Electrocatalytic nitrate and nitrous oxide reduction at interfaces between Pt-Pd nanoparticles and fluorine-doped tin oxide

We report the preparation of Pt and/or Pd nanoparticle-deposited fluorine-doped tin oxide (FTO) electrodes by an arc-plasma deposition (APD) technique and their electrocatalytic activity for nitrate (NO3-), nitrite (NO2-), nitric oxide (NO), and nitrous oxide (N2O) reduction reactions in acidic media. Cyclic voltammetry of the electrodes revealed that the co-presence of Pt and Pd on FTO showed higher catalytic activity than Pt or Pd on FTO for the NO3- reduction reaction, where the PtPd/Sn interface acts as the catalytic active site. The PtPd/Sn interface also showed higher catalytic activity for the N2O reduction reaction to dinitrogen than the Pt/Sn or Pd/ Sn interfaces, whereas it showed no drastic contribution to the electrocatalytic NO2 - and NO reduction reactions. Because the NO3- and N2O reduction reaction occur in the potential region of hydrogen adsorption on Pt and Pd electrodes, the PtPd/Sn interface could enhance NO3- and N2O adsorption and/or suppress the hydrogen adsorption. Our findings will be useful for the design of interfaces between noble metal mixture/alloy nano particles and Sn, leading to the practical application of denitrification to harmless dinitrogen.