Unveiling the Catalytic Merits of LaV₃O₉ over Conventional LaVO₄ Polymorphs to Boost Desired Kinetics of Humid NO_X Reduction and Poison Disintegration

SO_Z^2- (Z = 3-4)-functionalized metal vanadates vary with the type of metal cations (Mⁿ⁺) for the Mⁿ⁺-O^2--V⁵⁺ channels that fragment to impart Brönsted acidic bonds (BA^--H⁺; SO_Z^2--H⁺) and labile/mobile oxygens (O_L/O_M) with distinct populations and affinities for NO_X/O₂/H₂O/SO₂. SO_Z^2--modified Mⁿ⁺-O^2--V⁵⁺ fragments bind with NH₃ to activate Eley-Rideal (ER)-type selective catalytic NO_X reduction (SCR), yet, hardly enable O_L coordination with NO_X and are often hydrophilic, thereby limiting the activities of SCR or ammonium (bi)sulfate (AS/ABS) fragmentation, as gauged by the NO_X consumption (-r_NOX) and AS/ABS degradation rates (-r_AS/ABS), respectively. Here, we justified the use of nonreducible La³⁺-containing La³⁺-O^2--V⁵⁺ channels, whose merits in accelerating SCR and AS/ABS fragmentation were found to be more pronounced for SO_Z^2--modified LaV₃O₉ (LaV₃O₉-S) than for conventional/polymorphic LaVO₄ analogues (LaVO₄-S). Besides activating the ER-type SCR, LaV₃O₉-S bound with NO and activated Langmuir-Hinshelwood-type SCR, as opposed to LaVO₄-S. The pre-exponential factor (k′_APP,0) and -r_NOX were thus higher for LaV₃O₉-S than for LaVO₄-S and were coupled with the greater amount of O_M in the former, leading to superior SCR performance under wet gases. Moreover, compared to LaV₃O₉-S, its Sb₂O₅-promoted analogue (LaV₃O₉-Sb₂O₅-S) provided a larger number of NH₃-accessible BA^--H⁺ bonds to achieve higher k′_APP,0/-r_NOX alongside higher O_M mobility. Furthermore, the LaV₃O₉-S and Sb₂O₅-S of LaV₃O₉-Sb₂O₅-S elevated the hydrophobicity and number of ABS-accessible BA^--H⁺ bonds, respectively. LaV₃O₉-Sb₂O₅-S thus revealed a lower energy barrier and higher k′_APP,0 in AS/ABS pyrolysis than a commercial control (V₂O₅-WO₃-S), resulting in a higher -r_AS/ABS for the former. Consequently, LaV₃O₉-Sb₂O₅-S displayed superior SCR performance and greater hydrothermal resistance under SO₂-containing wet gases in comparison with V₂O₅-WO₃-S.