The electrochemical reduction of nitrite on a Pt electrode showed two peaks indicating at least two stages of reduction.
Likewise, the reduction of nitric acid at the Pt electrode gave ammonia, but traces of hydroxylamine were also detected.
However, we could not observe any other intermediates in our photocatalytic experiments.
In addition, during the irradiation of nitrate, when nitrite was added, an increase in the yield of ammonia was observed.
This suggests that nitrite is an intermediate in the photocatalytic reduction of nitrate to ammonia.
However, no nitrite could be detected during the photocatalytic reduction of nitrate to ammonia.
Presumably any nitrite formed as an intermediate is rapidly reduced to ammonia.