Regulating the Ammonia Oxidation Selectivity via the Quantified Provision of Molecular Oxygen

Molecular oxygen (O2) activation has been utilized as a feasible approach to promoting the oxidative capacity of general environmental and energy catalytic reactions. However, the selectivity of oxidation reactions regulated by quantification of molecular O2 activation has not yet been clarified. By adjusting the concentration of dissolved oxygen (CDO), the quantified provision of molecular O2 can be facilely accomplished, which could directly regulate the production of reactive oxygen species (ROS) for targeted oxidative products. Herein, by taking ammonia oxidation as a typical multielectron-involved reaction, the selectivity is precisely tailored by quantified activation of molecular O2, in which P25 is utilized as the photocatalyst. Under the sufficient provision of molecular O2 activation (CDO = 20.0 mg L–1), the deep oxidation of NH3 into NOx– (NO2– and NO3–) is achieved via the ROS-driven mechanism. In contrast, selective production of N2 from partial NH3 oxidation is noted along with the h+-driven direct oxidation mechanism (CDO = 0.1 mg L–1). Then comprehensive in situ characterization under different CDO and theoretical calculations are combined, revealing that the regulation of product selectivity by quantified provision of the O2 can be attributed to the selective generation of ROS. It is proposed that the strategy of quantified activation of molecular O2 can be developed as an effective method, which offers opportunities for regulating the oxidation selectivity for important environmental and energy reactions.