Bulk (in)stability as a possible source of surface reconstruction

Abstract

A density functional theory study is presented addressing the surface energy stabilization mechanisms of transition metal carbide and nitride surfaces of a crystal structure different from that of the most...

Size and Stoichiometry Effects on the Reactivity of MoCy Nanoparticles toward Ethylene

“…Thus, the C 2 H 4 E ads binding strength decays as β-Mo 2 C­(001)-Mo ≈ NPs > β-Mo 2 C­(001)-C > δ-MoC(001). Notice that for the latter the most stable reconstructed surface has been used as reference . Interestingly, the reported values for C 2 H 4 adsorption energy on a Pt(111) surface, −1.78 eV, and on Pt x ( x = 7–10) clusters, ranging from −1.4 to −1.7 eV, , are within the range found in this work for the MoC y NPs.…”

“…However, one must advert that in 38% of NPs the adsorption conformations for both first and second most stable adsorption modes should be thermally accessible at the high temperatures typical in catalytic experiments, particularly for Notice that for the latter the most stable reconstructed surface has been used as reference. 21 Interestingly, the reported values for C 2 H 4 adsorption energy on a Pt(111) surface, −1.78 eV, 45 and on Pt x (x = 7−10) clusters, ranging from −1.4 to −1.7 eV, 48,49 are within the range found in this work for the MoC y NPs. Notice that the adsorption energy on platinum clusters and the Pt(111) surface is very similar, which is in agreement with their similar catalytic performance toward ethylene hydrogenation.…”

“…20 The good performance of molybdenum carbides in catalysis has triggered new research aimed at investigating their possible improvement by nanostructuring. Recently, Figueras et al 21 presented experimental and theoretical evidence that MoC y nanoparticles supported on Au(111) can dissociate methane at room temperature. Additionally, this inverse catalyst system appears to be a good candidate for hydrogenation reactions as H 2 can easily dissociate and be stored on the supported nanoparticles 22 in a rather broad temperature range.…”

Adsorption and Activation of CO2 on Nitride MXenes: Composition, Temperature, and Pressure effects

“…This indicates that the chemistry of the hard‐to‐prepare TMN (111) can be more easily studied using the corresponding nitride MXenes. Before closing the discussion regarding adsorption energies, it is worth mentioning that the presence of the CO 2 on the (001) and (111) CrN, MoN, and WN surfaces promotes superficial deformations inducing reconstruction which has been attributed to the fact that the rock‐salt polymorph of these nitrides is not the most stable one [38] …”

“…Before closing the discussion regarding adsorption energies, it is worth mentioning that the presence of the CO 2 on the (001) and (111) CrN, MoN, and WN surfaces promotes superficial deformations inducing reconstruction which has been attributed to the fact that the rock-salt polymorph of these nitrides is not the most stable one. [38] The large adsorption energy of CO 2 on the (0001) nitride MXene surfaces is accompanied by a considerable charge transfer from the substrate towards CO 2 which we estimate by adding the net Bader charge in the atoms of the adsorbed molecule. To explore whether a large adsorption energy is coupled to a large charge transfer with a concomitant CO 2 activation we computed the topological Bader charge, Q, of the CO 2 molecule and plotted it versus E ads , see Figure 3.…”