Fuel Cell 5E40.xx

Overview: This is a demo of fuel cell technology. Through the recombination of hydrogen produced by electrolysis and oxygen from the air permeated over a membrane, one is able to produce electricity.  There are two steps to this demo, electrolysis of water and use of the fuel cell.

Materials:  fuel cell, fan, power supply (40V or higher), Pasco millimeter, 2000mL beaker filled with water, sulfuric acid, 2 stopcock funnels with platinum tipped wires, ring stand, 2 ring stand holders, two 90 degree clams, tubing, 2, hose clamps, 2 alligator clips, banana cables, small test tube (~13-100mm), matches, water, small beaker.

Setup: The stopped-cocked funnels are attached to the ring stand with the 90degree clams and ring stand holders.  The funnels are then lowered into the water filled beaker with the electrodes directly below the mouth of the opening.  (If wires are corroded, clean off the corrosion before lowering into the water.)  The stopcocks are opened to fill the funnels with water, then they are closed.  Sulfuric acid is added to the water.  The tubing is attached from the funnel with the positive electrode in it (red) to top nozzle of the H2 side of the fuel cell.  The bottom nozzle should have a tube on it connected to nothing but blocked off with a hose clamp.  The supply line from the H2 can also have a hose clamp attached to it instead of using to the stopcock to regulate the flow of H2.  The other side of the fuel cell should be the air luft such that it can use oxygen from the air.  (A setup can be used to supply oxygen directly to it to increase efficiency but it is unnecessary).  The power supply should be attached to the electrodes of the electrolysis setup.  The voltmeter and fan should be attached to the electrodes of the fuel cell.                        

Part 1: Electrolysis of Water: 

Electrolysis of Water part of the demo should be started well before the demo is to take place.  The power supply is turned on and turned up 40V or more works best.  Hydrogen will collect at the positive electrode and oxygen at the negative electrode.  Run the electrolysis before class until the hydrogen funnel is mostly full.

  Part 2: Fuel Cell Operation:

Once a supply of hydrogen is created, open the supply line with the stopcock and/or hose clamp(the one on the H2 line).  Purge the system by opening the other hose clamp very slightly then close. Watch the level of H2 so it does not all escape.   You should see the voltage slowly climb.  Supplying a low voltage from the power supply for a minuet can speed up the voltage climb.  The fan should start spinning at about 0.2V. The theoretical voltage that could be produced is about 1.4V though we have been able to get the fuelcell to only 0.7 volts.  

 Part 3: Showing the fuel for the fuel cell is hydrogen:

Take a small test tube(13x100mm) and fill with water to the very top until it is almost overflowing.  Invert into a small beaker of water (do not use the same beaker that you used for the electrolysis, that has acid in it).  Using a ring stand, clamp the test tube upside down in the beaker of water and then slowly remove the beaker of water.  The water in the test tube should remain in the test tube. 

Using a hose clamp, clamp the hose connected to the hydrogen fuel column of the electrolysis setup near the fuel cell.  Disconnect the hose from the fuel cell.  Watching the amount of water in the test tube, put the end of the hose in the water in the inverted fuel cell.  Slowly loosen the hose clamp and let enough hydrogen out to replace the water in the test tube.   Leaving the test tube inverted, light a match and bring it to the mouth of the test tube.  You should hear it pop.  

Go to this link:

http://fuelcellstore.com/information/fuel_cell_information_index.html 

Click on the last item in the list, #7, "An Introduction to Fuel Cells" by Brian Cook, and look at page 24, there are a number of reasons noted why fuel cells don't deliver as much power or voltage as expected. It is possible that the internal resistance of the electrode limits the voltage to .45 Volts. 

(OLDER) SETUP NOTES: First the hydrolysis portion of the experiment should be setup.  This involves filling a 2000mL beaker with water then mixing in the catalyst of 1or 2 drops sulfuric acid.  Place a ring stand behind the beaker and attach 2 ring stand test tube holders using right angle attachment.  Clamp the thin part of the inverted funnels with stopcock (and vinyl tubes, wires and carbon rods attached) using the test tube clamps.  Open the stopcock and lower both funnels individually into the the water solution until water level is at the level of the stopcock.  Make sure the solution fill the funnels.  Close the stop cocks on both test tubes.    

http://www.fuelcells.org/ 

http://www.howstuffworks.com/fuel-cell.htm