Simultaneous catalytic oxidation mechanism of NO and Hg0 over single-atom iron catalyst

• Simultaneous catalytic oxidation mechanism of NO and Hg 0 . • TER path favorable the removal of NO and Hg 0 disregarding molecular collisions. • Reaction path of NO and Hg 0 oxidation at atomic level. Among the many pollutants emitted from coal-fired power plants, elemental mercury (Hg 0 ) and nitrogen oxides (NO x ) are widely concerned and regarded as a global environmental problem. Catalytic oxidation is an effective method to remove the above power plant pollutants. Although the recent pioneering experiment found that single-atom catalysts (SACs) exhibit excellent performance for the oxidation of NO and Hg 0 , the reaction mechanism for the simultaneous removal of NO and Hg 0 has not been thoroughly revealed. In this work, a single-atom iron catalyst supported by a double vacancy doped graphene substrate with four N atoms (Fe 1 N 4 ) was used to explore the reaction mechanism of O 2 simultaneous catalytic of NO and Hg 0 . By using DFT method and energy span model, all possible paths of simultaneous catalytic oxidation of NO and Hg 0 are enumerated. Among the ten paths we found, Termolecular Eley-Rideal (TER) mechanism has the lowest energy barrier. The rate determining reaction barrier is 1.59 eV. Disregarding the contribution of molecular collisions, TER path is more kinetically favorable for the integrated removal of NO and Hg 0 . Comprehensive consideration of intermolecular collisions, the catalytic oxidation reaction follows the E-R mechanism. The study deepened the understanding of the reaction mechanism of simultaneous removal of NO and Hg 0 .