C–H Bond Activation of Methane via σ–d Interaction on the IrO₂(110) Surface: Density Functional Theory Study

Abstract

The adsorption and dissociation of methane on the IrO 2 (110) surface were investigated by density functional theory calculations. The adsorption energy of methane obtained in this study is −0.41 eV on the stoichiometric surface and −0.63 eV on the oxygen-rich surface, which are significantly higher than those calculated recently on other different catalytic systems. Analyses from density of states and electron density difference show a special interaction between the C−H bonding orbital and the d z 2 orbital of surface iridium atom. In addition, the first hydrogen atom abstraction of methane by the IrO 2 (110) surface is a reaction with low barrier and high exothermic energy. The lower reaction barrier than the desorption energy indicates that the IrO 2 (110) surface could provide not only high sticking coefficient but also high turnover frequency in methane dissociation reaction.

Ethylene formation by methane dehydrogenation and C–C coupling reaction on a stoichiometric IrO2 (110) surface – a density functional theory investigation

“…These results strengthen the prediction that CH 4 dissociation is more preferable than the desorption on the IrO 2 (110) surface. 41 These results also support the prediction of Weaver 55 that the dissociation process probably occur at temperatures lower than 150 K.…”

“…53,54 The conventional DFT calculation with the PBE functional gives the CH 4 binding energy of 0.41 eV, which is similar to the value reported by the PW91 functional. 41 When considering DFT with van der Waals correction, the binding energy increases to 0.76 eV, which is 0.10 eV higher than the estimated value reported by Weaver. 55 Non-local interaction of 0.35 eV is indeed important when studying the interaction between CH 4 and the IrO 2 (110) surface.…”

“…Likewise, Ir cus on the IrO 2 (110) surface is also expected to act in a similar manner as Pd cus in activating methane. 39,40 By using density function theory calculations, Wang and co-workers 41 reported that CH 4 is significantly activated when they are molecularly adsorbed on the IrO 2 (110) surface through an agostic interaction between the C-H bonding orbital and the d z 2 orbital of a surface Ir cus atom. This unique σ-d interaction weakens Ir-coordinated C-H bonds, making the barrier for C-H bond cleavage notably lower than the CH 4 desorption energy, suggesting that the trappingmediated mechanism is the preference of CH 4 dissociation at mild temperature on the IrO 2 (110) surface.…”

B, N‐co‐doped graphene‐supported Ir and Pt clusters for methane activation and C─C coupling: A density functional theory study

“…Graphene, co‐doped with B and N, has attracted attention as a supporting material because it increases metal dispersion, enhances chemical stability and electrical conductivity, and minimizes the cost of metals . The B and N‐co‐doped graphene can be synthesized experimentally at different concentrations, although the synthesis of B‐doped graphene or N‐doped graphene is challenging; in addition, the application of B and N to tune up the band gap of graphene at the Fermi level is difficult .…”

“…The B and N‐co‐doped graphene can be synthesized experimentally at different concentrations, although the synthesis of B‐doped graphene or N‐doped graphene is challenging; in addition, the application of B and N to tune up the band gap of graphene at the Fermi level is difficult . Furthermore, previous studies have demonstrated that methane can be molecularly adsorbed on the IrO 2 (110) surface and supported Ir clusters through agostic interactions . These agostic interactions help to weaken the metal coordinated C‐H bonds, which, in turn, help to lower the barrier of the C─H bond cleavage.…”