First-principles study of H adsorption on and absorption in Cu(111) surface

Biomass hydrodeoxygenation catalysts innovation from atomistic activity predictors

Circular economy emphasizes the idea of transforming products involving economic growth and improving the ecological system to reduce the negative consequences caused by the excessive use of raw materials. This can be achieved with the use of second-generation biomass that converts industrial and agricultural wastes into bulk chemicals. The use of catalytic processes is essential to achieve a viable upgrade of biofuels from the lignocellulosic biomass. We carried out density functional theory calculations to explore the relationship between 13 transition metals (TMs) properties, as catalysts, and their affinity for hydrogen and oxygen, as key species in the valourization of biomass. The relation of these parameters will define the trends of the hydrodeoxygenation (HDO) process on biomass-derived compounds. We found the hydrogen and oxygen adsorption energies in the most stable site have a linear relation with electronic properties of these metals that will rationalize the surface's ability to bind the biomass-derived compounds and break the C-O bonds. This will accelerate the catalyst innovation for low temperature and efficient HDO processes on biomass derivates, e.g. guaiacol and anisole, among others. Among the monometallic catalysts explored, the scaling relationship pointed out that Ni has a promising balance between hydrogen and oxygen affinities according to the d-band centre and d-band width models. The comparison of the calculated descriptors to the adsorption strength of guaiacol on the investigated surfaces indicates that the d-band properties alone are not best suited to describe the trend. Instead, we found that a linear combination of work function and d-band properties gives significantly better correlation. This article is part of a discussion meeting issue 'Science to enable the circular economy'.

Reduction of Fermi level pinning at Cu-BP interfaces by atomic passivation

Black phosphorus (BP) is a semiconducting material with a direct finite band gap in its monolayer, attracting intense attention for its application in field-effect transistors. However, strong Fermi level pinning (FLP) has been observed for contacts between BP and high work function metals, e.g., Cu. Such FLP presents an undesirable hurdle preventing the achievement of high performance field-effect devices. In this regard, there is a crucial need to understand the FLP occurring at the metal-BP interfaces and explore the possibility to reduce it. The present work studied atomic passivation in reducing FLP for the Cu-BP system using density functional theory calculations. The passivation by H, N, F, S, and Cl atoms on the Cu(111) surface has been considered. The results showed that the passivated atoms can shield the direct contact between Cu(111) and BP, thus reducing FLP at Cu-BP interfaces. In particular, S and Cl atoms were found to be highly effective agents to achieve a significant reduction of FLP, leading to Cu-BP contacts with ultralow Schottky barrier height (SBH) and suggesting the possibility of ohmic contact formation. Our findings demonstrate surface passivation as an effective method towards depinning the Fermi level at the metal-BP interface and subsequently controlling the SBH for BP-based electronic devices.

Density functional theory study of thermodynamic and kinetic isotope effects of H2/D2 dissociative adsorption on transition metals

Thermodynamic/kinetic isotope effects for H₂/D₂ dissociative adsorption calculated on metal surfaces offer a means to identify active sites.

First Principles Study of Adsorption of Hydrogen on Typical Alloying Elements and Inclusions in Molten 2219 Al Alloy

To better understand the effect of the components of molten 2219 Al alloy on the hydrogen content dissolved in it, the H adsorption on various positions of alloying element clusters of Cu, Mn and Al, as well as the inclusion of Al₂O₃, MgO and Al₄C₃, were investigated by means of first principles calculation, and the thermodynamic stability of H adsorbed on each possible site was also studied on the basis of formation energy. Results show that the interaction between Al, MgO, Al₄C₃ and H atoms is mainly repulsive and energetically unfavorable; a favorable interaction between Cu, Mn, Al₂O₃ and H atoms was determined, with H being more likely to be adsorbed on the top of the third atomic layer of Cu(111), the second atomic layer of Mn(111), and the O atom in the third atomic layer of Al₂O₃, compared with other sites. It was found that alloying elements Cu and Mn and including Al₂O₃ may increase the hydrogen adsorption in the molten 2219 Al alloy with Al₂O₃ being the most sensitive component in this regard.

Insights into the mechanism of ethanol synthesis and ethyl acetate inhibition from acetic acid hydrogenation over Cu2In(100): a DFT study

Incremental insights into the mechanism of ethanol synthesis from acetic acid and the unique effect on the inhibition of ethyl acetate formation.