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Electrochemistry of Mixed Ionic–Electronic Conductors
Published in P.J. Gellings, H.J.M. Bouwmeester, Electrochemistry, 2019
The electrodes in fuel cells, fuel |SE(O=)|air, are usually porous ones made of inert metals or semiconducting oxides.236 The electrode reaction is limited to the so-called “triple-phase boundary”, i.e., the narrow area along the edge of the pores in the electrodes where the three phases, electrode, SE, and gas, meet. Using MIEC as electrodes was suggested, thus turning the whole nominal area of the electrode into an active electrode area where the electrode reaction can take place.237–239 This might reduce the electrode impedance by orders of magnitude if other factors (such as the bulk resistance of the MIEC layer or space charge at the SE/MIEC interface) do not severely increase the impedance. (See Chapters 8 and 12 of this handbook for a more detailed discussion.)
Biomass-Fueled Direct Carbon Fuel Cells
Published in Vladimir Strezov, Hossain M. Anawar, Renewable Energy Systems from Biomass, 2018
Tao Kan, Vladimir Strezov, Graham Town, Peter Nelson
In the type II DC-SOFCs, the fuel has no direct physical contact with the anode. It is well accepted that in the anode chamber, the fuel is gasified by CO2 to CO via the Boudourd reaction (C + CO2 ↔ 2CO, Reaction 14.4). In the meantime, the generated CO is oxidized by O2− to CO2 and releases electrons (CO + O2− → CO2 + 2e−, Reaction 14.13) at the triple-phase boundary (TPB), which is an active interface of carbon fuel/anode/electrolyte (Gür 2013). The gasification may take place in-situ in the anode chamber. Fuel particles can also be gasified ex-situ, which means Reaction 14.4 is arranged in an external compartment (Giddey et al. 2012).
Fuel Cells Application of Atomically Dispersed Metallic Materials
Published in Wei Yan, Xifei Li, Shuhui Sun, Xueliang Sun, Jiujun Zhang, Atomically Dispersed Metallic Materials for Electrochemical Energy Technologies, 2023
A rationally designed electrode with balanced micro-, meso-, and macro-porosity is essential for constructing the triple-phase boundary and speeding up mass and charge transportation.107,108 Jaouen et al. recently designed a 3D Fe–N–C cathode architecture using an electrospinning technique (E-ZIF-8(Fe)/PAN-Ar) (Figure 4.17).109 For practical H2–air PEMFCs, operando X-ray tomography showed that the water-free macroporous gaps may help transport O2 molecules to active sites and have a favorable proton transport, both of which lead to better MEA efficiency.
Solid oxide fuel cells fueled by carbonaceous fuels: A thermodynamics-based approach for safe operation and experimental validation
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2022
Rakesh Narayana Sarma, Anand M. Shivapuji, Dasappa Srinivasaiah
At this juncture, it is worth mentioning that the fuel cell components have unique electrochemical and structural characteristics that determine the overall cell performance (Revankar and Majumdar 2014) and the cell-to-cell variations may be attributed to this, as minor differences during manufacturing and/or cell assembly can affect the performance. Further, Triple Phase Boundary (TPB) area available to the fuel and oxidizer, contacts between the cell components like interconnects, meshes, and electrode surfaces also influence the performance. In order to account for such inherent variations, the present study focuses on relative performance rather than an absolute analysis. The preliminary investigations at 1073 K were extended to 973 K to evaluate the implication of cell operating temperature. Tests were conducted with 1 SLPM H2 and 4 SLPM air. It is observed that the peak power density dropped to ~200 mW cm−2, while operating the cell at 973 K, from ~1000 mW cm−2, obtained while operating the Cell 1 at 1073 K, as shown in Figure 8. This is a rather significant drop. Considering the superiority of the cell performance at 1073 K, subsequent investigations have focused on operating the cell at 1073 K.