Proton transport for fuel cells

No abstract

Selective Hydrogenation of Furfural in a Proton Exchange Membrane Reactor Using Hybrid Pd/Pd Black on Alumina

Invited for this month’s cover picture are the groups of Dr. Peter Pintauro (Vanderbilt University, Tennessee, USA), Dr. Levi Thompson (University of Delaware, Delaware, USA), and Dr. William Tarpeh (Stanford University, California, USA). The cover picture shows the controlled variation of furfural hydrogenation product speciation based on varying cathode formulations of hybrid Pd black and Pd on alumina support. Read the full text of the article at 10.1002/celc.201901314.“The performance of different cathode compositions is evaluated at different current densities (which varies with hydrogen production) in terms of production rate, faradaic efficiency, and selectivity. To isolate the influences of the electrocatalyst in the hybrid catalyst, the performance of electrocatalyst Pd black is evaluated separately. These four variations of the hybrid cathode are investigated to test the hypothesis that the addition of the metal loaded on metal oxide to the electrocatalyst enhances the production rate for hydrogenated products compared to electrodes with only an electrocatalyst…“ Learn more about the story behind the research featured on the front cover in this issue’s Cover Profile. Read the corresponding Article at 10.1002/celc.201901314.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/152714/1/celc201901737.pd

A Comprehensive Study of an Acid-Based Reversible H2-Br2 Fuel Cell System

The regenerative H2-Br2 fuel cell has been a subject of notable interest and is considered as one of the suitable candidates for large scale electrical energy storage. In this study, the preliminary performance of a H2-Br2 fuel cell using both conventional as well as novel materials (Nafion and electrospun composite membranes along with Pt and RhxSy electrocatalysts) is discussed. The performance of the H2-Br2 fuel cell obtained with a conventional Nafion membrane and Pt electrocatalyst was enhanced upon employing a double-layer Br2 electrode while raising the cell temperature to 45°C. The active area and wetting characteristics of Br2 electrodes were improved upon by either pre-treating with HBr or boiling them in de-ionized water. On the other hand, similar or better performances were obtained using dual fiber electrospun composite membranes (PFSA/PPSU) versus using Nafion membranes. The RhxSy electrocatalyst proved to be more stable in the presence of HBr/Br2 than pure Pt. However, the H2 oxidation activity on RhxSy is quite low compared to that of Pt. In conclusion, a stable H2 electrocatalyst that can match the hydrogen oxidation activity obtained with Pt and a membrane with low Br2/Br− permeability are essential to prolong the lifetime of a H2-Br2 fuel cell

New Membrane Nano-Morphologies for Improved Fuel Cell Operation

Presented on February 4, 2009, from 4-5 pm in room G011 of the Molecular Science and Engineering Building on the Georgia Tech Campus.Runtime: 60:08 minutesPolymeric membranes play a crucial role during the generation of electricity in hydrogen/air and direct methanol proton-exchange membrane (PEM) fuel cells. The membrane in such devices has three functions: (1) to physically separate the positive and negative electrodes (so there is no electrical short circuit), (2) to prevent mixing of the fuel and oxidant, and (3) to provide a conduit for proton transport between the electrodes. For hydrogen fuel cells, the membrane must exhibit low gas permeability and high proton conductivity. For a direct liquid methanol PEM fuel cell, the ion-exchange membrane must conduct protons and be a good methanol barrier. For any fuel cell, the membrane must have good mechanical properties in the wet and dry states and be chemically stable under fuel cell operating conditions. DuPont’s Nafion® (a perfluorosulfonic acid polymer) has many attractive properties and has been widely studied in PEM fuel cells, but it does not meet all performance criteria. In a hydrogen/air fuel cell, Nafion loses water and the conductivity drops at temperatures 80oC, unless the water activity in the feed gases is near unity. Nafion has also been used in direct methanol fuel cells, but high methanol crossover (permeation) leads to low power output due to cathode depolarization. Polymer nano-morphology manipulation/control is a promising strategy to improve the performance of fuel cell membranes. Two examples of this approach will be discussed: (i) pre-stretched recast Nafion for direct methanol fuel cells and (ii) composite membranes based on proton conducting ionomeric nanofibers. Membrane fabrication methods and the results of membrane characterization tests will be described. Physical property data relevant to PEM fuel cell applications will be related to the membrane’s nanostructure and fuel cell performance data will be presented

Electrospun Hybrid Perfluorosulfonic Acid/Sulfonated Silica Composite Membranes

Electrospinning was employed to fabricate composite membranes containing perfluorosulfonic acid (PFSA) ionomer, poly(vinylidene fluoride) (PVDF) reinforcement and a sulfonated silica network, where the latter was incorporated either in the PFSA matrix or in the PVDF fibers. The best membrane, in terms of proton conductivity, was made by incorporating the sulfonated silica network in PFSA fibers (Type-A) while the lowest conductivity membrane was obtained when sulfonated silica was incorporated into the reinforcing PVDF fibers (Type-B). A Type-A membrane containing 65 wt.% PFSA with an embedded sulfonated silica network (at 15 wt.%) and with 20 wt.% PVDF reinforcing fibers proved superior to the pristine PFSA membrane in terms of both the proton conductivity in the 30–90% RH at 80 °C (a 25–35% increase) and lateral swelling (a 68% reduction). In addition, it was demonstrated that a Type-A membrane was superior to that of a neat 660 EW perfluoroimide acid (PFIA, from 3M Co.) films with respect to swelling and mechanical strength, while having a similar proton conductivity vs. relative humidity profile. This study demonstrates that an electrospun nanofiber composite membrane with a sulfonated silica network added to moderately low EW PFSA fibers is a viable alternative to an ultra-low EW fluorinated ionomer PEM, in terms of properties relevant to fuel cell applications