Microscopic functionality of FeN4 sites in polymeric carbon nitride for efficient H2S oxidation

• DFT calculations were performed for H 2 S selective oxidation on Fe@CN. • A new quasi Mars-van Krevelen mechanism including withdrawal and regenerating surface proton during catalysis is determined. • Fe atom prefers to form FeN 4 -CN with the barrier of 0.48 eV for H 2 S selective oxidation. The development of the low-cost and efficient catalysts for H 2 S removal is essential and provides an alternative to the traditional Claus process. However, the microscopic mechanism of thermocatalysis for H 2 S selective oxidation has rarely been systematically studied. Herein, we report the microscopic mechanism of H 2 S selective oxidation on the single atom Fe-doped carbon nitride (Fe@CN) by the density functional theory (DFT) calculations. The results indicate that Fe atom prefers to form FeN 4 -CN with the barrier of 0.48 eV for H 2 S selective oxidation, which agrees well with the experimental results. Furthermore, a new quasi Mars–van Krevelen (quasi-MvK) mechanism including extracting and refilling the proton on Fe@CN is determined. Overall, this work reports the mechanism for selective oxidation of H 2 S into elemental S at the atomic scale, which provide theoretical insights into the design and development of highly reactive and selective catalysts for H 2 S oxidation.