Fanghui Wang

Cobaltocenium-containing polybenzimidazole polymers for alkaline anion exchange membrane applications

A polybenzimidazole, containing cobaltocenium on its backbones, was used for anion exchange membranes (AEMs) for the first time. The polymer was synthesized by polymerizing 1,1′-dicarboxycobaltocenium and 3,3′,4,4′-biphenyltetramine in a microwave reactor. Before the polymer fabrication, we studied the alkaline stability of three different cobaltocenium cations—cobaltocenium, 1,1′-dimethylcobaltocenium and 1,1′-dicarboxycobaltocenium—by 1HNMR and 13CNMR spectroscopy and investigated the degradation mechanisms of these cations under alkaline conditions. Then the three corresponding cobaltocenium-containing polybenzimidazole membranes were synthesized, and the relationship between the structure and performance of these cobaltocenium-containing polybenzimidazole membranes was investigated by 1HNMR spectroscopy, FTIR spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and AC impedance spectrascopy. These AEMs, based on cobaltocenium-containing polybenzimidazole backbones, show high thermal stabilities, good chemical stabilities, comparable hydroxide conductivities, low swelling ratios and good mechanical properties. The 1,1′-cobaltocenium-5,5′-(2,2′-dimethyl)-bibenzimidazole (MCp2Co+OH−-PBI) membrane shows the best comprehensive performance in this study. The hydroxide conductivity of the MCp2Co+OH−-PBI membrane at 90 °C can reach 37.5 mS cm−1 with a low swelling ratio. Furthermore, the degradation mechanism of the MCp2Co+OH−-PBI membrane under alkaline conditions was investigated by 1HNMR spectroscopy. In summary, our work investigates the degradation mechanisms of the cobaltocenium cations and cobaltocenium-containing polybenzimidazole under alkaline conditions and presents a novel polymer structure for AEM applications.

A new method for improving the ion conductivity of anion exchange membranes by using TiO2 nanoparticles coated with ionic liquid

Recently a new method for increasing the ion conductivity of anion exchange membranes (AEM) was developed based on the novel materials ionic liquids (ILs). We mixed the ILs into the membrane directly instead of immobilizing onto the polymer backbone as in the traditional way. Nano-TiO2 was introduced to stabilize the ILs in the membrane. The ILs were immobilized by the nano-TiO2, acting as the “active sites” in the membrane, to enhance the mobility of the hydroxyl groups so as to increase the ion conductivity. Both pure ILs composite membranes and ILs–TiO2 composite membranes were synthesized, and their properties were compared. 1H nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy were used to analyze the structures of the composite membranes. The mechanical properties, thermal stabilities, ion conductivities, water uptakes, swelling ratios, and ion exchange capacities of the membranes were investigated. The interaction between the TiO2 and ionic liquids was confirmed by X-ray diffraction. The stability of the ILs in the membrane was measured comprehensively. All these results show that this novel method is effective and promising for AEM applications.

Study on Ultrasonic Single-Step Synthesis and Optical Properties of Nitrogen-Doped Carbon Fluorescent Quantum Dots

Nitrogen doped carbon fluorescent quantum dots (NDCFDs) with downconversion fluorescent and upconversion fluorescence properties were prepared by an ultrasonic one-step process. The raw materials and reagents were inexpensive and easy to obtain. The effect of ultrasonic time and reaction temperature on the fluorescent quantum yield and particle size was study. Optimal preparation conditions of NDCFDs with the highest fluorescence quantum yield were achieved by employing a reaction time of 14 h at 50°C. NDFCDs were characterized by TEM, FTIR, Raman spectroscopy, XPS, UV spectrophotometer, and fluorescence spectrometer. The results showed that the surface of NDCFDs were rich in hydroxyl, carbonyl hydrophilic group, etc. The DNCFDs not only had downconversion fluorescent, but also had good upconversion fluorescence. The effect of concentration and type of solution on the fluorescence properties of NDCFDs was studied. The formation mechanism, fluorescence emission mechanism and self-assembly behavior of NDCFDs were also investigated.

The Preparation of a Polyether Demulsifier Modified by Nano-SiO2 and the Effect on Asphaltenes and Resins

Abstract In order to enlarge the range of applications of nanomaterials and improve the performance of macromolecular polymer demulsifier, nano-SiO2 was integrated with polyether demulsifier TA1031 to form nanomodified demulsifier using an in situ synthesis method. Analysis of the polyether demulsifier modified by nano-SiO2 was performed using transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy. The result showed that applying nanomaterials to crude oil demulsifier greatly improves the performance of the original demulsifier. When the ratio of nano-SiO2 and TA1031 is 1:10, the performance of the nanomodified demulsifier was best, and the ratio of demulsification was improved by about 20%. The time of demulification and dewatering was also greatly shortened by about 30 min. The influence of nanomodified demulsifier on the asphaltenes and resins was studied by FTIR.

