RSC Adv. 2023 Jan 27;13(6):4032-4039. doi: 10.1039/d2ra06744g. eCollection 2023 Jan 24.

ABSTRACT

The detailed atomic-level mechanism of the effect induced by engineering the crystal facet of α-MnO2 catalysts on N2O formation during ammonia-selective catalytic reduction (NH3-SCR) was ascertained by combining density functional theory (DFT) calculations and thermodynamics/kinetic analysis. The surface energies of α-MnO2 with specific (100), (110), and (310) exposed planes were calculated, and the adsorptions of NH3, NO, and O2 on three surfaces were analyzed. The adsorption energies showed that NH3 and NO molecules could be strongly adsorbed on the surface of the α-MnO2 catalyst, while the adsorption of O2 was weak. Moreover, the key steps in the oxidative dehydrogenation of NH3 and the formation of NH2NO as well as dissociation of NH2 were studied to evaluate the catalytic ability of NH3-SCR reaction and N2 selectivity. The results revealed that the α-MnO2 catalyst exposed with the (310) plane exhibited the best NH3-SCR catalytic performance and highest N2 selectivity, mainly due to its low energy barriers in NH3 dehydrogenation and NH2NO generation, and difficulty in NH2 dissociation. This study deepens the comprehension of the facet-engineering of α-MnO2 on inhibiting N2O formation during the NH3-SCR, and points out a strategy to improve their catalytic ability and N2 selectivity for the low-temperature NH3-SCR process.

PMID:36756579 | PMC:PMC9890662 | DOI:10.1039/d2ra06744g