# Pale blue species forming during electrolysis of NaHCO3

I have a solution of 3500 ml $$\ce{H2O}$$ + 454 g $$\ce{NaHCO3}$$ in electrolysis at a potential of 12.5V using a lead anode and copper cathode. The surface areas aren't measured but they are enormous. I made the electrodes myself from lead and copper foil.

The idea was to make NaOH from $$\ce{NaHCO3}$$ (an inexpensive source $$\ce{NaHCO3}$$ 0.86/454g and NaOH \$7/500g) meanwhile producing the PbO2 layer on the lead anode.

Everything seemed to be going as expected until I see there's a pale blue species being produced. What could it be? I'm thinking H2O2, water having the potential to completely become peroxide, so I used the 5V output instead and the blue species vanished.

I've read electrolysis of salts in basic solution usually result in the salt reaching its highest state of oxidation at the anode.

Eg.:

$$\ce{NaCl + H2O ->Cl- + OH- -> HClO + OH- ->ClO2- + H2}$$ eventually becoming $$\ce{ClO4-}$$

(correct me if I'm wrong but I believe that's the way that reaction carries out),

or

$$\ce{(NH4)2SO4 -> (NH4)2S2O8}$$

EDIT It's just copper. Apparently in a solution of NaOH, there is some oxidation of a Cu cathode. I've seen it occur many times afterward. Hydrogen peroxide cannot be made without special laboratory equipment.

• Wasn't there a copper wire? Jan 15, 2019 at 0:19
• copper cathode so nope, and remember the blue color comes back when it's reacted with something else. I also reacted it with ammonia with no tetraamine formation. Jan 15, 2019 at 1:21
• Well, if there was copper then however you did it, it's much more probable then any peroxides or other highly oxidated species (which aren't colorful BTW). Jan 15, 2019 at 1:56
• Copper oxidation Jan 15, 2019 at 10:05