Unique Compensation Effects of Heavy Metals and Phosphorus Copoisoning over NOxReduction Catalysts

Selective catalytic reduction (SCR) of NOxfrom 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 NOxreduction catalysts and the introduction of heavy metals results in a dramatic recovery of NOxreduction activity for the P-poisoned CeO2/TiO2catalysts. 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 NH3adsorption. It has been demonstrated that heavy metal phosphate species generated over the copoisoned catalyst, which boosted the activation of NH3and NO, subsequently bringing about more active nitrate species to relieve the severe impact by phosphorus and maintain the NOxreduction over CeO2/TiO2catalysts. 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 NOxreduction. This work elaborates the unique compensation effects of heavy metals and phosphorus copoisoning over CeO2/TiO2catalysts for NOxreduction and provides a perspective for further designing multipoisoning-resistant CeO2-based catalysts to efficiently control NOxemissions in stationary sources.