Insights into the synergistic role of metal–lattice oxygen site pairs in four-centered C–H bond activation of methane: the case of CuO

Abstract

Of the three mechanisms for activation of methane on copper and copper oxide surfaces, the under-coordinated Cu–O site pair mediated mechanism on CuO surfaces has the lowest activation energy barriers.

Investigating metal oxides for C1 chemistry : a computational and experimental study

“…However, work done by Huang et al 88 to determine the influence of U-value on CO adsorption on Cerium oxide showed that the inclusion of the adsorbate-surface interaction and adsorption configurations in the DFT+U calculations lead to a better and relevant estimate of U-value in catalysis applications involving strongly correlated systems. (ii) DFT computed energy values were compared to the thermodynamic enthalpy data taken from standard thermodynamic tables which are non-surface specific and ignore the role and influence of active surfaces in the reaction chemistry (e.g., lattice oxygen binding strength on different facets of CuO will affect reaction enthalpy when lattice oxygen is consumed in the reaction via the Mars van Kreevelan mechanism [93][94] ). (iii) When a catalytic surface is formed, the breaking of z symmetry of the bulk phase leads to surface strains, defects, and a different atomic coordination from the bulk.…”

“…2.4d). Since the under coordinated surface sites are the active sites of the CuO surface [93][94] , the H2 dissociation products on the less active surface sites (saturated Cu4 and O4 surface sites) was not evaluated.…”

“…In (i), methane was passed over dry CuO surface at the 300° C, which is high enough to activate the first C-H bond with energy barriers 94 of 76.6 kJ mol -1 , as per the following reaction:…”

“…The clean structure of CuO (111) involves different types of Cu and O atoms on the surface. 51,113,119,121,[144][145] the 4-coordinated site (Osub) and the 3-coordinated site (Osuf), and the latter is also the active site for many reactions. 51,113,119 The structure of clean CuO (111) surface is shown in Fig.…”

“…Transition metal oxides (TMOs) are widely used in the form of pure, supported, and zeolite incorporated structures as catalysts for various industrially important reactions like chemical looping combustion, 27,110 selective oxidation, [111][112][113][114][115][116][117] and dehydrogenation of hydrocarbons to produce multiple highvalue chemicals. [117][118][119] Catalytic performance of TMOs for a particular reaction or a product is an interplay between (i) surface characteristics, such as the degree of unsaturated sites, acid-base characteristics, facet distribution (presence of one or more dominant facets), 51,119 lattice oxygen binding energies, ease of vacancy formation, presence of cationic or anionic vacancies, and the type and degree of doping…”