An Interface Heterostructure of NiO and CeO2 for Using Electrolytes of Low-Temperature Solid Oxide Fuel Cells

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.

Novel n–i CeO2/a-Al2O3 Heterostructure Electrolyte Derived from the Insulator a-Al2O3 for Fuel Cells

“…The CeO 2 /a-Al 2 O 3 composite will generate more oxygen vacancies through reduction under a H 2 atmosphere at the operating temperature of the cell for the migration of O 2– ions, thus exhibiting an output performance much higher than that of pure CeO 2 fuel cells. Besides, fuel cells based on the CeO 2 electrolyte always suffer from a short-circuiting problem because of the reduction of CeO 2 , ,, which leads to a serious problem of reduced OCV. Table S1 shows the OCV values of pure CeO 2 and the five groups of composite sample (9:1, 8:2, 7: 3, 6:4, and 5:5) fuel cells at 550 °C, which are 1.067, 1.103, 1.115, 1.141, 1.12, and 1.136 V, respectively.…”

“…Using this method, an ion conduction highway was built at the interface of two-phase materials, and thus, these composite samples attained high ionic conductivity and excellent power output. Another way to design electrolytes based on the band bending/alignment effect of heterojunctions also achieved preferable electrolyte properties. − For example, a p–n heterojunction constructed using p-type NiO and n-type CeO 2 for SOFC electrolytes exhibits high ionic conductivity along with excellent fuel cell performance, and an n–n heterojunction electrolyte based on n-type ZnO and n-type 3C-SiC also achieved an enhanced ionic conductivity of 0.12 S cm –1 and a fuel cell power density of 270 mW cm –2 with a high OCV of 1.1 V at 550 °C . It is noticeable that in the process of exploring heterostructure composite electrolytes with high performance, relatively high conductivity of the constituents is one of the important indicators for selecting materials; hence, in previous studies, insulation materials were rarely used as components of heterostructure electrolytes due to their lower conductivity.…”

Synthesis of ((CeO2)0.8(Sm2O3)0.2)@NiO Core-Shell Type Nanostructures and Microextrusion Printing of a Composite Anode Based on Them

“…The fact is that NiO is a p-type semiconductor, while CeO 2 (including that doped with samarium) is the n-type. Thus, a p-n junction occurs at the boundary between the core and the shell, leading to the convergence of band edges and, thus, the convergence of the Fermi levels of the materials [49,50]. This is particularly characteristic of the depletion layer at the boundary between the two phases.…”

Solvothermal Synthesis, Structural Characterization and Optical Properties of Pr-Doped CeO2 and Their Degradation for Acid Orange 7

“…Titanium dioxide (TiO 2 ) is the most studied and widely used photocatalyst in the removal of organic dyes because of its non-toxicity, low-cost and excellent photocatalytic properties [ 26 , 27 ]. CeO 2 , an N-type semiconductor, is one of the more active, versatile and inexpensive rare earth oxides [ 28 ], which should be an alternative candidate photocatalyst due to the readily available intrinsic oxygen vacancies in CeO 2 crystal. However, the use of CeO 2 as the main active component or as a single catalyst for the photocatalytic degradation of azo dyes is really just beginning.…”