Bimetallic Pd-Sn Catalytic Electrodes from Deep Eutectic Solvents for Selective Nitrate Reduction Toward Nitrogen

Nitrate is one of the most widespread water contaminants globally. Nitrate levels in groundwater and surface water can rise to unhealthy levels as a result of nitrogen fertilizer runoff from lawns and farms. This research aims to selectively convert nitrate to gaseous nitrogen using Palladium-Tin (Pd-Sn) bimetallic electrodes electrodeposited on stainless-steel (SS). Inductively coupled plasma optical emission spectrometry, scanning electron microscope, and X-ray diffraction are used to analyze the composition, surface morphology, and crystal structure of the electrodes. The XRD analysis reveals that the Pd-Sn/SS electrode has a crystalline nature when a Pd molar ratio >0.5 while an amorphous phase is detected over a Pd molar ratio (≤0.5). The electrochemical nitrate reduction is carried out in a 0.1 M HClO4 / 8 mM NaNO3 solution for 5 h using electrodes prepared in deep eutectic solvent (DES) system. The Pd0.93Sn0.07/SS electrode shows the best catalytic performance in terms of high nitrate conversion of 97%, N2 selectivity of 88%, and N2 yield of 86% compared to counter electrodes. These findings demonstrate a considerable impact of the electrode preparation process on nitrogen conversion, selectivity, and yield.