Quantifying the activation energies of ROS-induced NOx conversion: Suppressed toxic intermediates generation and clarified reaction mechanism.

• The activation energies are ascertained for ROS generation and transformation. • The facet engineering of BiOCl photocatalyst benefits the NO x removal efficiency. • The generation of intermediate NO 2 is significantly suppressed. • Experimental and theoretical methods are combined to reveal the reaction mechanism. The generation and transformation of reactive oxygen species (ROS) is a key parameter in catalyzing photocatalytic gas-phase oxidation reactions for environmental remediation. Thus the determination, quantification and kinetic tracking of ROS are conclusively required to realize complete pollutant conversion and intermediates suppression. By quantifying the activation energies (E a) and ascertaining the rate-determining step (RDS), a panoramic understanding is established in ROS-induced NO x oxidation reactions. To be specific, the BiOCl photocatalyst with tailored facets were designed and fabricated as model catalysts. It is proposed that the ROS generation and transformation pathways are along the path of OH → H 2 O 2 → O 2 −, in which the H 2 O 2 dissociation is the RDS for O 2 − generation. Moreover, it is concluded that NO 2 is the primary intermediate in NO oxidation reaction, and the further transformation of NO 2 requires the highest E a among all the elementary reactions. Significantly decreased E a and suppressed NO 2 accumulation are realized on the {0 1 0} facet of BiOCl to achieve efficient NO x conversion. A new perspective is stated in this research to establish a comprehensive understanding between ROS generation mechanism and intermediates suppression for efficient NO x removal, which provides new insights into the application of photocatalysis technology for air pollution control area. [ABSTRACT FROM AUTHOR]