Unique Compensation Effects of Heavy Metals and Phosphorus Copoisoning over NO Reduction Catalysts

Selective catalytic reduction (SCR) of NO from the flue gas is still a grand challenge due to the easy deactivation of catalysts. The copoisoning mechanisms and multipoisoning-resistant strategies for SCR catalysts in the coexistence of heavy metals and phosphorus are barely explored. Herein, we unexpectedly found unique compensation effects of heavy metals and phosphorus copoisoning over NO reduction catalysts and the introduction of heavy metals results in a dramatic recovery of NO reduction activity for the P-poisoned CeO₂/TiO₂ catalysts. P preferentially combines with Ce as a phosphate species to reduce the redox capacity and inhibit NO adsorption. Heavy metals preferentially reduced the Brønsted acid sites of the catalyst and inhibited NH₃ adsorption. It has been demonstrated that heavy metal phosphate species generated over the copoisoned catalyst, which boosted the activation of NH₃ and NO, subsequently bringing about more active nitrate species to relieve the severe impact by phosphorus and maintain the NO reduction over CeO₂/TiO₂ catalysts. The heavy metals and P copoisoned catalysts also possessed more acidic sites, redox sites, and surface adsorbed oxygen species, which thus contributed to the highly efficient NO reduction. This work elaborates the unique compensation effects of heavy metals and phosphorus copoisoning over CeO₂/TiO₂ catalysts for NO reduction and provides a perspective for further designing multipoisoning-resistant CeO₂-based catalysts to efficiently control NO emissions in stationary sources.