PNNL

Abstract

Hydrogen evolution is one of the major side reactions that is detrimental to the operation of all-vanadium redox flow batteries, especially for long-term cycling. Effective, low-cost, and accurate online detection methods for hydrogen generation are not yet available. In this work, we designed an online, noninvasive ultrasonic probing approach for detecting hydrogen gas bubbles generated in anolyte solutions. The technique employs a pulse-echo method to measure the sound speed and the acoustic attenuation coefficient of the anolyte solution. Through static offline experiments and online in operando experiments, we have demonstrated that when hydrogen gas is generated in anolyte solutions, large variations are observed in both sound speed and acoustic attenuation coefficient measurements. We found that these variations are highly correlated (correlation coefficients >0.9) with the gas flow rate. Our acoustic monitoring method can effectively detect the presence of gas bubbles in an anolyte solution and, thus, provide information about the state of health for operation and management of flow battery systems.