Electrocatalytic reduction of nitrous oxide on metal and oxide electrodes in aqueous solution

Electrochemical reduction of N2O was investigated using various metal and oxide electrodes. The Faradaic efficiency for the N2O reduction strongly depended on the electrode materials. The metal electrodes whose current-potential curves under N2O were shifted more positively than those under Ar showed high Faradaic efficiency. Pd electrodes efficiently reduced N2O to N2 with the smallest overpotential among the tested metal electrodes. The electrochemical reduction mechanism is considered as follows: (i) the adsorbed oxygen species formed by the decomposition of N2O is electrochemically reduced on Cu, Ag and Au electrodes, (ii) the surface oxide layers which are formed by N2O oxidation resulting in the formation of N2 are electrochemically reduced on Fe, In, Sn and Pb electrodes, and (iii) the adsorbed N2O is reduced with adsorbed hydrogen formed by the electrochemical reduction of H+ on Pd and Pt electrodes. ZnO, In2O3 and SnO2 of m-type semiconductor electrodes also reduced N2O efficiently.