explain, in detail, why you think that the best fuel cell worked better than the others?

Debate fuel cells.

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