Hossein Ghassemi

Improved Methanol Barrier Property of Nafion Hybrid Membrane by Incorporating Nanofibrous Interlayer Self-Immobilized with High Level of Phosphotungstic Acid

High level of phosphotungstic acid (PWA) was self-immobilized on electrospun nylon nanofiberous sheet to fabricate highly selective methanol barrier layer for sandwich structured proton conducting membranes. Simple tuning for the assembly conditions of central layer and thickness of outer Nafion layers allowed obtaining different composite membranes with superior methanol barrier properties (namely, P=3.59×10(-8) cm2 s(-1)) coupled with proton conductivities reaching 58.6 mS cm(-1) at 30 °C. Comparable activation energy for proton transport and more than 20 times higher selectivity than Nafion 115 confirm the effectiveness of the central layer and resulting membranes for application in direct methanol fuel cells (DMFCs). When tested in DMFC single cell, the performance of hybrid membrane was far better than Nafion 115 especially at higher methanol concentrations.

Phase separated nanofibrous anion exchange membranes with polycationic side chains

Anion exchange membranes (AEMs) have gained significant interest in electrochemical energy devices with a unique set of benefits. However, none of the commercial AEMs behave ideally under alkaline operation conditions and developing appropriate membranes is one of the major hurdles to the durability and performance of anion exchange membrane fuel cells. Here we demonstrate a simple and efficient strategy of using nanofibrous materials, activated by radiation and functionalized with ionic groups to fabricate highly durable and conductive membranes with polycationic side chains. Two series of AEMs were prepared by radiation induced emulsion grafting of vinylbenzyl chloride onto syndiotactic polypropylene and nylon-66 nanofibrous sheets followed by crosslinking and introducing quaternary ammonium groups. A strong correlation was found between the choice of nanofibrous substrate as well as crosslinking degrees with water uptake, ion conductivity and stability of the membranes. A well-developed phase separated morphology was confirmed and the membranes with ion exchange capacities of 1.6–2.1 mmol g−1 showed high ionic conductivity, low methanol permeability and excellent alkaline stability. A hydroxide ion conductivity as high as 132 mS cm−1 was achieved at 80 °C and it was exceptionally retained at up to 90% after evaluation by accelerated degradation testing in 1 M NaOH at 80 °C for 672 h. A Pt-catalyzed fuel cell using these nanofibrous composite membranes showed a peak power density of above 120 mW cm−2 at 80 °C under 90% relative humidity. This strategy and observed properties pave the way for highly conductive and durable ion conducting membranes with tunable characteristics.

FUEL CELLS – PROTON-EXCHANGE MEMBRANE FUEL CELLS | Membrane: Life-Limiting Considerations

An overview of the state of the art related to membrane durability for proton-exchange membrane fuel cells (PEMFCs) is presented. In particular, we discuss (1) causes of membrane failure in PEMFCs; (2) degradation reactions of perfluorosulfonic acid (PFSA) membranes as revealed by exposure of model compounds to peroxide in the presence of active metals and ultraviolet irradiation; and (3) currently emerging mitigation methods. We close with some brief comments on future prospects, notably the need for similar mechanistic elucidation of non-PFSA membranes.

Triazole-based Electrolytes for Fuel Cell Applications: Material Properties and Proton Transfer Capabilities

4,5-Dicyano-1H-[1,2,3]-Triazole (DCTz) exhibits a very low proton affinity. This makes it a possible water replacement for proton transport in high temperature polymer electrolyte membranes. A detailed investigation is carried out to define various physical properties as well as the proton transfer characteristics of DCTz. Thermogravimetric analysis showed that DCTz as well as DCTz salts are thermally stable at high temperature (> 100°C). H NMR spectra reveal proton exchange in DCTz solutions. The NMR spectroscopy reveals the dependence of proton transport on concentration, temperature and the presence of excess protons added as acid dopants.