Model Approach to Thermal Conductivity in Hybrid Graphene-Polymer Nanocomposites

The thermal conductivity of epoxy nanocomposites filled with self-assembled hybrid nanoparticles composed of multilayered graphene nanoplatelets and anatase nanoparticles was described using an analytical model based on the effective medium approximation with a reasonable amount of input data. The proposed effective thickness approach allowed for the simplification of the thermal conductivity simulations in hybrid graphene@anatase TiO2 nanosheets by including the phenomenological thermal boundary resistance. The sensitivity of the modeled thermal conductivity to the geometrical and material parameters of filling particles and the host polymer matrix, filler's mass concentration, self-assembling degree, and Kapitza thermal boundary resistances at emerging interfaces was numerically evaluated. A fair agreement of the calculated and measured room-temperature thermal conductivity was obtained.

Anion Exchange Membranes with 1D, 2D and 3D Fillers: A Review

Hydroxide exchange membrane fuel cells (AEMFC) are clean energy conversion devices that are an attractive alternative to the more common proton exchange membrane fuel cells (PEMFCs), because they present, among others, the advantage of not using noble metals like platinum as catalysts for the oxygen reduction reaction. The interest in this technology has increased exponentially over the recent years. Unfortunately, the low durability of anion exchange membranes (AEM) in basic conditions limits their use on a large scale. We present in this review composite AEM with one-dimensional, two-dimensional and three-dimensional fillers, an approach commonly used to enhance the fuel cell performance and stability. The most important filler types, which are discussed in this review, are carbon and titanate nanotubes, graphene and graphene oxide, layered double hydroxides, silica and zirconia nanoparticles. The functionalization of the fillers is the most important key to successful property improvement. The recent progress of mechanical properties, ionic conductivity and FC performances of composite AEM is critically reviewed.

Hydrophilic Flexible Ether Containing, Cross-Linked Anion-Exchange Membrane Quaternized with DABCO

Anion-exchange membranes (AEM) with high ion content usually suffer from excessive water absorption and dilution effects that impair conductivity and mechanical properties. We herein report a novel ether containing a cross-linking strategy without adopting high ion-exchange capacity (IEC). The ether-containing cross-links and the quaternized structure are created simultaneously by introducing an ether-containing flexible hydrophilic spacer between two 1,4-diazabicyclo[2,2,2,2]octane or DABCO molecules; the resultant bi-DABCO structure was further employed to react with chloromethylated polysulfone. The long spacer with the ether moiety may benefit the hydroxide ion transport, and the cross-links will control the swelling and water absorption of the AEM. The two ether groups in the long spacer of the cross-links will also shield the DABCO cation from OH^- attack due to an electron-donating effect. The prepared membranes exhibited an improved conductivity of 31 mS/cm (at 25 °C) at a comparatively low IEC (1.08 mmol/g) with a rational water absorption and low swelling ratio (95.0 and 27.1%, respectively); they also displayed an enhanced alkaline stability in 1 M NaOH aqueous solution at 80 °C for 150 h. The density functional theory study and physical characterization after the alkaline treatment further confirm the better chemical stability of the cross-linked membrane over its counterpart. Our work presents an effective strategy to balance AEM conductivity and robustness.

Enhanced water transport in AEMs based on poly(styrene–ethylene–butylene–styrene) triblock copolymer for high fuel cell performance

Anion exchange membrane fuel cells (AEMFCs) have received a considerable amount of attention in the past decades as a lower cost alternative to proton exchange membrane fuel cells (PEMFCs).

Enhanced Conductivity of Anion-Exchange Membrane by Incorporation of Quaternized Cellulose Nanocrystal

High ion conductivity of anion-exchange membrane is essential for the operation of alkaline anion-exchange membrane fuel cell. In this work, we demonstrated an effective strategy to enhance the conductivity of anion-exchange membrane (AEM), by incorporation of quaternized cellulose nanocrystal (QCNC) for the first time. Morphology observation demonstrated a uniform distribution of QCNC within QPPO matrix, as well as a clear QCNC network, which led to significant enhancement in hydroxide conductivities of composite membranes, for example, 2 wt % QCNC/QPPO membrane possessed a conductivity of 160% (60 mS cm^-1, @80 °C) of that of QPPO. Furthermore, H₂/O₂ cell performance of membrane electrode assembly based on 2 wt % QCNC/QPPO AEM showed an excellent peak power density of 392 mV cm^-2 at 60 °C without back pressure, whereas that of neat QPPO AEM was only 270 mV cm^-2.

High performance anion exchange ionomer for anion exchange membrane fuel cells

The anion exchange ionomer incorporated into the electrodes of an anion exchange membrane fuel cell (AEMFC) enhances anion transport in the catalyst layer of the electrode, and thus improves performance and durability of the AEMFC.

A facile construction of quaternized polymer brush-grafted graphene modified polysulfone based composite anion exchange membranes with enhanced performance

Novel quaternized polymer brush-functionalized graphenes (QPbGs) were synthesized and a series of composite anion exchange membranes for alkaline fuel cells were fabricated by incorporating different amounts of QPbGs into quaternized polysulfone.

Covalently functionalized graphene oxide and quaternized polysulfone nanocomposite membranes for fuel cells

Anion-exchange membranes based on quaternized polysulfone and modified graphene oxide showed good alkaline stability.