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• The diffusion process of carbon in graphene formation via nickel catalyst was studied from experiments and simulations. • The diffusion barrier of carbon in nickel was calculated based on first principles. • Carbon diffused along nickel grain boundaries preferentially because of the lower diffusion barrier. • Graphene was formed on nickel surface due to metal-induced and diffusion-assisted mechanism. Graphene can be synthesized via metal catalysis using solid carbon source. In this paper, graphene was fabricated using amorphous carbon. We further elucidated the process of carbon diffusion and graphene formation at low temperatures using a comprehensive experimental and theoretical strategy. The diffusion barrier of carbon in nickel crystal is different from that of carbon along nickel grain boundaries, resulting in that the layer of graphene is uncontrollable. Based on our findings, we identified the causes of graphene heterogeneity and the process of carbon diffusion. [ABSTRACT FROM AUTHOR]

Lithium-selenium (Li-Se) batteries have attracted widely attention due to their high volume specific capacity (3260 mAh cm−3) and good electronic conductivity (1 × 10−3 S m−1) of selenium. However, the rapid capacity fading, high volume changes and shuttle effect of lithium polyselenides (LiPSes) limit its further application. Herein, a zinc-cobalt bimetallic catalysts on nitrogen-doped 3D ordered porous carbon (ZnCo-NC) has been constructed and applied as cathode for Li-Se batteries. Such a material could provide unique structure for the adsorption and catalytic conversion of the LiPSes during charge/discharge. As expected, the ZnCo-NC/Se cathode exhibits a high discharge capacity of 549 mAh g−1 after 100 cycles at 0.2 C and 396 mAh g−1 after 1000 cycles at 2 C with a Coulombic efficiency of ∼100%, significantly better than the single-metal counterparts of Co-NC/Se and Zn-NC/Se. • A 3D honeycomb-like carbon host with ordered pores and ZnCo catalytic sites was developed by hard template method. • Such a structure offered a high specific area of 561 m2 g−1 and a total pore volume of 0.57 cm3 g−1. • For Li-Se batteries, the host material achieved 428 mAh g−1 at 4 C, and 354 mAh g−1 after 1000 cycles at 2 C. [ABSTRACT FROM AUTHOR]