Xingju Zhao

Deciphering the precise catalytic growth mechanism of atomically thin graphene-based lateral heterostructures is of great interest in low-dimensional physics and materials. Here, based on first-principles calculations and extensive screenings, we reveal that the deposited transition metal atoms (TM = Mn, Zr, Nb, Mo, Hf, Ta, and W), particularly Mo, act as single-atom catalysts (SACs) to effectively promote C adatom dimerization both energetically and kinetically on a C-dimer-unpreferred Rh(111) substrate. Meanwhile, the TM-SAC increases the stability of the boron-nitride (BN) dimer, which promotes rapid growth of a hexagonal boron nitride-graphene (h-BN-G) lateral heterostructure. Specifically, taking TM = Mo as a typical example, we demonstrate that the Mo–C(BN) couplings weaken the C(BN)-substrate interactions, which sharply reduces the kinetic barriers for both C and BN nucleation and migration in the initial stage of growing the h-BN-G lateral heterostructure on Rh(111). Interestingly, Mo-SAC can dynamically involve and migrate out of the h-BN-G interface during the growth processes for C₂ dimers as feeding blocks. Moreover, the presence of Mo-SAC can effectively tune the patching boundary of the 1D h-BN-G heterostructure, i.e., from C–N to C–B linking with half-metallicity. The present findings provide significantly new insights into controllable catalytic growth of two-dimensional (2D) lateral heterostructures with various important potential applications, such as transport in spintronic devices.

Material stability is the focus on both experiments and calculations, which includes the energetic stability at the static state and the thermodynamic stability at the kinetic state. To show whether energetics or kinetics dominates on material stability, this study focuses on the Pd-13 clusters, because of their observable magnetic moment in experiment. Energetically, the CALYPSO searching method and first-principles calculations find that Pd-13(C-2) is the ground state at 0 K while the static frequency calculations demonstrate that the icosahedron Pd-13(I-h) becomes more favorable on free energy as temperature increases. However, their magnetic moments (8 mu(B)) are not in agreement with the experimental value (<5.2 mu(B)). Kinetically, ab initio molecular dynamics simulations reveal that Pd-13(C-3v) (6 mu(B)) has supreme isomerization temperature and the other 11 low-lying isomers transform to Pd-13(C-3v) directly or indirectly, demonstrating that Pd-13(C-3v) has the maximum probability to be observed in experiment. The magnetic moment difference between experiment (<5.2 mu(B)) and this calculation (6 mu(B)) may be due to the spin multiplicities. Our result suggests that the magnetic moment disparity between theory and experiment (in Pd-13 clusters) originates from the kinetic stability.

We establish a new strategy for constructing spin-polarized single Bi/Sb atoms on defect-free TiO₂(110), showing excellent catalytic activities for spin-triplet O₂ activation and CO oxidation with low rate-limiting reaction barrier of ∼0.6 eV.

Achieving high-performance materials with superior mechanical properties and electrical conductivity, especially in large-sized bulk forms, has always been the goal. However, it remains a grand challenge due to the inherent trade-off between these properties. Herein, by employing nanodiamonds as precursors, centimeter-sized diamond/graphene composites were synthesized under moderate pressure and temperature conditions (12 GPa and 1,300 to 1,500 °C), and the composites consisted of ultrafine diamond grains and few-layer graphene domains interconnected through covalently bonded interfaces. The composites exhibit a remarkable electrical conductivity of 2.0 × 10 ⁴ S m ⁻¹ at room temperature, a Vickers hardness of up to ~55.8 GPa, and a toughness of 10.8 to 19.8 MPa m ^1/2 . Theoretical calculations indicate that the transformation energy barrier for the graphitization of diamond surface is lower than that for diamond growth directly from conventional sp ² carbon materials, allowing the synthesis of such diamond composites under mild conditions. The above results pave the way for realizing large-sized diamond-based materials with ultrahigh electrical conductivity and superior mechanical properties simultaneously under moderate synthesis conditions, which will facilitate their large-scale applications in a variety of fields.

The development of an effective method for mass production of single crystalline two-dimensional (2D) materials is still a standing challenge. Here, using first-principles calculations, we predict the crucial role of the simplest and the most abundant element in the universe, hydrogen, as a surfactant in mass production of single crystalline borophene grown on Ag(111). Specifically, hydrogen not only readily induces the dissolved B atoms to segregate onto the Ag(111) substrate, but also promotes the B atoms to fast nucleate via changing the repulsive pairwise interactions of B atoms to be attractive. Importantly, the introduction of a small amount of hydrogen saturation on the edges (the H/B ratio is lower than 1 : 6) effectively lifts the degeneracy of the baby-islands between two most stable borophene phases that are experimentally fabricated, effectively promoting single crystalline growth, via distinct minimization of their edge energies as rationalized by the generalized Wulff construction. The present findings may open a new avenue toward mass production of borophene and other single crystalline 2D materials, and the hydrogen passivation on the edges may facilitate the exfoliation of borophene grown on metal substrates and thus promote the subsequent characterization or applications.