SEARCH · Engineering Papers
Results for “Cell membranes”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Cardiolipin remodeling maintains the inner mitochondrial membrane in cells with saturated lipidomes
Not Available
Experimental and computational study of the microporous layer and hydrophobic treatment in the gas diffusion layer of a proton exchange membrane fuel cell
Enabling fuel cell operation at high current density is critical for developing competitive alternative power system to replace internal combustion engine. However, liquid water management continues to be a challenge for high humidity or high current density operation. Water condensation in the porous media hinders efficient oxygen transport to the catalyst layer, which in turns, reduces fuel cell performance. To improve water management capability, the gas diffusion layer is often impregnated with Polytetrafluoroethylene (PTFE) and coated with a thin microporous layer, which have shown to improve fuel cell performance, especially under wet conditions. However, the fundamental mechanism that drives the performance enhancement is still not well understood. In this work, the effects of PTFE impregnation and MPL were studied using both experimental and computational techniques. Both limiting current and polarization tests under dry and wet operating condition are conducted to study the oxygen transport resistance and fuel cell performance. In addition, a 2-D, two-phase, multi-physics PEMFC model is developed to simulate performance and gain a fundamental understanding of local water saturation and oxygen concentration. The combined results show that 5 wt% PTFE impregnation with MPL significantly enhances liquid water management, which enables higher current density operation of a fuel cell.
Palladium-ceria catalysts with enhanced alkaline hydrogen oxidation activity for anion exchange membrane fuel cells
Explore the source record for details and available documents.
Engineering Ionomer–Substrate Interface to Improve Thin-Film Proton Conductivity in Proton Exchange Membrane Fuel Cells
Not provided.
A High-Performance Gas-Fed Direct Ammonia Hydroxide Exchange Membrane Fuel Cell
Not provided.
Triple ionic–electronic conducting oxides for next-generation electrochemical devices
Triple ionic–electronic conductors (TIECs) are materials that can simultaneously transport electronic species alongside two ionic species. The recent emergence of TIECs provides intriguing opportunities to maximize performance in a variety of electrochemical devices, including fuel cells, membrane reactors and electrolysis cells. However, the potential application of these nascent materials is limited by lack of fundamental knowledge of their transport properties and electrocatalytic activity. The goal of this Review is to summarize and analyse the current understanding of TIEC transport and electrochemistry in single-phase materials, including defect formation and conduction mechanisms. In this work, we particularly focus on the discovery criteria (for example, crystal structure and ion electronegativity), design principles (for example, cation and anion substitution chemistry) and operating conditions (for example, atmosphere) of materials that enable deliberate tuning of the conductivity of each charge carrier. Lastly, we identify important areas for further advances, including higher chemical stability, lower operating temperatures and discovery of n-type TIEC materials.
Identification of durable and non-durable FeN x sites in Fe–N–C materials for proton exchange membrane fuel cells
We report that while Fe–N–C materials are a promising alternative to platinum for catalysing the oxygen reduction reaction in acidic polymer fuel cells, limited understanding of their operando degradation restricts rational approaches towards improved durability. Here we show that Fe–N–C catalysts initially comprising two distinct FeN x sites (S1 and S2) degrade via the transformation of S1 into iron oxides while the structure and number of S2 were unmodified. Structure–activity correlations drawn from end-of-test 57 Fe Mössbauer spectroscopy reveal that both sites initially contribute to the oxygen reduction reaction activity but only S2 substantially contributes after 50 h of operation. From in situ 57 Fe Mössbauer spectroscopy in inert gas coupled to calculations of the Mössbauer signature of FeN x moieties in different electronic states, we identify S1 to be a high-spin FeN 4 C 12 moiety and S2 a low- or intermediate-spin FeN 4 C 10 moiety. These insights lay the groundwork for rational approaches towards Fe–N–C cathodes with improved durability in acidic fuel cells.
Operando X-ray absorption spectroscopy of a Pd/γ-NiOOH 2 nm cubes hydrogen oxidation catalyst in an alkaline membrane fuel cell
The mechanism of Pd/γ-NiOOH 2 nm cubes hydrogen oxidation catalyst for alkaline fuel cell is investigated by operando X-ray absorption spectroscopy.
Fluoroalkyl phosphonic acid radical scavengers for proton exchange membrane fuel cells
Fluoroalkyl phosphonic acids are demonstrated to be an efficient radical scavenger for Nafion™, showing a 58% lower fluoride emission rate than the state of the art, cerium.
Modeling proton-exchange-membrane fuel cell performance/degradation tradeoffs with chemical scavengers
Not Available
Pore-Filled PEMs from Poly(Phenylene Sulfonic Acid)s and Electrospun Poly(Phenylene Sulfone) Fiber Mats
A novel, composite, non-PFSA-based fuel cell membrane has been fabricated using a pore filling technique. The membrane consists of a mechanically stabilizing skeleton from an electrospun poly(phenylene sulfone) (PPSU) fiber mat and a thermally crosslinkable poly(phenylene sulfonic acid) (cPPSA) proton conducting ionomer that fills the interfiber voids. cPPSA copolymer was synthesized using Ullmann coupling copolymerization of 4,4-dibromobiphenyl 3,3-disulfonic acid with 1,4-dibromobenzene-2,5-disulfonic, followed by grafting a certain fraction of backbone sulfonic acid groups with biphenyl linker. The PPSU fiber mat was electrospun from NMP/acetone solution. Pore-filling was carried out by pouring a solution of cPPSA in methanol over the mat, followed by heating at 70°C to evaporate solvent. The cPPSA was crosslinked by an additional heating step, in a vacuum oven at 210°C for 5 hours. Here the resultant membrane had excellent proton conductivity, 5 times greater than that of Nafion® 211 in the 40-90% RH range at 80°C.