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A thermoelectric material consisting of Cu 2 Se incorporated with up to 0.45 wt% of graphene nanoplates is reported. The carbon-reinforced Cu 2 Se exhibits an ultra-high thermoelectric figure-of-merit of zT = 2.44 ± 0.25 at 870 K. Microstructural characterization reveals dense, nanostructured grains of Cu 2 Se with multilayer-graphene and graphite agglomerations located at grain boundaries. High temperature X-ray diffraction shows that the graphene incorporated Cu 2 Se matrix retains a cubic structure and the composite microstructure is chemically stable. Based on the experimental structure, density functional theory was used to calculate the formation energy of carbon point defects and the associated phonon density of states. The isolated carbon inclusion is shown to have a high formation energy in Cu 2 Se whereas graphene and graphite phases are enthalpically stable relative to the solid solution. Neutron 2 spectroscopy proves that there is a frequency mismatch in the phonon density of states between the carbon honeycomb phases and cubic Cu 2 Se. This provides a mechanism for the strong scattering of phonons at the composite interfaces, which significantly impedes the conduction of heat and enhances thermoelectric performance.

Highly dense Cu 2Àx S bulks, fabricated by a melt-solidification technique, show high thermoelectric performance with zT of $1.9 at 970 K. The Cu 2Àx S bulks show good thermal heat flow and diffusivity stability, and they exhibit excellent mechanical properties, with hardness of $1 GPa. Density functional theory calculations indicate that Cu 2Àx S is an intrinsic p-type conductor.

Scheme 1. Schematic illustration for the preparation process of cobalt oxides with cationic vacancies.

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To enhance the performance of Li-ion batteries, hierarchical carbon-based hollow frameworks embedded with cobalt nanoparticles are prepared by the pyrolysis of core-shell ZIF-8@ZIF-67 polyhedrals prepared via a seedmediated growth method. The resultant hollow frameworks are composed of the N-doped carbon as the inner shells and the porous graphitic carbon embedded with cobalt nanoparticles as the outer shells. Benefiting from the unique hollow architecture with large surface area and good electrical conductivity, the electrode materials exhibit good electrochemical performance with improved specific capacities, high-rate capability, and good cycling stability for Li-ion batteries. More importantly, the quantitative kinetic analysis reveals the crucial contributions of N doping and the porous structure of graphitic carbon with cobalt nanoparticles for boosting the performance of carbon-based materials. The rational design of the unique carbon-based architecture and the understanding of the underlying mechanism for the charge storage process are crucial to construct advanced carbon-based materials for high-performance Li-ion batteries.

MnO@C microcages with robust sponge-like internal structure exhibit excellent Li-storage performance, holding favorable commercial potential as anodes for Li-ion batteries.

The function of the interfacial effect caused by MoO2/Mo2C heterostructures was proved by DFT and DOS calculations, promoting ultrastable cycling performance.