An Efficient High-Entropy Perovskite-Type Air Electrode for Reversible Oxygen Reduction and Water Splitting in Protonic Ceramic Cells.

He, Fan; Zhou, Yucun; Hu, Tong; Xu, Yangsen; Hou, Mingyang; Zhu, Feng; Liu, Dongliang; Zhang, Hua et al. · Adv Mater · 2023

basic_science · Level V

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Abstract

Reversible protonic ceramic electrochemical cells (R-PCECs) are emerging as ideal devices for highly efficient energy conversion (generating electricity) and storage (producing H<sub>2</sub> ) at intermediate temperatures (400-700 °C). However, their commercialization is largely hindered by the development of highly efficient air electrodes for oxygen reduction and water-splitting reactions. Here, the findings in the design of a highly active and durable air electrode are reported: high-entropy Pr<sub>0.2</sub> Ba<sub>0.2</sub> Sr<sub>0.2</sub> La<sub>0.2</sub> Ca<sub>0.2</sub> CoO<sub>3-</sub> <sub>δ</sub> (HE-PBSLCC), which exhibits impressive activity and stability for oxygen reduction and water-splitting reactions, as confirmed by electrochemical characterizations and structural analysis. When used as an air electrode of R-PCEC, the HE-PBSLCC achieves encouraging performances in dual modes of fuel cells (FCs) and electrolysis cells (ECs) at 650 °C, demonstrating a maximum power density of 1.51 W cm<sup>-2</sup> in FC mode, and a current density of -2.68 A cm<sup>-2</sup> at 1.3 V in EC mode. Furthermore, the cells display good operational durabilities in FC and EC modes for over 270 and 500 h, respectively, and promising cycling durability for 70 h with reasonable Faradaic efficiencies. This study offers an effective strategy for the design of active and durable air electrodes for efficient oxygen reduction and water splitting.