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Electrochemical water splitting into hydrogen is a promising strategy for hydrogen production powered by solar energy. However, the cell voltage of an electrolyzer is still too high for practical application, which is mainly limited by the sluggish oxygen evolution reaction process. To this end, hybrid water electrolyzers have drawn tremendous attention. Herein, coaxial Ni/Ni3S2@N-doped nanofibers are directly grown on nickel foam (NF), which is highly active for hydrogen evolution reaction. Meanwhile, the Ni3S2@N-doped nanofibers on NF prepared in an Ar atmosphere display superior urea oxidation reaction performance to previously reported catalysts. The cell voltage is about 1.50 V in urea electrolysis to deliver a current density of 20 mA cm-2, lower than that of a traditional water electrolyzer (1.82 V). The current density is around 77% relative to its initial value of 20 mA cm-2 after 20 h, superior to Pt/C|Ir/C-based urea electrolysis (14%). It is found that the synergistic effect between metallic Ni and Ni3S2, as well as the interfacial effect between metal centers and N-doped carbon, favors the initial dissociation of H2O and the adsorption/desorption of H* with thermal neutral Gibbs free energy. Meanwhile, the in-situ generated NiOOH on the outer surface of Ni3S2 possessed lower electrochemical activation energy for urea decomposition. Meanwhile, the abundant oxygen vacancies in electrodes could expose more active sites for the adsorption of intermediates, including H* and OOH*. It is also found that the hierarchical nanostructure of densely packed nanowires provides ideal electronic and ionic transport paths for fast electrocatalytic kinetics. The present work indicated that the modulation of compositions and hierarchical nanostructure is effective to prepare efficient catalysts for H2 production via urea electrolysis.

Tin disulfide (SnS2) has a larger band gap (>2.0 eV) than other two-dimensional (2D) materials, which can achieve a higher on/off current ratio, a much lower off-current, and standby power dissipat...

Searching for a facile and sustainable chlorination method to modify graphene has drawn tremendous attention due to the modulation of its electronic property and surface chemistry. In contrast to t...

The search for efficient overall water-splitting electrocatalysts plays an important role for low-cost hydrogen production. Metal phosphides are promising for integrating hydrogen evolution reactio...

Two-dimensional (2D) layered materials, such as MoS2, are greatly attractive for flexible devices due to their unique layered structures, novel physical and electronic properties, and high mechanical strength. However, their limited mechanical strains (

Endothermic hydrocarbon fuel has many advantages as a cooling medium in hypersonic aircraft; however substantial application has been greatly hindered due to easy coking, uncontrollable gas product...

The electrocatalytic hydrogen evolution reaction (HER) has attracted increasing attention in the field of hydrogen-based economy, whereat developing cheap and efficient catalysts to reduce the use of Pt-based catalysts is highly required. Tin disulfide (SnS2) as a new rising star has exhibited intriguing properties in energy storage and conversion applications, while showing slow progress in HER due to the inherent poor activity. Herein, we demonstrate the successful structural engineering and simultaneous integration of trace amount Pt in SnS2 nanosheets via a facile and effective in situ cycling voltammetry activation process, leading to the efficiently synergistic HER. Defect-rich SnS2 nanosheets decorated with a trace amount (0.37 wt %) of Pt exhibit greatly enhanced HER activity due to the synergy between them, revealing low onset potential of 32 mV and overpotential of 117 mV at 10 mA/cm2, small Tafel slope of 69 mV/dec, and large exchange current density of 394.46 μA/cm2. Present work provides an i...

Considering the unique layered structure and novel optoelectronic properties of individual MoS2 and MoSe2, as well as the quantum coherence or donor–acceptor coupling effects between these two components, rational design and artificial growth of in-plane mosaic MoS2/MoSe2 lateral heterojunctions film on conventional amorphous SiO2/Si substrate are in high demand. In this article, large-area, uniform, high-quality mosaic MoS2/MoSe2 lateral heterojunctions film was successfully grown on SiO2/Si substrate for the first time by chemical vapor deposition (CVD) technique. MoSe2 film was grown along MoS2 triangle edges and occupied the blanks of the substrate, finally leading to the formation of mosaic MoS2/MoSe2 lateral heterojunctions film. The composition and microstructure of mosaic MoS2/MoSe2 lateral heterojunctions film were characterized by various analytic techniques. Photodetectors based on mosaic MoS2/MoSe2 lateral heterojunctions film, triangular MoS2 monolayer, and multilayer MoSe2 film are systemati...

