Sonoelectrochemical (20 khz) production of hydrogen from aqueous solutions

Abstract

There are various methods of producing Hydrogen. These include electrolysis, which this work is based upon, and steam reforming; currently the most commercially viable method. The research herein investigates methods of producing ‘green’ Hydrogen more efficiently by using ultrasound (20 kHz) combined to electrolysis. Previous studies have shown that ultrasound enhances mass-transfer of electro-active species from the bulk solution to the electrode surface in any electrolytic system and mechanically removes gas bubbles on the electrode surface. This work takes this previous research further by quantifying actual hydrogen gas output. The hydrogen evolution reaction was then directly compared with that calculated using the Ideal Gas Equation to quantify the efficiency of the electrolysis system. It was observed that ultrasound lowers the anodic and cathodic overpotentials due to gas removal at the electrode surface induced by cavitation and increased mass-transfer. However, it was found that ultrasound did not increase the rate of Hydrogen production. During experimentation it was seen that the force exhibited on the electrodes by ultrasonic waves limited bubble evolution on the electrode surface. Issues associated with the ultrasonic reactor geometry and the ultrasonic transducer size are also discussed as potential reasons for this result