Descriptor-Led Nonmetal Doping of MnO2 Enables Selective NH3-SCR With Suppressed N2O Formation.

Low-temperature ammonia-selective catalytic reduction (NH3-SCR) over MnO2 is attractive for nitrogen oxides (NOx) abatement yet is intrinsically penalized by nitrous oxide (N2O) formation, a potent greenhouse byproduct. Here, we show that oxygen-site nonmetal substitution in β-MnO2 can simultaneously suppress N2O and accelerate NH3-selective SCR, enabled by a feasibility-to-mechanism computational workflow. Screening by structural compatibility, orbital hybridization, thermochemical and kinetic stability identifies viable dopants, among which F and S most effectively rewire reaction branching. Kinetics estimated by the density functional theory calculations reveal that F and S raise the N2O-forming rate-determining barrier from 0.80 eV to 0.93/0.92 eV, while lowering the N2-forming barrier from 0.48 eV to 0.40/0.42 eV. At 200°C, F- and S-doped β-MnO2 increase TOF by a factor of 8.40 and 4.24, respectively, and enhance kinetic N2 selectivity by a factor of 1.66 and 1.38, respectively. We identify Mn(d)-nonmetal(p) band center alignment as a mechanistic descriptor that points to a volcano-like trend for the energy barriers of N2O and N2, supported by Bader charge, COHP/ICOHP, and ELF analyses. These results serve as a theoretical design reference for tuning the activity-selectivity trade-off in oxygen-site-modified oxide SCR catalysts.