The substitution of the toxic mercuric chloride catalyst in polyvinyl chloride production via acetylene hydrochlorination is an imperative step to reduce the environmental impact of this long-established industrial technology.¹ In this context, merging fundamental and applied research to derive structure-activity relations of promising metal-based catalysts (Au, Ru, Pt, Ir, and Rh) is key to guide the development of a more sustainable process. For this purpose, we synthesized a platform of metal nanostructures, ranging from single atoms with tunable oxidation state to metallic nanoparticles, by varying the structure of functionalized carbon and controlled thermal activation. Combining advanced characterization techniques, steady-state experiments, density functional theory, and mechanistic studies, we identified two main catalyst families, (i) Au-, Pt- and (ii) Ru-, Ir-, Rh-based systems, which show fundamental differences regarding the structure of the active site (single atoms versus nanoparticles, Figure 1) and the prevailing deactivation mechanisms (single atom agglomeration versus nanoparticle re-dispersion). With this understanding, we developed system-oriented optimization strategies, including single-layer graphene encapsulation of metal nanoparticles to prevent undesired re-dispersion and oxygen co-feeding to inhibit coke formation at the metal sites, fostering the design of high-performance hydrochlorination catalysts.²

Figure 1 Single atoms versus nanoparticles as the active site in acetylene hydrochlorination.

[1] R. Lin, A. P. Amrute, J. Pérez-Ramírez, Chem. Rev. 2017, 117, 4182.
[2] K. Kaiser, R. Lin, S. Mitchell, E. Fako, F. Krumeich, R. Hauert, O. V. Safonova, V. A. Kondratenko, E. V. Kondratenko, S. M. Collins, P. A. Midgley, N. López, J. Pérez-Ramírez, Chem. Sci. 2019, 10, 359.