Among numerous active electrode materials, nickel hydroxide is a promising electrode in electrochemical capacitors. Nickel hydroxide research has thus far focused on the crystalline rather than the amorphous phase, despite the impressive electrochemical properties of the latter, which includes an improved electrochemical efficiency due to disorder. Here we demonstrate high-performance electrochemical supercapacitors prepared from amorphous nickel hydroxide nanospheres synthesized via simple, green electrochemistry. The amorphous nickel hydroxide electrode exhibits high capacitance (2,188 F g−1), and the asymmetric pseudocapacitors of the amorphous nickel hydroxide exhibit high capacitance (153 F g−1), high energy density (35.7 W h kg−1 at a power density of 490 W kg−1) and super-long cycle life (97% and 81% charge retentions after 5,000 and 10,000 cycles, respectively). The integrated electrochemical performance of the amorphous nickel hydroxide is commensurate with crystalline materials in supercapacitors. These findings promote the application of amorphous nanostructures as advanced electrochemical pseudocapacitor materials.

Because of their considerable science and technical interest, nanodiamonds (3-5 nm) are often used as a model to study the phase transformation between graphite and diamond. Here we demonstrated that a reversible nanodiamond-carbon onion phase transformation can become true when laser irradiates colloidal suspensions of nanodiamonds at the ambient temperature and pressure. Nanodiamonds are first transformed to carbon onions driven by the laser-induced high temperature in which an intermediary bucky diamond phase is observed. Sequentially, carbon onions are transformed back to nanodiamonds driven by the laser-induced high temperature and high pressure from carbon onions as nanoscaled temperature and pressure cell upon the laser irradiation process in liquid. Similarly, the same bucky diamond phase serving as an intermediate phase is found during the carbon onion-to-nanodiamond transition. To have a clear insight into the unique phase transformation the thermodynamic approaches on the nanoscale were proposed to elucidate the reversible phase transformation of nanodiamond-to-carbon onion-to-nanodiamond via an intermediary bucky diamond phase upon the laser irradiation in liquid. This reversible transition reveals a series of phase transformations between diamond and carbon allotropes, such as carbon onion and bucky diamond, having a general insight into the basic physics involved in these phase transformations. These results give a clue to the root of meteoritic nanodiamonds that are commonly found in primitive meteorites but their origin is puzzling and offers one suitable approach for breaking controllable pathways between diamond and carbon allotropes.

A new kinetic model is suggested to describe the self-limiting oxidation of Si nanowires by only considering the diffusion step with the influence of stress due to the two-dimension nonuniform deformation of the oxide but not including any rate-limiting step for interfacial reaction. It is assumed the stress results in the change of distribution of diffusion activation energy in the high density region which rises monotonically along with the oxidation, and may be the main physical origin of the self-limiting oxidation behavior of SiNWs. Moreover, the present kinetic model can excellently describe the experimental results for the wide initial diameter over the range of self-limiting oxidation temperature.

To have a clear physical insight into the nanocrystal formation upon pulsed-laser ablation in liquid, we proposed a theoretical kinetic approach to elucidate the nucleation and growth of nanocrystals with respect to the capillary effect of the nanometer-sized curvature of crystalline nuclei. Taking the nanodiamond synthesis by pulsed-laser ablating a graphite target in water as an example, we predicted the nucleation time, growth velocity, and the grown size of nanodiamonds on the basis of the proposed kinetic model, and found that these theoretical results are in well agreement with our experiment cases. We expected that the kinetic approach is generally applicable to understanding the basic physics of nanocrystal formation in pulsed-laser ablation in liquid.

A novel nanostructure comprised of Sb2O3/Sb@graphene NPs anchored on a carbon sheet network is reported, with excellent cycling stability, a long cycle life and a good rate capability as a sodium ion battery anode.