Kinetics of the activated dissociative adsorption of methane on the low index planes of nickel single crystal surfaces

Abstract

We have measured the kinetics of the methane decomposition reaction on Ni(111), Ni(100), and Ni(110) single crystal surfaces under the high incident flux conditions of 1 Torr methane. We find for these processes apparent activation energies of 12.6, 6.4, and 13.3 kcal mol−1, respectively. Initial methane sticking coefficients at 500 K vary with the Ni surface, but are all ∼10−8 to 10−7. The Ni(110) surface is the most active, followed by Ni(100) and Ni(111). A large (∼ factor of 20) kinetic isotope effect is seen for CH4 vs CD4 on the Ni(100) surface, whereas none is seen on the Ni(110) surface. A comparison is made between measured thermal sticking coefficients and those calculated from the results of recent molecular beam experiments of CH4 on Ni(111) and Ni(100) surfaces. Agreement of our results with the Ni(100) beam results is poor, whereas agreement with the Ni(111) beam results is very good. A comparison is also made between our results and rates of the catalytic steam reforming reaction of methane.

Conversion of CO2to CO with CH4over Ni/SiO2Catalyst: Photoacoustic Measurements of Reaction Rate

“…9 Osaki et al 10 and Sakai et al 11 reported the activation energy of 13 kcal/mol for the CH 4 consumption in the CO 2 reforming of methane over Ni/SiO 2 catalyst, which was very close to the value of 11.1 kcal/mol obtained in this work. Generally the activation energy for the CO 2 consumption in the CO 2 -CH 4 reaction is somewhat lower than that for the CH 4 consumption.…”

Mechanisms for catalytic carbon nanofiber growth studied byab initiodensity functional theory calculations

“…The decomposition preferentially takes place in the vicinity of low-coordinated metal surface atoms such as stepedge atoms. 16,25,26 For methane, the activation of the first C-H bond is rate-limiting for the decomposition and it is associated with an activation energy barrier, obtained from DFT, of less than 1 eV at the undercoordinated step sites on Ni. 16,27 The decomposition barrier is less than the barriers we identify for graphene growth, and methane decomposition will, therefore, not be considered further in the following.…”

Kinetic Investigation of CO2Reforming of CH4over Ni Catalyst Deposited on Silicon Wafer Using Photoacoustic Spectroscopy

“…The Ni (111) plane is not active for the CO2 dissociation, 12 but active for the CH 4 dissociation. 13 Hence, the CH 4 dissociation is believed to occur prior to the CO2 dissociation over the present catalyst. Although there are some disagreements in the reaction mechanism of catalytic CO2-CH4 reaction, it is generally accepted that methane is dissociatively adsorbed on the surface of the metal catalyst to form both CHx fragment and H(ads) 1,14 : CH 4 (g) ⇌ CH x (ads) + (4-x) H (ads).…”