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Replacement of Hg with non-toxic Au based catalysts for industrial hydrochlorination of acetylene to vinyl chloride is urgently required. However Au catalysts suffer from progressive deactivation caused by auto-reduction of Au(I) and Au(III) active sites and irreversible aggregation of Au(0) inactive sites. Here we show from synchrotron X-ray absorption, STEM imaging and DFT modelling that the availability of ceria(110) surface renders Au(0)/Au(I) as active pairs. Thus, Au(0) is directly involved in the catalysis. Owing to the strong mediating properties of Ce(IV)/Ce(III) with one electron complementary redox coupling reactions, the ceria promotion to Au catalysts gives enhanced activity and stability. Total pre-reduction of Au species to inactive Au nanoparticles of Au/CeO2&AC when placed in a C2H2/HCl stream can also rapidly rejuvenate. This is dramatically achieved by re-dispersing the Au particles to Au(0) atoms and oxidising to Au(I) entities, whereas Au/AC does not recover from the deactivation.

Vulcan carbon was pre-treated at 850 o C at a ramp rate of 5 o C/min and maintained for 24 hours under 5% H2 in Ar. Cs-Ru modified MgO and AC preparationTypically, Ru3(CO)12 was dispersed in THF for 2 hours under sonication. The mixture was then transferred to the MgO or activated carbon (AC) and allowed to sonicate at ambient

Altering the exposed facet of CeO2 nanocrystallites and hence the control of surface chemistry on the nano level have been shown to significantly change their performances in various catalytic reactions. The chemical state of surface Ce, which is associated with Lewis acidity and hence the adsorption/activation energy of reactants on the surface, is expected to vary with their hosted facets. Unfortunately, traditional surface tools fail to differentiate/quantify them among hosted facets and thus have led to different interpretations among researchers in the past decades. Herein, probe-assisted nuclear magnetic resonance is employed for the surface investigation of different CeO2 facets. They not only allow differentiation of the surface Ce atoms between hosted facets at high resolution but can also provide their corresponding concentrations. The as-established facet fingerprint of CeO2 can thus report on the facet distribution/concentration of a given CeO2 sample. Dephosphorylation and H2O2 reduction were tested as probe reactions to demonstrate the importance of obtaining comprehensive surface Ce information for the active site identification and the rational design of CeO2-based catalysts. Around 1000 and 4500% increase in activity of those reactions can be easily achieved on pristine CeO2 without further surface engineering when its terminal facet is wisely chosen. Our results thus imply that the basic surface knowledge of even a simple catalyst can be more important than the continuous development of their fancy derivatives without clear guidance.

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