TiO2-modified two-dimensional composite of nitrogen-doped molybdenum trioxide nanosheets as a high-performance anode for lithium-ion batteries.

Nitrogen-doped molybdenum trioxide (MoO3/NC) has drawbacks such as volume expansion during long-term charging and discharging cycles, which severely limit its further application. This work proposes the addition of titanium dioxide nanoparticles (TiO2 NPs) for performance improvement of MoO3/NC. TiO2 NPs embedded on the surface of a MoO3/NC nanosheet can alleviate its volume expansion and the accumulation of lithiated products and improve the conductivity of the electrode material. The results show that the MoO3/NC nanosheet decorated with TiO2 NPs (TiO2@MoO3/NC), when used as an electrode material, exhibited a discharge specific capacity of 419 mA h g-1 at a current density of 0.05 A g-1 and retained a discharge specific capacity of 517 mA h g-1 after 600 cycles at a current density of 1 A g-1.

Facile synthesis of Bi2Se3/nitrogen-doped carbon dot nanoplates for aqueous zinc ion battery cathodes.

Bi2Se3 is a promising cathode material for aqueous zinc ion batteries (AZIBs), but its limited capacity and poor cycling stability deter its further use in the development of AZIBs. To solve this issue, Bi2Se3/NCD composites have been synthesized via a simple two-step solvothermal method. The introduction of nitrogen-doped carbon dots (NCDs) provides more active sites and makes the composite surface rich in functional groups, which facilitates contact with aqueous electrolytes. The results showed that Bi2Se3/NCDs improved the zinc storage properties of Bi2Se3 as a cathode material. The discharge specific capacity is 318 mA h g-1 at 0.1 A g-1. The cycling performance of Bi2Se3/NCDs was also relatively excellent compared to that of Bi2Se3. This work offers a productive and feasible strategy for metal chalcogenides (MCs) as cathode materials for AZIBs to improve the zinc storage capacity.

Ni3N/Co4N nanosheet heterojunction electrocatalyst for hydrogen evolution reaction in alkaline fresh water/simulated seawater.

Ni3N/Co4N nanosheet arrays on nickel foam were fabricated by using simple hydrothermal and nitriding two-step strategies. Their excellent performance is due to the synergistic effect between Ni3N and Co4N, the sufficient exposed active spots and the overall interaction of the three-dimensional cross-linking network formed by the nanosheet arrays and the porous nickel foam. Ni3N/Co4N exhibits high hydrogen evolution reaction activity. To yield a current density of 10 mA cm-2, Ni3N/Co4N requires overpotentials of 58 and 85 mV in alkaline fresh water and simulated seawater, respectively. This work provides new understanding of developing feasible heterostructured electrocatalysts based on transition metal nitrides.

Anchoring Co3S4 nanowires on NiCo2O4 nanosheet arrays as high-performance electrocatalyst for hydrogen and oxygen evolution.

The development of catalysts which can substitute expensive metals to efficiently split water is currently a hot research topic. Here, a multi-layered NF/NiCo2O4/Co3S4 nanocomposite was prepared on 3D porous nickel foam by hydrothermal and annealing processes. The electrode is a multi-layered, highly conductive and high specific surface area network without a binder, which facilitates electron transport and exposure of active sites, enhances full contact of the electrolyte/electrode interface, and accelerates H2 and O2 diffusion during water electrolysis. As expected, NF/NiCo2O4/Co3S4 exhibits surprising electrocatalytic activity, and only required 71 and 170 mV to reach 10 mA cm-2 in the hydrogen and oxygen evolution reactions, respectively, and exhibited stability up to 36 h. This strategy provides an efficient, durable, and low-cost bifunctional catalyst.

Heterostructured ZnCo2O4-CoOOH nanosheets on Ni foam for a high performance bifunctional alkaline water splitting catalyst.

It is of utmost importance to explore bifunctional electrocatalysts for water splitting. Herein, unique ZnCo2O4-CoOOH heterostructured ultrathin nanosheets on Ni foam are reported that combines a two-step hydrothermal method. This catalyst exhibits excellent catalytic performances to achieve a current density of 10 mA cm-2 with an ultralow overpotential of 115 mV for HER, attaining an overpotential of 238 mV at 20 mA cm-2 for OER. Remarkably, ZnCo2O4-CoOOH/Ni shows a voltage of 1.494 V to drive a current density of 10 mA cm-2. Such performances are due to the inter-penetrative pores present in the ultrathin nanosheets that provide large surface areas and expose massive active sites to enhance activities. In addition, the unique nanosheet structure and the 3D Ni foam substrate possess large specific surface areas, which can facilitate mass diffusion. This excellent performance is ascribed to the ZnCo2O4-CoOOH heterostructure that manipulates strong synergy to improve the electrochemical activity. This study offers new insight on an innovative approach for the exploitation of effective bifunctional electrocatalysts with a heterostructure.

