Cathode catalyst Carbonate

Nabae Y, Moriya S, Matsubayashi K, Lyth SM, Malmi M, Wu L, Islam NM, Koshigoe Y, Kuroki S, Kakimoto M-a, Miyata S, Ozaki J-i (2010) The role of Fe species in the pyrolysis of Fe phthalocyanine and phenolic resin for preparatimi of carbmi-based cathode catalysts. Carbon 48(9) 2613-2624... 

The catalyst inks were prepared by dispersing the catalyst nanoparticles into an appropriate amoimt of Millipore water and 5wt% Nafion solution. Then, both the anode and cathode catalyst inks were directly painted using a direct painting technique onto either side of a Nafion 117 membrane. A carbon cloth diffusion layer was placed on to top of both the anode and cathode catalyst layers [3-5]. The active cell area was 2.25cm. ... 

Recently, rhodium and ruthenium-based carbon-supported sulfide electrocatalysts were synthesized by different established methods and evaluated as ODP cathodic catalysts in a chlorine-saturated hydrochloric acid environment with respect to both economic and industrial considerations [46]. In particular, patented E-TEK methods as well as a non-aqueous method were used to produce binary RhjcSy and Ru Sy in addition, some of the more popular Mo, Co, Rh, and Redoped RuxSy catalysts for acid electrolyte fuel cell ORR applications were also prepared. The roles of both crystallinity and morphology of the electrocatalysts were investigated. Their activity for ORR was compared to state-of-the-art Pt/C and Rh/C systems. The Rh Sy/C, CojcRuyS /C, and Ru Sy/C materials synthesized by the E-TEK methods exhibited appreciable stability and activity for ORR under these conditions. The Ru-based materials showed good depolarizing behavior. Considering that ruthenium is about seven times less expensive than rhodium, these Ru-based electrocatalysts may prove to be a viable low-cost alternative to Rh Sy systems for the ODC HCl electrolysis industry. 

One of the critical issues with regard to low temperamre fuel cells is the gradual loss of performance due to the degradation of the cathode catalyst layer under the harsh operating conditions, which mainly consist of two aspects electrochemical surface area (ECA) loss of the carbon-supported Pt nanoparticles and corrosion of the carbon support itself. Extensive studies of cathode catalyst layer degradation in phosphoric acid fuel cells (PAECs) have shown that ECA loss is mainly caused by three mechanisms ... 

Fuel cell applications Manganese dioxide as a new cathode catalyst in microbial fuel cells [118] OMS-2 catalysts in proton exchange membrane fuel cell applications [119] An improved cathode for alkaline fuel cells [120] Nanostructured manganese oxide as a cathodic catalyst for enhanced oxygen reduction in a microbial fuel cell [121] Carbon-supported tetragonal MnOOH catalysts for oxygen reduction reaction in alkaline media [122]... 

FIGURE 15.9. Performance comparison of RSn anode based direct ethanol fuel cells at 90°C. Anode catalysts Carbon supported PtSn with a R loading of 1.5 mg/cm, ethanol concentration 1.0 mol/L, flow rate 1.0 mL/min. Cathode (20 Pt wt.%, Johnson Matthey Inc.) with a R loading of 1.0 mg/cm, Pq2 = 2 bar. Electrolyte Naflon -115 membrane. 

Mitsubishi Electric Corporation investigated alloyed catalysts, processes to produce thinner electrolytes, and increases in utilization of the catalyst layer (20). These improvements resulted in an initial atmospheric performance of 0.65 mV at 300 mA/cm or 0.195 W/cm, which is higher than the IFC performance mentioned above (presented in Table 5-2 for comparison). Note that this performance was obtained on small 100 cm cells and may not yet have been demonstrated with full-scale cells in stacks. Approaches to increase life are to use series fuel gas flow in the stack to alleviate corrosion, provide well-balanced micro-pore size reservoirs to avoid electrolyte flooding, and use a high corrosion resistant carbon support for the cathode catalyst. These improvements have resulted in the lowest PAFC degradation rate publicly acknowledged, 2 mV/1000 hours for 10,000 hours at 200 to 250 mA/cm in a short stack with 3600 cm area cells. 

