Paper HC+2D+SS-WeM2
Selective Alkane Chemistry on IrO₂(110) Surfaces

Wednesday, October 23, 2019, 8:20 am, Room A213

Selective conversion of alkanes to higher value species using heterogeneous catalysts is of great interest with the increasing availability of light alkanes from shale fracking. We have used a combination of temperature programmed reaction spectroscopy (TPRS) and density functional theory (DFT) to demonstrate that the stoichiometric terminated IrO₂(110) surface can activate methane and ethane below room temperatures, and furthermore, that this surface can be selective towards ethane dehydrogenation to ethylene. For ethane, DFT shows that adsorption and initial C-H bond cleavage to surface bound C₂H₄* is facile and the selectivity step occurs between further C-H bond breaking leading to complete oxidation versus ethylene desorption. The reactivity of this surface is mediated by the presence of undercoordinated Ir (Ir_cus) and adjacent bridge O atoms (O_br). Using the combination of TPRS and DFT we find that pre-hydrogenating the IrO₂(110) surface results in the formation of HO_br sites that increases the selectivity towards ethylene by increasing the barrier to C-H bond cleavage for C₂H₄* and decreasing the desorption energy of C₂H₄*. We will discuss efforts to use DFT and microkinetic modeling to explore doping strategies of both the Ir_cus and O_br sites to promote selectivity towards ethylene formation.