Fast ionic conduction in semiconductor CeO2-δ electrolyte fuel cells

By Baoyuan Wang, B. Zhu, Sining Yun, Wei Zhang, Chen Xia, M. Afzal, Yixiao Cai, Yanyan Liu, Yi Wang, Hao Wang. NPG Asia Materials, 2019

244 citations recorded by the source corpus.

AbstractProducing electrolytes with high ionic conductivity has been a critical challenge in the progressive development of solid oxide fuel cells (SOFCs) for practical applications. The conventional methodology uses the ion doping method to develop electrolyte materials, e.g., samarium-doped ceria (SDC) and yttrium-stabilized zirconia (YSZ), but challenges remain. In the present work, we introduce a logical design of non-stoichiometric CeO2-δ based on non-doped ceria with a focus on the surface properties of the particles. The CeO2−δ reached an ionic conductivity of 0.1 S/cm and was used as the electrolyte in a fuel cell, resulting in a remarkable power output of 660 mW/cm2 at 550 °C. Scanning transmission electron microscopy (STEM) combined with electron energy-loss spectroscopy (EELS) clearly clarified that a surface buried layer on the order of a few nanometers was composed of Ce3+ on ceria particles to form a CeO2−δ@CeO2 core–shell heterostructure. The oxygen deficient layer on the surface provided ionic transport pathways. Simultaneously, band energy alignment is proposed to address the short circuiting issue. This work provides a simple and feasible methodology beyond common structural (bulk) doping to produce sufficient ionic conductivity. This work also demonstrates a new approach to progress from material fundamentals to an advanced low-temperature SOFC technology.Fuel cells: Surface modifications make a differenceThe performance of non-doping ceria used in solid oxide fuel cells for generating electricity has been improved by modifying its surface. A logical design of non-stoichiometric CeO2-δ was in-situ formed by fuel cell to make ions, e.g., the oxygen ion conducted through the pathway built in ceria surface for the electrolyte to realize the fuel cell reactions, enabling an electrical current to flow. Optimizing the properties of the electrolyte is vital for maximizing the efficiency of the fuel cell. Baoyuan Wang and Bin Zhu from Hubei University, Wuhan, China and coworkers from China, Germany and Sweden set out to improve the electrical conductivity of the surface on non-doping ceria, an oxide of the rare earth metal cerium succeeded in excellent electrolyte functions. The modified surface states created new electrical pathways useful for fuel cell applications.This study highlights a new methodology to develop electrical property of CeO2 without doping based on characteristic surface defects. The CeO2 surface approach presented in this work addresses the electrolyte material challenge faced by solid state oxide fuel cells (SOFCs) over 100 years. In our approach, we take advantage of the energy band structure and surface defect to develop new functional electrolyte material based on non-doped ceria. The oxygen vacancies and defects in surface state of the CeO2 result in new electrical and band properties, thus giving rise in superionic conduction for successful SOFCs application.

Subfields: Materials Chemistry, Renewable Energy, Sustainability and the Environment

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