Science Buddies: "Ask an Expert"

Not clear how the 1.23 volt number came up? its not shown in the procedure how that number has been derived.

Hello gpanguluru,

I’m assuming that you’re working on the project described here:

https://www.sciencebuddies.org/science- ... p099.shtml

The voltage you asked about is the standard cell potential for splitting water into oxygen and hydrogen.
It means that at least 1.23 volts are required to make the reaction proceed. Some more information is provided at the following link.

https://en.wikipedia.org/wiki/Electrolysis_of_water

I hope this helps and good luck with your project. Please post again if you have more questions.

A. Norman

Thank you Mr. Norman

Steps 7 and 8 of "Adding the Cobalt Catalyst and Measuring Its Effects" in the instructions...

-The voltage reading was lower while forming the catalyst in step 7.
-The voltage reading then increased with fresh buffer solution in step 8.

Am I doing something wrong?

Hello gpanguluru,

As you form the catalyst the voltage should drop relative to the baseline voltage that you measured in step 2. I think you might get a small voltage increase after changing to the fresh buffer because you’ve removed the excess cobalt nitrate from the cell. As the instructions point out, you should be careful not to move the electrodes when you change solutions. You could cause a voltage change if the electrodes are moved closer together or farther apart. If you didn’t move the electrodes when changing the buffer you’re probably OK.

I hope this helps. Please post again if you have more questions.

A. Norman

Thank you Mr. Norman.

In the procedure under 'Creating the Galvanostatic Electrochemical Cell'...

Step3 says 'make sure the circuit reads >30V'. But, this is after the 10k ohm resistor, and if there is a 30V drop across the resistor, then it should show 6V (36V - 30V) ... correct?

Much appreciate your help.

Hi gpanguluru,

I think you are correct and the “>30V” notation in step 3 might be a typo. It appears to me that Figure 1 shows the voltmeter probes connected between the negative battery terminal and the 10k ohm resistor. The voltage reading there should be about 6V as you pointed out.

I hope this helps. Please post again if you have more questions.

A. Norman

What is the name of the catalyst that is formed on the cathode in the water to fuel to water experiment?

Hi Mr.Norman
Can you please tell the name of the catalyst formed on the cathode in the 'water to fuel to water' experiment?

Hi gpanguluru,

The catalyst that you made in your experiment is called “Co-Pi” in the background section of the project description. This cobalt-phosphate oxygen evolving compound was discovered and reported by a group at MIT in 2009. There are several links in the project background section and many more articles available online about this very interesting catalyst.

I hope this helps. Please post again if you have more questions.

A. Norman

Hi Mr.Norman,
Electroplating generally occurs at cathode. But in this experiment (water to fuel to water) electroplating occurs at anode. Why? Can you please explain it.

Hi gpanguluru,

Electroplating is a process where positively charged ions (cations) are reduced to metal. The negative electrode (cathode) “donates” electrons to the cations. Metal is then deposited or “plated” on the cathode.

In your experiment, the cobalt forms complexes which are negatively charged ions (anions). The anions “donate” electrons to the positive electrode (anode) and a neutral cobalt compound is deposited on the anode. Oxygen formed at the anode reacts with the cobalt compound to form a cobalt oxide.

I hope this helps. Please post again if you have more questions.

A. Norman

Hi Mr Norman,
Can you suggest any other catalysts, other than cobalt we can try for this experiment?

Thanks

Hi gpanguluru,

There’s great interest in finding ways to produce hydrogen more efficiently. Less expensive production might enable widespread use hydrogen as a fuel. Because of this, a lot of research is currently aimed at developing catalysts for water splitting. These catalysts, like the one you investigated in your project, can reduce the energy needed to produce hydrogen and make the process less expensive.

An online search on “water splitting catalyst” revealed numerous recent articles on catalysts. The following links are just a couple of examples.

http://news.stanford.edu/news/2015/june ... 62315.html

http://science.sciencemag.org/content/347/6225/970

Some catalysts may be too exotic or difficult to make at home for a science project. But you may be able to find one that that is straightforward to prepare at home (like the cobalt compound from your project).

I hope this helps. Please post again if you have more questions.

A. Norman

Hi Mr Norman,
Can you please suggest any other compounds ,instead of cobalt nitrate? Can we use copper or nickel or iron salts instead of cobalt nitrate. can we use iron nitrate or magnesium nitrate? Will they catalyse electrolysis of water in phosphate buffer ph 7? We want to try with different salts other than cobalt nitrate. Can you please help?



Thanks.

Hi gpanguluru,

Water splitting catalysts based on iron, nickel and magnesium have been reported. But I don’t know the details of how any of these catalysts are prepared. You may be able to find articles describing preparation methods for these catalysts by searching on Google Scholar. As I mentioned in my previous post, some catalysts might specialized lab equipment or procedures. But you may find something as simple as the substitution of a different nitrate compound as you suggest. If you do identify a catalyst you want to try to prepare and test, please keep in mind that you need to plan for safe handling of all chemicals that you’ll use.

I hope this helps. Please post again if you have more questions.

A. Norman