BiOCl micro-assembles consisting of ultrafine nanoplates: A high performance electro-catalyst for air electrode of Al–air batteries

•BiOCl micro-assembles consisting of ultrafine nanoplates.•Excellent oxygen reduction properties.•Novel catalyst for air electrode of aluminum air batteries.•The electro-catalytic activity is closely related to the density of oxygen vacancy on the surface of the BiOCl samples.•A higher ratio of the {001} facets in BiOCl crystals is favorable for the enhancement of the electrocatalytic activity.

BiOCl micro-assembles appearing spherical and plate-like in shape consisting of ultrafine nanoplates were successfully synthesized by a simple hydrothermal method. The obtained BiOCl micro-assembles were characterized as oxygen reduction reaction (ORR) catalyst for air electrode of aluminum air batteries by using linear polarization and constant-current discharge techniques. The effect of precursor concentration on the electrochemical properties of the air electrodes based on the synthesized BiOCl micro-assembles was intensively investigated. The results demonstrated that the BiOCl catalyst exhibited promising ORR performance. Koutecky–Levich analysis indicated that a two-electron reaction was favored for the ORR mechanism of the BiOCl (0.18) sample.