Pt/Al2O3 catalysts are widely used as oxidation catalysts for emissions control. Oxidation reactions over Pt/Al2O3 catalysts typically follow redox mechanisms, involving changes in the oxidation state of Pt. Global kinetic models without considering the redox of Pt sites do not accurately capture the underlying catalytic chemistry. The oxidation state of Pt is challenging to track under operando conditions. On the other hand, spectroscopic methods, such as X-ray absorption near edge structure (XANES) are resource-consuming and require specialized equipment. In this study, we present a simplified reactor-based nitric oxide temperature programmed reduction (NO-TPR) method to track the oxidation state of Pt over Pt/Al2O3 oxidation catalysts. Integral NO2 formation during NO-TPR correlates with the number density of PtOx on the catalyst, supported by inductively coupled plasma optical emission spectroscopy (ICP-OES) and CO-chemisorption results. The NO-TPR method is further verified on catalysts with varying Pt loading. The NO-TPR method enables tracking the oxidation state of Pt over Pt/Al2O3 catalysts under reaction conditions.

Nitric oxide temperature programmed reduction (NO-TPR) for quantification of PtOx on Al2O3-supported oxidation catalysts

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