Fang Duan

Atomic‐Scale Core/Shell Structure Engineering Induces Precise Tensile Strain to Boost Hydrogen Evolution Catalysis

Tuning surface strain is a new strategy for boosting catalytic activity to achieve sustainable energy supplies; however, correlating the surface strain with catalytic performance is scarce because such mechanistic studies strongly require the capability of tailoring surface strain on catalysts as precisely as possible. Herein, a conceptual strategy of precisely tuning tensile surface strain on Co9 S8 /MoS2 core/shell nanocrystals for boosting the hydrogen evolution reaction (HER) activity by controlling the MoS2 shell numbers is demonstrated. It is found that the tensile surface strain of Co9 S8 /MoS2 core/shell nanocrystals can be precisely tuned from 3.5% to 0% by changing the MoS2 shell layer from 5L to 1L, in which the strained Co9 S8 /1L MoS2 (3.5%) exhibits the best HER performance with an overpotential of only 97 mV (10 mA cm-2 ) and a Tafel slope of 71 mV dec-1 . The density functional theory calculation reveals that the Co9 S8 /1L MoS2 core/shell nanostructure yields the lowest hydrogen adsorption energy (∆EH ) of -1.03 eV and transition state energy barrier (∆E2H* ) of 0.29 eV (MoS2 , ∆EH = -0.86 eV and ∆E2H* = 0.49 eV), which are the key in boosting HER activity by stabilizing the HER intermediate, seizing H ions, and releasing H2 gas.

A self-supported electrochemical sensor for simultaneous sensitive detection of trace heavy metal ions based on PtAu alloy/carbon nanofibers

The key issue in efficient electrochemical detection of trace heavy metal ions (HMIs) is to design hierarchical nanostructure electrodes with high sensitivity and low detection limit. In this study, bimetallic PtAu alloy nanoparticles (PtAuNPs) with uniform size and distribution were constructed in electrospun carbon nanofibers (CNFs) by combining an electrospinning procedure and an in situ thermal reduction process. The PtAu/CNF membrane can be directly used as a sensor electrode for simultaneous detection of trace Cd2+, Pb2+, and Cu2+ by square wave anodic stripping voltammetry (SWASV). The prepared PtAu/CNF membrane is capable of simultaneously detecting Cd2+, Pb2+, and Cu2+ with a sensitivity of 0.10 μM and correlation coefficients of 0.976, 0.993, and 0.976, respectively, indicating high sensitivity and good linear relation. The excellent sensitivity and low detection limit for HMI detection were ascribed to the high conductivity of CNFs, fast response of PtAu alloy NPs, and high specific surface area of the hybrid structure. The present research provides a convenient and efficient way to construct new sensors for simultaneous trace detection of HMIs.

Fabrication of Uniform Nanocomposite by “Anchoring” Polyaniline Nanofibers on the Surface of Graphene Oxide for Supercapacitors

In this research, polyaniline/graphene oxide (PANI/GO) nanocomposite was prepared via covalent grafting by anchoring PANI on the surface of GO. Firstly, aniline (ANI) was anchored on the surface of GO by a series of chemistry reactions to obtain ANI modified GO (GO-ANI). The subsequent in situ polymerization of ANI monomer on the surface of GO led to the fabrication of a uniform PANI/GO nanocomposite. The morphology and structure of the products were characterized by X-ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR), ultraviolet-visible spectrophotometer (UV-vis), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results showed the formation of the uniform PANI/GO nanocomposite with the PANI nanofibers anchoring on the GO surface. Such structure afforded high specific capacitance during the charge-discharge process for supercapacitor electrodes. The specific capacitance of the nanocomposite was 275 F/g, which was higher than that of pure PANI (192 F/g). The nanocomposite exhibits good electrochemical property and is a good candidate for supercapacitor electrodes.

Preparation and adsorption properties of laponite–cyclodextrin complex

Abstract Laponite–cyclodextrin complex was synthesised by amidation of carboxylated cyclodextrin and amine-modified laponite, which were first modified by amine-terminated silane coupling agents with different chain lengths and functional groups. The structures of the laponite before and after modification were characterised by Fourier transform infrared and proton nuclear magnetic resonance. The effect of the silane coupling agents on the loading amounts of cyclodextrin onto laponite was investigated by thermogravimetric analyser. The results showed that the loading amounts of cyclodextrin and silane coupling agents increased with the increasing chain lengths and the decreasing alkoxyl groups of silane coupling agents. The laponite–cyclodextrin complexes gathered the advantages of adsorbing aromatic organic compounds by cyclodextrin via host–guest inclusion interaction and adsorbing metal ions by laponite via ion exchange. The laponite–cyclodextrin complex presents great applications in the aspect of wastewater treatment.