Metal-organic framework derived carbon-encapsulated hollow CuO/Cu2O heterostructure heterohedron as an efficient electrocatalyst for hydrogen evolution reaction.

It is of pivotal significance to probe highly efficient, cost-effective and low-cost catalysts for the hydrogen evolution reaction. Herein, a closely packed carbon-encapsulated CuO/Cu2O heterohedron with a heterojunction structure is reported that combines chemical etching and thermal oxidation processes. CuO/Cu2O@C-10 has remarkable catalytic activity for HER with an overpotential of 121 mV at a current density of 10 mA cm-2 and a Tafel slope of 81.58 mV dec-1, along with excellent stability in alkaline media under optimal conditions. Benefiting from CuO/Cu2O nanoparticles embedded in a carbon matrix, it forms a porous heterohedron structure by a close packing mode, owing to the unique CuO/Cu2O heterostructure with an ultrathin coated carbon layer and an interconnected conductive carbon network structure. These characteristics make a great contribution to the massive number of active interfacial sites, alleviating the aggregation of active substances, enhancing ion diffusion and the conductivity of the materials. This facile strategy sheds new light on a rational synthesis for a highly efficient hydrogen evolution catalyst with a heterostructure.

Rectification of excitation with bathochromic shift induced by intense absorption of organic ligands during emission measurement of Eu(III) complex.

Bathochromic shift in excitation spectrum was observed during emission measurement of Eu(DBM)(3)Phen containing dilute solution in methyl methacrylate (MMA). Detailed analysis shows that the reason of bathochromic shift is not the formation of molecule aggregation. It is caused by the intense absorption of ligands in the complex. Based on this model, a new method has been established to rectify excitation spectra before emission measurement of systems with different concentration. There exists a critical value of the absorption strength, which is 0.87 from calculation. Higher absorption than this value will cause the bathochromic shift of excitation peak. The wavelength whose absorbance is 0.87 will be the position of the strongest excitation peak. With 200 ppm and 500 ppm Eu(DBM)(3)Phen as the standard sample, relations between relative concentration and wavelength of excitation peak in Eu(DBM)(3)Phen system were deduced and plotted. Theoretical curves are in good agreement with experiment data except extra-dilute concentration, for partial decomplexation of the beta-diketonate and phenanthroline ligands.

Combinatorial method for the study of new co-fluorescence enhancement system.

The new co-fluorescence enhancement system was found in polymer matrix and studied with a combinatorial approach based on Re(DBM)3phen (Re3+: Tb3+, La3+, Gd3+, Y3+; dbm: dibenzoylmethane; phen: phenanthroline) and Sm3+ complex co-doped poly(methyl methacrylate)(PMMA). We have presents a new methodology for the rapid optimization of the luminescence conditions of thin-film sample in arrays of microwells. Two libraries were generated in order to study the effect of the species and content of enhancing ions on the luminescence enhancing efficiency, respectively. At the optimal content of 20 wt.% Sm(DBM)3phen, the maximum sensitization efficiency of Tb(DBM)3phen is about nine times. The intramolecular and intermolecular energy transfer processes in rare-earth complex-doped PMMA are discussed. The energy transfer processes make the co-fluorescence effect come true. Although, the methodology described here was implemented for optimization of co-fluorescence conditions, it is can be further implemented for a variety of applications in which optimization of parameters can be studied in situ using spectroscopic tool.

Sm(DBM)3Phen-doped poly(methyl methacrylate) for three-dimensional multilayered optical memory.

We report on the formation of submicrometer voids within Sm(DBM)3Phen-doped poly(methyl methacrylate) (PMMA) under multiphoton absorption excited by an infrared laser beam. An ultrashort-pulsed laser beam with a pulse width of 200 fs at a wavelength of 800 nm is focused into doped PMMA. The large changes in refractive index and the fluorescence associated with a void allow conventional optical microscopy and reflection-type confocal microscopy to be used as detection methods. Voids can be arranged in a three-dimensional multilayered structure for high-density optical data storage.