An anti-poisoning defective catalyst without metal active sites for NH3-SCR via in situ stabilization

Abstract

NO_x emission can be controlled through selective catalytic reduction (SCR) by ammonia in industry. However, the SCR catalysts are sensitive to contaminants. Searching for anti-poisoning catalysts has become a perpetual quest for large-scale SCR. Here, we report that hydrogenated titanium dioxide particles containing oxygen vacancies undergo in situ N-doping during NH₃-SCR reaction. The N-doped hydrogenated TiO_2−x exhibits high denitrification activity and selectivity, long-term stability, H₂O and SO₂ tolerance, and high poisoning resistance. The DRIFT spectra combined with density functional theory computations demonstrate that the N-dopant as the catalytic active site can enhance O₂ and NO adsorption, which can be reduced by NH₃via the Eley–Rideal mechanism. This is greatly different from traditional catalysts with metal active sites for NH₃ adsorption. The high anti-poisoning performance can be ascribed to the weak interaction between N and toxic reactants. This discovery creates a new concept that non-metal active sites can replace conventional precious/transition metals to avoid poisoning, while being stabilized by in situ doping with reactants.