Optimisation and Stability of Rh Particles on Noble Metal Films Immobilised on H⁺ Conducting Solid Polymer Electrolyte in Attaining Efficient Nitrate Removal

During the electrocatalytic reduction of nitrate, nitrite is often evolved as a product along with ammonia due to the sluggish nitrite-to-ammonia conversion process compared to the nitrate-to-nitrite conversion step. Rhodium metal has been proven to enhance nitrite-to-ammonia conversion rates, yielding ammonia as the only final product. In the present article, we have shown how effectively Rh nanoparticles immobilized on Pt and Pd films deposited on H⁺ conducting Nafion-117 membranes eliminate intermediate nitrite ions during the progress of the nitrate reduction reaction in a flow type reactor. In this research, we also demonstrated the optimization of Rh nanoparticles on the cathode surface to attain effective nitrate reduction along with a reproducibility check. The dissolution of loosely held Rh nanoparticles on the cathodic surface was observed, which tends to be redeposited during cathodic electrolysis, causing stable performance. Finally, Tafel analysis was performed to show the relative kinetic feasibility of the Rh-modified Pt and Pd electrodes in attaining nitrate reduction reactions in neutral medium.