SO2-induced dual active sites formation over VOx/Fe2O3 for accelerating NH3 selective catalytic reduction of NOx.

[Display omitted] • VO x /Fe 2 O 3 -S catalyst with low V loading is fabricated via simple impregnation method. • SO 2 pretreatment induces the generation of Fe 2 (SO 4) 3 on Fe 2 O 3 -S and VO x /Fe 2 O 3 -S. • The high active polymeric vanadyl species are formed on VO x /Fe 2 O 3 -S rather than VO x /Fe 2 O 3. • The synergistic effect of Fe 2 (SO 4) and polymeric vanadyl boost the SCR reaction of VO x /Fe 2 O 3 -S. • The NH 3 -SCR reaction over Fe 2 O 3 -S and VO x /Fe 2 O 3 -S followed the L-H and E-R mechanism synchronously. The construction of plausible alternatives of V 2 O 5 -WO 3 /TiO 2 for effectual NO x purification is becoming a research hotspot. Herein, a robust VO x /Fe 2 O 3 -S catalyst with SO 2 tailored surface acid sites and active VO x sites was engineered for boosting the NO x reduction performance. The VO x /Fe 2 O 3 -S catalyst afforded above 90% NO x conversion and 90 % N 2 selectivity at 275–425 °C, coupled with the exceptional long-term SO 2 + H 2 O resistance. Py-IR and in situ DRIFTS disclosed that the formation of Fe 2 (SO 4) 3 endowed Fe 2 O 3 -S and VO x /Fe 2 O 3 -S with abundant medium-strong Lewis and Brønsted acid sites rather than covering the active sites, strengthening the NH 3 adsorption and suppressing the overoxidation of NH 3 on the reducible Fe 2 O 3 support. Raman analysis revealed the generation of new species of polymeric vanadyl species on VO x /Fe 2 O 3 -S induced by the SO 2. In-depth mechanistic understanding through DFT analyses indicated that the NO x reduction reaction over the Fe 2 O 3 -S and VO x /Fe 2 O 3 -S obeyed the Langmuir-Hinshelwood and Eley-Rideal mechanism simultaneously. Moreover, the presence of polymeric vanadyl species dramatically lower the overall energy barrier for NO x reduction, thus speeding up the SCR reaction of VO x /Fe 2 O 3 -S. This study can shed light on the more rational design of VO x -based catalysts for highly efficient NO x reduction in industry. [ABSTRACT FROM AUTHOR]