Xiuli Song

Electrochemical synthesis of flower shaped morphology MOFs in an ionic liquid system and their electrocatalytic application to the hydrogen evolution reaction

An important functional material, MOF-5, with unique flower shaped morphology, which is usually synthesized through hydrothermal or solvothermal methods at high temperature and pressure with high energy consumption, was successfully prepared by a mild in situ electrochemical synthesis method in a tunable ionic liquid (IL) system. In the reaction, H2BDC (BDC = 1,4-benzene-dicarboxylate) was chosen as the organic ligand, and the ionic liquid was Bmim (Bmim = 1-butyl-3-methylimidazole) bromine which functioned as a templating agent. The π–π stacking interaction between the imidazole groups, and the ionic band between the Zn2+ and Cl−, cause the directional arrangement of the MOF-5 crystal. Results show that the reaction results in a more perfect MOF-5 crystalline phase in comparison to other methods. The product, MOF-5(IL), presents a distinctive flower shaped morphology with a diameter of about 10 microns, and possesses a homogeneous morphology, stable structure and high thermal stability (up to 380 °C in N2 atmosphere). The electrochemical reaction in the ionic liquid Bmim bromine is a quasi-reversible redox reaction. The cyclic voltammetric curve of the MOF-5(IL) modified carbon paste electrode (CPE) illustrates that the flower shaped MOF-5(IL) has a better ability to catalyze the hydrogen evolution reaction than cubic MOF-5 prepared by other methods. The electrochemical method in the ionic liquid system can also be used to synthesize other MOF materials and nanomaterials by changing the metal ions, ligands and ionic liquid types.

In situ electrochemical synthesis of MOF-5 and its application in improving photocatalytic activity of BiOBr

Abstract Metal–organic frameworks (MOFs) are important functional materials. MOF-5 (IL) (Zn 4 O(BDC) 3 (BDC=1,4-benzene- dicarboxylate) was in situ synthesized by the electrochemical method using a tunable ionic liquid (IL), 1-butyl-3-methylimidazolium chloride, as template. The crystallization of distinctly spherical MOF-5 (IL) synthsized in ionic liquid by the electrochemical method is attributed to π–π stacking effect, ionic bond, and coordination bond. The analysis results show that the product MOF-5(IL) exhibits better crystallinity and higher thermal stability than MOF-5 generated using the solvothermal method. The cyclic voltammetry reveals that the electrosynthesis reaction is irreversible and controlled by the diffusion. The experiments on methylorange degradation show that the unique structure characteristics of MOF-5(IL) can enhance the photocatalytic ability of BiOBr. Therefore, MOFs can replace noble metals to improve the photocatalytic properties of bismuth oxyhalide.

A photocatalytic graphene quantum dots–Cu2O/bipolar membrane as a separator for water splitting

Graphene quantum dots–Cu2O (GQDs–Cu2O) is introduced to a bipolar membrane (BPM) interlayer and shown to be a novel, efficient water dissociation catalyst. This paper reports the use of the GQDs–Cu2O/BPM composite as a separator to prevent the crossover of hydrogen and oxygen. Under reverse bias and sunlight irradiation conditions, GQDs–Cu2O/BPM exhibits lower membrane resistance than BPM. GQDs–Cu2O/BPM also minimizes pH gradient formation, resulting in a decreased potential loss with respect to that of BPM. The efficiency of GQDs–Cu2O/BPM as a diaphragm in H2 generation and energy conservation was assessed. GQDs–Cu2O/BPM was found to be 88.6% and 14.5% more efficient than BPM in H2 generation at the current density of 90 mA cm−2 and under sunlight irradiation, respectively. The composite also saved about 22.6% energy with respect to that of BPM at 90 mA cm−2.

A BiOCl/bipolar membrane as a separator for regenerating NaOH in water-splitting cells

Photoconductive BiOCl has been introduced into a bipolar membrane (BPM) interlayer to prepare a BiOCl/BPM. This paper reports the use of the BiOCl/BPM composite to regenerate NaOH. Under reverse bias and sunlight irradiation conditions, the BiOCl/BPM resistance and cell voltage can be significantly decreased due to the photoconductivity of the BiOCl photocatalyst, which lead to the energy consumption decline in regenerating NaOH. Moreover, the electric field in the interlayer of the BiOCl/BPM contributes in separating the photo-generated electron–hole pairs of the BiOCl photocatalyst, thereby increasing the current efficiency of regenerating NaOH.

Electrochemical Behavior of Electrocatalytic Synthesis of Oxalic Acid from Acetylene at Pt Electrode

Abstract Electrocatalytic synthesis of oxalic acid from acetylene has been achieved at Pt electrode. The electrocatalytically synthesized oxalic acid has been characterized by FTIR (Fourier transform infrared spectroscopy) and UV-Vis (UV-Vis spectrophotometry). Influence of electrode material, Na2SO4 concentration, acetone volume fraction, temperature and scan rate have been investigated by CV (cyclic voltammetry). The analysis results show that oxalic acid has been successfully electrocatalytically synthesized from acetylene at the very stable Pt electrode under ambient temperature and pressure, the supporting electrolyte is Na2SO4 (0.5 M) with acetone (2% by volume), the reaction time is 8 h and the conversion efficiency is larger than 20%. The Ea (apparent activation energy) of electrocatalytic oxidation reaction of acetylene at the Pt electrode is 14.42 kJ·mol-1, the electrocatalytic oxidation process of acetylene is irreversible and under adsorption control. In addition, the reaction mechanism of the electrocatalytic oxidation process of acetylene to oxalic acid has been envisaged successfully based on the principle of adsorption and desorption at Pt electrode surface. It exhibits the excellent electrocatalytic performance of Pt in the electrocatalytic oxidation process of acetylene and heralds more broad potential application prospect of acetylene in chemical industry field.