Originally Posted By: Astro14
Makes no difference. Clearly, the author has no scientific understanding. Stating that this is cleaner is also false.
The energy required to split H2O into its component elements (known as hydrolysis) remains the same for every molecule split. Scale doesn't change efficiency. It takes a lot of energy to liberate the hydrogen. This device simply uses a different catalyst, but that doesn't change the energy required.
The author ignores the energy source throughout the article and gets the energy source wrong in the steam reformation do natural gas (the natural gas is being split up...it's not a global warming contributor...however, the energy required to run the process has to come from somewhere). Sadly, a working knowledge of thermodynamics did not inform the opinions in the article.
So, if you do it with a little battery, you'll get a little hydrogen.
Ironically, you'll get more electricity from the little battery than you will from running a fuel cell on the little bit of hydrogen created by this science project because of the imperfect efficiency of hydrogen creation and of the fuel cell...
So, they have cleverly turned the little bit of electricity in the battery into an even smaller amount of electricity by using two very expensive bits of technology....their new device and a fuel cell...
At best, a small step backwards!
You're missing the point. Catalysis is indeed a means of reducing the activation energy of a chemical reaction.
If you look at chemical activity and Gibbs free energy, and calculate based upon Nernst, you get somewhere around 1.2v as the standard potential of water electrolysis. Phase changes and thermal issues (losses and other enthalpic effects) makes it more like 1.5v, and the usually some additional overpotential is applied.
Doing this via a proton shuttle (PEM) vs an oxygen shuttle (hi-temp SOFC) can have efficiency differences.
Yes, a mole of water requires two moles of electrons to split. That is what it is. And recall that a coulomb is around 10^18 electrons (so not quite a mole) and that it is also an A*s. So an ampere is really depictable in terms of moles of electrons. So for a mole of water, the amperes required will not change from a number of atoms or number of electrons basis, but the potential that the electrolysis can occur at, or more specifically, the overpotential (waste) required, can be reduced with appropriate catalysis. So what happens is that for a given number of moles, at a lower overpotential, a lower total number of watts are required, since V*A=W.
Then if you apply an effective flow rate and time based term in there, what you ultimately can get is Wh/quantity of H2, all going back to fewer watts because fewer volts, because of better catalysis of the electrolysis, and cheaper to boot.
So there is an effective energy savings due to reduction of overpotential, which is really all that is being stated. Specifically, "The nickel/nickel-oxide catalyst significantly lowers the voltage required to split water, which could eventually save hydrogen producers billions of dollars in electricity costs". The cost aspect is not only in electricity, but also in precious metals acquisition cost. Nafion isn't cheap either.
If you make a polarization curve for a PEM fuel cell, there are distinct regions. They are activation losses, oh if losses, and mass transport losses. Catalysis reduces the activation losses, and superior designs can reduce ohmic losses as well. That can be a non-trivial amount of overpotential that is removed.