Issue Date: January 15, 2018
Activating C–H bonds with isolated atoms
Sprinkling individual platinum atoms across a copper surface yields an energy-efficient and durable bimetallic catalyst that effectively mediates reactions involving C–H bond activation, according to a study (Nat. Chem. 2018, DOI: 10.1038/nchem.2915). Breaking C–H bonds is the first step in converting relatively inert compounds such as methane and other alkanes to more valuable fuels and chemicals.
Industrial processes for carrying out this type of chemistry are well developed. Many manufacturers rely on steam cracking, for example, to convert ethane to ethylene. But that process is energy intensive. Catalysts can mediate C–H-activation chemistry and reduce the required energy input, but they have shortcomings.
Platinum, for example, can dramatically reduce the temperature for C–H activation, but it is expensive. Nickel, which is relatively inexpensive, also works as a C–H activation catalyst, but both it and platinum are prone to coking, a process that generates a film of carbon (coke) that gunks up the catalyst surface and blocks reagents’ access to catalytic sites. Copper resists coking but it is a weak catalyst.
So in a follow-up to earlier work with single-atom catalysts, E. Charles H. Sykes and Maria Flytzani-Stephanopoulos of Tufts University and Michail Stamatakis of University College London conducted catalytic reaction tests on methyl groups, methane, and butane using copper surfaces dotted with isolated platinum atoms. The team found that compared with pure copper, the bimetallic catalysts avoid coking and lower the C–H activation temperature by 100 °C or more depending on the reaction. The bimetallic catalysts address the platinum cost problem by using the metal as sparingly as possible on the copper surfaces.
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