Different classications of electrochemical reactors can be made depending on their conguration (divided, undivided cathodic, and anodic compartments) electrode geometry (bi-and tri-dimensional), the uid ow through the reactor (mixing, plug-ow, uidized baths), among others. There are several demands for electrochemical reactors (Pletcher and Walsh, 1990; Molina et al., 2004):

Security, safety, low cost, ease in operation, and, eventually, automatic control• Controlled, uniform potential distribution, and current density between • the electrodes Low cell voltage as possible for minimizing energetic cost• Electrode surface/reactor volume ratio must be as high as possible• Low pressure drop and easy gas evacuation• Control of mass transport and heat transport in the reactor•

The methodology used in chemical engineering to describe the performance of chemical reactors can be adapted to the study of electrochemical cells. Electrosynthesis of a variety of industrially relevant products has been studied; for instance, the synthesis of ammonia from natural gas at atmospheric pressure (Marnellos et al., 2001; Wang et al., 2007).