The synergistic effect of PdO–Pd interfaces improved N2 adsorption and activation for excellent N2 reduction activity and stability.

We report a simple and environmentally friendly route to prepare platinum/reduced graphene oxide (Pt/rGO) nanocomposites (NCs) with highly reactive MnOx colloids as reducing agents and sacrificial templates. The colloids are obtained by laser ablation of a metallic Mn target in graphene oxide (GO)-containing solution. Structural and morphological investigations of the as-prepared NCs revealed that ultrafine Pt nanoparticles (NPs) with an average size of 1.8 (±0.6) nm are uniformly dispersed on the surfaces of rGO nanosheets. Compared with commercial Pt/C catalysts, Pt/rGO NCs with highly electrochemically active surface areas show remarkably improved catalytic activity and durability toward methanol oxidation. All of these superior characteristics can be attributed to the small particle size and uniform distribution of the Pt NPs, as well as the excellent electrical conductivity and stability of the rGO catalyst support. These findings suggest that Pt/rGO electrocatalysts are promising candidate materials for practical use in fuel cells.

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Morphology control and impurity doping are two widely applied strategies to improve the electrochemical performance of nanomaterials. Herein, we report an environmentally friendly approach to obtain Co-doped Ni(OH) 2 nanosheet networks using a laser-induced cobalt colloid as a doping precursor followed by an aging treatment in a hybrid medium of nickel ions. The shape and specific surface area of the doped Ni(OH) 2 can be successfully adjusted by changing the concentration of sodium thiosulfate. Furthermore, a Co-doped Ni(OH) 2 nanosheet network was further converted into Co-doped NiO with its pristine morphology retained via facile thermal decomposition in air. The structure and electrochemical performance of the as-prepared samples are investigated with scanning and transmission electron microscopy, energy dispersive X-ray analysis, X-ray diffraction, Fourier transform infrared spectroscopy, the nitrogen adsorption-desorption isotherm technique, and electrochemical measurements. The Codoped Ni(OH) 2 electrode shows an ultrahigh specific capacitance of 1421 F g À1 at a current density of 6 A g À1 , and a good retention level of 76% after 1000 cycles, in sharp contrast with only a 47% retention level of the pure Ni(OH) 2 electrode at the same current density. In addition, the Co-doped NiO electrode exhibits a capacitance of 720 F g À1 at 6 A g À1 and 92% retention after 1000 cycles, which is also superior to the corresponding values of relevant pure NiO electrodes. The Co 2+ partially substitutes for Ni 2+ in the metal hydroxide and oxide, resulting in an increase of free holes in the valence band, and, therefore, enhancement of the p-type conductivity of Ni(OH) 2 and NiO. Moreover, such novel mesoporous nanosheet network structures are also able to enlarge the electrode-electrolyte contact area and shorten the path length for ion transport. The synergetic effect of these two results is responsible for the observed ultrahigh pseudocapacitor performance.

Understanding the thermodynamic behavior and growth kinetics of colloidal nanoparticles (NPs) is essential to synthesize materials with desirable structures and properties. In this paper, we present specific uncapped Te colloidal NPs obtained through laser ablation of Te in various protic or aprotic solvents. At ambient temperature and pressure, the uncapped Te NPs spontaneously exhibited analogous evolution and growth of “nanoparticle-nanochain-agglomerate-microsphere” in different solvents. The distinctive growth kinetics of the formation of nanochains strongly depended on the polarity and dielectric constant of solvent molecules. The growth rate of agglomerates and microspheres was closely related to the zeta potential of the colloidal solution of Te nanochains and the average size of Te agglomerates. Furthermore, the resulting uncapped Te NPs and Te nanochains displayed a prominent size-dependent and structure-inherited chemical reductive ability. These findings provide insights into the growth of active uncapped nanoparticles in various dispersion media. This study also provides an alternative route in designing novel nanostructures of alloys, telluride, and functional composites using Te as a unique reactive precursor.

We report a facile approach to immobilize magnetic ZnFe 2 O 4 nanoparticles (NPs) onto reduced grapheme oxide (rGO) network by using highly reactive ZnO x (OH) y and FeO x colloids as precursors, which were respectively obtained by laser ablation of metallic zinc (Zn) and iron (Fe) target in pure water. Microstructure investigation of such nanocomposites (NCs) revealed that ZnFe 2 O 4 NPs are well-dispersed 10 onto rGO sheets. Such structure was helpful for separating the photoexcited electron-hole pairs and accelerating the electrons transfer. Electrochemical impedance measurements indicated the remarkably decrease of interfacial layer resistance of composite structure in compared to that of pure ZnFe 2 O 4 NPs. As a result of these advantages, such NCs present a prominent enhancement in photodegradation efficiency of methylene blue dye. Besides, the excellent magnetic properties of ZnFe 2 O 4 NPs allow the 15 catalysts being easily separated from the solution by a magnet for recycle utilization. This effort not only provided a new approach to fabricate ZnFe 2 O 4 -rGO NCs, also expanded the application of ZnFe 2 O 4 NPs used as a visible-light excited photocatalysts in application of organic pollutants degradation. 65 indicated that the MB has been degraded completely within 300 min. The degradation rates of the MB solution by using different photocatalysts were calculated as shown in Figure 4b. First, as a blank contrast, when the MB solution was only added with H 2 O 2 , the absorption peak at 664 nm is nearly unchanged after 70 irradiation for 300 min. Subsequently, when the pure ZnFe 2 O 4 A colloidal approach was developed to immobilize magnetic ZnFe 2 O 4 onto simultaneously reduced GO toward degradation of dyes under visible-light irradiation.

Two-dimensional (2D) semiconductors with anisotropic properties (e.g., mechanical, optical, and electric transport anisotropy) have long been sought in materials research, especially 2D semiconducting sheets with strong anisotropy in carrier mobility, e.g., n-type in one direction and p-type in another direction. Here, we report a comprehensive study of the carrier mobility and electric transport anisotropy of a class of 2D IV–V monolayers, XAs (X = Si or Ge), by using density functional theory methods coupled with deformation potential theory and non-equilibrium Green’s function method. We find that the polarity of room-temperature carrier mobility μ of the 2D XAs monolayer is highly dependent on the lattice direction. In particular, for the SiAs monolayer, the μ values of the electron (e) and hole (h) are 1.25 × 103 and 0.39 × 103 cm2 V–1 s–1, respectively, in the a direction and 0.31 × 103 and 1.12 × 103 cm2 V–1 s–1, respectively, for the b direction. The computed electric transport properties also show that the SiAs monolayer exhibits strong anisotropy in the biased voltage in the range of −1 to 1 V. In particular, the current reflects the ON state in the a direction but the OFF state in the b direction. In addition, we find that the uniaxial strain can significantly improve the electric transport performance and even lead to the negative differential conductance at 10% strain. The unique transport properties of the 2D XAs monolayers can be exploited for potential applications in nanoelectronics.

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