At 06:14 PM 9/21/2012, Jeff Berkowitz wrote:
I got email on the from a lurker about this too. Agree. In an electrolytic cell, the cathode is the one connected to the negative terminal of the power supply, and this is the business end for H2.
Yes, the cathode is supplied with negative voltage. It supplies electrons to H+ ions in the water, de-ionizing them and they combine to form H2, which bubbles up -- or is rapidly absorbed by palladium, in those experiments.
There actually was an attempted replication in 1989 where a physicist got it backwards. It's easy to get confuse -- except that obviously the fellow didn't understand the chemistry -- or didn't think about it. A physicist would know that a negative battery terminal will supply electrons.
The confusion is somewhat based on the convention for current flow, that current flows from positive to negative.
From the Wikipediat article, "Anode"
An anode is an <http://en.wikipedia.org/wiki/Electrode>electrode through which <http://en.wikipedia.org/wiki/Electric_current>electric current flows into a polarized electrical device. The direction of electric current is, by convention, opposite to the direction of electron flow. In other words, the electrons flow from the anode into, for example, an <http://en.wikipedia.org/wiki/Electrical_circuit>electrical circuit. <http://en.wikipedia.org/wiki/Mnemonic>Mnemonic: ACID (Anode Current Into Device).
Reading the Wikipedia articles on Cathode and Anode, I feel really, really stupid. It all seems wrong. My own confusion is probably based on that "current flow" thing. I think about electrons, and I think of electrons moving in a certain direction as current flow. But that's backwards from the convention. The convention is that "current" flows from positive to negative.
Current *can* be a flow of positive charges, but that's not what flows through wires.
