Reduction of nitrite on tin-modified noble metal electrodes

The electrocatalytic activity and product distribution of the nitrite reduction on Sn-modified noble metal (Ru, Pd, Rh, Pt, and Ir) electrodes, as well as unmodified noble metal electrodes, were examined in a 0.1 M HClO4 solution. The most effective coverages were 0.35 and 0.55 for the Sn/Pt and Sn/Pd, respectively. The activity of the Sn/Ru, Sn/Rh, and Sn/Ir electrodes simply increased with an increase in the Sn coverage. From the maximum current densities at −0.1 V, the orders of the reduction activity for the unmodified and Sn-modified electrodes were Ir > Pt > Pd > Ru > Rh and Sn/Ir ≈ Sn/Ru > Sn/Rh ≈ Sn/Pt > Sn/Pd, respectively. The electrolysis of nitrite for 5 h was carried out on each electrode in 0.1 M HClO4 at −0.2 V. The conversion of nitrite increased due to the Sn modification (4–27% conversion). The highest N2 selectivity (53%) was obtained using the unmodified Pt electrode. Sn was not effective for the N2 selectivity.