Cathode/electrolyte interface polarization

Sol-gel technique has been used to deposit solid electrolyte layers within the LSM cathode. The layer deposited near the cathode/electrolyte interface can provide ionic path for oxide ions, spreading reaction sites into the electrode. Deposition of YSZ or samaria-doped ceria (SDC, Smo.2Ceo.8O2) films in the pore surface of the cathode increased the area of TPB, resulting in a decrease of cathode polarization and increase of cell performance [15],... 

The IR drop is caused by current flow through the soil, pipe coating, and metallic path [5]. AH cathodic protection potential measurements contain an IR drop component when CP current or interference current is present. The measured potential ( J is the sum of polarized potential ( p) measured near the cathode electrolyte interface and IR drop along the... 

During the electrolytic process, current flows at a fine rate, but overpotential drop emerges due to connectors and wiring system, and electrolyte electrical resistance at the cathode-electrolyte interface. Also, overpotential may occur when concentration polarization is due to mass transfer by diffusion [1]. 

Activation polarization effect, which is associated with the kinetics of the electrochemical oxidation-reduction or charge-transfer reactions occurring at the electrode/electrolyte interfaces of the anode and the cathode. 

A similar cathodic limiting current has also been observed for the electroreduction of peroxide on LaNi03 (Fig. 18) [48] and this behavior occurs at potentials where the reduction of the solid surface takes place changing the potential distribution at the oxide-electrolyte interface. This change of surface properties is quite similar to the behavior of NiO [347] under cathodic polarization and is also reflected in the inhibition of electron transfer to or from redox couples in solution [81] and capacitance Mott-Schottky type plots [87, 290, 291] of these interfaces. 

Since the externally applied voltage occurs only across the Helmholtz layer at the metal electrolyte interface, the energy levels on both sides of the interface are shifted against each other as illustrated in Fig. 7.5. Upon cathodic polarization, an electron transfer occurs from the occupied states in the metal where the latter overlap with the... 

At intermediate temperature, one of the main limiting factors is the high polarization resistance of usual cathode materials, such as LSM oxides, which limits SOFC power densities. Consequently, much attention has recently been focused on improving the cathodic performance by both using mixed ionic and electronic conductor materials and improving the microstructural design at the eathode/electrolyte interface [17]. 

Electrochemical polarization experiments are performed to study the kinetics of charge-transfer reactions at the electrode-electrolyte interface. When cathodic current is applied to the electrode, the electrons accumulate in the metal as a result of the slow charge transfer. This phenomenon causes the cathodic polarization, to be always negative. Conversely, when electrons are removed from the metal as in the case of anode polarization, the polarization is always positive. 

Cathodic protection (CP) is defined as the reduction or elimination of corrosion by making the metal a cathode by means of impressed current or sacrificial anode (usually magnesimn, aluminum, or zinc) [11]. This method uses cathodic polarization to control electrode kinetics occurring on the metal-electrolyte interface. The principle of cathodic protection can be explained by the Wagner-Traud mixed potential theory [12]. 

A negative polarized potential of at least 850 mV relative to a saturated copper/copper sulfate reference electrode is another criterion. Polarized potential is defined as the potential across the structure/electrolyte interface that is the sum of the corrosion potential and the cathodic polarization. 

Though water vapor plays a significant role in the fuel cell performance, the humidification of H2 and O2 is not necessary under fuel cell operating conditions. The water vapors produced at the cathode compartment are enough for the humidification of the membrane by the back-transport process from the cathode to the anode compartment of the cell (Fig. 21), thus affecting the ionic conductivity of the membrane electrolyte and, as shown below, on the polarization of the electrode/electrolyte interfaces. 

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