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

Molecular oxygen (O-2) activation has beenutilized asa feasible approach to promoting the oxidative capacity of generalenvironmental and energy catalytic reactions. However, the selectivityof oxidation reactions regulated by quantification of molecular O-2 activation has not yet been clarified. By adjusting the concentrationof dissolved oxygen (C (DO)), the quantifiedprovision 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 oxidationas a typical multielectron-involved reaction, the selectivity is preciselytailored by quantified activation of molecular O-2, in whichP25 is utilized as the photocatalyst. Under the sufficient provisionof molecular O-2 activation (C (DO) = 20.0 mg L-1), the deep oxidation of NH3 into NO x (-) (NO2 (-) and NO3 (-))is achieved via the ROS-driven mechanism. In contrast, selective productionof N-2 from partial NH3 oxidation is noted alongwith 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, revealingthat the regulation of product selectivity by quantified provisionof the O-2 can be attributed to the selective generationof ROS. It is proposed that the strategy of quantified activationof molecular O-2 can be developed as an effective method,which offers opportunities for regulating the oxidation selectivityfor important environmental and energy reactions.