This implies that the presence of a metal on the semiconductor is necessary for the photocatalytic reduction of nitrite (nitrate) to ammonia.
Indeed, we observed that the bare semiconductor itself showed no activity.
Thus the metal (with a low overpotential for hydrogen) dissociates the chemisorbed hydrogen to give rise to Had, and this reduces the nitrite (nitrate) through a series of steps to evolve ammonia as shown in Fig. 1.
The effect of other noble-metal-loaded TiO2 catalysts on the photocatalytic reduction of nitrite and nitrate
will be discussed in a subsequent detailed publication.