Ammonia chemistry: Sounds better with ultrasound

Hydrazine is a chemical of utmost importance in our society, either for organic synthesis or energy use. The direct conversion of NH 3 to hydrazine is highly appealing, but it remains a very difficult task because the degradation of hydrazine is thermodynamically more feasible than the cleavage of the N−H bond of NH 3 . As a result, any catalyst capable of activating NH 3 will thus unavoidably decompose N 2 H 4 . Here, we show that cavitation bubbles, created by ultrasonic irradiation of aqueous NH 3 at a high frequency, act as microreactors to activate and convert NH 3 to NH species, without assistance of any catalyst, yielding hydrazine at the bubble–liquid interface. The compartmentation of in-situ-produced hydrazine in the bulk solution, which is maintained close to 30 °C, advantageously prevents its thermal degradation, a recurrent problem faced by previous technologies. This work also points towards a path to scavenge .OH radicals by adjusting the NH 3 concentration.