The most important thing in scale-up of an electrochemical reactor is the current and potential distribution similarity in scale-up especially in a fixed bed type. You can read my book chapter scale-up electrochemical reactor also my research paper 2007 scale-up of fixed bed -----
This depends very heavily on the type of the electrochemical reactor that you are scaling up and the reaction regime you are operating in. Many electrochemical reactions that are scaled up will operate in the mass transfer limited regime. Mass transfer may not scale linearly and will be different for many modes of transport (e.g. along flow path, into catalyst particles, in boundary layers at the electrode surface, etc).