Perspective in the industrial applications of sonoelectrochemical hydrogen production

Sonoelectrochemistry is the incorporation of power ultrasound in electrochemistry. The use of ultrasound in electrochemical processes such as water electrolysis can lead to an energy efficiency enhancement in the range of 2–25% in low-temperature water electrolysers (LT-WE). However, this improvement greatly depends upon several factors such as the cell reactor design, the ultrasonic frequency, the transmitted acoustic power, and the distance between the ultrasonic transducer and the electrode. The main objectives of this review are to highlight recent advancements in using power ultrasound in water electrolysis and shed some light on possible commercial development by addressing the fundamental obstacles that lie in this technology. Several research works have highlighted that the efficiency improvement in ultrasound-aided water electrolysis is principally due to the gas bubble removal from the electrode surface, which ultimately reduces the ohmic resistance of the electrolytic cell. However, even with the observed higher efficiencies from the sonoelectrolysers for hydrogen production in R&D labs, this technology still faces challenges for further development due to the efficiency in competing with commercial LT-WEs, which are already in the range of 60–70%. If sonoelectrolysers are to succeed for commercial development and large-scale industrial applications, they would need to achieve overall efficiency much higher than current commercial LT-WEs. • Sonoelectrochemical hydrogen production is reviewed. • Power ultrasound enhances electrochemical hydrogen production by 2–25%. • The energy efficiency gain depends on the ultrasonic parameters and the cell design. • Power ultrasound cannot be used in zero-gap cells due to their compact designs. • Direct sonication by high-frequency transducers is suitable for industrial use.