Question

Why much graphite is required for electrolysis purpose?

Answer 1

Graphite has some useful properties that make it desirable as an electrode in multiple applications, like electric arc steel production. The reasons being that graphite is cheap, plentiful, very stable over a broad range of operating conditions, scalable, durable/hard, and a good electrical conductor and heat conductor (a lot of heat is generated in electric arc steel production).

Answer 2

During the electrolysis process aluminium is deposited at cathode and oxygen is liberated at the anode .Some of this oxygen reacts with carbon in the graphite to form carbondioxide,thus slowly burning away the anode.