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The interface doping with transition metal elements (TM = Ti, Cr, Co, Ni) has been experimentally proved to be an effective pathway to improve the weak interface bonding of graphene/copper (Gr/Cu) composites. In this paper, the microscopic influencing mechanism of TM doping on the interface interaction and mechanical properties of Gr/Cu was investigated by the first-principles calculations. The sandwich model with graphene embedded in Cu matrix was adopted here to simulate the TM-doped interfaces. It is revealed that the introduction of TM doping elements can significantly improve the work of separation, which relates to the electronegativity difference between TM and Cu elements based on the analysis of the interface electronic structure. Then, the mechanical properties of the clean and TM-doped interfaces were studied by the rigid stretching and the relaxed stretching. We found that, in rigid case, the theoretical tensile strengths of different interfaces are positively correlated with the work of separation, and the electronegativity is also a main factor affecting the mechanical properties. Furthermore, a fitting function containing the element electronegativity was applied to get the stress–strain relationship curve, and the quantitative relationship between the interface bonding and mechanical properties determined in this work can be served as a favorable support for the experimental design of Gr/Cu composites.

While many metal compounds have been widely studied as electrocatalysts for hydrogen evolution reaction (HER), the mechanism of HER on these materials is still not well understood nor why one compound is more electrocatalytically active than another. Here, we report our findings in synthesis and characterization of several Co compounds (CoP, CoS and Co3O4) with similar morphology and uniform size but dramatically different HER activities. Electrochemical measurements indicate that CoP has the best HER activity, achieving an overpotential of 80 mV at 10 mA cm−2, which is much smaller than those for CoS and Co3O4. DFT-based computations suggest that electron delocalization resulting from the p-d orbits coupling at the surfaces facilitates HER charge transfer kinetics and an optimal balance between the surface adsorption of H atom and desorption of H2. Both experimental and computational analyses reveal that the HER activity of the Co compounds is correlated closely with the energy gap between the anion p-band and the Co d-band centers, which can be used as an effective descriptor for HER activity. This work offers the scientific basis for rational design of more efficient metal compound electrocatalysts with high HER activity.

We investigated the atomic and electronic structures and interface interaction of graphene/copper interface with rare earth elements (REEs) modified using density functional theory. The effect of interface interaction enhancement induced by interfacial modification is revealed, which results in significant improvement of the mechanical properties of graphene/copper. Thereby, we applied a novel strategy to incorporate Y element at the interface of graphene nanoplatelets/copper (GNPs/Cu) to improve mechanical properties of composites. Tensile tests demonstrated that the yield strength of composites increases by 95.4% via very low fraction (0.2 wt. %) of Y modification with elongation comparable to Cu, which exhibits excellent matched relationship between strength and ductility. Simultaneously, the composite equips with improved electrical conductivity compared with that of the matrix. We illustrated the strengthening effects of REEs modification at the interface that give rise to the effective load transfer, in consistence with the theoretical predication. Furthermore, the GNPs/Cu composites with the interface Ce/Sc elements modified were also fabricated, both of which showed excellent strength-ductility combination. Therefore, the universality of the present method is verified for the preparation of metal matrix composites with excellent mechanical properties through interface modification with REEs.

Diamond reinforced metal matrix composites are considered as a promising thermal management material. The interface between diamond and metal matrix determines the properties of the material to some extent. In this paper, the atomic structure, work of adhesion and binding characteristics of diamond (1 1 1)/Al (Cu) (1 1 1) clean interface are studied using first principles calculations. The influence of Mo doping on the interface interaction, tensile properties and thermal conductivity of diamond (1 1 1)/Al (Cu) (1 1 1) interface is discussed. It is revealed that the work of adhesion of diamond/Al interface is much higher than that of diamond/Cu interface and the magnetic moments also prove this point of view. Mo doping increases the binding of diamond/Al interface and diamond/Cu interface, with an increase rate of 7.2% and 28.4%, respectively. The tensile strength is decreased due to the Mo doping, but the breaking elongation of diamond/Al (Cu) composites is effectively improved, which is intimately related to the charge density distribution and the localization of density states at the Fermi level. Furthermore, Mo is a good additive element to improve the thermal conductivity of diamond/Cu interface, which gives an interpretation of the reported experimental results through the view of the atomic and electronic structures.