TAME -a Quantum Mechanics Study of the Reaction Mechanism for Methoxylation of Isoamylenes

The present paper describes the quantum mechanics study regarding a tertiary-alkyl methyl ether synthesis mechanism. As octane number boosters, ethers such as TAME (2-methoxy-2-methylbutane) represent a solution for increasing the amount of oxygen in gasolines and for decreasing their isoamylenes content, for more environmentally-friendly fuels. The quantum mechanics modeling targeted the elucidation of the isoamylenes methoxylation mechanism, defining the transition states involved in the reaction of 2-methyl-2-butene (2M2B) with methanol, using benzenesulfonic acid to simulate cation-exchange resins catalytic involvement

Role of the Band Gap for the Interaction Energy of Coadsorbed Fragments

Understanding the interaction between adsorbants and metal surfaces has led to descriptors for bindings and catalysis which have a major impact on the design of metal catalysts. On semiconductor oxides, these understandings are still lacking. We show an important element in understanding binding on semiconductors. We propose here a correlation between the cooperative interaction energy, i.e., the energy difference between the adsorption energies of coadsorbed electron donor–acceptor pair and isolated fragments and the band gap of the clean oxide surface. We demonstrate this effect for a number of oxides and donor–acceptor pairs and explain it with the shift in the Fermi level before and after the adsorption. The conclusion is that the adsorption of acceptor–donor pairs is considerably more favorable compared to unpaired fragments, and this energy difference is approximately equal to the value of the band gap. The implications of this understanding in relation to the improvement and discovery of novel catalysts on the band gap oxides are also discussed

First principle studies of oxygen reduction reaction on N doped graphene: Impact of N concentration, position and co-adsorbate effect

Density Functional Theory calculations were performed on N doped graphene sheet to investigate the trends for adsorption energy variation of oxygen reduction reaction intermediates (HOO*, O*, HO*) when the N concentration increases from 0N (0%) to 1N (33%), to 2N (67%) and to 3N (100%) around the C active site. The impact of the distance between the doping N atoms and the C active site is also studied. Last, the impact of additionally co-adsorbed HO*/O* intermediates was probed. For all the studied systems the magnitudes with which varies the adsorption energies are shaped by the HO*/HOO* capability of accommodating less charge than O* (i.e according to octet rule 1e− vs. 2e−). When N concentration increases, adsorption energy of O* increases with a much higher magnitude than that of HO*/HOO* (i.e with 5 eV vs. 2.7 eV, when going from 0N to 3N). In the presence of the O* co-adsorbate, adsorption energy of intermediates on the investigated active site decrease with a much higher magnitude than when 1HO* is present as co-adsorbate (≈2 eV vs. 1 eV). The theoretical overpotential trends are evaluated using ΔGHO*-ΔGO* descriptor and are found to be significantly influenced by all these environmental changes around the active site. By applying the water stabilization effects, the activity trends remain the same as when it is not taken into account. These results reveal aspects of ORR activity variations that take place when N is clustering on graphene sheets, structures that can be possible as a function of synthesis procedures that could lead to unevenly distribution of dopants in the matrix

First principle studies of oxygen reduction reaction on N doped graphene: Impact of N concentration, position and co-adsorbate effect

Density Functional Theory calculations were performed on N doped graphene sheet to investigate the trends for adsorption energy variation of oxygen reduction reaction intermediates (HOO*, O*, HO*) when the N concentration increases from 0N (0%) to 1N (33%), to 2N (67%) and to 3N (100%) around the C active site. The impact of the distance between the doping N atoms and the C active site is also studied. Last, the impact of additionally co-adsorbed HO*/O* intermediates was probed. For all the studied systems the magnitudes with which varies the adsorption energies are shaped by the HO*/HOO* capability of accommodating less charge than O* (i.e according to octet rule 1e− vs. 2e−). When N concentration increases, adsorption energy of O* increases with a much higher magnitude than that of HO*/HOO* (i.e with 5 eV vs. 2.7 eV, when going from 0N to 3N). In the presence of the O* co-adsorbate, adsorption energy of intermediates on the investigated active site decrease with a much higher magnitude than when 1HO* is present as co-adsorbate (≈2 eV vs. 1 eV). The theoretical overpotential trends are evaluated using ΔGHO*-ΔGO* descriptor and are found to be significantly influenced by all these environmental changes around the active site. By applying the water stabilization effects, the activity trends remain the same as when it is not taken into account. These results reveal aspects of ORR activity variations that take place when N is clustering on graphene sheets, structures that can be possible as a function of synthesis procedures that could lead to unevenly distribution of dopants in the matrix

Supporting data - Effects of the cooperative interaction on the diffusion of hydrogen on MgO(100)

This dataset is the supporting data for the manuscript <i>"Effects of the cooperative interaction on the diffusion of hydrogen on MgO(100)"</i>, I.E. Castelli, Stefan G. Soriga, Isabela C. Man, J. Chem. Phys. 49, 034704 (2018). In the manuscript, we have investigated the role of pre-adsorbed fragments on H diffusion on MgO(100).<br><br>The data set contains all the relaxed structures and Nudged Elastic Bands (NEB) calculations in xyz and traj (Atomic Simulation Environment - ASE) format. Each structure can be visualized with the command:<br>ase gui filename.traj (or .xyz)<br>The NEB calculations with:<br>ase gui -n -1 *initial.traj *im?.traj *final.traj<br>and then select NEB from Tools. An example of the plot of a NEB calculation is the figure included here.<br><br>The scripts used to run and analyze the calculations are included in the archive. <br><br>A README file with more information about the data set and links have been provided.<br><br>The ASE code can be found here: https://wiki.fysik.dtu.dk/ase/<br><br