C-H activation is an important step in a range of chemistries from bench top synthesis to megaton per year chemical conversions. Furthermore, the recent availability of shale gas has created an urgent need for C-H activation heterogeneous catalysts that are both active and stable. Elements like Pt, Pd and Ni are capable of activating C-H bonds, but the catalysts themselves are highly susceptible to deactivation via carbon buildup (coking). Cu on the other hand has a high energetic barrier to C-H activation but is not susceptible to coking due to its ability to perform C-C coupling chemistry. We have taken a new approach to C-H activation by alloying very small amounts of Pt in Cu, which is dispersed at the single atom limit. We find that these PtCu Single-Atom Alloys catalyze C-H/C-D exchange reaction at 250°C compared to 550°C on Cu nanoparticles, and most importantly, are stable during the conversion of butane to butene and hydrogen. Pt nanoparticles activate the reaction at temperatures as low as 100°C, but quickly deactivate. Temperature programmed oxidation revealed significant carbon buildup on the Pt nanoparticles while none was observed on the PtCu single-atom alloy catalysts. These findings, taken collectively with our surface science studies and simulations, illustrate that PtCu single-atom alloys are promising catalysts for C-H bond activation in small alkanes at moderate temperatures, and can be further developed as robust catalysts resistant to coking that plagues traditional Pt, Pd and Ni catalysts. Furthermore, our study constitutes a rare example of translating the results of single crystal studies to the design of a practical catalyst.

Single-atom alloy catalysis for coke-free non-oxidative alkane dehydrogenation

ACS Fall 2021

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