Optimal time-varying potential profile for batch electrochemical reactor is evaluated for a major industrial electro-organic synthesis, the electro-hydro-dimerization of acrylonitrile to adiponitrile. The control vector iteration technique is used for computing the optimal profiles. As the technique is continuous on both state and adjoint variables, it can give more accurate profile with no need for any polynomial approximation. A heterogeneous model of the reactor is uniquely used for the formulation of dynamic optimization problem statements by expressing the differential constraints in terms of concentration variations in bulk as well as at the electrode surface. In addition to taking an account of surface concentration variations, the separation of total current as faradic and non-faradic currents is also considered as an additional equality constraint. A path constraint on the electrode potential is imposed for safe reactor function and economical operation. The results of optimum time-varying potential profile are compared with those of applying a steady potential. (C) 2008 Elsevier Ltd. All rights reserved.