Structural, energetic, electronic, and magnetic properties of Co monomer, dimer, and trimer adsorbed on a single-layer boron nitride (BN) with a grain boundary (GB) consisting of tetragons and octagons (4 vertical bar 8) are theoretically explored via density functional calculations. Due to the presence of 4 vertical bar 8 GB, the adsorption energies (EAs) of small Co clusters are generally enhanced by similar to 10% as compared with those adsorbed on pristine BN, e.g., the EA of Co monomer, and dimer increase by similar to 0.1 eV on a global amount of 0.87 eV, and similar to 0.2 eV for the case of Co trimer. Most interestingly, the increase in adsorption energy exhibits a strong correlation to the number of atoms directly bonded to the substrate. The enhanced binding of Co adatom on the BN with 4 vertical bar 8 GBs (BN48) is due to the strong hybridization of d orbitals of Co adatom and the localized defect states at the 4 vertical bar 8 GBs. However, the GBs have negligible influence on the electronic and magnetic properties of adsorbates. Hence, the two-dimensional (2D) nanosheets with linear GBs might be a better candidate for anchoring the transition metal atoms than pristine BN. Such a strategy may also be applied to other 2D materials, e.g., MoS2 and phosphorene, to enhance the binding of adatom on them, or to utilize them as 1D templates to assemble transition metal atoms into nanowires.
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