Like electrooxidation, the process electroreduction also can be divided into two groups: direct and indirect reduction processes. Direct reduction process is more popular for nitrate reduction, where electrons from the cathode surface react with nitrate compound to form nitrogen gas and hydroxyl ions [34]. However, some undesirable by-products such as nitrite and ammonia are also formed during nitrate electroreduction. These two by-products can be eliminated by redox reactions where nitrite is reduced to nitrogen at the cathodic side and ammonia is oxidized at the anodic side, as shown in Eqs. (9), (10) and (11)[35] and [36].