Boosting SO2-Tolerant Catalytic Reduction of NOx via Selective Adsorption and Activation of Reactants over Ce4+–SO42– Pair Sites

Developing highly SO2-tolerant catalysts at low and moderate temperatures remains a crucial bottleneck in selective catalytic reduction (SCR) of NOx by NH3. Herein, SO2-tolerant SCR of NOx is boosted via selective adsorption and activation of reactants over Ce4+–SO42– pair sites on CeO2 catalysts by sulfur doping. Interestingly, a sulfur dopant, characterized as bulk sulfate bidentate coordinating over (sub)surface of CeO2 catalysts, utilizes strong electronegativity to induce the neighboring Ce atoms to be charge-deficient. This electronic effect simultaneously weakens the electronic interaction between CeO2 and SO2 as well as alleviates the oxidation capacity of CeO2 catalysts, resulting in the suppression of adsorption and oxidation of SO2. Meanwhile, the oxidation of NO is also alleviated to generate SCR reactive NO2/nitrite species accompanied by increased Brønsted acid sites over Ce4+–SO42– pair sites. This work deepens the understanding of the SO2-tolerant SCR mechanism and provides an efficient strategy for further designing highly efficient SO2-tolerant SCR catalysts.