The •OH-induced direct ammonia oxidation pathway for nitric acid photosynthesis

As one of the most important bulk chemicals, nitric acid is primarily produced by the Ostwald process with extensive energy consumption and carbon emission. Therefore, it is necessary to develop alternative green routes for nitric acid synthesis. Photocatalytic nitrate synthesis via complete ammonia oxidation is a promising strategy for efficiently producing nitrate under ambient conditions. However, the reaction route of ammonia oxidation is complex with diverse product distribution since it is a multi-electron involved reaction. It is a great challenge to directionally regulate the selectivity for the targeted conversion of ammonia into nitrate with a high conversion ratio. Herein, the CuO x clusters are constructed on the TiO 2 substrate as the active sites to facilitate ammonia-to-nitrate photosynthesis via the enhanced activation of H 2 O molecules. It is revealed that a new reaction pathway is established, in which the •OH-driven direct ammonia oxidation contributes to the promoted nitrate synthesis rate at 116.8 ± 3.5 μmol·q·h −1 . Moreover, the competitive conversion ratio for ammonia (91.1 ± 1.2 %) and selectivity for nitrate (91.7 ± 0.8 %) are reached, manifesting the significance of effective nitrate production with low energy consumption and carbon emission. A new opportunity is provided in this work for the artificial nitrogen cycle and N-involving resource utilization.