Targeted capture of thallium by cerium sulfate enables efficient NOx reduction in poisoned SCR catalysts

Severe thallium (Tl) contamination released from cement kiln flue gas profoundly deactivates commercial selective catalytic reduction (SCR) catalysts, restricting their long-term service stability. Highly volatile Tl species preferentially bind to essential V=O redox active sites to form inert V-O-Tl structures, aggressively disrupting surface acidity and redox synergy. Herein, we report a targeted modification strategy where surface sulfate groups on a Ce(SO₄)₂-modified vanadium-based catalyst act as sacrificial sites. Even under conditions of severe Tl poisoning, this modified catalyst maintains the NO_x conversion rate exceeding 95% within the high-temperature window, in contrast to the catalytic failure of the unmodified catalyst. Tl species preferentially bind and immobilize onto surface sulfate sites of the catalyst, and this targeted capture mechanism spatially and electronically isolates toxic Tl from V active centers. The DFT calculations indicate that the formation of thallium sulfate is thermodynamically more favorable, and this sacrificial trapping mechanism restores surface acid and redox sites, maintaining intact NOₓ adsorption intermediates and unobstructed SCR reaction pathways. This study provides new mechanism regarding the Tl tolerance of SCR catalysts, and these insights for the rational design of highly stable catalysts for industrial NO_x removal under complex flue gas conditions.