Tuning the van der Waals Interaction of Graphene with Molecules via Doping

We use scanning tunneling microscopy to visualize and thermal desorption spectroscopy to quantitatively measure that the binding of naphthalene molecules to graphene (Gr), a case of pure van der Waals (vdW) interaction, strengthens with $n$- and weakens with $p$-doping of Gr. Density functional theory calculations that include the vdW interaction in a seamless, ab initio way accurately reproduce the observed trend in binding energies. Based on a model calculation, we propose that the vdW interaction is modified by changing the spatial extent of Gr's $\pi$ orbitals via doping

Comparative density functional theory study for predicting oxygen reduction activity of single-atom catalyst

It has been well established that nitrogen coordinated transition metal, TM-N$_{4}$-C (TM$=$Fe and Co) moieties, are responsible for the higher catalytic activity for the electrochemical oxygen reduction reaction. However, the results obtained using density functional theory calculations vary from one to another, which can lead to controversy. Herein, we assess the accuracy of the theoretical approach using different class of exchange-correlation functionals, i.e., Perdew-Burke-Ernzerhof (PBE) and revised PBE (RPBE), those with the Grimme's semiempirical dispersion correction (PBE+D3 and RPBE+D3), and the Bayesian error estimate functional with the nonlocal correlation (BEEF-vdW) on the reaction energies of oxygen reduction reaction on TM-N$_{4}$ moieties in graphene and those with OH-termination. We found that the predicted overpotentials using RPBE+D3 are comparable and consistent with those using BEEF-vdW. Our finding indicates that a proper choice of the exchange-correlation functional is crucial to a precise description of the catalytic activity of this system

Oxygen Reduction Reaction on Single-Atom Catalysts From Density Functional Theory Calculations Combined with an Implicit Solvation Model

We present a density functional theory study of the oxygen reduction reaction (ORR) on a single atom catalyst embedded in graphene, namely, TM-N$_{4}$-C (TM = Fe and Co), using the effective screening medium method combined with the reference interaction site model (ESM-RISM). It was found that Fe-N$_{4}$-C and Co-N$_{4}$-C show comparable ORR activities from the constant electrode potential simulations, in contrast to the results obtained using the constant (neutral) charge simulation, in which the superior performance of Co-N$_{4}$-C has been predicted. The constant potential method allows the variable charge and thus results in a potential dependence of the reaction-free energies different from that with the constant charge method in which the potential dependence is included as an ad hoc manner. We suggest the importance of the variable charge in the simulation of the electrochemical reaction, which is enabled by ESM-RISM

Self-limiting processes in thermal atomic layer etching of nickel by hexafluoroacetylacetone

Abdulrahman H. Basher, Ikutaro Hamada, and Satoshi Hamaguchi. Jpn. J. Appl. Phys. 59 090905

Interplay of hydrogen boride sheets with water: An insight into edge stability

Rojas K.I.M., Morikawa Y., Hamada I. Interplay of hydrogen boride sheets with water: An insight into edge stability. Physical Review Materials 8, 114004 (2024); https://doi.org/10.1103/PhysRevMaterials.8.114004.Hydrogen boride (HB) sheets, a two-dimensional material composed of hexagonal boron (B) with bridging hydrogen (H), have recently been synthesized and shown significant potential in electronic devices and catalytic applications. Recent studies have shown that HB sheets are generally stable against water, in contrast to many boron hydride materials which undergo hydrolysis. This stability is attributed to the interplay between the negatively charged B and the strong B-B bond network. Despite this stability, experiments have shown that hydrolysis still takes place, albeit minimally. It is possible that the source of this minimal hydrolysis is related to regions with a less prominent B-B bond network; however, the microscopic details remain unclear. In this work, we investigated the various configurations of HB nanoribbon edges as representative of regions with less prominent B-B bond network and show their distinct region-specific behavior with water. We found that zigzag and armchair nanoribbons were generally stable against water, whereas in the case of the hydrogen-vacant armchair nanoribbon, an oxygen-boron bonding was observed, showcasing a chemisorption mechanism. Additionally, it was found that water dissociation is easier to proceed near the edge as opposed to the surface, signifying the more reactive nature of the edge. These results shed light on the mechanism of the partial hydrolysis observed in the experiment

Theoretical Investigation of Hydrogen Desorption Process in Hydrogen Boride sheet for Catalytic Applications

大規模計算機システム利用者研究報