A new kind of nitrogen-doped graphene/carbon nanotube nanocomposite can be synthesized by a facile hydrothermal process under mild conditions, which exhibits synergistically enhanced electrochemical activity for the oxygen reduction reaction. This research provides a new route to access a metal-free electrocatalyst with high activity under mild conditions.

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Nitrogen-doped graphene (GN) has great potential applications in many fields because doping with nitrogen can alter the electrical properties of graphene. It is still a challenge to develop a convenient method for synthesis of GN sheets. In this paper, we first report the synthesis of a nitrogen-doped graphene/ZnSe nanocomposite (GN-ZnSe) by a one-pot hydrothermal process at low temperature using graphene oxide nanosheets and [ZnSe](DETA)(0.5) nanobelts as precursors. ZnSe nanorods composed of ZnSe nanoparticles were found to deposit on the surface of the GN sheets. The results demonstrated that [ZnSe](DETA)(0.5) nanobelts were used not only as the source of ZnSe nanoparticles but also as the nitrogen source. Interestingly, it was found that the as-prepared nanocomposites exhibit remarkably enhanced electrochemical performance for oxygen reduction reaction and photocatalytic activities for the bleaching of methyl orange dye under visible-light irradiation. This facile and catalyst-free approach for depositing ZnSe nanoparticles onto the graphene sheets may provide an alternative way for preparation of other nanocomposites based on GN sheets under mild conditions, which show their potential applications in wastewater treatment, fuel cells, energy storage, nanodevices, and so on.

The ambient metastability of the rock-salt phase in well-defined model systems comprising nanospheres or nanorods of cadmium selenide, cadmium sulfide, or both was investigated as a function of composition, initial crystal phase, particle structure, shape, surface functionalization, and ordering level of their assemblies. Our experiments show that these nanocrystal systems exhibit ligand-tailorable reversibility in the rock salt–to–zinc blende solid-phase transformation. Interparticle sintering was used to engineer kinetic barriers in the phase transformation to produce ambient-pressure metastable rock-salt structures in a controllable manner. Interconnected nanocrystal networks were identified as an essential structure that hosted metastable high-energy phases at ambient conditions. These findings suggest general rules for transformation-barrier engineering that are useful in the rational design of next-generation materials.

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