Dissimilar catalytic trails of nitrate reduction on Cu-modified Pt surface immobilized on H+ conducting solid polymer

• Pt–Cu catalyst reduces nitrate ions using a consecutive mechanism.
• The electron transfer reaction favors ammonia formation.
• The catalytic hydrogenation reaction favors molecular nitrogen formation.

Cathodic reduction of nitrate ions has been carried out using a sandwich type membrane reactor having a configuration of Pt|Nafion|Pt–Cu in absence of any supporting electrolyte. Both Pt and Cu metals are in polycrystalline form on the cathodic surface immobilized on Nafion membrane. The globular Cu particles have a wide range of sizes (70–120 nm). During the course of electrolysis in the reactor, the bimetallic Pt–Cu surface reduces NO3− into NH3 and N2 by means of electrochemical and catalytic hydrogenation reactions, respectively. The electrochemical contribution of nitrate reduction has been investigated in details by using voltammetric and electrolysis techniques. The NO3− ions are electrochemically reduced using a consecutive reaction. On the consecutive way of reduction, the intermediate NO2− and the final product NH3 are generated at −0.74 V and −1.1 V versus Ag/AgCl (std. KCl), respectively. The molecular N2 is generated by means of catalytic reactions followed by electrochemical hydrogen evolution.

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