Boron nitride (BN), which is an insulator with a wide band gap, supported on Au is theoretically suggested and experimentally proved to act as an electrocatalyst for oxygen reduction reaction (ORR). Density-functional theory calculations show that the band gap of a free h-BN monolayer is 4.6 eV but a slight protrusion of the unoccupied BN states toward the Fermi level is observed if BN is supported on Au(111) due to the BN-Au interaction. A theoretically predicted metastable configuration of O2 on h-BN/Au(111), which can serve as precursors for ORR, and free energy diagrams for ORR on h-BN/Au(111) via two- and four-electron pathways show that ORR to H2O2 is possible at this electrode. It is experimentally proved that overpotential for ORR at the gold electrode is significantly reduced by depositing BN nanosheets. No such effect is observed at the glassy carbon electrode, demonstrating the importance of BN-substrate interaction for h-BN to act as the ORR electrocatalyst. A possible role of the edge of the BN islands for ORR is also discussed.

Bottom-up strategies can be effectively implemented for the fabrication of atomically precise graphene nanoribbons. Recently, using 10,10'-dibromo-9,9'-bianthracene (DBBA) as a molecular precursor to grow armchair nanoribbons on Au(111) and Cu(111), we have shown that substrate activity considerably affects the dynamics of ribbon formation, nonetheless without significant modifications in the growth mechanism. In this paper we compare the on-surface reaction pathways for DBBA molecules on Cu(111) and Cu(110). Evolution of both systems has been studied via a combination of core-level X-ray spectroscopies, scanning tunneling microscopy, and theoretical calculations. Experimental and theoretical results reveal a significant increase in reactivity for the open and anisotropic Cu(110) surface in comparison with the close-packed Cu(111). This increased reactivity results in a predominance of the molecular-substrate interaction over the intermolecular one, which has a critical impact on the transformations of DBBA on Cu(110). Unlike DBBA on Cu(111), the Ullmann coupling cannot be realized for DBBA/Cu(110) and the growth of nanoribbons via this mechanism is blocked. Instead, annealing of DBBA on Cu(110) at 250 °C results in the formation of a new structure: quasi-zero-dimensional flat nanographenes. Each nanographene unit has dehydrogenated zigzag edges bonded to the underlying Cu rows and oriented with the hydrogen-terminated armchair edge parallel to the [1-10] direction. Strong bonding of nanographene to the substrate manifests itself in a high adsorption energy of -12.7 eV and significant charge transfer of 3.46e from the copper surface. Nanographene units coordinated with bromine adatoms are able to arrange in highly regular arrays potentially suitable for nanotemplating.

The catalytic activity for the oxygen reduction reaction (ORR) of a hexagonal boron nitride (h-BN) monolayer supported on a Ni(111) surface has been studied theoretically using density-functional theory. It is shown that the Ni(111) support can critically change the chemical and physical properties of defect-free monolayer h-BN, considerably promoting the adsorption of O2, OOH, OH, and O species, and therefore, it is demonstrated that inert defect-free monolayer h-BN can be functionalized by the metal support and become catalytically active for the ORR. Although simple potential-dependent modeling of the energetics of the ORR on h-BN/Ni(111) indicates the limitation of the ORR process due to the large overpotential, our calculations demonstrate the ability to functionalize inert materials for the ORR and open new ways to design effective Pt-free catalysts for fuel-cell technology.

The catalytic activity for oxygen reduction reaction (ORR) of the pristine and defected hexagonal boron nitride (h-BN) monolayer and H-terminated nanoribbon have been studied theoretically using density functional theory. It is demonstrated that inert h-BN monolayer can be functionalized and become catalytically active by nitrogen doping. It is shown that energetics of adsorption of O 2 , O, OH, OOH, and H 2 O on N atom impurity in h-BN monolayer (N B @h-BN) is quite similar to that known for Pt (111) surface. The specific mechanism of destructive and cooperative adsorption of ORR intermediates on the surface point defects is discussed. It is demonstrated that accounting for entropy and zero-point energy (ZPE) corrections results in destabilization of the ORR intermediates adsorbed on N B @h-BN, while solvent effects lead to their stabilization. Therefore, entropy, ZPE and solvent effects partly cancel each other and have to be taken into account simultaneously. Analysis of the free energy changes along the ORR pathway allows us to suggest that N-doped h-BN monolayer can demonstrate catalytic properties for ORR under condition that the electron transport to the catalytically active center is provided.

