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Pd nanocatalysts were successfully synthesized by the ethylene glycol reduction method using graphene as supports and applied to the selective hydrogenation of o-chloronitrobenzene (o-CNB) to o-chloroaniline (o-CAN). The results indicate that the low transfer resistance and strong metal-support interactions between RGO and Pd nanoparticles of Pd/RGO can efficiently improve the selectively. The low transfer resistance can shorten the stay time of the product molecule o-chloroaniline (o-CAN) on the surface of the catalyst sites and then reduce the dechlorination side-reaction of o-CAN. The strong metal-support interactions can lead to the electron-deficient state of the Pd nanoparticles which weakened the extent of electron feedback from the Pd nanoparticles to the aromatic ring and suppressed the hydrodechlorination of o-CAN. Moreover, the selectivity can be further improved for the hydrogenation of o-CNB after grafting sodium polystyrenesulfonate on the Pd/RGO to cover the low-coordinated surface Pd atoms.

The heterogeneous catalysts based on ternary Pd/CeO2-nitrogen-doped graphene (NG) were prepared and utilized for solvent-free aerobic oxidation of benzyl alcohol to benzaldehyde in the presence of green oxidant O2. Characterization results revealed that CeO2 dramatically enhanced the dispersion of Pd nanoparticles, reduced their particle size and inhibited the Pd oxidation formation. With high lattice oxygen storage capability of CeO2, excellent electrical conductivity of NG and high catalytic activity of Pd, the ternary catalyst was designed by combining the complementary superiorities of these three components. The ternary composite Pd/5CeO2-NG exhibited significantly higher catalytic activity with turnover frequency (TOF) of 30.74 s−1 for solvent-free aerobic oxidation of benzyl alcohol compared with the corresponding binary composites including 5CeO2-NG, Pd/NG and Pd/CeO2, verifying the synergistic effect among Pd, CeO2 and NG. The ternary composite was stable and could be recycled up to 6 times without remarkable loss in the activity and selectivity towards benzaldehyde. Owing to its excellent activity, high selectivity, and exceptional stability and recyclability, the Pd/CeO2-NG composite has great application potential in the fields of organic synthesis, electrochemical biosensors and fuel cells.

Biomass carbon source is generally cheap, environmentally friendly and readily available in high quality and quantity. In this work, a series of loofah sponge-derived activated carbon (SAC-x) with hierarchical porous structures are prepared by KOH chemical activation and used as electrode materials for supercapacitors. The pore size can be easily controllable by changing the dosage of KOH. The optimized material (SAC-4) exhibits a high specific capacitance of 309.6 F g−1 at 1 A g−1 in the three-electrode system using 6 M KOH electrolyte. More importantly, the as-assembled symmetric supercapacitor based on SAC-4 exhibits a high energy density of 16.1 Wh kg−1 at a power density of 160.0 W kg−1 using 1 M Na2SO4 electrolyte. These remarkable results demonstrate the exciting commercial potential of SAC-x for high-performance supercapacitor applications due to their high specific surface area, appropriately porous structure, and the trace heteroatom (O and N) functionalities.

In present work, we prepared the bimetallic Cu-Co nanocatalysts on poly (diallyldimethylammonium chloride) functionalized halloysite nanotubes (Cu-Co/PDDA-HNTs) by a deposition-reduction technique at room temperature. The analysis of XRD, SEM, TEM, HAADF-STEM and XPS were employed to systematically investigate the morphology, particle size, structure and surface properties of the nanocomposite. The results reveal that the PDDA coating with thickness of ∼15 nm could be formed on the surface of HNTs, and the existence of PDDA is beneficial to deposit Cu and Co nanoparticles (NPs) with high dispersibility on the surface. While the cost-effective nanocomposite was used for the hydrolytic dehydrogenation of ammonia-borane (NH3BH3), the nanocatalyst showed extraordinary catalytic properties with high total turnover frequency of 30.8 molH2/(molmetal min), low activation energy of 35.15 kJ mol−1 and high recycling stability (>90% conversion at 10th reuse). These results indicate that the bimetallic Cu-Co nanocatalysts on PDDA functionalized HNTs have particular potential for application in release hydrogen process.

