During high power density operations, the performance of polymer electrolyte membrane fuel cells (PEMFCs) may be limited by high water saturation levels in the cathode catalyst layer due to high wettability of the ionic polymer phase. A new heat-treatment method was used to create and lock-in the surface structure of Nafion 212. Several surface characterization techniques were used to verify the membrane's surface after heat-treatment, including contact angle, atomic force microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. We found that specific heat-treatment conditions led to the formation of either a hydrophobic or hydrophilic surface. The modified membrane's surface remained intact even after the membranes were boiled in water for 1 h. Next, a 4-point conductivity technique was used to verify that the heat-treatment conditions which led to a hydrophobic surface did not negatively impact the membrane's internal conductivity. Finally, this novel heat-treatment method was applied to the cathode catalyst layer of a H 2 -Air PEMFC to create a hydrophobic polymer-gas interface inside the gas pores of the cathode catalyst layer. Preliminary results showed 33% increase in peak power. The results of this research will guide the design of a new class of PEMFC catalyst layers. PEMFCs offer the advantages of high power density and energy conversion efficiency, simplicity in design and operation, the added environmental benefits such as zero carbon emissions, and the production of benign by-products such as water when using the H 2 -O 2 /(Air) fuel cell.1,2 Additionally, reversible fuel cells (flow batteries) offer a viable solution to the highly desired need for economical grid energy storage in order to take full advantage of load leveling. [3][4][5] As the use of intermittent energy sources such as wind and solar power continue to rise throughout the world, the need for reliable, efficient and economical energy storage solutions will grow. Excessive liquid water buildup in the fuel cell catalyst layer (CL) at high current densities can lead to electrode flooding, thus restricting transport of gaseous reactants to the catalyst reaction sites. In order to realize the economic viability of fuel cells, the fuel cell CL needs to be redesigned to overcome the negative hydration effects common with PEMFCs.Water management in a PEMFC is important for peak performance and long lifetime.6 A large amount of research has been generated to minimize the impact of water production in the PEMFC catalyst layer. One of the first areas of exploration to improve water management pertains to membranes. Critical membrane parameters include ionic conductivity, water and gas permeability, and mechanical strength. Di Vona and Iwai et al. demonstrated how cross-linking polymers greatly stabilizes the polymer in terms of thermal, mechanical, and hydrolytic degradation. 7,8 Pintauro et al. demonstrated reduced swelling and increased strength by electrospinning nanofiber composite membranes together.9 By melting an inert polymer ...

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The regenerative H 2 -Br 2 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 H 2 -Br 2 fuel cell using both conventional as well as novel materials (Nafion and electrospun composite membranes along with Pt and Rh x S y electrocatalysts) is discussed. The performance of the H 2 -Br 2 fuel cell obtained with a conventional Nafion membrane and Pt electrocatalyst was enhanced upon employing a double-layer Br 2 electrode while raising the cell temperature to 45 • C. The active area and wetting characteristics of Br 2 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 Rh x S y electrocatalyst proved to be more stable in the presence of HBr/Br 2 than pure Pt. However, the H 2 oxidation activity on Rh x S y is quite low compared to that of Pt. In conclusion, a stable H 2 electrocatalyst that can match the hydrogen oxidation activity obtained with Pt and a membrane with low Br 2 /Br − permeability are essential to prolong the lifetime of a H 2 -Br 2 fuel cell. Electrochemical energy storage using flow batteries or reversible fuel cell devices are considered feasible options for taking advantage of renewable energy sources such as wind and solar. [1][2][3][4] An ideal reversible fuel cell should possess qualities such as swift reaction kinetics, inexpensive reactants, high round trip efficiency, and durability. Several research efforts conducted in this area have identified the reversible hydrogen-bromine (H 2 -Br 2 ) fuel cell as a suitable system for large scale electrical energy storage because of its numerous advantages such as rapid Br 2 and H 2 reaction kinetics, low cost ($1-$3 per kg of hydrobromic acid), and relative abundance of the active materials used in this system. [5][6][7][8][9][10][11][12][13] However, the toxicity and corrosivity of the HBr/Br 2 electrolyte used in this system pose major safety and durability challenges that need to be addressed.A conventional H 2 -Br 2 fuel cell consists of a H 2 electrode and a Br 2 electrode separated by a proton exchange membrane. However, microporous membrane and membrane-less versions of several fuel cell systems have been investigated. [13][14][15] Recently, Braff et al. developed a membrane-less version of the H 2 -Br 2 flow battery to reduce the cost and ease the hydration requirements associated with the system. 13The starting material in the H 2 -Br 2 fuel cell system is hydrobromic acid (HBr). With excess energy from either wind or solar, the HBr solution is electrolyzed to form H 2 and Br 2 at their respective electrodes (charge process) and the process is reversed during discharge. Also, the bromide (Br − ) ion in the solution may react with neutral bromine (Br 2 ) species to form a tri-bromide (Br 3 − ) complex....

The surface area of carbon electrodes in redox flow batteries and fuel cells governs the rates of electrochemical reactions. Carbon cloth electrodes offer greater durability and serve as a potential substitute for conventional carbon paper electrodes. Growing multi-walled carbon nanotubes (MWCNTs) on carbon cloth electrodes is an effective way to increase the surface area and overall performance of these devices. In this study, electrodeposited cobalt nanoparticles were used as seed catalysts to synthesize MWCNTs onto carbon cloth through chemical vapor deposition. Scanning electron microscopy and energy dispersive X-ray analysis confirmed cobalt deposition and uniform MWCNT growth throughout the carbon cloth electrode. The MWCNT cloth, MWCNT paper, and plain carbon cloth were tested in a 3-electrode electrochemical arrangement and a hydrogen-vanadium reversible fuel cell to determine surface enhancement factors and fuel cell performances, respectively. The MWCNT cloth and MWCNT paper have 2-3 times the surface area of their respective conventional substrates. The hydrogen-vanadium reversible fuel cell with MWCNT carbon cloth electrode has a peak power performance of 0.61 W mg −1 cm −2 , compared to 0.54 W mg As the demand for energy continues to rise, there is a desire for clean, efficient energy production and storage. While renewables, such as solar and wind, are promising alternative energy technologies, their inherent intermittencies inhibit grid-scale, market penetration without low-cost energy storage technology. Therefore, electrochemical devices, such as redox flow batteries, have gained much attention for their ability to convert electrical energy directly to chemical energy for storage.

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