Autor/a:
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Kaiser, Selina K.; Lin, Ronghe; Mitchell, Sharon; Fako, Edvin; Krumeich, Frank; Hauert, Roland; Safonova, Olga V.; Kondratenko, Vita A.; Kondratenko, Evgenii V.; Collins, Sean M.; Midgley, Paul A.; López, Núria; Pérez-Ramírez, Javier
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Abstract:
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Carbon-supported gold catalysts have the potential to replace the toxic mercuric chloride-based system
applied industrially for acetylene hydrochlorination, a key technology for the manufacture of polyvinyl
chloride. However, the design of an optimal catalyst is essentially hindered by the difficulties in assessing
the nature of the active site. Herein, we present a platform of carbon supported gold nanostructures at
a fixed metal loading, ranging from single atoms of tunable oxidation state and coordination to metallic
nanoparticles, by varying the structure of functionalised carbons and use of thermal activation. While on
activated carbon particle aggregation occurs progressively above 473 K, on nitrogen-doped carbon gold
single atoms exhibit outstanding stability up to temperatures of 1073 K and under reaction conditions. By
combining steady-state experiments, density functional theory, and transient mechanistic studies, we
assess the relation between the metal speciation, electronic properties, and catalytic activity. The results
indicate that the activity of gold-based catalysts correlates with the population of Au(I)Cl single atoms
and the reaction follows a Langmuir–Hinshelwood mechanism. Strong interaction with HCl and
thermodynamically favoured acetylene activation were identified as the key features of the Au(I)Cl sites
that endow their superior catalytic performance in comparison to N-stabilised Au(III) counterparts and
gold nanoparticles. Finally, we show that the carrier (activated carbon versus nitrogen-doped carbon)
does not affect the catalytic response, but determines the deactivation mechanism (gold particle
aggregation and pore blockage, respectively), which opens up different options for the development of
stable, high-performance hydrochlorination catalysts |