Improving Grain Boundary Conductivity of Ce_0.9Gd_0.1O_2 − δ Electrolyte through Compositing with Carbonate or Semiconductor

Abstract

In the solid oxide fuel cell field, heterogeneous ion doping is a common methodology to improve the ionic conductivity of electrolytes, but overwhelming grain boundary resistance is still the main obstacle for low‐temperature applications. According to previous reports, building rapid ion transport at the grain boundary through compositing methods was considered as a proposed design for electrolytes to decrease the grain boundary resistance and obtain high ionic conductivity. Herein, Ce0.9Gd0.1O2 − δ (GDC) is selected as the matrix material and composited with Na2CO3 and NdBa0.5Sr0.5Cu2O5 + δ (NBSCu) to form GDC‐Na2CO3 nanocomposite and GDC‐NBSCu composite. The grain boundary conductivity (σb) is delicately separated from the EIS results, demonstrating that the σb of GDC‐NBSCu and GDC‐Na2CO3 composite are both substantially higher than that of pure GDC. Therefore, the power density maximum of GDC‐NBSCu and GDC‐Na2CO3 electrolyte is 726 mW cm−2 at 600 °C and 797 mW cm−2 at 575 °C, respectively. Variety of characterization reveales that the proton contributes to the enhancement of σb in GDC‐Na2CO3, while the band energy alignment between GDC and NBSCu works as an accelerator to promote the ionic conduction for GDC‐NBSCu.

Toward next-generation fuel cell materials

“…Furthermore, the morphology of NCAL reveals the fluffy and well-porous structure assists in mass transfer with the extension of the triple-phase boundary depicted in Figure 7 C. At the same time, GDC-Na 2 CO 3 seems too dense without pores after sintering at 575 C, and the desired density assists in separating the H 2 and air gases or prevents the contact between air and H 2, as illustrated in Figure 7 D. The XRD of GDC and GDC-Na 2 CO 3 reveal a pure fluorite structure. Still, with the addition of Na 2 CO 3, the peak intensity is lower, and slight expansion is noticed, confirming the formation of a GDC-Na 2 CO 3 structure without impurity peaks, as demonstrated in Figure 7 E. 22 , 67 During the fuel cell operation, it is known that Na 2 CO 3 changes into a molten state and makes connections or bonds with other materials, as seen in the examples with SDC-Na 2 CO 3 , GDC-Na 2 CO 3, etc., to attain nanocomposite material characteristics. 67 The relationship between the functions of the different particles as quick ions transport channels simultaneously speeds up the process leading to enhanced electrochemical fuel cell performance with a power density of 800 mW/cm 2 at 575 C shown in Figure 7 F. Moreover, several studies have been reported to enhance the ionic conduction and boost the fuel cell performance using the above stated phenomena.…”

“…Still, with the addition of Na 2 CO 3, the peak intensity is lower, and slight expansion is noticed, confirming the formation of a GDC-Na 2 CO 3 structure without impurity peaks, as demonstrated in Figure 7 E. 22 , 67 During the fuel cell operation, it is known that Na 2 CO 3 changes into a molten state and makes connections or bonds with other materials, as seen in the examples with SDC-Na 2 CO 3 , GDC-Na 2 CO 3, etc., to attain nanocomposite material characteristics. 67 The relationship between the functions of the different particles as quick ions transport channels simultaneously speeds up the process leading to enhanced electrochemical fuel cell performance with a power density of 800 mW/cm 2 at 575 C shown in Figure 7 F. Moreover, several studies have been reported to enhance the ionic conduction and boost the fuel cell performance using the above stated phenomena. 37 , 45 , 62 , 67 , 68 , 69

Figure 7 Conduction path for protons and ions along with morphology, stuctural and electrochemical properties of GDC/NCO (A and B) Schematic diagram of fuel cell device with GDC-Na 2 CO 3 electrolyte and NCAL electrode along with the conduction path of protons and oxide ions, (C and D) SEM image of NCAL porous electrode and electrolyte membrane GDC-Na 2 CO 3 , (E and F) XRD analysis of GDC, GDC-Na 2 CO 3, and performance of GDC-Na 2 CO 3 electrolyte membrane 67 with permission of John Wiley and Sons.

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“… 67 The relationship between the functions of the different particles as quick ions transport channels simultaneously speeds up the process leading to enhanced electrochemical fuel cell performance with a power density of 800 mW/cm 2 at 575 C shown in Figure 7 F. Moreover, several studies have been reported to enhance the ionic conduction and boost the fuel cell performance using the above stated phenomena. 37 , 45 , 62 , 67 , 68 , 69

Figure 7 Conduction path for protons and ions along with morphology, stuctural and electrochemical properties of GDC/NCO (A and B) Schematic diagram of fuel cell device with GDC-Na 2 CO 3 electrolyte and NCAL electrode along with the conduction path of protons and oxide ions, (C and D) SEM image of NCAL porous electrode and electrolyte membrane GDC-Na 2 CO 3 , (E and F) XRD analysis of GDC, GDC-Na 2 CO 3, and performance of GDC-Na 2 CO 3 electrolyte membrane 67 with permission of John Wiley and Sons.

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“…Figure 7 A illustrates a structural schematic diagram of the GDC-Na 2 CO 3 fuel cell. 67 Symmetrical electrodes Ni 0.8 Co 0.15 Al 0.05 LiO 2-δ (NCAL) were used for redox functionality, whereas GDC-Na 2 CO 3 works as an electrolyte to conduct the ions. Figure 7 B shows the conduction path of protons and oxide ions through the electrolyte to accomplish the fuel cell reactions.…”

“… (A and B) Schematic diagram of fuel cell device with GDC-Na 2 CO 3 electrolyte and NCAL electrode along with the conduction path of protons and oxide ions, (C and D) SEM image of NCAL porous electrode and electrolyte membrane GDC-Na 2 CO 3 , (E and F) XRD analysis of GDC, GDC-Na 2 CO 3, and performance of GDC-Na 2 CO 3 electrolyte membrane 67 with permission of John Wiley and Sons. …”