Enhanced Proton Transport of β″-AlO Modified by LiAlO as a High-Performance Electrolyte for a Low-Temperature Solid Oxide Fuel Cell and an Electrolyzer.

β-AlO has been proven as a fast ionic conductor in solid batteries due to its unique structure. In this work, β-AlO was further modified by LiAlO and employed as the electrolyte material for low-temperature solid oxide fuel cells and electrolyzers, i.e., proton-conducting ceramic fuel cells and electrolysis cells, named as PCFC and PCEC, respectively. At 550 °C, thanks to this superior electrolyte with a remarkable conductivity of 0.161 S·cm, the PCFC reached a high power density up to 1029 mW·cm, and the PCEC demonstrated a significant current density of 1.49 A·cm at a low operation voltage of 2.0 V. It has been found that the introduction of the LiAlO phase into β-AlO reduces the total impedance, while it increases the oxygen vacancy concentration and thus promotes the proton transport process with the reduced activation energy. This work provides a new approach for exploring two-dimensional materials with high-ionic conductivity that can be applied for solid oxide fuel cells and water electrolyzers and more wider power-to-X devices such as electrosynthesis for green ammonia production.