Electrical Conductivity Response of Poly(Phenylene-vinylene)/Zeolite Composites Exposed to Ammonium Nitrate

Poly(p-phenylenevinylene) (PPV) was chemically synthesized via the polymerization of p-xylene-bis(tetrahydrothiophenium chloride) monomer and doped with H2SO4. To improve the electrical conductivity sensitivity of the conductive polymer, Zeolites Y (Si/Al = 5.1, 30, 60, 80) were added into the conductive polymer matrix. All composite samples show definite positive responses towards NH4NO3. The electrical conductivity sensitivities of the composite sensors increase linearly with increasing Si/Al ratio: with values of 0.201, 1.37, 2.80 and 3.18, respectively. The interactions between NH4NO3 molecules and the PPV/zeolite composites with respect to the electrical conductivity sensitivity were investigated through the infrared spectroscopy

Simple Solid-state Ag/AgCl Reference Electrode and Its Integration with Conducting Polypyrrole Electrode for the Production of All-solid-state pH Sensor

In this work, a solid-state Ag/AgCl electrode was successfully fabricated via electrodeposition of silver, followed by chlorination in the presence of ferric chloride to obtain silver chloride. Stainless steel rod was used as the supporting electrode. XPS and SEM were performed on the surfaces of silver to investigate the changes in surface composition and morphology, revealing the successful formation of silver chloride on the silver layer after the chlorination process. Calibrated against the commercial Ag/AgCl electrode, the developed solid-state Ag/AgCl electrode showed insensitive potentiometric response in different buffer solutions with the response time of 10 s. All-solid-state pH sensor, constructed by integrating the solid-state Ag/AgCl electrode with the polypyrrole-based pH indicative electrode, showed a linear potentiometric sensitivity of –53.55±1.33 mV.pH-1 (r2 > 0.99) over pH range of 2–12 with excellent reproducibility. The pH measurement in the selected real solutions was demonstrated, suggesting that the constructed all-solid-state pH sensor showed the comparable sensing performance to the commercial glass pH electrode. The all-solid-state sensor is currently miniaturized for the further use in microfluidics and flow injection analysis system

A novel pH sensor based on hydroquinone monosulfonate-doped conducting polypyrrole

Functionalized polypyrrole (PPy) with hydroquinone monosulfonate (HQS) incorporated as the dopant has been prepared by a simple one-step electropolymerization of pyrrole at a stainless steel electrode from aqueous solution. Potentiometric pH responses of the HQS-doped PPy electrodes showed a response slope of -50.54 ± 1.67 mV/pH (28 °C), a linear working range of pH 2-12 and a response time less than 100 s. The electrode stability was maintained over the period of a month. Compared with other PPy-based pH electrodes reported previously, the HQS-doped PPy electrode shows significantly improved potentiometric response slope, response time, reproducibility and stability. Interference studies with several ions showed minimal effects on the potentiometric response of the modified electrode. A combination of X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary-ion mass spectrometry (ToF-SIMS) was performed to investigate the surface composition and characteristics of the electrodes, including the chemical basis of the electrode performance. Cyclic voltammetry revealed the expected electrochemical response of the HQS, which was electroactive in response to pH changes. HQS-doped PPy shows excellent potential as a novel pH sensor, incorporating both the electroactive species and conducting support in an integrated form, for a variety of applications requiring pH monitoring.</p

A sensitive and highly stable polypyrrole-based pH sensor with hydroquinone monosulfonate and oxalate co-doping

A polymer-based pH electrode has been successfully fabricated via a simple electropolymerization of pyrrole on stainless steel using a co-doping system. Hydroquinone monosulfonate (HQS) was selected as a functional dopant while oxalic acid was used as a co-dopant. A combination of cyclic voltammetry and X-ray photoelectron spectroscopy revealed that passive layers of iron oxalate and chromium oxalate formed on the stainless steel surface at the initial stage of electropolymerization. The potentiometric characteristics of the co-doped polypyrrole (PPy) electrode exhibited a response slope of -54.67 ± 0.70 mV/pH at 28 °C, a linearity range from pH 2 to 12 and correlation coefficient greater than 0.995. The open-circuit potential was stable in buffer solutions with a response time less than 10 s, regardless of the age of electrode. The co-doped PPy electrode could be used as a multi-use pH sensor up to 60 days without any effect to the potentiometric response. Interferences from most of common ions are acceptably small. In comparison with a HQS-doped PPy electrode, the co-doped PPy electrode provides a superior pH measurement in solution due to the higher pH sensitivity and longer lifetime. Co-doping results in an improvement in the adhesion strength of the co-doped PPy film with the stainless steel electrode. Easy fabrication and the low production cost of the co-doped PPy electrodes offer an alternative to pH sensors having a comparable potentiometric performance with commercial glass electrodes.</p

Performance Evaluation for Ultra-Lightweight Epoxy-Based Bipolar Plate Production with Cycle Time Reduction of Reactive Molding Process

The commercial viability of fuel cells for vehicle application has been examined in the context of lightweight material options, as well as in combination with improvements in fuel cell powertrain. Investigation into ultra-lightweight bipolar plates (BPs), the main component in terms of the weight effect, is of great importance to enhance energy efficiency. This research aims to fabricate a layered carbon fiber/epoxy composite structure for BPs. Two types of carbon fillers (COOH-MWCNT and COOH-GNP) reinforced with woven carbon fiber sheets (WCFS) have been utilized. The conceptual idea is to reduce molding cycle time by improving the structural, electrical, and mechanical properties of BPs. Reducing the reactive molding cycle time is required for commercial production possibility. The desired crosslink density of 97%, observed at reactive molding time, was reduced by 83% at 140 °C processing temperature. The as-fabricated BPs demonstrate excellent electrical conductivity and mechanical strength that achieved the DOE standard. Under actual fuel cell operation, the as-fabricated BPs show superior performance to commercial furan-based composite BPs in terms of the cell potential and maximum power. This research demonstrates the practical and straightforward way to produce high-performance and reliable BPs with a rapid production rate for actual PEMFC utilization

Evaluation of the Possibility for Using Polypropylene/Graphene Composite as Bipolar Plate Material Instead of Polypropylene/Graphite Composite

To reduce the bipolar plate weight and keep the desired power density of a low temperature fuel cell, thermoplastic composite bipolar plates have been fabricated for low temperature fuel cell applications. Concerns over material weight, electrical conductivity, mechanical properties, and injection processability of the thermoplastic nanocomposites have brought forth the idea of producing a polypropylene/graphene nanocomposite for an injection moulded bipolar plate application. In this article, the properties of produced polypropylene/graphene nanocomposites were also compared with the properties of polypropylene/graphite composites to assess the feasibility for using polypropylene/graphene nanocomposites as a bipolar plate material. The effects of graphene contents and sizes on electrical conductivity and mechanical properties were reported in this work. Moreover, the obtained results were discussed in terms of morphology and state of dispersion and distribution of the graphene within the polypropylene matrix. This work is a preliminary study that offers insight into the material selection and development for low temperature fuel cells toward the ultimate goal of broad commercialization.