Minimization of electrode polarization effect by nanogap electrodes for biosensor applications

Author(s):  
S. Oh ◽  
J.S. Lee ◽  
K.H. Jeong ◽  
L.P. Lee
2019 ◽  
Vol 21 (2) ◽  
pp. 681-691 ◽  
Author(s):  
Zahra Ghobaei Namhil ◽  
Cordula Kemp ◽  
Emanuele Verrelli ◽  
Alex Iles ◽  
Nicole Pamme ◽  
...  

A significant impediment to the use of impedance spectroscopy in bio-sensing is the electrode polarization effect that arises from the movement of free ions to the electrode–solution interface, forming an electrical double layer (EDL).


2011 ◽  
Vol 311-313 ◽  
pp. 2309-2314 ◽  
Author(s):  
Wen Xia Zhu ◽  
Zhe Lü ◽  
Le Xin Wang ◽  
Xiao Yan Guan ◽  
Xin Yan Zhang

°Abstract. In order to develop new cathodes for reduced temperature SOFCs, Ba0.5Sr0.5Co0.8Fe0.2O3-δ-Ag composite cathode was investigated in intermediate-temperature Solid Oxide Fuel Cells (IT-SOFCs). The XRD results suggested that no chemical reactions between BSCF and Ag in the composite cathode were found. The resistance measurements showed that the addition of Ag into BSCF improved electrical conductivity of pure BSCF, and the improved conductivity resulted in attractive cathode performance. In addition, electrochemical impedance spectra exhibited the better performance of BSCF-Ag composite cathodes than pure BSCF, e.g., the polarization resistance value of BSCF-Ag was only 0.36Ω cm2 at 650°C, which was nearly 80% lower than that of BSCF electrode. Polarization curves showed the overpotential decreased with the addition of Ag. The current density value of BSCF-Ag was 0.88Acm-2 under –120mV, about five times of that BSCF measured at 650°C. As a summary, compared to a pure BSCF cathode, it was found that adding Ag in the cathode enhanced the BSCF performance significantly.


Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 746
Author(s):  
Jianfeng Lu ◽  
Senfeng Yang ◽  
Gechuanqi Pan ◽  
Jing Ding ◽  
Shule Liu ◽  
...  

Molten chloride salt is recognized as a promising heat transfer and storage medium in concentrating solar power in recent years, but there is a serious lack for thermal property data of molten chloride salts. In this work, local structures and thermal properties for molten chloride salt—including NaCl, MgCl2, and ZnCl2—were precisely simulated by Born–Mayer–Huggins (BMH) potential in a rigid ion model (RIM) and a polarizable ion model (PIM). Compared with experimental data, distances between cations, densities, and heat capacities of molten chloride slats calculated from PIM agree remarkably better than those from RIM. The polarization effect brings an extra contribution to screen large repulsive Coulombic interaction of cation–cation, and then it makes shorter distance between cations, larger density and lower heat capacity. For NaCl, MgCl2, and ZnCl2, PIM simulation deviations of distances between cations are respectively 3.8%, 3.7%, and 0.3%. The deviations of density and heat capacity for NaCl between PIM simulation and experiments are only 0.6% and 2.2%, and those for MgCl2 and ZnCl2 are 0.7–10.7%. As the temperature rises, the distance between cations increases and the structure turns into loose state, so the density and thermal conductivity decrease, while the ionic self-diffusion coefficient increases, which also agree well with the experimental results.


2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Yixiao Cai ◽  
Yang Chen ◽  
Muhammad Akbar ◽  
Bin Jin ◽  
Zhengwen Tu ◽  
...  

AbstractSince colossal ionic conductivity was detected in the planar heterostructures consisting of fluorite and perovskite, heterostructures have drawn great research interest as potential electrolytes for solid oxide fuel cells (SOFCs). However, so far, the practical uses of such promising material have failed to materialize in SOFCs due to the short circuit risk caused by SrTiO3. In this study, a series of fluorite/perovskite heterostructures made of Sm-doped CeO2 and SrTiO3 (SDC–STO) are developed in a new bulk-heterostructure form and evaluated as electrolytes. The prepared cells exhibit a peak power density of 892 mW cm−2 along with open circuit voltage of 1.1 V at 550 °C for the optimal composition of 4SDC–6STO. Further electrical studies reveal a high ionic conductivity of 0.05–0.14 S cm−1 at 450–550 °C, which shows remarkable enhancement compared to that of simplex SDC. Via AC impedance analysis, it has been shown that the small grain-boundary and electrode polarization resistances play the major roles in resulting in the superior performance. Furthermore, a Schottky junction effect is proposed by considering the work functions and electronic affinities to interpret the avoidance of short circuit in the SDC–STO cell. Our findings thus indicate a new insight to design electrolytes for low-temperature SOFCs.


Geophysics ◽  
1984 ◽  
Vol 49 (7) ◽  
pp. 1105-1114 ◽  
Author(s):  
James D. Klein ◽  
Tom Biegler ◽  
M.D. Horne

A phenomenological laboratory investigation has been conducted of the IP response of pyrite, chalcopyrite, and chalcocite. The technique that was used is standard in electrochemistry and employs rotating disk electrodes. The effect of rotation is to stir the electrolyte and thus to restrict the maximum distance available for diffusion of electroactive aqueous species. For high rotation speed and low excitation frequencies, the mean diffusion length exceeds the thickness of the diffusion layer. The net effect is to reduce the electrode impedance at low frequency. The thickness of the diffusion layer and thus the impedance at low frequency can be controlled by the rotation speed. Measurements using rotating disk electrodes have been conducted in both the time domain and the frequency domain. For both pyrite and chalcopyrite, the results were the same: no dependence on rotation was observed. For frequency domain measurements with chalcocite, a strong dependence on rotation was observed. The interpreted diffusion layer thickness was found to depend on rotation speed to the [Formula: see text] power, in agreement with results predicted by hydrodynamic theory. The results of this study imply that there are two physical processes responsible for electrode polarization in the IP method. For chalcocite and perhaps other related copper sulfide minerals, the probable mechanism is diffusion of copper ions in the groundwater. In case, the phenomenon is correctly described by the Warburg impedance. Chalcocite’s distinctive response is thought to be related to its forming a reversible oxidation‐reduction couple with cupric ions in solution. No other common sulfide mineral forms a reversible couple with its cations in solution. For the other minerals of this study, the lack of dependence on rotation implies that diffusion of active species in the electrolyte is not the controlling process. Possible alternate mechanisms include surface controlled processes such as surface diffusion or adsorption phenomena. Ancillary data obtained during this study indicate the interface impedance of chalcopyrite is proportional to the electrode potential which in turn can be controlled by rotation speed, electrolyte composition, or application of an external dc current or voltage. This implies that the surface concentration of active species is dependent on electrode potential.


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