Electrocatalytic Reduction of Nitrate Using Cu–Pd and Cu–Pt Cathodes/Hþ-Conducting Solid Polymer Electrolyte Membrane Assemblies

The electrocatalytic reduction of nitrate ions (NO3−) was investigated using Cu–Pd and Cu–Pt bimetallic cathodes deposited on a Nafion-117 H+-conducting polymer membrane. The primary objective was to enhance the catalytic efficiency for reducing NO3− to less harmful compounds. The methodology involved applying a direct current (DC) to the membrane–electrode assembly (MEA), enabling the generation of hydrogen on the cathode which facilitated the degradation of nitrate. Results indicated that the reaction followed a consecutive pathway, with copper significantly enhancing the catalytic activity for the first reduction step from NO3− to NO2−. The Cu–Pd and Cu–Pt cathodes demonstrated optimal reduction rates with a composition of 38 and 20 mol % Cu, respectively. Furthermore, the selectivity of products varied based on Cu concentration, with the Cu–Pd cathode showing lower selectivity for NO2− and higher selectivity for NH4+. The application of CO2 further increased the nitrate reduction rate by maintaining a lower pH, promoting the reaction towards forming nitrogen gas and water. Overall, these findings provide insights into efficient methods for nitrate mitigation in water, addressing environmental concerns linked to agricultural overfertilization.