Solid polymer electrolyte electrochemical energy conversion devices that operate under highly alkaline conditions afford faster reaction kinetics and the deployment of inexpensive electrocatalysts ...compared with their acidic counterparts. The hydroxide anion exchange polymer is a key component of any solid polymer electrolyte device that operates under alkaline conditions. However, durable hydroxide-conducting polymer electrolytes in highly caustic media have proved elusive, because polymers bearing cations are inherently unstable under highly caustic conditions. Here we report a systematic investigation of novel arylimidazolium and bis-arylimidazolium compounds that lead to the rationale design of robust, sterically protected poly(arylimidazolium) hydroxide anion exchange polymers that possess a combination of high ion-exchange capacity and exceptional stability.
Two classes of novel sulfonated phenylated polyphenylene ionomers are investigated as polyaromatic‐based proton exchange membranes. Both types of ionomer possess high ion exchange capacities yet are ...insoluble in water at elevated temperatures. They exhibit high proton conductivity under both fully hydrated conditions and reduced relative humidity, and are markedly resilient to free radical attack. Fuel cells constructed with membrane‐electrode assemblies containing each ionomer membrane yield high in situ proton conductivity and peak power densities that are greater than obtained using Nafion reference membranes. In situ chemical stability accelerated stress tests reveal that this class of the polyaromatic membranes allow significantly lower gas crossover and lower rates of degradation than Nafion benchmark systems. These results point to a promising future for molecularly designed sulfonated phenylated polyphenylenes as proton‐conducting media in electrochemical technologies.
Passing stress test: Two classes of novel sulfonated polyphenylene ionomers were investigated as proton exchange membranes. Both possess high ion‐exchange capacities yet are insoluble in water. They exhibit high proton conductivity under both fully hydrated conditions and reduced relative humidity, and are markedly resilient to free‐radical attack.
The copolymerization of a prefunctionalized, tetrasulfonated oligophenylene monomer was investigated. The corresponding physical and electrochemical properties of the polymers were tuned by varying ...the ratio of hydrophobic to hydrophilic units within the polymers. Membranes prepared from these polymers possessed ion exchange capacities ranging from 1.86 to 3.50 meq g−1 and exhibited proton conductivities of up to 338 mS cm−1 (80 °C, 95 % relative humidity). Small‐angle X‐ray scattering and small‐angle neutron scattering were used to elucidate the effect of the monomer ratios on the polymer morphology. The utility of these materials as low gas crossover, highly conductive membranes was demonstrated in fuel cell devices. Gas crossover currents through the membranes of as low as 4 % (0.16±0.03 mA cm−2) for a perfluorosulfonic acid reference membrane were demonstrated. As ionomers in the catalyst layer, the copolymers yielded highly active porous electrodes and overcame kinetic losses typically observed for hydrocarbon‐based catalyst layers. Fully hydrocarbon, nonfluorous, solid polymer electrolyte fuel cells are demonstrated with peak power densities of 770 mW cm−2 with oxygen and 456 mW cm−2 with air.
In tune in the membrane! The physical and electrochemical properties of tetrasulfonated oligophenylene copolymers were tuned by varying the ratio of hydrophobic to hydrophilic units within the polymers. These materials were utilized as low gas crossover, highly conductive membranes in fuel cell devices. As ionomers in the catalyst layer, the copolymers yielded highly active porous electrodes and overcome kinetic losses typically observed for hydrocarbon‐based catalyst layers.
Acoustic telemetry is one of the primary technologies for studying the behavior and survival of fishes throughout the world. The size and performance of the transmitter are key limiting factors. The ...newly developed injectable transmitter is the first acoustic transmitter that can be implanted via injection instead of surgery. A two-part field study was conducted to evaluate the performance of the injectable transmitter and its effect on the survival of implanted fish. The injectable transmitter performed well and similarly to the proceeding generation of commercially-available JSATS transmitters tested concurrently. Snake River subyearling Chinook salmon smolts implanted with the injectable transmitter had a higher survival probability from release to each of eleven downstream detection arrays, because reach-specific survival estimates were significantly higher for the injectable group in three of the eleven reaches examined. Overall, the injectable group had a 0.263 (SE = 0.017) survival probability over the entire 500 km study area compared to 0.199 (0.012) for the surgically implanted group. The reduction in size and ability to implant the new transmitter via injection has reduced the tag or tagging effect bias associated with studying small fishes. The information gathered with this new technology is helping to evaluate the impacts of dams on fishes.
We developed an approach to quantify early life history diversity for Chinook salmon (Oncorhynchus tshawytscha). Early life history diversity (ELHD) is the variation in morphological and behavioral ...traits expressed within and among populations by individual juvenile salmon during downstream migration. A standard quantitative method does not exist for this prominent concept in salmon biology. For Chinook salmon, ELHD reflects the multitude of possible strategies undertaken during the juvenile (fry through smolt) phases of their life cycle, where a life history strategy (or pattern) describes the combination of traits exhibited by an organism throughout its life cycle. Increasing life history diversity to improve resilience and aid recovery of diminished salmon and steelhead populations is a common objective in fish population recovery efforts. In this paper, we characterized early life history traits and prioritize timing and fish size as two appropriate, measurable dimensions for an ELHD index. We studied diversity index literature, identified an indexing approach based on the effective number of time-size trait combinations, and tested several candidate indices for performance and usefulness in case studies using juvenile salmon catch data from the lower Columbia River and estuary. The recommended ELHD index is diversity expressed as the effective number of time-size trait combinations for the Shannon Index, modified to include an adjustment for missing time-size trait combinations and a sample coverage factor. This index applies to multiple life history strategies of juvenile salmonids; incorporates fish abundance, richness, and evenness; and produces readily interpretable values. The ELHD index can support comparisons across like locales and examinations of trends through time at a given locale. It has application as a high-level indicator to track trends in the status of the recovery of salmon and steelhead populations in the Columbia River basin and elsewhere where salmon recovery efforts are under way.
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