Electrocatalytic reduction of nitrate on tin-modified palladium electrodes

The electrocatalytic reduction of nitrate was investigated in acidic media on Sn-modified polycrystalline palladium and Sn-modified palladium film electrodes (deposited on gold) by means of voltammetry in combination with on-line electrochemical mass spectrometry and on-line ion chromatography. The catalytic activity for this reaction is strongly enhanced by modification with Sn as pure Pd is not found to have a measurable activity for the nitrate reduction. Dominant volatile products are found to be N2O and in a smaller amount N2, while NH2OH is found to be the dominant non-volatile product. Furthermore, the influence of hydrogen absorption in Pd is investigated by using a multilayer Pd film and a submonolayer Pd film on a polycrystalline Au electrode. By comparing the product distribution of these electrodes with the bulk Pd electrode the effect of hydrogen absorption is found to be of negligible importance for the nitrate reduction as the product distribution and formation as a function of potential are similar compared to the bulk Pd electrode.