As benzonitrile (BN) is the product detected following bulk electrolysis, eqs 17-20 are used to simulate the oxidative reduction of 4-BrBN. This 4-step mechanism follows the well-established ECEC mechanism for the electrochemical hydrodehalogenation of 4-BrBN, where the reductant, rather than being an electron from the cathode surface, is CO2 •-generated at the anode by a mediation reaction.