Highly stretchable and conductive core–sheath nanofibers are significant for flexible and wearable microelectronics. Core–sheath fibers were massively fabricated from ultralong chemical vapor deposition (CVD)-grown graphene bundles. They exhibited superior conductivity and excellent mechanical properties that exceeded those of the reduced graphene oxide fibers. The intrinsic dynamic fracture procedure and mechanism of the core–sheath nanofibers were investigated. Furthermore, safe strain sensors based on as-prepared core–sheath CVD graphene fibers have been demonstrated as a proof-of-concept application. The performance of strain sensors has been greatly improved by using CVD graphene fibers.

We have shown that various porphyrin-containing nanostructures can be easily synthesized by a surfactant-assisted self-assembly (SAS) method, where an oil/aqueous medium is employed. When a chloroform solution of zinc 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine (ZnTPyP) was added dropwise into cetyltrimethylammonium bromide (CTAB) aqueous solution, diverse ZnTPyP-based nanostructures, including hollow nanospheres, solid nanospheres, nanotubes, nanorods, and nanofibers, were successfully assembled. Depending on the aging time, when a low-concentration CTAB aqueous solution was employed, hollow nanospheres or nanotubes were produced. In contrast, either solid nanospheres or nanorods were obtained by using a CTAB aqueous solution in moderate concentration. Moreover, solid nanospheres or nanofibers were produced, when a high-concentration CTAB aqueous solution was used. We have further shown that the nanorods can be hierarchically organized into a regular nanoarray on silicon substrates over a large area, while the other nanostructures cannot. Interestingly, the nanorods displayed distinct supramolecular chirality although the employed ZnTPyP is achiral. On the basis of the information obtained from scanning electron microscopy, high-resolution transmission electron microscopy, fast Fourier transformation, energy-dispersive X-ray spectroscopy, X-ray diffraction, and UV-vis and circular dichroism spectra, a tentative explanation has been proposed. Our investigation suggests that the SAS method via an oil/aqueous medium is an efficient way to synthesize organic nanostructures in a controlled manner, and that such nanostructures can show different chiroptical and assembly properties.

The aggregation and supramolecular chirality of the interfacial assemblies of an achiral phthalcyanine derivative, zinc 2,3,9,10,16,17,23,24-octakis(octyloxy)-29 H,31 H-phthaloxyanine (ZnPc), were investigated, and a surface pressure dependent behavior was observed. It was found that ZnPc could be spread as a Langmuir film on water surface and transferred onto solid substrates by the horizontal lifting method. The compound formed mixed J- and H-aggregates in the transferred Langmuir-Blodgett (LB) films. Deconvolution of the broaden Q-band revealed three main components of the spectra, which corresponded to H- and J-aggregates and medium transition aggregates, whose relative contents could be modulated by the surface pressure at which the films were transferred. On the other hand, the transferred LB films composed of these aggregates showed Cotton effects in circular dichroism spectra when the floating film was compressed over a certain surface pressure although the compound itself was achiral. The cooperative arrangement of the macrocylic ring in a helical manner through the interfacial organization was suggested to be responsible for such optical activity in the LB films. A possible explanation based on the cooperative arrangement of the ZnPc building blocks in a helical sense stacking in the aggregates was proposed.

Electrochromic multilayer films consisting of polyoxometalate (POM) cluster alpha-K(10)[P(2)W(17)O(61)].17H(2)O (P(2)W(17)), copper(II) complex [Cu(II)(phen)(2)](NO(3))(2) (phen = 1,10-phenithroline), and iron complex [Fe(II)(phen)(3)](ClO(4))(2) were fabricated on silicon, quartz and ITO substrates by layer-by-layer self-assembly method. The multilayer films, PSS/Cu(II)(phen)(2)/[(P(2)W(17)/Cu(II)(phen)(2))](n) and PSS/Fe(II)(phen)(3)/[(P(2)W(17)/Fe(II) (phen)(3))](n) were characterized by UV-vis spectra, X-ray photoelectron spectra, cyclic voltammetry (CV), chronoamperometric (CA) and in-situ spectral electrochemical measurements. The interesting feature of the electrochromic film is its adjustable color by reduction of both transition metal complex and polyoxometalate at different potentials. The multilayer films also exhibit high optical contrast, suitable response time and low operation potential due to the presence of mono-lacunary-substituted polyoxometalate and transition metal complex. This is the first example that the color of electrochromic film can be adjustable, which gives valuable information for exploring new electrochromic materials with tunable colors.