SO₂-Tolerant NO_x Reduction by Marvelously Suppressing SO₂ Adsorption over Fe_δCe_1−δVO₄ Catalysts

SO₂-tolerant selective catalytic reduction (SCR) of NO_x at low temperature is still challenging. Traditional metal oxide catalysts are prone to be sulfated and the as-formed sulfates are difficult to decompose. In this study, we discovered that SO₂ adsorption could be largely restrained over Fe_δCe_1−δVO₄ catalysts, which effectively restrained the deposition of sulfate species and endowed catalysts with strong SO₂ tolerance at an extremely low temperature of 240 °C. The increasing oxygen vacancies, enhanced redox properties, and improved acidity contributed to the SCR activity of the Fe_δCe_1−δVO₄ catalyst. The reaction pathway changed from the reaction between bidentate nitrate and the NH₃ species over CeVO₄ catalysts via the Langmuir–Hinshelwood mechanism to that between gaseous NO_x and the NH₄⁺/NH₃ species over Fe_δCe_1−δVO₄ catalysts via the Eley–Rideal mechanism. The effective suppression of SO₂ adsorption allowed Fe_δCe_1−δVO₄ catalysts to maintain the Eley–Rideal pathways on account of the reduced formation of sulfate species. This work demonstrated an effective route to improve SO₂ tolerance via modulating SO₂ adsorption on Ce-based vanadate catalysts, which presented a new point for the development of high-performance SO₂-tolerant SCR catalysts.