Lian-Kui Wu

A nanostructured nickel–cobalt alloy with an oxide layer for an efficient oxygen evolution reaction

A nanostructured nickel–cobalt alloy with an oxide layer was fabricated and its superior catalytic activity towards the electrochemical oxygen evolution reaction in alkaline media was investigated. Firstly, a NiCo–SiO2 composite film was prepared via a potentiostatic electro-codeposition method. Then the SiO2 template was etched and the NiCo component was activated leading to the generation of a NiCoOx layer during consecutive CV scans in concentrated alkaline solution. The results show that this nanostructured NiCo alloy with the oxide layer can provide a current density of 100 mA cm−2 in 1.0 M KOH at a low overpotential of 326 mV and exhibits good stability towards water oxidation. The excellent OER performance is enabled with the unique metal-oxide structure, which allows high electrical conductivity in the metal and high catalytic activity on the oxide.

Copper-promoted cementation of antimony in hydrochloric acid system: A green protocol

A new method of recovering antimony in hydrochloric acid system by cementation with copper powder was proposed and carried out at laboratory scale. Thermodynamic analysis and cyclic voltammetry test were conducted to study the cementation process. This is a novel antimony removal technology and quite meets the requirements of green chemistry. The main cement product Cu2Sb is a promising anodic material for lithium and sodium ion battery. And nearly all consumed copper powder are transformed into CuCl which is an important industrial material. The effect of reaction temperature, stoichiometric ratio of Cu to Sb(III), stirring rate and concentration of HCl on the cementation efficiency of antimony were investigated in detail. Optimized cementation condition is obtained at 60 °C for 120 min and stirring rate of 600 rpm with Cu/Sb(III) stoichiometric ratio of 6 in 3 mol L(-1) HCl. At this time, nearly all antimony can be removed by copper powder and the cementation efficiency is over 99%. The structure and morphologies of the cement products were characterized by X-ray diffraction and scanning electron microscopy, respectively. Results show that the reaction temperature has little influence on the morphology of the cement products which consist of particles with various sizes. The activation energy of the cementation antimony on copper is 37.75 kJ mol(-1), indicating a chemically controlled step. Inductively coupled plasma mass spectrometry results show that no stibine generates during the cementation process.

Highly porous copper ferrite foam: A promising adsorbent for efficient removal of As(III) and As(V) from water

A novel copper ferrite foam fabricated on Fe-Ni foam substrate was synthesized via a simple hydrothermal method to efficiently remove arsenic from aqueous solution. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-Ray diffraction pattern (XRD) and Raman spectra were used to characterize the morphology and surface composition of the copper ferrite foam (CFF). The adsorption behavior of As(III) and As(V) onto this CFF is studied as a function of solution pH, temperature, contact time, and different concentrations. Results shown that this CFF has high adsorption capacity and excellent recyclability. Adsorption isotherms study indicates Langmuir model of adsorption. The maximum adsorption capability of As(III) and As(V) on CuFe2O4 foam is observed about 44.0 mg g-1 and 85.4 mg g-1, respectively. Regeneration experiment indicates that arsenic could be easily desorbed from CFF with 0.10 mol L-1 NaOH and the high adsorption capacity can be maintained for six regeneration cycle.

Effective cementation and removal of arsenic with copper powder in a hydrochloric acid system

This work investigated the removal and cementation of arsenic from a hydrochloric acid system with copper powder. Thermodynamic analysis and cyclic voltammetry test were conducted to evaluate the feasibility of cementation. The effect of reaction temperature, mole ratio of Cu to As(III), stirring rate, reaction time and HCl concentration on the cementation efficiency of arsenic were investigated systematically. 94.75% of the arsenic could be removed under optimized conditions: mole ratio of Cu/As = 8 at 45 °C for 60 min. The structure and morphologies of the cement products were characterized by X-ray diffraction and scanning electron microscopy, respectively. The results show that the reaction temperature has little influence on the morphology of the cement products which consist of particles with various sizes, but has a great influence on the cementation efficiency. During the cementation process, the rate-controlling mechanisms are changed at different temperatures. It is diffusion controlled at the high temperature region (45–50 °C) with an activation energy of 26.7 kJ mol−1, while it is surface reaction controlled at the lower temperature region (30–45 °C) with an activation energy of 145.7 kJ mol−1. Ammonium citrate can efficiently inhibit the evolution of arsane, while has little influence on the cementation efficiency of arsenic.