Ultrasonic assisted electrolysis enables massive production of hydrogen bulk nanobubbles

The controllable and efficient generation of bulk nanobubbles (BNBs) is critical for advancing applications in energy catalysis, biomedicine, and environmental remediation. Herein, we designed a customized electrolytic cell with separated cathode and anode chambers to enable the independent production of hydrogen bulk nanobubbles (H₂-BNBs) and oxygen bulk nanobubbles (O₂-BNBs). Notably, the introduction of ultrasonic waves during water electrolysis resulted in an approximately six-fold increase in H₂-BNBs concentration compared to conventional electrolysis. Systematic investigations were conducted to elucidate the effects of key parameters, including ultrasonic-electrolysis duration, applied voltage, electrolyte type, and electrolyte concentration. Under optimized electrochemical conditions, stable H₂-BNBs with a number concentration of ∼ 2.0 × 10⁸ particles mL^-1 were achieved. Furthermore, H₂-BNBs exhibited superior stability in alkaline solutions compared to acidic environments, maintaining a long lifetime for over 24 h. This study established a robust methodology for the scalable production of H₂-BNBs, offering strategic implications for their utilization in diverse industrial and scientific domains.