Cathodes air-breathing

Microfluidic Fuel Cells, Fig. 3 Microfluidic fuel cell designs with oxygen-saturated catholyte (a) and air-breathing cathode (b) (Reproduced with permission from Jayashree et al. [5])... 

Most developers focus on a diffusion-driven air supply with air breathing cathodes. This can be realized by planar fuel cell designs, where the cells are not stacked, as in high-power fuel cells, but rather are oriented side-by-side in one plane (Figure 5.3). 

Elouarzaki K, Haddad R, Holzingta M, Goff AL, Thery J, Cosnier S (2014) MWCNT-supptHted phthalocyanine cobalt as air-breathing cathodic catalyst in glucose/02 fuel cells. J Powtn Sources 255 24—28... 

Duteanu, N., Erable, B., Senthil Kumar, S.M., Ghangrekar, M.M. Scott, K. Effect of chemicalty modified Vulcan XC-72R on the performance of air-breathing cathode in a single-chamber microbial fuel-cell. Bioresource Technol. 101 (2010), pp. 5250-5255. 

Due to the low solubility of oxygen in water, the mass transfer of oxygen at the cathode can severely affect the cell performance. Therefore, it is desirable to develop an air-breathing cathode for oxygen reduction. The air-breathing cathode is also called a gas diffusion electrode (GDE), which is widely used in fuel cell technology. The details of air-breathing cathode fabrication can be found in previous literature. 

Jayashree etal. (33) Methanol (1M) Ak Sutfiiricadd (05M) or potassium hydroxide <1M) lOir cm" Pt-Ru 50 50 atom alloy painted on graphite 055 n cm Pt with additional 2mgcai Pt painted on Toray carbon paper as air-breathing cathode 2 mm tfikk PMMA Graphite plate (at anode side... 

Whipple etoL [35] Methanol <0.1-15 M) Air H2S04<0.5M) lOmgcm" Pt/Ru on carbon paper 2 mg cm" Pt black or Ru Se as methanol tola t catalyst painted on Toray carbon paper as air-breathing cathode 2 mm thick PMMA Graphite plate for anode side... 

Flow Architecture and Fabrication of LFFC with Air-Breathing Cathode... 

Proof of concept of membraneless LFFC with air-breathing cathode was proposed by Kenis research group in 2005 [32]. As shown in Figure 9.5a and b, GDE, made of Toray carbon paper covered by catalyst ink containing platinum... 

Figure 9.5 Membraneless LFFCs with air-breathing cathodes, (a) Schematic illustration for the arrangement of fuel and electrolyte streams in the channel. Adapted from Ref. [32]. (b) Cross section and carrier...

Rincon RA, Lau C, Luckarifl HR, Garcia KE, Adkins E, Johnson GR, Atanassov P. Enzymatic fuel cells integrating flow-through anode and air-breathing cathode into a membrane-less biofuel cell design. Biosens Bioelectron 2011 27 132 136. 

Higgins S, Lau C, Minteer SD, Atanassov P, Cooney M. Hybrid biofuel cell microbial fuel cell with an enz)miatic air-breathing cathode. AC5 Catal 2011 1 994-997. 

Application of the conventional half-MEA air-breathing cathode in EFC can be problematic because of mechanical integrity of the MEA assembly. Sulfonated tetrafluoroethylene membranes (such as Nafion) work well as electrical separators between anode and cathode and can provide an effective seal to prevent fuel leakage. In an asymmetric MEA, the bare Nafion side is exposed to the aqueous fuel solution in the EEC, which can result in swelling of the membrane and high shear forces that can lead to fast structural disintegration of the cathode. 

Oxygen reduction can be catalyzed by enzymes, and air-breathing cathodes with laccase and bUimbin oxidase as enzymatic catalysts, for example, have been demonstrated [10-15]. Enzymatically catalyzed cathodes avoid many of the problems discussed for platinum and other precious metal catalysts, but they often provide lower power density and Umited stability. Specifically with air-breathing cathodes, enzymes that catalyze oxygen reduction must be immobilized at the tripoint between hydrophilic (H" conductivity), hydrophobic (O2 supply), and conductive (e conductivity) interfaces for effective catalysis (Figure 16.1) (see Chapter 3). 

In 1967, Jacobson presented a glucose/Oa fuel cell prototype with an air-breathing cathode having a stable electrochemical output, generating a power density of 165 pW cm within the initial 24h of operation (total 240 h) [ 10]. Later experiments showed differences in behavior of the device under physiological conditions when it was tested in pleural fluids and plant saps, in all likelihood due to protein adsorption on the electrode surface. 

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