Molecular orbital studies of the adsorption of CH3, CH2, and ch on Rh(111) and Ni(111) surfaces

Chemisorption and Transformation of CHx Fragments (x = 0−3) on a Pd(111) Surface: A Periodic Density Functional Study

“…The order in chemisorption energy is the following, where H has been taken from ref and this is in general agreement with all cluster calculations on Ni(111). Concerning binding sites for CH x species, the simple picture that emerges from our calculations is that the surface metal coordination of the CH x fragments tends to restore the tetravalency of carbon in agreement with the picture of bonding between CH x and a metal surface drawn from previous extended Hückel calculations on Pt and Rh. − This contrasts, however, with the results of ab initio cluster calculations where all species were found on the hollow site for Ni(111). − The DFT calculations on Ni(111) agree for the top site for CH 3 but suggest a hollow site for CH 2 . It should be noted, however, that the hollow site in our calculations is less stable by only 0.07 eV for CH 3 and 0.14 eV for CH 2 .…”

“…Quantum chemistry is a technique of choice in order to address these structural and energetic problems. The chemisorption of CH x fragments has been studied by extended Hückel type methods on Ni(111), Rh(111), , and Pt(111). , In all cases, the hydrocarbon fragments show a configuration that optimizes hybridation and tends to complete carbon tetravalency: CH 3 is on a top site, CH 2 favors a 2-fold site, and CH and C are in 3-fold sites. The case of Ni(111) was later adressed by first-principle calculations, the surface being modeled by a cluster.…”

Study on Methane Conversion to Synthesis Gas over Nano Pt/MgO Catalysts: II. Characterization of Pt-IV Catalysts

“…show that the Pt-IV catalysts are active for carbon dioxide reforming of CH 4 , and the higher the Pt loading, the higher the activity. Minot et al [16] and Koster and van Santen [17] have studied the adsorbed CH x fragments on Pt (111) using variations of the extended Hückel method, and their results showed that CH x fragments were preferentially located at tetravalent sites on the metal surface; i.e. the decomposition of CH 4 into CH x fragments (1≤x≤3) on Pt(111) should follow the general stoichiometry, CH x+1 -(3-x) M + 2 M → CH x -(4 -x) M + H-M, where M was a surface metal atom.…”

Review of Plasma-Assisted Catalysis for Selective Generation of Oxygenates from CO2 and CH4

“…The CH x radicals in CH 4 plasma may also be adsorbed to catalyst surfaces. According to studies over Rh, Ni, and Pd surfaces, adsorbed CH 3 is much more stable compared to adsorbed CH and CH 2 . − On the surface of metal oxides (e.g., TiO 2 ), CH 3 and CH 2 mainly adsorb at the oxygen vacancies, while CH adsorbs both away from and at these vacancy sites . In the surface reactions that follow, the adsorbed CH 3 and CH 2 participate as reactive intermediates, while CH contributes little due to its low concentration and short lifetime. , …”