Reduction of nitrate ions on tin-modified palladium thin film electrodes

The electrocatalytic activity of tin-modified palladium on gold electrodes (Sn/Pd/Au) for the reduction of nitrate ions was examined in 0.1 M HClO4 as a function of tin coverage, θSn and the amount of palladium deposited on gold, which is shown by the number of palladium layers, nPd, corresponding to the deposition amount. The maximum activity of 10.3 mA cm−2, obtained at θSn ⩾ 0.65 and nPd ⩾ 1.3, is the highest among the electrodes so far examined for this reaction. The specific activity, defined as the activity per unit area of the Pd surface, at nPd ⩽ 0.6 is about three times that at nPd ⩾ 2.4. Reaction products are, on the other hand, almost independent of nPd and θSn, and N2O was formed with a selectivity of >75%.