| 1. |
- Liu, Xueqi, et al.
(författare)
-
Study on charge transportation in the layer-structured oxide composite of SOFCs
- 2018
-
Ingår i: International journal of hydrogen energy. - : Elsevier. - 0360-3199 .- 1879-3487. ; 43:28, s. 12773-12781
-
Tidskriftsartikel (refereegranskat)abstract
- In the past few years, triple (H+/O2-/e(-)) conducting materials have been regarded as one of the most promising electrode categories for solid oxide fuel cells (SOFCs). In this work, a layer-structured LiNi0.8Co0.15Al0.05O2-delta (LNCA) with triple conduction has been studied. The semiconductor-ionic conductor (SIC) LNCA-SDC composite has been fabricated by compositing the LNCA material with ionic conductor, i.e., samarium doped ceria (SDC). The electrochemical performance of the LNCA-SDC composite was studied by electrochemical impedance spectroscopy, while its electronic conductivity was confirmed by d.c. polarization method. It is found that the ionic conductivity of the composite is higher than the electronic conductivity by several orders of magnitude. The charge carriers and transportation properties of LNCA-SDC were studied using H+ and O2- blocking layer cells respectively. Results prove that the LNCA-SDC composite is a hybrid oxygen ion-proton conducting material. The oxygen ion conduction is dominated at low temperature (425 -500 degrees C), however, it is comparable with H+ conduction at high temperature (550 degrees C). Additionally, the formation of Li2CO3 under fuel cell operation environment was observed and the mechanism of the hybrid conductivity of LNCA-SDC was studied.
|
|
| 2. |
- Xia, Chen, et al.
(författare)
-
Semiconductor electrolyte for low-operating-temperature solid oxide fuel cell : Li-doped ZnO
- 2018
-
Ingår i: International journal of hydrogen energy. - : Elsevier. - 0360-3199 .- 1879-3487. ; 43:28, s. 12825-12834
-
Tidskriftsartikel (refereegranskat)abstract
- Semiconductors have been successfully demonstrated as the electrolytes for solid oxide fuel cells (SOFCs) in recent years. Many such semiconductors have shown their potentials as a competent ionic conductor for fuel cell operation, indicated by the appreciable ionic conduction and electrochemical performance. In the present study, we depart from traditional electrolyte concept to introduce a new semiconductor electrolyte, Li-doped ZnO to low-operating-temperature SOFCs. The used material was synthesized via a co-precipitation method and investigated from phase structure, morphology and UV-vis absorption perspectives. Utilizing Li-doped ZnO as electrolyte layer, we found the corresponding fuel cell exhibited a remarkable maximum power density of 443 mW cm(-2) along with open circuit voltage (OCV) of 1.07 V at 550 degrees C, and represented a lower-temperature operation feasibility with power outputs of 138-165 mW cm(-2) at 425-450 degrees C. Besides, high ionic conductivities of 0.028-0.087 S cm(-1) and low activation energy of 0.5 eV were also found in the synthesized Li-doped ZnO at 425-550 degrees C. Our investigation in terms of electrochemical impedance spectra (EIS) analysis manifested that Li-doped ZnO as the electrolyte layer boosted the electrode reactions of the device, which resulted in rather small polarization resistances and eventually realized good low-temperature performances. Further study based on the rectification characteristic of Ni/Li-doped ZnO contact verified the Schottky junction formation of Li-doped ZnO with anodic Ni, which can avoid the underlying electronic short-circuiting problem. These findings show a profound significance of using doped semiconductor for the future exploitation of SOFC electrolytes.
|
|