Electrorheological effect induced quaternized poly(2,6-dimethyl phenylene oxide)-layered double hydroxide composite membranes for anion exchange membrane fuel cells

To improve the performance of anion exchange membranes (AEMs), we fabricated quaternized poly(2,6-dimethyl phenylene oxide)-layered double hydroxide composite membranes by combining the advantages of the two components. Also, the electrorheological effect was employed during the casting process to induce the formation of ion conducting channels along the through-plane direction. The membrane with 3% layered double hydroxide (LDH) (QPPO-Im-3% LDH) showed the largest increase in ionic conductivity over that of the pure membrane (QPPO-Im) (15.85 mS cm−1 at 30 °C to 22.52 mS cm−1 at 80 °C vs. 5.93 mS cm−1 at 30 °C to 11.63 mS cm−1 at 80 °C). The ionic conductivity was further improved by applying the electric field treatment, confirming that the addition of LDH and the electric field greatly affect the ionic conductivity of the AEMs. Moreover, the morphology, thermal and mechanical properties, ion-exchange capacity (IEC), water uptake (WU) and swelling ratio (SR) were also studied systematically to determine the effects of LDH and electric field on the membranes.

Pt–Co deposited on polyaniline-modified carbon for the electro-reduction of oxygen: the interaction between Pt–Co nanoparticles and polyaniline

Polyaniline-modified carbon black supported platinum–cobalt alloy nanoparticle (Pt–Co/C-PANI) catalysts were prepared via a microwave-assisted polyol method and subsequent high temperature annealing. X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and derivative thermogravimetric (DTG) analysis were used to characterize the structure of the catalysts. We find that the electron delocalization between the metal d orbitals and PANI is beneficial for improving the ORR performance and the PANI on carbon can prevent the aggregation of Pt–Co nanoparticles during high temperature treatments. Electrochemical evaluations reveal that the obtained Pt–Co/C-PANI catalysts annealed at 500 °C show the highest mass activity of 1.33 A mgPt−1 and a specific activity of 1.29 mA cm−2, which are 7.8 and 5.4 times higher than those of the commercial JM Pt/C catalyst, respectively. X-ray photoelectron spectroscopy (XPS) results show that only part of PANI is decomposed at 500 °C and the metal–nitrogen (M–N) bonds are formed in Pt–Co/C-PANI-500 °C, which are attributed to the impressive ORR activity enhancement in Pt–Co/C-PANI-500 °C.

Montmorillonite–Polybenzimidazole Inorganic-Organic Composite Membrane with Electric Field-Aligned Proton Transport Channel for High Temperature Proton Exchange Membranes

ABSTRACT The conductivity of high temperature proton exchange membranes (HTPEM) was improved by adding Montmorillonite (MMT) with proton counter-ions H+to polybenzimidazole containing ether units (PBI-O) based membrane. During casting procedure an external AC electric field was applied to the MMT-PBI-O-based composite membranes casting solution. The introduction of MMT nanoplatelets in HTPEM significantly improved the acid doping level and conductivity, without modifying the electrochemical/chemical stability,, dimensional stability and mechanical properties of composite membranes. The conductivity of 5%-MMT-PBI-O composite membranes was improved nearly 400% compared to pure PBI-O membranes, proving that the present technique is a potential method for fabricating HTPEM with oriented MMT nanoplatelets and taking full advantage of the bulk conductivity of the MMT nanoplatelets. GRAPHICAL ABSTRACT

Chitosan-Modified Poly(2,6-dimethyl-1,4-phenylene Oxide) for Anion-Exchange Membrane in Fuel Cell Technology

ABSTRACT A series of cross-linking chitosan-modified quaternary ammonium poly(2,6-dimethyl-1,4-phenylene oxide)s membranes (CS-QAPPO) were prepared by the Menshutkin reaction. The mechanical property, dimensional stability, and alkaline stability of the CS-QAPPO membrane have been impressively improved by introducing CS into PPO backbone. Even the hydroxide conductivity of CS-QAPPO membranes is higher than that of the pristine QAPPO membrane. The 20% chitosan-modified QAPPO membrane shows the best performance, and the hydroxide conductivity is 32 mS cm−1 at 90°C. The alkaline stability measurements demonstrated excellent chemical stability of the CS-QAPPO membrane in 2 M NaOH solution at room temperature after 2,000 h. GRAPHICAL ABSTRACT

Scalable Preparation of the Chemically Ordered Pt–Fe–Au Nanocatalysts with High Catalytic Reactivity and Stability for Oxygen Reduction Reactions

Carbon-supported Au-Pt xFe y nanoparticles were synthesized via microwave heating polyol process, followed by annealing for the formation of the ordered structure. The structure characterizations indicate that Au is alloyed with intermetallic Pt-Fe nanoparticles and therefore the surface electronic properties are tuned. The electrochemical tests show that the microwave heating polyol process is more effective than oil bath heating polyol process for synthesizing the highly active catalysts. The introduction of trace Au (0.2 wt % Au) significantly improves the oxygen reduction reaction (ORR) catalytic activity of Pt xFe y catalysts. Au-PtFe/C-H (0.66 A/mgPt) and Au-PtFe3/C-H (0.63 A/mgPt) prepared in a batch of 10.0 g show significantly improved catalytic activities than their counterparts (PtFe/C-H and PtFe3/C-H) as well as commercial Johnson Matthey Pt/C (0.17 A/mgPt). In addition, the as-prepared Au-PtFe/C-H and Au-PtFe3/C-H display highly enhanced stability toward the ORR compared to the commercial Pt/C. The superior catalytic performance is attributed to the synergistic effect of chemically ordered intermetallic structure and Au. This work provides a scalable synthesis of the multimetallic chemically ordered Au-Pt xFe y catalysts with high ORR catalytic performance in acidic condition.