Unveiling the promotional performance of CO oxidation over Na-doped Pt-0.5P&W/TiO2 catalyst: "SMSI" effect of Na in catalysis

The dopant WO3 of the catalyst Pt-0.5P&W/TiO2 enhanced the SO2 resistance of the catalyst for CO oxidation in sintering waste gas, but it also had an impact on strong metal-support interactions (SMSI), which decreased the CO catalytic activity. Adding alkali metal Na to Pt-0.5P&W/TiO2 can effectively improve the CO catalytic performance. The Pt-O-Na bond replaced the Pt-O-Ti bond, allowing Na to act as an electron and structure promoter instead of TiO2 to contribute the electronic and synergistic effects in catalysis. XPS and EPR date indicated that the positively charged group centered on Pt adsorbed hydroxyl groups by electrostatic interaction, which coacted with Na to form Pt-Ox(OH)yNa. In situ infrared data indicated that Na promoted the electron density on the Pt surface leading to the disproportionation of CO on the Pt surface to produce inactive C*. The production of C* facilitated the adsorption and activation of O2 by blocking the single-layer adsorption of CO on Pt. The active oxygen species adsorbed on the catalyst surface increased the CO activity of the catalyst. In sulfur-containing flue gas conditions, SO2 reacted with Na around Pt to generate sodium sulfate, which enhanced the local acidity of the active site and the sulfur resistance of the catalyst.