Hydrolysis and hydrogen production: byproducts?

[Jaevko]

So I'm running a current through distilled water with baking soda to produce hydrogen (to make stuff float :) ). I'm using carbon graphite electrodes and baking soda to avoid any dangerous gases like chlorine. Now its been almost a decade since I took chemistry classes and I'm wondering what other things are produced? I think CO2 is coming in somewhere from the baking soda? Does the graphite react as well?

The reason I ask is because if I'm collecting the hydrogen gas from one electrode, I want to know how pure it is. So please let me know what other chemicals are being produced due to the graphite and baking soda (and anything else I didn't think of, nothing else I think since it's distilled water) and please tell me if those chemicals are gases and which electrode they are coming off of. Thanks!

 

[manivas]

As per my experience, when i did electrolysis of brine.
Chlorine came only when i use graphite as +ve electrode
Hydrogen came out with any -ve electrode

 

[elegysix]

I did some research on hydrolysis last year, and I'd built a unit that used stainless steel plating as the electrodes. We used distilled water and a small amount of sulfuric acid as our charge carriers - the H2SO4 breaks down into (H^+) + (HSO4^-) + (SO4^2-). We chose that because we were confident that there would be no almost nothing aside from hydrogen gas and oxygen produced. Also, you can get sulfuric acid pretty cheap at an auto parts store, sold as battery acid. Hope this helps