Enhanced Proton Transport of β″-Al 2 O 3 Modified by LiAlO 2 as a High-Performance Electrolyte for a Low-Temperature Solid Oxide Fuel Cell and an Electrolyzer.

β ″ -Al 2 O 3 has been proven as a fast ionic conductor in solid batteries due to its unique structure. In this work, β ″ -Al 2 O 3 was further modified by LiAlO 2 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 -1 , the PCFC reached a high power density up to 1029 mW·cm -2 , and the PCEC demonstrated a significant current density of 1.49 A·cm -2 at a low operation voltage of 2.0 V. It has been found that the introduction of the LiAlO 2 phase into β ″ -Al 2 O 3 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.