Electrochemically induced bulk nanobubbles

We describe the generation of bulk nanobubbles using electrolysis of aqueous alkaline, neutral or acidic electrolytes. The technique can be used in either an undivided electrolytic cell to generate a mixture of bulk nanobubbles filled with different gases, for example, a hydrogen- and oxygen-filled bulk nanobubble suspension, or in a divided electrolytic cell to prepare separate hydrogen- and oxygen-filled bulk nanobubble suspensions. We systematically study the effects of the operating parameters on the characteristics of the nanobubbles formed and the effectiveness of their generation. A greater current input, longer operating time, higher electrolyte concentration or lower water operating temperature enhance the production of nanobubbles. The type of electrolyte determines the colloidal stability of the nanobubbles formed. In all types of electrolyte solutions, the initial bubble size is on the order of 100 nm. Bulk nanobubbles in an alkaline electrolyte exist in a stable cluster form, but they dissociate into tiny primary nanobubbles on the order of 1 nm in neutral and acidic electrolytes, which is consistent with our previous findings on the clustering of bulk nanobubbles.