Electrochemical reduction of nitrogen oxyanions in 1 M sodium hydroxide solutions at silver, copper and CuInSe2 electrodes

The reduction of nitrate and nitrite ions was studied in 1 M NaOH supporting electrolyte. Voltammetric investigations show that, on silver cathodes, nitrate reduction begins at potentials about 500 mV more positive than nitrite reduction, the latter being superimposed on hydrogen evolution. Electrolyses of nitrate solutions at - 1.4V/SCE give nitrite with good selectivity. On copper cathodes, nitrate and nitrite reductions occur in the same region of potentials and show similar voltammetric profiles. The dominant product of nitrite reduction is ammonia, whereas nitrate may be reduced to nitrite at - 1.1 V/SCE and to ammonia with high yields at - 1.4 V/SCE. Reduction of nitrogen oxyanions may also be performed on CuInSe2 (photo)cathodes. Photoassisted reductions of nitrate performed on p-CuInSe2 at - 1.4 V/SCE gave mixtures of ammonia, nitrite and hydrogen.