3.2.2. Nitrogen compounds selectivity
The concentrations of nitrite and ammonium, both of which are the aqueous by-products of the photocatalytic nitrate reduction, are shown in Fig. 8. With the progression of the reactions, the concentrations of both nitrite and ammonium slowly increased. However, the highest concentration levels of nitrite and ammonium were in the range of 1.5 × 10−2–2.8 × 10−2 and 2.5 × 10−3–5.2 × 10−3 mM, respectively, thereby indicating that both by-products were the intermediates of the reactions and were readily converted into the final product, i.e. the nitrogen gas