In Situ S-Doping Engineering for Highly Efficient NH₃–SCR over Metal-Free Carbon Catalysts: A Novel Synergetic Promotional Mechanism

Abstract

Cyclic desulfurization−regeneration−denitrification based on metal-free carbon materials is one of the most promising ways to remove NO x and SO 2 simultaneously. However, the impact of S-doping induced by the cyclic desulfurization and regeneration (C-S−R) process on the selective catalytic reduction (SCR) is not well understood. Herein, it is demonstrated that the C-S−R process at 500 °C induces in situ S-doping with a significant accumulation of C−S−C structures. NO x conversion was dramatically enhanced from 18.95% of the original sample to 84.55% of the S-doped sample. Density functional theory calculations revealed that the C−S−C structure significantly regulates the electronic structure of the C atom adjacent to the ketonic carbonyl group, thereby significantly altering the NH 3 adsorption configuration with superior adsorption capacity. Moreover, Sdoping induces an extra electron transfer between the N atom of the NH 3 molecule and the C atom of the carbon plane, thereby promoting the activation of NH 3 over the ketonic carbonyl group with a reduced energy barrier. This study elucidates a synergetic promotional mechanism between the ketonic carbonyl group and the C− S−C structure for SCR, offering a novel design strategy for high-performance heteroatom-doped carbon catalysts in industrial applications.

Atom Pairing Enhances Sulfur Resistance in Low-Temperature SCR via Upshifting the Lowest Unoccupied States of Cerium

“…As one of the producers for forming ozone and PM 2.5 , nitrogen oxides (NO x ) are harmful to the global environment . Selective catalytic reduction (SCR) of NO x with NH 3 using V 2 O 5 –WO 3 (MoO 3 )/TiO 2 as catalysts is effective for abating NO x emissions from industries. , However, because vanadium has toxicity, new active components that can replace vanadium have been actively searched. − Environmentally benign cerium-based catalysts are promising alternatives to vanadium-based catalysts owing to the excellent oxygen storage–release capacity and redox properties of CeO x via the Ce 4+ ↔ Ce 3+ transition. , However, the deactivation of cerium-based catalysts due to SO 2 poisoning is one of the obstacles impeding their industrial applications. , Therefore, it is necessary to improve the SO 2 resistance of cerium-based catalysts.…”