Atomic-Level Design of Acid-Base Pairs in Oxides for Selective Catalytic Reduction of Nitrogen Oxides with Ammonia.

Abstract

Selective catalytic reduction of nitrogen oxides (NO_x) with NH₃ (NH₃-SCR) poses considerable potential in the abatement of NO_x emissions. However, the efficient adsorption and speedy reaction of reactants following the specific mechanism in a favorable way is still a challenge for enhancing catalysis. Herein, we propose the strategy aimed at adjusting electronic properties of Ce-O_v-W acid-base pairs through constructing oxygen vacancies on Ce/WO_x, thereby fostering SCR activity. Experimental and theoretical results reveal that Ce-O_v-W acid-base pairs not only provide more Ce³⁺ sites for promoting the reactivity of adsorbed NO, but also accelerate the reaction between NH₃ and gaseous NO owing to the generation of W⁵⁺ species with superior surface acidity, which enhance Langmuir-Hinshelwood and Eley-Rideal mechanisms, respectively. Consequently, the designed catalysts achieve over 90% NO_x conversion above 250 °C and exhibit higher activity than normal Ce/WO₃ and V/W-TiO₂ commercial catalysts, with anti-poisoning of SO₂ and H₂O under harsh working conditions, expecting to provide the guidance for promoting de-NO_x industrial application.