Nitrogen-doped graphene aerogel nanomesh (N-GANM) has been hydrothermally prepared from graphene oxide and ammonium hydroxide using iron nitrate as the etching agent. The results showed that N-GANM with an interesting nanomesh structure on the graphene sheets maintained the 3D architecture of graphene aerogel (GA). Furthermore, it exhibited excellent electrochemical capacitive behavior and the specific capacitance value (290.0 F g −1 at 1 A g −1 ) remained approximately 90.3% after 2000 cycles in the three-electrode system. In addition, N-GANM displayed an energy density of 30.9 Wh kg −1 at the power density of 450.3 W kg −1 and excellent cycling stability retention (98%) after 10,000 cycles in the two-electrode symmetric device. The resulting N-GANM was expected to be a much favorable supercapacitor electrode material due to the heteroatom-doping and its unique porous structure.

The electrooxidation of urea is identified as a prospective route for the degradation of urea-rich wastewater and hydrogen generation. Here, we report a controllable synthetic strategy to develop CuO-Ni(OH)2-d nanosheets by deliberately selecting S2O32− as the coordinating etchant toward to Cu2O template and optimize the reaction conditions. The CuO-Ni(OH)2-d is composed of CuO quadrangle nanosheets (100–200 nm) dispersed with Ni(OH)2 nanoparticles. As predicted, The CuO-Ni(OH)2-d nanosheets catalysts exhibit high UOR activities at 1.41 V vs. RHE to achieve the current density of 10 mA cm−2 under the condition of 1 M KOH with 0.33 M urea. The CuO-Ni(OH)2-d nanosheets catalyst also emerges a higher current density of 21.5 mA cm−2, which is about 5.3, 6.8, 30, and 2 times larger than those of commercial Ni(OH)2, CuO-Ni(OH)2-a, CuO-Ni(OH)2-b and CuO-Ni(OH)2-c at 1.52 V vs. RHE, respectively. In particular, the CuO-Ni(OH)2-d nanosheets catalysts exhibited the best catalytic stability performance. After the 36 h I-T test, the current density has no noticeable decreasing compared with the initial current density. This work could present a strategy for the design of advanced electrode materials that can be further applied in urea-rich wastewater remediation.

Graphene doped nickel phosphate/graphene composite (NiPO/G) is prepared by the one-pot hydrothermal synthesis. NiPO/G shows a combined structure of nanospheres and flakes aggregate as well as graphene layered structure. There is strong guest-host interaction between the nickel phosphate (NiPO) and graphene. The change of the charge density of NiPO is revealed by Ni 2p XPS spectra where a down shift is observed on NiPO/G compared with the pure VSB-5. Impressively, the NiPO/G exhibits much higher electro-catalytic activity (12 times compared with VSB-5) and lower over-potential for methanol electro-oxidation than the pure VSB-5 in alkaline medium. The positive correlation between the scan rates and the anodic currents implys a single diffusion-controlled kinetic process. The enhancement of the electro-catalytic activity is due to the synergistic interaction effect between graphene and NiPO.

We investigate the carrier dynamics in monolayer-WS2/SiO2 and WS2/GaAs heterojunctions using time-resolved photoluminescence in this study. The exciton lifetime and radiative lifetime for WS2/GaAs sample were determined to be 497 ps and 46 ns, respectively, which are much larger than those of the WS2/SiO2 sample. Then the energy band structure at the WS2/GaAs heterojunction was explored using x-ray photoelectron spectroscopy. A type-Ⅱ band alignment was confirmed at the interface with the conduction band offset about 1.415 eV and valence band offset 0.55 eV, which was further proved by ultraviolet photoelectron spectroscopy. As a result, the WS2/GaAs junction facilitated electron and hole separation by the aid of built-in field, and in turn enlarged the carrier lifetime. This work provided a promising integration of 2D materials with traditional bulk semiconductors for future high efficiency, highly reliable applications in photonic and optoelectronic devices.