Silver modified platinum surface/H+ conducting Nafion membrane for cathodic reduction of nitrate ions

► Catalytic effects are observed when Ag particles are deposited on Pt film. ► The reduction process is diffusion controlled and follows first order kinetics. ► The reactivity and selectivity are controlled by potential. ► Decrease of roughness causes deactivation of the performance. Electrocatalytic reduction of NO3− was performed at an Ag modified Pt electrodes supported on a H+ conducting Nafion-117 polymer electrolyte. The cyclic voltammetric and electrolysis experiments showed that the reduction process was a two-electron transfer reaction. The conversion of nitrate to nitrite follows first order kinetics. Controlled potential electrolysis experiments revealed that the highest reduction rate (k1; 95.1×10−3min−1) could be obtained at −1.3V versus Ag/AgCl (std. KCl) reference electrode. Meanwhile, substantial nitrate removal (ca. 89%) could be attained by a flow system when the flow rate is as low as 0.1mlmin−1. The Ag particles on the Pt film were a in polycrystalline state having roughness value of 0.45μm, which was reduced to 0.30μm after 270min of undergoing electrolysis.