High electrocatalytic performance of Pd/Sn/Au electrodes for nitrate reduction

Highly active and stable electrocatalysts for the reduction of nitrate ions were prepared by the adsorption of PdCl42− ions onto a tin monolayer on Au(1 1 1) followed by reduction of the adsorbed PdCl42−. The maximum atomic ratio of Pd to Sn, and hence the surface Au, determined using a quartz crystal microbalance, X-ray photoelectron spectroscopy and cyclic voltammetry, was 0.87, which corresponds to 0.3 μg-Pd cm−2. Despite such an extremely low loading of Pd, the Pd/Sn/Au electrodes showed high electrocatalytic activity (−3.5 mA cm−2 at −0.1 V vs. Ag∣AgCl) and N2 selectivity (37%), both of which are comparable to the highest values reported at different electrodes. In addition, the reduction current on the Pd/Sn/Au electrodes remained constant for hours and decreased only due to the exhaustion of nitrate ions in solution.