Abstract Proton‐exchange membrane fuel cell vehicles offer a low‐carbon alternative to traditional oil fuel vehicles, but their performances still need improvement to be competitive. Raising their operating temperature to 120 °C will enhance their efficiency but is currently unfeasible due to the poor mechanical properties at high temperatures of the state‐of‐the‐art proton‐exchange membranes consisting of perfluorosulfonic acid (PFSA) ionomers. To address this issue, xx designed composite membranes made of two networks: a mat of hybrid fibers to maintain the mechanical properties filled with a matrix of PFSA‐based ionomer to ensure the proton conductivity. The hybrid fibers obtained by electrospinning are composed of intermixed domains of sulfonated silica and a fluorinated polymer. The inter‐fiber porosity is then filled with a PFSA ionomer to obtain dense composite membranes with a controlled fibers‐to‐ionomer ratio. At 80 °C, these obtained composite membranes show comparable performances to a pure PFSA commercial membrane. At 120 °C however, the tensile strength of the PFSA membrane drastically drop down to 0.2 MPa, while it is maintained at 7.0 MPa for the composite membrane. In addition, the composite membrane shows a good conductivity of up to 0.1 S cm −1 at 120 °C/90% RH, which increases with the ionomer content.
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Nitro-oxidized carboxylated cellulose nanofiber based nanopapers and their PEM fuel cell performance
The fuel cell is the best alternative to compensate for today's energy demand, but the high cost of fabrication of membranes ( e.g. , Nafion) hampers the widespread commercialization. Plant-derived nanocellulose is renewable, most abundant, and biocompatible with high strength and tunable surface chemistry. Here we have demonstrated the jute derived-nitro-oxidized carboxycellulose nanofibers (NOCNFs) as a viable and sustainable substitute for synthetic ionomer membranes used in proton exchange fuel cells (PEFCs). NOCNFs were obtained in two functionalities: carboxylate and carboxylic acid which were then transformed into nanopaper I and II, respectively. This is the first report where NOCNFs with two different functionalities were tested in PEFCs. The results indicated that nanopaper II performed better than nanopaper I with a high proton conductivity of 14.2 mS cm −1 and power density of 19.1 mW cm −2 at high temperature (80 °C) operation in PEFCs, along with excellent durability even for 24 h of operation.
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- Award ID(s):
- 2216585
- NSF-PAR ID:
- 10432284
- Date Published:
- Journal Name:
- Sustainable Energy & Fuels
- Volume:
- 6
- Issue:
- 15
- ISSN:
- 2398-4902
- Page Range / eLocation ID:
- 3669 to 3680
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract In this study, pentablock terpolymers with methylpyrrolidinium cations were characterized and investigated as anion exchange membranes and ionomers for solid‐state alkaline fuel cells. The pentablock terpolymer (with methylpyrrolidinium cations) membranes exhibited higher fuel cell power density and durability than commercial FuMA‐Tech (with quaternary ammonium cations) membranes at 30 °C, 100% relative humidity (RH). Optimization of the catalyst ink composition (i.e., solids and solvent ratio) and fuel cell performance of membrane electrode assemblies (MEAs) with pentablock terpolymers as both the membrane and ionomer were also investigated. Optimization of the fuel cell operating conditions corroborates with the
in situ electrochemical impedance spectroscopy results. The pentablock terpolymer MEA exhibited a maximum power density of 83.3 mW cm−2and voltage decay rate of 0.7 mV h−1after 100 h of operation under 40 °C, 100% RH. These results show promise for pentablock terptolymers with methylpyrrolidinium cations as a commercially attractive low‐cost alternative anion exchange membrane and ionomer for solid‐state alkaline fuel cells. -
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Abstract Next‐generation implantable devices such as sensors, drug‐delivery systems, and electroceuticals require efficient, reliable, and highly miniaturized power sources. Existing power sources such as the Li–I2pacemaker battery exhibit limited scale‐down potential without sacrificing capacity, and therefore, alternatives are needed to power miniaturized implants. This work shows that ceramic electrolytes can be used in potentially implantable glucose fuel cells with unprecedented miniaturization. Specifically, a ceramic glucose fuel cell—based on the proton‐conducting electrolyte ceria—that is composed of a freestanding membrane of thickness below 400 nm and fully integrated into silicon for easy integration into bioelectronics is demonstrated. In contrast to polymeric membranes, all materials used are highly temperature stable, making thermal sterilization for implantation trivial. A peak power density of 43 µW cm−2, and an unusually high statistical verification of successful fabrication and electrochemical function across 150 devices for open‐circuit voltage and 12 devices for power density, enabled by a specifically designed testing apparatus and protocol, is demonstrated. The findings demonstrate that ceramic‐based micro‐glucose‐fuel‐cells constitute the smallest potentially implantable power sources to date and are viable options to power the next generation of highly miniaturized implantable medical devices.
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Abstract Global changes and associated droughts, heat waves, logging activities, and forest fragmentation may intensify fires in Amazonia by altering forest microclimate and fuel dynamics. To isolate the effects of fuel loads on fire behavior and fire‐induced changes in forest carbon cycling, we manipulated fine fuel loads in a fire experiment located in southeast Amazonia. We predicted that a 50% increase in fine fuel loads would disproportionally increase fire intensity and severity (i.e., tree mortality and losses in carbon stocks) due to multiplicative effects of fine fuel loads on the rate of fire spread, fuel consumption, and burned area. The experiment followed a fully replicated randomized block design (
N = 6) comprised of unburned control plots and burned plots that were treated with and without fine fuel additions. The fuel addition treatment significantly increased burned area (+22%) and consequently canopy openness (+10%), fine fuel combustion (+5%), and mortality of individuals ≥5 cm in diameter at breast height (dbh; +37%). Surprisingly, we observed nonsignificant effects of the fuel addition treatment on fireline intensity, and no significant differences among the three treatments for (i) mortality of large trees (≥30 cm dbh), (ii) aboveground forest carbon stocks, and (iii) soil respiration. It was also surprising that postfire tree growth and wood increment were higher in the burned plots treated with fuels than in the unburned control. These results suggest that (i) fine fuel load accumulation increases the likelihood of larger understory fires and (ii) single, low‐intensity fires weakly influence carbon cycling of this primary neotropical forest, although delayed postfire mortality of large trees may lower carbon stocks over the long term. Overall, our findings indicate that increased fine fuel loads alone are unlikely to create threshold conditions for high‐intensity, catastrophic fires during nondrought years. -
null (Ed.)The decreasing cost of electricity produced using solar and wind and the need to avoid CO 2 emissions from fossil fuels has heightened interest in hydrogen gas production by water electrolysis. Offshore and coastal hydrogen gas production using seawater and renewable electricity is of particular interest, but it is currently economically infeasible due to the high costs of ion exchange membranes and the need to desalinate seawater in existing electrolyzer designs. A new approach is described here that uses relatively inexpensive commercially available membranes developed for reverse osmosis (RO) to selectively transport favorable ions. In an applied electric field, RO membranes have a substantial capacity for proton and hydroxide transport through the active layer while excluding salt anions and cations. A perchlorate salt was used to provide an inert and contained anolyte, with charge balanced by proton and hydroxide ion flow across the RO membrane. Synthetic seawater (NaCl) was used as the catholyte, where it provided continuous hydrogen gas evolution. The RO membrane resistance was 21.7 ± 3.5 Ω cm 2 in 1 M NaCl and the voltages needed to split water in a model electrolysis cell at current densities of 10–40 mA cm −2 were comparable to those found when using two commonly used, more expensive ion exchange membranes.more » « less
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D2SE00442A
