Density functional study of the adsorption and van der Waals binding of aromatic and conjugated compounds on the basal plane of MoS2

Accurate calculations of adsorption energies of cyclic molecules are of key importance in investigations of, e.g., hydrodesulfurization (HDS) catalysis. The present density functional theory (DFT) study of a set of important reactants, products, and inhibitors in HDS catalysis demonstrates that van der Waals interactions are essential for binding energies on MoS2 surfaces and that DFT with a recently developed exchange-correlation functional (vdW-DF) accurately calculates the van der Waals energy. Values are calculated for the adsorption energies of butadiene, thiophene, benzothiophene, pyridine, quinoline, benzene, and naphthalene on the basal plane of MoS2, showing good agreement with available experimental data, and the equilibrium geometry is found as flat at a separation of about 3.5 \uc5 for all studied molecules. This adsorption is found to be due to mainly van der Waals interactions. Furthermore, the manifold of adsorption-energy values allows trend analyses to be made, and they are found to have a linear correlation with the number of main atoms. \ua9 2009 American Institute of Physics

Topotactic Growth of Edge-Terminated MoS₂ from MoO₂Nanocrystals

Layered transition metal dichalcogenides have distinct physicochemical properties at their edge-terminations. The production of an abundant density of edge structures is, however, impeded by the excess surface energy of edges compared to basal planes and would benefit from insight into the atomic growth mechanisms. Here, we show that edge-terminated MoS₂ nanostructures can form during sulfidation of MoO₂ nanocrystals by using <i>in situ</i> transmission electron microscopy (TEM). Time-resolved TEM image series reveal that the MoO₂ surface can sulfide by inward progression of MoO₂(202̅):MoS₂(002) interfaces, resulting in upright-oriented and edge-exposing MoS₂ sheets. This topotactic growth is rationalized in the interplay with density functional theory calculations by successive O–S exchange and Mo sublattice restructuring steps. The analysis shows that formation of edge-terminated MoS₂ is energetically favorable at MoO₂(110) surfaces and provides a necessary requirement for the propensity of a specific MoO₂ surface termination to form edge-terminated MoS₂. Thus, the present findings should benefit the rational development of transition metal dichalcogenide nanomaterials with abundant edge terminations

Renewable Electricity as a Feed Stock for the Chemical Industry

Presented online December 8, 2021 from 3:30 p.m.- 4:30 p.m., Georgia Tech, Atlanta, GA.2011 to present at Haldor Topsoe A/S, Presently head of Solid oxide technology development, previous responsibilities, Exploratory R&D, Project manager for Topsoe’s strategy for a fossil free future, Department manager for atomics scale analysis department (microscopy, spectroscopy, computational chemistry). Before coming to Topsoe , in 2008 Ph.D Applied Physics, Technical University of Denmark, and 3 years of Post Doc at UCSB Materials department and Stanford Chemical engineering. My research has focused on materials for energy and chemical conversions, with applications in fuels, chemical synthesis, emission control and electrocatalysis.Runtime: 54:03 minutesHeavy industry and long-haul transportation are responsible for a large percentage of humanity's greenhouse-gas emissions. In these sectors, direct electrification is not enough. They need energy-dense green fuels – similar to the fuels used today, but made from renewable sources. In this presentation a set of solutions will be presented. Solutions based on combining proven technologies from the chemical industry with new technology to produce essential chemicals and fuels such as green hydrogen, green ammonia, eMethanol, and other clean fuels from non-fossil feedstocks such as biomass, waste and renewable electricity. The most critical new technology in terms of cost and energy loss is water electrolysis for hydrogen production. A deep dive on the most efficient electrolysis technology, high temperature solid oxide electrolysis will be given ranging from basic thermodynamics to process integration for chemicals production

Modeling the active sites of Co-promoted MoS₂ particles by DFT

The atomic-scale structure of CoMoS and the nature of its active sites for hydrodesulfurization and hydrogen evolution are determined based on DFT simulations.</p

Methanol to Dimethyl Ether over ZSM-22: A Periodic Density Functional Theory Study

Methanol-to-DME conversion over ZSM-22 Brønsted acid sites is investigated on the basis of periodic density functional theory calculations. DME formation has been speculated to take place via the dissociative or associative pathway. It is shown that the dissociative pathway is the predominant pathway. We find that water lowers the activation energies of key reactions but that the lowering of the activation energies is insufficient to increase the rate because of the entropy loss associated with water adsorption. The consequence of acid strength on the methanol-to-DME conversion pathways is investigated on the basis of Al-, Ga-, or In-induced Brønsted acid sites. We show that linear correlations between activation energies and acid strength exist. It is found that weaker acidity leads to higher activation energies. We find that changes in acidity will not change the conclusion that the dissociative pathway is the predominant pathway