Na0.6Co3O4- La/Pr co-Doped Ceria as Semiconductor-Ionic Heterostructure Material for Fuel Cell Application

Abstract

Functional Sodium-doped cobalt oxide (Na0.6Co3O4, NCO) was incorporated to regulate and improve the electrochemical performance of La/Pr co-doped ceria (LCP) electrolytic materials with good operative stability, forming an p-n heterostructure electrolyte (LCP-NCO) for low-temperature solid oxide fuel cell (LTSOFC) application. LCP-NCO is a new potential semiconductor-ionic material, achieving a maximum power density of 1075 mW cm−2 along with a high open-circuit voltage of 1.061 V at 520 °C. Scanning electron microscopy combined with transmission electron microscopy unveiled the crystallographic microstructure of heterostructure interface between LCP and NCO. Raman spectra and Fourier transform infrared spectroscopy spectra were analyzed to distinguish the functional groups and the vibrational properties. Ultraviolet–visible absorption and ultraviolet photoelectron spectroscopy have determined the accurate band edge positions of LCP and NCO and p-n heterojunction nature. Built-in electric field in semiconductor heterostructure and more oxygen vacancies created through the variation of Co3+/Co2+ ratio in LCP-NCO during the fuel cell test, contributed to the enhanced ionic transport. Characteristic of competent conductivity of 0.26–0.42 S cm−1 at 400 °C–520 °C, and the improved cell duration, revealed that the LCP-NCO as a hybrid oxygen ion and protonic conductor would be a potential electrolyte for LTSOFC.