One-Pot Biosynthesis of Carbon-Coated Silver Nanoparticles Using Palm Leaves as a Reductant and a Carbon Source.

In this study, carbon-coated silver nanoparticles (Ag@C NPs) were synthesized with a one-pot hydrothermal method using palm leaves as a reductant and a carbon source. SEM, TEM, XRD, Raman, and UV-vis analyses were employed to characterize the as-prepared Ag@C NPs. Results showed that the diameter of silver nanoparticles (Ag NPs) and the coating thickness could be controlled by changing the amount of biomass and the reaction temperature. The diameter ranged from 68.33 to 143.15 nm, while the coating thickness ranged from 1.74 to 4.70 nm. As the biomass amount and the reaction temperature increased, the diameter of Ag NPs and the coating thickness became larger. Thus, this work provided a green, simple, and feasible method for the preparation of metal nanocrystals.

Enhanced electrically and thermally conductive free-standing graphene films with two-dimensional copper sheets as the catalyst and bridge.

Two-dimensional copper sheets were introduced as the catalyst and bridge to enhance the electrical and thermal conductivity of graphene films prepared from graphene oxide nanosheets via a thermal reduction method. The effects of adding different amounts of copper sheets in the composite films were investigated, and the results show that the electrical and thermal conductivity of the graphene films could be increased by 3 times and 64.9%, respectively. The two-dimensional copper sheets not only play an important role as a catalyst toward improving the graphitization degree of reduced graphene oxide, but also act as a bridge and promote the interconnection of the electrical and thermal conduction paths in the composite films due to the good electrical and thermal conductivity of copper. Moreover, the heat dissipation experiment shows that this enhanced graphene composite film has potential applications in the heat management of electronics.

Synthesis of Silver Nanowires Using a Polyvinylpyrrolidone-Free Method with an Alpinia zerumbet Leaf Based on the Oriented Attachment Mechanism.

In this study, silver nanowires (AgNWs) were successfully synthesized by using a polyvinylpyrrolidone (PVP)-free hydrothermal method with an Alpinia zerumbet leaf chunk as a reducing agent and template. Meanwhile, the mechanism of biomass synthesis of AgNWs is also explored. The AgNWs have a diameter of ∼77 nm and a length of ∼10 µm. During the hydrothermal process, the biomass initially serves as a reducing agent to reduce silver ions. As the reaction proceeds, the biomass will form a pipe-shaped soft template by hydrothermal carbonization. Silver ions are adsorbed and reduced along the pipe-shaped soft templates to form silver nanorods, and adjacent nanorods are merged to AgNWs. Thus, AgNWs are grown along the pipeline soft template based on the oriented attachment mechanism. Inspired by this, the mechanism of the polyol method was further investigated. In the initial growth stage, AgNWs synthesized by the polyol method have a V-shaped notch. Therefore, AgNWs synthesized by the polyol method may also grow on the basis of the oriented attachment mechanism with PVP as a template.

A processable Prussian blue analogue-mediated route to promote alkaline electrocatalytic water splitting over bifunctional copper phosphide.

Prussian blue analogues (PBAs) as a class of metal-organic frameworks demonstrate a promising platform to develop cost-effective high-performance electrocatalysts. However, the construction of delicate micro/nanostructures and controllable doping are still a challenging task for the fabrication of highly efficient copper-based electrocatalysts. Herein, we report a facile synthesis of copper foam supported Cu3P@Co-Cu3P (CH@PBA-P/CF) sub-microwire arrays as an active electrocatalyst for alkaline water splitting. The Co-Cu3P shell derived from the Cu3[Co(CN)6]2 PBA serves as the source of active sites. Co doping and construction of core-shell structures endow the CH@PBA-P/CF electrocatalyst with abundant catalytic sites, enhanced intrinsic activity, and low charge transport resistance. The catalytic electrode integrated with 3D copper foam and 1D sub-microwire arrays is highly conductive and stable, which promotes the charge transport and improves the structural stability. As a consequence, CH@PBA-P/CF shows impressive catalytic performances toward the HER and OER in terms of low overpotentials of 231 and 312 mV at a current density of 50 mA cm-2 in 1 M KOH, respectively. Notably, the water electrolyzer using the CH@PBA-P/CF electrode exhibits better water splitting performance than the one using noble metal-based couples.

One-pot synthesis of two-dimensional multilayered graphitic carbon nanosheets by low-temperature hydrothermal carbonization using the in situ formed copper as a template and catalyst.

Two-dimensional (2D) multilayered graphitic carbon nanosheets are prepared via a facile, green, and mild method of one-pot hydrothermal carbonization at a temperature below 300 °C. Copper with a 2D structure is formed in situ and serves as both a template and catalyst. The obtained multilayered carbon nanosheets exhibit well-defined shapes and a radius-to-thickness ratio as high as 104, with monolayer thickness as small as 2.86 nm.

Flowerlike NiCo2S4 Hollow Sub-Microspheres with Mesoporous Nanoshells Support Pd Nanoparticles for Enhanced Hydrogen Evolution Reaction Electrocatalysis in Both Acidic and Alkaline Conditions.

Flowerlike NiCo2S4 hollow sub-microspheres are synthesized through Cu2O templates to support Pd nanoparticles as high-efficiency catalysts for the hydrogen evolution reaction (HER). The diameter and shell size of NiCo2S4 hollow sub-microspheres are about 400 and 16 nm, respectively. In addition, the surface of the shells is constructed by petallike nanosheets. About 3 nm Pd particles uniformly incorporate with the flowerlike NiCo2S4 hollow sub-microsphere to form the NiCo2S4/Pd heterostructure. The NiCo2S4/Pd catalysts exhibit significantly lower overpotential of only 87 and 83 mV at 10 mA/cm2 for the HER in both acidic and alkaline conditions, respectively, relative to NiCo2S4 (247, 226 mV) and Pd (175, 385 mV) catalysts. Besides, the NiCo2S4/Pd catalysts also exhibit excellent stability of HER in these two conditions. The superior HER performance of NiCo2S4/Pd might be resulted from the unique architecture of metal nanoparticles anchored on the bimetallic sulfide flowerlike hollow sub-microspheres, which could provide high surface area, lots of active sites, strong synergetic effect, and stable structure.

Hollow PdCo alloy nanospheres with mesoporous shells as high-performance catalysts for methanol oxidation.

Monodisperse hollow mesoporous PdCo alloy nanospheres are prepared via a simple galvanic replacement reaction. The as-prepared PdCo hollow nanospheres have small diameter, such as Pd78Co22 nanospheres of diameter about 25 nm and mesoporous shells about 4-5 nm. The Pd78Co22 hollow mesoporous nanospheres possess the largest electrochemical active surface areas (ECSA, 53.91 m2 g-1), mass activity (1488 mA mg-1) and specific activity (2.76 mA cm-2) towards to methanol oxidation relative to the Pd68Co32, Pd92Co8 hollow mesoporous nanospheres and commercial Pd/C catalysts. Moreover, the activity of Pd78Co22 after long-term stability tests is still the best and even better than those of fresh Pd68Co32 and commercial Pd/C catalysts. The PdCo catalysts not only effectively reduce the Pd usage by forming hollow structure, but also fully realize the Pd-Co alloying effects for enhancing the methanol oxidation catalytic performance.