Sulfation enabled dynamic activation and single-atom extraction forming Pt1-SO4 motif against SO2 poisoning

The sulfate formation from the residual SO2 in the industrial exhaust has long been recognized as the primary cause of sulfur poisoning in the oxidative removal of volatile organic compounds (VOCs). Contrary to the conventional understanding, here we showed in situ sulfation enables dynamic activation of Pt1/MnxTi1-xO2 single atom catalysts against sulfur poisoning, forming dynamically Pt1/MnSO4 with highly active Pt1-SO4 motif that results in excellent benzene oxidation of 6.3×10-6 mol·g-1 cat·s-1 in presence of 100 ppm SO2 at 240 °C, and unprecedented SO2-resistant stability up to 300 h. State-of-the-art in situ characterizations along with density functional theory (DFT) calculations, clearly revealed dynamic transformation of two distinct sulfur oxo-salts from chemisorbed (SO3)ads sulfite to SO42- sulfate during reaction and their specific role in SO2 resistant benzene oxidation. The as-formed (SO3)ads adsorbates blocked the Pt sites on MnxTi1-xO2 consequently resulting in irreversible deactivation. In contrast, in situ sulfation promoted the dynamic activation of poisonous (SO3)ads into SO42- sulfate, and simultaneously enables Pt single-atom extraction from MnxTi1-xO2 onto the as-formed MnSO4 sulfate. In situ DRIFTS measurements further revealed that the square-planar Pt1-SO4 motif on the as-formed Pt1/MnSO4 can effectively prevent the SO2 adsorption, preserving highly exposed Pt single-atom sites for deep oxidation of benzene to carboxylate. This work provides dynamic insights for sulfation of Pt single-atom catalyst against SO2 poisoning, and benefits the general design of Pt1-SO4 motif for SO2 resistant oxidation of a broad range of VOCs, including benzene, propane and ethylene.