50% H2SO4 solution is electrolyzed using inter electrodes. The product obtained at anode is
H2S2O5
H2S2O7
H2S2O8
H2SO5
2H2SO4 ⇌ 2H++2HSO4−
Anode
2HSO4− → H2S2O8 + 2e−
Cathode
2H++2e− → H2