(681e) Tuning Single Atom Catalyst - Support Interactions for Facile Methane Activation

As we transition away from the use of petroleum, it will become necessary for chemical industry to find alternative ways to produce platform chemicals. Methane (CH₄) is a molecule that could be upgraded into platform chemicals, but direct conversion technologies are needed. Methane activation is quite challenging due to the stable nature of this symmetric molecule; catalyst design first focuses on the need to break the first C-H bond of methane to allow for further reaction. Single atom catalysts (SACs) can selectively activate methane for further conversion, such as through nonoxidative C-C coupling processes. The rationale selection of SAC-support combination to facilitate C-H dissociative adsorption remains unclear. Here, we probe the effect of support on the catalytic activity of Pt SACs for methane activation using density functional theory (DFT). Depending on the choice of support, the energy barrier for methane activation can vary from barrierless to 1 eV, despite use of the same Pt single atom catalyst. The activation barrier depends on a variety of factors including coordination environment, Pt oxidation state, energetic and spatial location of frontier orbitals. The supported Pt atom oxidation state plays an especially important role in dictating the Pt adatom activity. Generally, neutrally charged Pt adatoms are better at activating methane than either positive or negatively charged species, though this correlation is imperfect due as the additional descriptors also impact reaction energetics. The DFT dataset on Pt includes a series of doped and undoped oxide supports, and extension to other SAC/support combinations is discussed in the search for descriptors that predict methane conversion activity.