Dilute PdAu alloy catalysts are selective for a number of oxidative and hydrogenation reactions, but their selectivity is highly sensitive to pre-treatment conditions, which indicates a dynamic surface composition. Their dilute nature means that the surface composition and distribution is difficult to resolve even using high resolution spectroscopic and microscopic techniques (e.g. XAS, TEM). A direct method for probing the state of a catalyst surface is to titrate active species using quantified pulses of reactants. We quantitatively determine a three-fold increase in Pd site density on the surface of a dilute Pd<sub>0.08</sub> Au<sub>0.92</sub> alloy by titrating the oxidised surface with CO. Further, the pulses demonstrate that two active surfaces exist during the titration experiment.

Quantifying oxygen induced surface enrichment of a dilute PdAu alloy catalyst

ACS Spring 2022

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