Unveiling the crucial active sites responsible for CO, n-heptane, and toluene oxidation over Pt/ZrO2 catalyst

Abstract

The surface Pt species and adsorbed oxygen on the Pt/ZrO2 catalyst were successfully modulated by altering the preparation methods, resulting in distinct catalytic behaviors for CO, n-heptane, and toluene oxidation. The Pt/ZrO2 catalyst was initially prepared via wetness impregnation and subsequently reduced in an H2 atmosphere to obtain the Pt/ZrO2-R catalyst. In contrast, the Pt/ZrO2-E catalyst was synthesized using ethanol solvent (also serving as a reducing agent) instead of water during wetness impregnation. Moreover, the pre-prepared Pt nanoparticles were loaded onto the ZrO2 surface using polyvinylpyrrolidine (as a protective and structure directing agent) dissolved in ethanol solvent to fabricate the Pt/ZrO2-EP catalyst. Among these catalysts, the Pt/ZrO2-R exhibits superior catalytic activity towards CO oxidation due to its abundant metallic Pt species. It is found that activity of Pt/ZrO2 catalyst for n-heptane oxidation is positively correlated with its surface adsorbed oxygen concentration, thus the highest activity is achieved over the Pt/ZrO2-EP catalyst possessing a higher concentration of surface adsorbed oxygen species. Unlike CO and n-heptane oxidation, toluene oxidation activity is affected by multiple factors, it is primarily promoted by synergistic catalysis between metallic Pt species (Pt0) and surface adsorbed oxygen species over the Pt/ZrO2-EP catalyst. Our preliminary findings underscore that precise modulation of sensitive active sites on surfaces plays a critical role in specific catalytic reactions.