Electrochemical denitrification has

Electrochemical denitrification has become increasingly attractive in water treatment practices due to its environmental compatibility,work safety, reaction selectivity, robustness, and versatility. Applying an appropriate voltage on the working electrode enables electrochemical nitrate reduction. Under proper operation conditions, electrochemical process can minimize the production of secondary contaminants, and reduces process costs relative to biological denitrification and other chemical treatments. Studies have demonstrated that the electrochemical reduction of nitrate can take place over a wide variety of cathodic metals and alloys including Cu [20,21], Zn [22], Al [22], Pb [22], Rh [23], Cu-Ni [17], Cu-Zn [22], Cu-Sn [22], Cu-Pd [14,24–26], and Sn-Pd [27]. It appears that bimetallic catalysts,composed of a hydrogen-absorbing metal (e.g., Pd, Rh or Ru) [28,29] and an oxygen-absorbing metal (e.g., Cu or Sn) [30], generally exhibit superior performance than monometallic electrodes [31–34]. In the case of monometallic electrodes, adsorption of both oxygen and hydrogen atoms on the same metal decreased nitrate reduction rate [35].Roué and co-workers studied the conversion of nitrate to nitrogen over Cu monometallic electrode [21] and Cu0.7Ni0.3 bimetallic electrode [17] and reported that the nitrogen yield over the Cu0.7Ni0.3 electrode was about two times that on the Cu electrode [17,21]. Other studies reported the nitrate reduction capability, in terms of N2 yield, follow the decreasing order: Pd0.62Cu0.38 (76%) [36] > Pd0.4Cu0.6 (N2 yield = 41%) [14] > Al (38.1%) [22] > Sn0.85Cu0.15 (34.4%) [22] > Pb (16%) [22] > Cu (9%) [22]. Generally bimetallic catalysts exhibit greater nitrogen selectivity than monometallic ones, except perhaps Al. The composition of bimetallic catalysts is one of the most important parameters controlling nitrogen selectivity.