The optimized structure and electronic properties of neutral and singly charged magnesium clusters have been investigated using ab initio theoretical methods based on density-functional theory and systematic post-Hartree-Fock many-body perturbation theory accounting for all electrons in the system. We have systematically calculated the optimized geometries of neutral and singly charged magnesium clusters consisting of up to 21 atoms, electronic shell closures, binding energies per atom, ionization potentials and the gap between the highest occupied and the lowest unoccupied molecular orbitals. We have investigated the transition to the hcp structure and metallic evolution of the magnesium clusters, as well as the stability of linear chains and rings of magnesium atoms. The results obtained are compared with the available experimental data and the results of other theoretical works.

Artificial two-dimensional (2D) materials, which host electronic or spatial structure and properties not typical for their bulk allotropes, can be grown epitaxially on atomically flat surfaces; the design and investigation of these materials are thus at the forefront of current research. Here we report the formation of borophene, a planar boron allotrope, on the surface of Ir(111) by exposing it to the flux of elemental boron and consequent annealing. By means of scanning tunneling microscopy and density functional theory calculations, we reveal the complex structure of this borophene, different from all planar boron allotropes reported earlier. This structure forms as a single phase on iridium substrate in a wide range of experimental conditions and may be then decoupled from the substrate via intercalation. These findings allow for production of large, defect-free borophene sheets and advance theoretical understanding of polymorphism in borophene.

We investigate the bottom-up growth of N = 7 armchair graphene nanoribbons (7-AGNRs) from the 10,10′-dibromo-9,9′-bianthracene (DBBA) molecules on Ag(111) with the focus on the role of the organometallic (OM) intermediates. It is demonstrated that DBBA molecules on Ag(111) are partially debrominated at room temperature and lose all bromine atoms at elevated temperatures. Similar to DBBA on Cu(111), debrominated molecules form OM chains on Ag(111). Nevertheless, in contrast with the Cu(111) substrate, formation of polyanthracene chains from OM intermediates via an Ullmann-type reaction is feasible on Ag(111). Cleavage of C–Ag bonds occurs before the thermal threshold for the surface-catalyzed activation of C–H bonds on Ag(111) is reached, while on Cu(111) activation of C–H bonds occurs in parallel with the cleavage of the stronger C–Cu bonds. Consequently, while OM intermediates obstruct the Ullmann reaction between DBBA molecules on the Cu(111) substrate, they are required for the formation of polyanthracene chains on Ag(111). If the Ullmann-type reaction on Ag(111) is inhibited, heating of the OM chains produces nanographenes instead. Heating of the polyanthracene chains produces 7-AGNRs, while heating of nanographenes causes the formation of the disordered structures with the possible admixture of short GNRs.

The structural, electronic, and catalytic properties of Au and Au2 supported on the pristine and defected hexagonal boron nitride (h-BN) surface have been studied theoretically using density functional theory. It is demonstrated that adsorption and catalytic activation of O2 on the h-BN supported Au and Au2 can be affected by the interaction with the support via electron pushing and donor/acceptor mechanisms. It is shown that even weak interaction of Au and Au2 with the defect-free "inert" h-BN surface can have an unusually strong influence on the binding and catalytic activation of the molecular oxygen. This effect occurs due to the mixing of the 5d orbitals of the supported Au and Au2 with the N-pz orbitals. Although the defect-free h-BN surface does not act as a good electron donor for the supported O2-Au, it promotes an electron transfer from the Au to O2, pushing electrons from the gold to the adsorbed oxygen. In the case of the defected h-BN surface, Au and Au2 can be trapped effectively by N or B vacancy and impurity point defects. Strong adsorption on the surface defects is accompanied by the large charge transfer to/from the adsorbate. The excess of the positive or negative charge on the supported Au and Au2 can considerably promote their catalytic activity. Therefore, the h-BN surface (pristine or defected) cannot be considered as an inert support for Au and Au2