SO₃²⁻/SO₄²⁻ functionalization-tailorable catalytic surface features of Sb-promoted Cu₃V₂O₈ on TiO₂ for selective catalytic reduction of NO_X with NH₃

SO₂ is notorious to poison the catalytic surface during the selective catalytic reduction of NO_X with NH₃ (NH₃-SCR). Nonetheless, the use of poisonous SO₂ and O₂ as surface modifiers to generate the surface metal-SO_Y²⁻ species (Y = 3 or 4) can be one of the viable ways for promoting catalytic NH₃-SCR consequence. To develop a novel catalyst that is highly active in and selective to NH₃-SCR, we previously explored four catalytic copper vanadates and determined the optimum active phase (i.e., Cu₃V₂O₈, denoted as Cu₃) that revealed the greatest NH₃-SCR performance, when combining with a proper Sb quantity of 1.4 wt. %. While using anatase (TiO₂) as a support, this study investigated the effect of SO_Y²⁻ functionalization temperature on the surface property of the optimum catalyst, Sb-promoted Cu₃V₂O₈ on TiO₂ (Cu₃-Sb_1.4/TiO₂). Cu₃-Sb_1.4/TiO₂ was subjected to SO_Y²⁻ functionalization at 300, 400, and 500 °C, leading to the formation of S300, S400, and S500. Although the catalyst surface was not fully functionalized with the SO_Y²⁻ species in S300-S500, various metal sulfate or sulfite species appeared on the surfaces and showed distinct surface features. The SO_Y²⁻ functionalization of Cu₃-Sb_1.4/TiO₂ could not increase the quantity of Lewis acid sites. However, 400 °C was deemed as an adequate SO_Y²⁻ functionalization temperature for increasing the quantity of Brӧnsted acid sites and the redox behavior of the intact Cu₃-Sb_1.4/TiO₂. This could result from the increase in the surface abundance of Cu(SO₄) or from a proper combination of the metal-bound SO_Y²⁻ species with mono-dentate and bi-dentate binding configurations. Apart from exhibiting moderate tolerance to hydrothermal aging, S400 was also validated to improve its resistance to alkali-metal, H₂O, SO₂, (NH₄)₂SO₄, or (NH₄)HSO₄ in comparison to its SO_Y²⁻-unfunctionalized counterpart, S300, and S500.