Two-dimensional (2D) hexagonal boron nitride (h-BN) exhibits promising properties for electronic and photoelectric devices, while the growth of high-quality h-BN remains challenging. Here we theoretically explored the mechanism of epitaxial growth of high-quality h-BN by using the preoxidized and hydrogen-annealed copper substrate, i.e., Cu2O. It is revealed thermodynamically that the unidirectional nucleation of h-BN can be rationalized on the symmetry-matched Cu2O(111) surface rather than the antiparallel nucleation on the Cu(111) surface. Kinetically, the dehydrogenation of feedstock of h-BN on the Cu2O(111) surface is also much easier than that on the Cu(111) surface. Both the B and N atoms are energetically more preferred to stay on the surface rather than inside the body of Cu2O, which leads to a surface-diffusion-based growth behavior on the Cu2O(111) surface instead of the precipitation-diffusion mixed case on the Cu(111) surface. Our work may guide future experimental design for the controllable growth of wafer-scale single-crystal h-BN.

Single atom catalysts (SAC) for water splitting hold the promise of producing H-2 in a highly efficient and economical way. As the performance of SACs depends on the interaction between the adsorbate atom and supporting substrate, developing more efficient SACs with suitable substrates is of significance. In this work, inspired by the successful fabrications of borophene in experiments, we systematically study the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) activities of a series of 3d transition metal-based SACs supported by various borophene monolayers (BMs=alpha_sheet, alpha(1)_sheet, and beta(1)_sheet borophene), TM/BMs, using density functional theory calculations and kinetic simulations. All of the TM/BMs systems exhibit superior HER performance compared to Pt with close to zero thermoneutral Gibbs free energy (Delta G(H*)) of H adsorption. Furthermore, three Ni-deposited systems, namely, Ni/alpha_BM, Ni/alpha(1)_BM and Ni/beta(1)_BM, were identified to be superior OER catalysts with remarkably reduced overpotentials. Based on these results, Ni/BMs can be expected to serve as stunning bifunctional electrocatalysts for water splitting. This work provides a guideline for developing efficient bifunctional electrocatalysts.

Organometallic sandwich complexes, composed of cyclic hydrocarbon ligands and transition-metal atoms, display unique physical and chemical properties. In this work, the electronic and spin transport properties of one-dimensional (1D) VBz2 ligand bimetallic sandwich complexes, VBz2–TM (TM = Cr, Mn, and Fe), are systematically investigated using density functional theory and nonequilibrium Green's function method. The results show that all the 1D infinite molecular wires [(VBz2)TM]∞ (TM = Cr–Fe) are found to be thermodynamically stable with high binding energies (∼1.0–3.45 eV). In particular, they are predicted to be ferromagnetic half metals. Moreover, the I–V curves exhibit negative differential resistance for one, two, and three VBz2–TM wires at TM = Cr, Mn, and Fe, respectively, which is of great significance for certain electronic applications. Our findings strongly suggest that the benzene ligand bimetallic sandwich molecular wires are good candidates for potential electronics and spintronics.

The structures and properties of one-dimensional (1D) sandwich molecular wires constructed with altering 3d transition metal (TM) and the metallofullerene (Tm@C-60) entities, [TM&(TM@C-60)](infinity), are studied using density functional theory calculations. Different from the bonding character insensitivity to TM of previously reported 1D [TMBz](infinity) and [TMCp](infinity) analogues, the bonding characters of the investigated 1D [TM&(TM@C-60)](infinity) molecular wires depend heavily on the identity of metal elements. In 1D [TM&(TM@C-60)](infinity), molecular wires with early TMs like Ti and V, TM-eta(5) coordinate bonds are favored. In contrast, TM-eta(6) bonding conformations are energetically preferred for those with later TMs, for example, Cr-Ni. Bader charge analysis reveals that valence electrons are transferred from both encapsulated and sandwiched TM atoms to the C-60 ligand. More importantly, all the molecular wires in ground states are robust antiferromagnetic semiconductors because of the peierls distortion of the configurations and the moderate binding energies. Therefore, the fabrication of endohedral metallofullerenes offers an effective route to regulate the magnetism and electronic properties of C-60-ligand sandwich complexes.