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

It is still a novel yet challenging task to influence and alter reaction pathways by regulating active sites, while the Ce-O_v-W acid–base pairs regulated by oxygen vacancies accelerate the reaction between NH₃ and gaseous/adsorbed NO, following enhanced Langmuir–Hinshelwood and Eley–Rideal mechanisms. The strategy tunes the catalytic activity at the atomic scale and provides fresh hints for rationally controlling the reaction pathways toward efficient nitrogen oxide (NO_x) removal.

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.

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