Zhenhai Liang

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.

Photoelectrocatalytic activity of two antimony doped SnO2 films for oxidation of phenol pollutants

Abstract Two types of Sb-doped SnO2 films on titanium substrate were prepared by the combination of electro-deposition and dip-coating (Ti/SnO2-Sb2O4/SnO2-Sb2O4) and single dip-coating (Ti/SnO2-Sb2O4), respectively. The surface morphology and crystalline structure of both film electrodes were characterized using X-ray diffractometry(XRD) and scanning electron microscopy(SEM). XRD spectra indicate that the rutile SnO2 forms in two films and a TiO2 crystallite exists only in Ti/SnO2-Sb2O4 electrode. SEM images show that the surface morphology of two films is typically cracked-mud structure. The photooxidation experiment was proceeded to further confirm the two electrode activity. The results show that the photoelectrocatalytic degradation efficiency of Ti/SnO2-Sb2O4 electrode with sub-layer is higher than that of simple Ti/SnO2-Sb2O4 electrode using phenol as a model organic pollutant. The Ti/SnO2-Sb2O4/SnO2-Sb2O4 photoanode has a better photoelectrochemical performance than Ti/SnO2-Sb2O4 photoanode for the removal of organic pollutants from water.

A novel photoelectrocatalytic approach for water splitting by an I-BiOCl/bipolar membrane sandwich structure

A novel photoelectrocatalytic approach for water splitting through an I-BiOCl/bipolar membrane sandwich structure with photoelectro-synergistic catalysis is proposed in this study. The I-BiOCl/bipolar membrane sandwich structure could facilitate separation of photoexcited electrons and holes, thereby promoting the splitting of water, increasing the efficiency of H2 generation and saving energy consumption.

Performance of sodium bromate as cathodic electron acceptor in microbial fuel cell

The potential of using sodium bromate as a cathodic electron acceptor in a microbial fuel cell (MFC) was determined in this study. The effects of sodium bromate concentration and initial catholyte pH on the electricity production of the MFC were investigated. The MFC performance improved with increasing sodium bromate concentration and decreasing catholyte pH. The maximum voltage output (0.538 V), power density (1.4908 W m(-3)), optimal open circuit potential (1.635 V), coulombic efficiency (11.1%), exchange current density (0.538 A m(-3)) and charge transfer resistance (4274.1 Ω) were obtained at pH 3.0 and 100 mM sodium bromate. This work is the first to confirm that sodium bromate could be used as an electron acceptor in MFCs.

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.

Enhanced photoelectric performance of (2Al, S) co-doped rutile SnO2

In this study, theoretical calculations and experiments have been carried out to investigate the photoelectric performance of (2Al, S) co-doped rutile SnO2. The electronic structures are studied by density functional theory (DFT). It is found that the metal Al can assist the bonding of the incorporated S with the neighboring O in SnO2, introducing new energy levels in the forbidden band of SnO2, which enhance the photoelectric performance. Meanwhile, the experiments are conducted to verify this. The (2Al, S) co-doped SnO2 with different doping ratios are prepared by a hydrothermal method. The samples are characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Results show that all the samples have rutile structure without any extra phase, and the dopant S2− ion was implanted into the crystalline lattice of (2Al, S) co-doped SnO2 and Al dopants replaced Sn atoms. The photoelectric performance tests show Al and S co-doping can improve the photoelectric performance, especially with a doping ratio of 5%, when the photocurrent reaches maximum of 3.0 μA cm−2 which is almost twice as much as pure SnO2, and the impedance is the smallest. The experiments results are consistent with our theoretical calculations. These findings are expected to be helpful for the design of highly active tin oxide-based photoelectric materials.

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.