Nanocomposite electrodes for high current density over 3\u2009A\u2009cm\u22122 in solid oxide electrolysis cells

Hiroyuki Shimada,Haruo Kishimoto,Yuki Yamaguchi,Katsuhiro Nomura,Hirofumi Sumi,Toshiaki Yamaguchi,Yoshinobu Fujishiro

doi:10.1038/s41467-019-13426-5

Hiroyuki Shimada, Haruo Kishimoto + Show 5 more

Open Access

https://doi.org/10.1038/s41467-019-13426-5

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Abstract

Solid oxide electrolysis cells can theoretically achieve high energy-conversion efficiency, but current density must be further increased to improve the hydrogen production rate, which is essential to realize widespread application. Here, we report a structure technology for solid oxide electrolysis cells to achieve a current density higher than 3 A cm−2, which exceeds that of state-of-the-art electrolyzers. Bimodal-structured nanocomposite oxygen electrodes are developed where nanometer-scale Sm0.5Sr0.5CoO3−δ and Ce0.8Sm0.2O1.9 are highly dispersed and where submicrometer-scale particles form conductive networks with broad pore channels. Such structure is realized by fabricating the electrode structure from the raw powder material stage using spray pyrolysis. The solid oxide electrolysis cells with the nanocomposite electrodes exhibit high current density in steam electrolysis operation (e.g., at 1.3 V), reaching 3.13 A cm−2 at 750 °C and 4.08 A cm−2 at 800 °C, corresponding to a hydrogen production rate of 1.31 and 1.71 L h−1 cm−2 respectively.

Highlights

Solid oxide electrolysis cells can theoretically achieve high energy-conversion efficiency, but current density must be further increased to improve the hydrogen production rate, which is essential to realize widespread application
SOECs can be used for reversible solid oxide fuel cells (SOFCs) that in a single device can operate both in fuel cell mode to generate electric power and in electrolysis mode to produce chemical energy carriers
To achieve extremely high current density operation over 3 A cm−2 in SOECs, we focus on improving the oxygen electrode performance by controlling both the material chemical composition and electrode structure

Summary

Introduction

Solid oxide electrolysis cells can theoretically achieve high energy-conversion efficiency, but current density must be further increased to improve the hydrogen production rate, which is essential to realize widespread application. In addition to using high catalytic and high conductive materials for oxygen electrodes, achieving an extremely high current density requires a finely controlled electrode structure, where the electrochemically active triple-phase boundary (TPB) region among the electronic, ionic, and gas phases is expanded as much as possible while maintaining the electronic, ionic, and pore channels. To achieve extremely high current density operation over 3 A cm−2 in SOECs, we focus on improving the oxygen electrode performance by controlling both the material chemical composition and electrode structure. We evaluate the electrochemical performance of SOECs with these SSC-SDC nanocomposite electrodes in steam electrolysis, and demonstrate that high current density operation is achieved

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Conclusion