Regulating the Ammonia Oxidation Selectivity via the Quantified Provision of Molecular Oxygen
Jielin Wang, Xin Li, Shujie Shen, Ruimin Chen, Qin Ren, Jieyuan Li, Fan Dong
Abstract
Molecular oxygen (O 2 ) 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 O 2 activation has not yet been clarified. By adjusting the concentration of dissolved oxygen ( C DO ), the quantified provision of molecular O 2 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 O 2, in which P25 is utilized as the photocatalyst. Under the sufficient provision of molecular O 2 activation ( C DO = 20.0 mg L –1 ), the deep oxidation of NH 3 into NO x – (NO 2 – and NO 3 – ) is achieved via the ROS-driven mechanism. In contrast, selective production of N 2 from partial NH 3 oxidation is noted along with the h + -driven direct oxidation mechanism ( C DO = 0.1 mg L –1 ). Then comprehensive in situ characterization under different C DO and theoretical calculations are combined, revealing that the regulation of product selectivity by quantified provision of the O 2 can be attributed to the selective generation of ROS. It is proposed that the strategy of quantified activation of molecular O 2 can be developed as an effective method, which offers opportunities for regulating the oxidation selectivity for important environmental and energy reactions.