Abstract
Interface engineering can be used to tune the properties of heterostructure materials at an atomic level, yielding exceptional final physical properties. In this work, we synthesized a heterostructure of a p-type semiconductor (NiO) and an n-type semiconductor (CeO2) for solid oxide fuel cell electrolytes. The CeO2-NiO heterostructure exhibited high ionic conductivity of 0.2 S cm−1 at 530 °C, which was further improved to 0.29 S cm−1 by the introduction of Na+ ions. When it was applied in the fuel cell, an excellent power density of 571 mW cm−1 was obtained, indicating that the CeO2-NiO heterostructure can provide favorable electrolyte functionality. The prepared CeO2-NiO heterostructures possessed both proton and oxygen ionic conductivities, with oxygen ionic conductivity dominating the fuel cell reaction. Further investigations in terms of electrical conductivity and electrode polarization, a proton and oxygen ionic co-conducting mechanism, and a mechanism for blocking electron transport showed that the reconstruction of the energy band at the interfaces was responsible for the enhanced ionic conductivity and cell power output. This work presents a new methodology and scientific understanding of semiconductor-based heterostructures for advanced ceramic fuel cells.
Highlights
Fuel cells efficiently convert the chemical energy of different fuels (e.g., H2, CH4 ) into electricity, avoiding the limitations of the Carnot cycle
SOFCs are often used at high temperatures (700–1000 ◦ C), making them the most promising candidates for clean energy since they do not require precious metal catalysts and their all-solid structure alleviates potential erosion [2]
Based on the above-mentioned strategy of interfacial ionic conductivity between two phases and the potentially attractive properties of CeO2, we discovered in this study that a semiconductor CeO2 -NiO heterostructure has both proton and oxygen ionic conductivities
Summary
Fuel cells efficiently convert the chemical energy of different fuels (e.g., H2 , CH4 ) into electricity, avoiding the limitations of the Carnot cycle. Wang et al introduced a logical design for non-stoichiometric CeO2-δ based on undoped CeO2 [18] They constructed a CeO2−δ @CeO2 core-shell heterostructure as an electrolyte for low-temperature SOFCs. A remarkable power output of 660 mW cm−2 was achieved at 550 ◦ C. A maximum power density of 697 mW cm−2 was obtained based on the charged layers formed at the interface of the CeO2−δ /CeO2 heterostructure at 520 ◦ C This introduced a new generation of proton ceramic fuel cells. Cai et al developed bulkheterostructure electrolytes based on Ce0.8 Sm0.2 O2−δ and SrTiO3 to reduce the operational temperature of SOFCs [21] They achieved a high peak power density of 892 mW cm−2 and an open circuit voltage of 1.1 V at 550 ◦ C.
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