I'm separating water into hydrogen and oxygen by connecting a DC current to 99.9% pure nickel electrodes in a solution of NaOH in deionized water.
It works great, except that any attempts to increase the rate of production by increasing current, increasing NaOH, bringing electrodes closer together, etc. also result in an increase in heat.
At the moment the bottleneck for my production rate is trying to keep the water from boiling or otherwise causing heat damage to the apparatus.
I've considered investing in a cooling system, but I'm also interested in knowing whether or not it is possible to somehow improve the efficiency of the electrolysis and thereby improve separation rate without increasing heat.
(In case you're wondering, I'm using hydrogen to fill balloons. It works quite well, I can fill a normal sized balloon in a few minutes, but then I need to wait an hour for everything to cool down. (Yes I know hydrogen and fire don't mix well.))