Core-shell materials for selective catalytic reducing of NOx with ammonia: Synthesis, anti-poisoning performance, and remaining challenges

Nitrogen oxides (NOx) are one of the major air pollutants. The selective catalytic reduction with ammonia (NH3-SCR) is one of the state-of-the-art and proven technologies for removing NOx from the flue gases. However, high SCR activity of catalysts at low temperature with excellent resistance to poisoning are urgently desirable to satisfy the increasingly strict emission standards for flue gases. Core-shell materials possess the advantages of size, the synergy of core-shell, confinement effect shielding effect and protection of the core by the shell layer, all of which make them obtain wide application and consideration in catalysis in improving the selectivity, activity, and stability of catalytic reactions as well as anti-poisoning ability. Herein, this paper firstly reviews the classification of core-shell structured materials and their synthesis methods, and then emphasizes on the applications of core-shell structured catalysts in NH3-SCR process. Afterward, the research progress of their sulfur and/or water resistance and resistance to alkali metal and alkaline earth metal poisoning are reviewed. Additionally, challenges and future developments of SCR catalysts are discussed. This review will favor further design of core-shell structured catalysts with superior activity and high resistance to NH3-SCR catalysts.