Young Brett T, Pathan Md Afjal Khan, Jiang Tao, Le Duy, Marrow Nikki, Nguyen Trong, Jordan Cody E, Rahman Talat S, Popolan-Vaida Denisia M, Vaida Mihai E
Department of Chemistry, University of Central Florida, Orlando, Florida 32816, USA.
Department of Physics, University of Central Florida, Orlando, Florida 32816, USA.
J Chem Phys. 2020 Feb 21;152(7):074706. doi: 10.1063/1.5129712.
Rational design of novel catalytic materials used to synthesize storable fuels via the CO hydrogenation reaction has recently received considerable attention. In this work, defect poor and defect rich 2D-MoS as well as 2D-MoS decorated with Mo clusters are employed as catalysts for the generation of acetylene (CH) via the CO hydrogenation reaction. Temperature programmed desorption is used to study the interaction of CO and H molecules with the MoS surface as well as the formation of reaction products. The experiments indicate the presence of four CO adsorption sites below room temperature and a competitive adsorption between the CO and H molecules. The investigations show that CO hydrogenation is not possible on defect poor MoS at low temperatures. However, on defect rich 2D-MoS, small amounts of CH are produced, which desorb from the surface at temperatures between 170 K and 250 K. A similar CH signal is detected from defect poor 2D-MoS decorated with Mo clusters, which indicates that low coordinated Mo atoms on 2D-MoS are responsible for the formation of CH. Density functional theory investigations are performed to explore possible adsorption sites of CO and understand the formation mechanism of CH on MoS and Mo/MoS. The theoretical investigation indicates a strong binding of CH on the Mo sites of MoS preventing the direct desorption of CH at low temperatures as observed experimentally. Instead, the theoretical results suggest that the experimental data are consistent with a mechanism in which CHO radical dimers lead to the formation of CH that presents an exothermic desorption.
