Inhibitory effects of residual Cl− on the NO + CO reaction over a supported Pt catalyst†

H₂PtCl₆·6H₂O is a widely used platinum precursor, but it can form residual chlorine on catalysts' surface. This study explores the effects of residual Cl⁻ on the NO + CO reaction and demonstrates that the presence of Cl⁻ is detrimental to the reaction performance of CeO₂-supported Pt catalysts. Residual Cl⁻ has negligible effect on the dispersion state of the catalytically active Pt component, and it exerts profound effects on tuning the NO dissociation and CO adsorption abilities of the Pt catalyst. The reduction of NO over the Cl-containing Pt catalyst (Cl–Pt/CeO₂) initiating at high temperature can be attributed to fewer oxygen vacancies on its surface, which are not conducive to the dissociation of NO, in contrast with the Pt/CeO₂ catalyst. In addition, CO interacts strongly with anchored Pt²⁺, and NO occupies fewer Pt²⁺ sites in the Cl–Pt/CeO₂ catalyst. Hence, fewer NO dissociation sites are present on the Cl–Pt/CeO₂ catalyst, deteriorating NO + CO reaction performance. This work paves a way to comprehensively understand the influence of residual Cl⁻ on the NO + CO reaction and can provide insights for selecting suitable metal precursors to avoid harmful interference from residues.