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- Xia, Chen, et al.
(author)
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Semiconductor electrolyte for low-operating-temperature solid oxide fuel cell : Li-doped ZnO
- 2018
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In: International journal of hydrogen energy. - : Elsevier. - 0360-3199 .- 1879-3487. ; 43:28, s. 12825-12834
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Journal article (peer-reviewed)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.
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