Airborne ultrasound catalyzed saltwater Al/Mg-air flow batteries

In this work, we demonstrate an ultrasonic catalysis method for promoting the ORR rate and enhancing discharge performance of saltwater Al/Mg-air flow batteries, in which focused airborne ultrasound (FAU) is utilized. Experimental results show that compared with the batteries not sonicated, the percentage increase of peak power density of batteries catalyzed by FAU can reach 28.61% for the Al-air flow battery and 33.77% for the Mg-air flow one, respectively, when the ultrasonic frequency is 608.4 kHz. The measured optimal peak power densities are up to 18.9 mW cm−2 and 73.4 mW cm−2 for the Al/Mg-air flow batteries catalyzed by FAU, respectively, when the electric catalysts loaded with Pt/C are employed for the cathode. Our numerical simulation indicates that the sound pressure and acoustic streaming on the cathode surface may enhance the oxygen diffusion. To the best of our knowledge, this is the first attempt to utilize the gas-borne ultrasonic catalysis effect to promote the ORR of metal-air flow batteries.