In practice, the catalyst used in the thin-layer CLs for both anode and cathode is carbon-supported Pt catalyst (Pt/C) or Pt alloy, such as PtRu/C, although nonsupported catalysts can be used. In terms of the overall electrode structure, an electrode with a thin CL generally contains three layers ... 

Li, W, Wang, X., Chen, Z., Waje, M., and Yan, Y. Carbon nanotube film by filtration as cathode catalyst support for proton-exchange membrane fuel cell. Langmuir 2005 21 9386-9389. 

Influence of PTFE content in the anode DL of a DMFC. Operating conditions 90°C cell temperature anode at ambient pressure cathode at 2 bar pressure methanol concentration of 2 mol dm methanol flow rate of 0.84 cm min. The air flow rate was not specified there was a parallel flow field for both sides. The anode catalyst layer had 13 wt% PTFE, Pt 20 wt%, Ru 10 wt% on Vulcan XC-73R carbon TGP-H-090 with 10 wt% PTFE as cathode DL. The cathode catalyst layer had 13 wt% PTFE, Pt 10 wt% on carbon catalyst with a loading 1 mg cm Pt black with 10 wt% Nafion. The membrane was a Nafion 117. (Reprinted from K. Scott et al. Journal of Applied Electrochemistry 28 (1998) 1389-1397. With permission from Springer.)... 

The impregnation of porous nickel discs with CoPc was difficult because of the limited solubility of the chelate in the usual solvents. CoPc cathodes with carbon as substrate were therefore prepared for use in H2/O2 fuel cells. A mixture of 72 mg CoPc and 48 mg acetylene black, with PTFE as binder, was pressed into a nickel mesh of area 5 cm2. Electrodes of this type were tested in an H2/O2 fuel cell with 35% KOH electrolyte in an asbestos matrix at 80° C. Figure 5 compares the current/voltage characteristics of CoPc cathodes (14 mg/cm2) with those of other catalysts, including platinum (9 mg/cm2), silver (40 mg/cm2), and pure acetylene black (20 mg/cm2). An hydrogen electrode (9 mg Pt/cm2) was used as the anode in all tests. To facilitate comparison of the activity of different cathodes, the pure ohmic internal resistance of the cells (of the order of 0.02 ohm) was eliminated. 

The anode layer of polymer electrolyte membrane fuel cells typically includes a catalyst and a binder, often a dispersion of poly(tetraflu-oroethylene) or other hydrophobic polymers, and may also include a filler, e.g., acetylene black carbon. Anode layers may also contain a mixture of a catalyst, ionomer and binder. The presence of a ionomer in the catalyst layer effectively increases the electrochemically active surface area of the catalyst, which requires a ionically conductive pathway to the cathode catalyst to generate electric current (16). 

Consequently, since graphitized carbon-supports have lower carbon corrosion rates, the use of cathode catalysts with graphitized supports significantly reduces H2/air-front start-stop damage.12,22 Furthermore, if the ORR activity of the anode electrode is reduced by lowering anode Pt loading, H2/air-front start-stop degradation is decreased.22,23... 

Equations (18-20) are discretized by the control volume method53 and solved numerically to obtain distributions of species (H2, 02, and N2) concentration, phase potential (solid and electrolyte), and the current resulting from each electrode reaction, in particular, carbon corrosion and oxygen evolution currents at the cathode catalyst layer, with the following initial and boundary conditions ... 

The catalysts and electrode materials used in PAFCs are also similar to those in acidic H2/air fuel cells. Carbon-supported Pt is used as the catalyst at both anode and cathode, porous carbon paper serves as the electrode substrate, and graphite carbon forms the bipolar plates. Since a liquid electrolyte is used, an efficient water removal system is extremely important. Otherwise, the liquid electrolyte is easily lost with the removed water. An electrolyte matrix is needed to support the liquid phosphoric acid. In general, a Teflon -bonded silicon carbide is used as the matrix. 

Li, W. et al.. Carbon nanotubes as support for cathode catalyst of a direct methanol fuel cell. Carbon, 40, 791, 2002. 

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