Xiaoyue Duan

Structure and effects of electroless Ni–Sn–P transition layer during acid electroless plating on magnesium alloys

Abstract An electroless ternary Ni–Sn–P transition layer with high corrosion resistance was applied for acid electroless nickel plating on magnesium alloys. The surface morphologies and microstructure of the traditional alkaline electroless Ni–P and novel Ni–Sn–P transition layers were compared by SEM and XRD, and the bonding strengths between the transition layers and AZ31 magnesium alloys were tested. The corrosion resistance of the samples was analyzed by porosity test, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) in acid electroless solution at pH 4.5 and immersion test in 10% HCl. The results indicate that the transition layer is essential for acid electroless plating Ni–P coatings on magnesium alloys. Under the same thin thickness (~6 μm), the electroless Ni–Sn–P transition layer possesses superior properties to the traditional Ni–P transition layer, including high amorphization, smooth and dense surface without pores, enhanced bonding strength and corrosion resistance. Most importantly, acid electroless Ni–P coatings can be successfully deposited on magnesium alloys by using Ni–Sn–P transition layer.

Capacitive Deionization Performance of Activated Carbon Electrodes Prepared by a Novel Liquid Binder

A novel liquid binder, which is called AA in this paper, was synthesized with acrylic acid and azodiisobutyronitrile to prepare electrodes from activated carbon (AC, ACE) for capacitive deionization (CDI). The ACE prepared with AA (ACE-AA) was carbonized to improve its CDI performance. As a result, its wettability was significantly improved, and the specific capacitance was increased by a factor of 8. The optimization showed that electrodes with a mass fraction of AC of 35 wt% had the best CDI performance. Compared with ACEs prepared with phenolic resin (PR), polytetrafluoroethylene (PTFE) and epoxy resin (ER), electrodes prepared using AA binder showed improved flexibility, durability, wettability, and desalination ratio. Therefore, the ACE-AA seems to be a very promising carbon electrode for CDI.

Fabrication and characterization of a novel PbO2 electrode with a CNT interlayer

A novel PbO2 electrode (marked as CNT–PbO2) with a carbon nanotube (CNT) interlayer was prepared by electrophoretic deposition and electro-deposition. The surface morphology, structure, electrochemical activity and stability of the CNT–PbO2 electrodes were characterized by scanning electronic microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ·OH production test, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), bulk electrolysis and accelerated life test. The results show that, compared with the traditional PbO2 electrode, the CNT–PbO2 electrodes electrodeposited β-PbO2 outer layer above the CNT interlayer had a higher crystallinity. The CNT–PbO2-5 min electrode had a higher active surface area and lower charge transfer resistance than traditional PbO2, CNT–PbO2-10 min, and CNT–PbO2-15 min electrodes due to a large number of exposed CNTs. However, the CNT–PbO2-10 min electrode exhibited a stronger ability of ·OH production, higher direct oxidation capacity for degradation of 4-chlorophenol (4-CP) and longer service lifetime than other electrodes, whose apparent rate constant for 4-CP degradation and service lifetime was 2.7 times and 1.7 times those of traditional PbO2 electrode, respectively. Thus, the proposed CNT–PbO2-10 min electrode in this study is a promising anode for the electrochemical oxidation of refractory toxic organic pollutants.

Preparation and characterization of Cu–rare earth/Al2O3 catalysts and their application in the electrochemical removal of p-nitrophenol

Cu and rare earth composite catalysts (Cu–rare earth/Al2O3) were prepared on Al2O3 particles using an impregnation method for the electro-catalytic oxidation of p-nitrophenol in this study. The surface topography and crystal structure of the products were characterized using scanning electron microscopy and X-ray diffraction. Results show that the Cu–rare earth/Al2O3 particles have a beneficial effect on p-nitrophenol removal by improving the ˙OH radical generation rate, especially the Cu–Bi/Al2O3 catalyst. The effects of the heat treatment conditions for the Cu–Bi/Al2O3 catalyst on its electro-catalytic activity were investigated. For a temperature of 550 °C and a time of 5 h, the obtained Cu–Bi/Al2O3 catalyst exhibited the highest p-nitrophenol removal, nearly 100% after 60 min electrolysis, and this was decreased by only 4.5% after 10 cycles. In addition, the intermediates formed during degradation were identified using high-performance liquid chromatography, and the major intermediates formed during degradation were benzoquinone, hydroquinone, catechol, p-aminophenol, phenol, maleic acid, succinic acid, and oxalic acid. On the basis of the reaction products identified, a possible degradation pathway for p-nitrophenol was proposed.