Insight into synergistic effects of oxygen and nitrogen dual-dopants in carbon catalysts on selective catalytic reduction of NOx with NH3: A combined computational and experimental verification

Abstract

Heteroatom doping in carbon catalysts has been shown to enhance the low-temperature selective catalytic reduction of NOx with NH3 (NH3-SCR); however, precise identification of active structure and activity origin remains challenging as various heteroatoms co-existence. Here, we provide a new insight into the synergistic effects of oxygen and nitrogen dual-dopants on carbon-catalyzed NH3-SCR. Density functional theory calculations reveal a new reaction pathway that the quaternary N enhances O2 activation and NO oxidation, and carboxyl as Bronsted acid site coupling H2O as H mediator decreases energy barriers of intermediate NH2NO evolution by enhancing H transfer, which was further experimentally verified by model activated cokes with controllable doping patterns. The dual-doped activated coke delivers superior NO conversion (∼90 %) and N2 selectivity (above 90 %) with H2O presence and corresponding kinetic and in-situ characterizations evidence the reaction pathway on dual-doped carbon. This work guides the design of high-performance heteroatom doped carbon catalysts for NH3-SCR.