Morphology and Structure of Ni/Zr0.84Sc0.16O1.92 Electrode Material Synthesized via Glycine-Nitrate Combustion Method for Solid Oxide Electrochemical Cell

Renz Garcia,Rinlee Cervera

doi:10.3390/app9020264

Abstract

Nickel oxide and Sc-doped ZrO2 electrode material with a 1:1 wt % composition of NiO and Zr0.84Sc0.16O1.92 was synthesized via a single-step glycine-nitrate combustion method. Different glycine to nitrate (g/n) molar ratios of 0.27, 0.54, and 1.1 were used to investigate its effect on the structural, morphological, and electrical properties of the heat-treated samples. X-ray diffraction (XRD) patterns of the as-sintered samples for all the g/n ratios were indexed to cubic phases of NiO and ScSZ. Upon reduction at 700 °C, NiO was fully reduced to Ni. In-situ XRD patterns showed that the composite Ni/Zr0.84Sc0.16O1.92 electrode material retains its cubic structure at intermediate temperatures from 500 °C to 800 °C. High magnification scanning electron microscopy (SEM) images revealed that nanoparticles of Ni are also formed and situated at the surfaces of ScSZ grains, apart from agglomerated submicron particles of Ni. SEM and electron-dispersive spectroscopy mapping revealed interconnected grains of ScSZ oxide-ion conducting phase. From the calculated conductivity based on electrochemical impedance spectroscopy results, the 0.27 g/n ratio showed an order of magnitude-higher total conductivity among the other prepared samples.

Highlights

Solid oxide electrochemical cells such as solid oxide fuel cell (SOFC) or solid oxide electrolysis cells (SOEC) are promising future green energy technologies for energy generation and production of hydrogen
SOEC and SOFC are typically composed of an anode, cathode, and a solid electrolyte as the three basic cell components, where the SOFC anode becomes the cathode in SOEC when operated in the reverse mode
In order to circumvent the problems associated with high temperature of operation, such as degradation during long-term high temperature exposure, ongoing research efforts have been dedicated to developing new material components or tailoring the existing material in order to lower the operation to intermediate temperatures of around 500–800 ◦ C [1,2,3]

Summary

Introduction

Solid oxide electrochemical cells such as solid oxide fuel cell (SOFC) or solid oxide electrolysis cells (SOEC) are promising future green energy technologies for energy generation and production of hydrogen. SOEC is a solid oxide fuel cell that works in a reversed mode of operation. SOEC and SOFC are typically composed of an anode, cathode, and a solid electrolyte as the three basic cell components, where the SOFC anode becomes the cathode in SOEC when operated in the reverse mode. In order to circumvent the problems associated with high temperature of operation (around 1000 ◦ C), such as degradation during long-term high temperature exposure, ongoing research efforts have been dedicated to developing new material components or tailoring the existing material in order to lower the operation to intermediate temperatures of around 500–800 ◦ C [1,2,3]. The typically studied cathode material for SOEC is Ni/yttrium-stabilized zirconia (YSZ) due to the use of YSZ as a solid electrolyte. YSZ is a typical solid electrolyte that is widely studied due to its high phase stability and high ionic conductivity [2].

Methods

Results

Conclusion