Continuous ammonia synthesis from water and nitrogen via contact electrification

We synthesized ammonia (NH3) by bubbling nitrogen (N-2) gas into bulk liquid water (200 mL) containing 50 mg polytetrafluoroethylene (PTFE) particles (similar to 5 mu m in diameter) suspended with the help of a surfactant (Tween 20, similar to 0.05 vol.%) at room temperature (25 degrees C). Electron spin resonance spectroscopy and density functional theory calculations reveal that water acts as the proton donor for the reduction of N2. Moreover, isotopic labeling of the N2 gas shows that it is the source of nitrogen in the ammonia. We propose a mechanism for ammonia generation based on the activation of N-2 caused by electron transfer and reduction processes driven by contact electrification. We optimized the pH of the PTFE suspension at 6.5 to 7.0 and employed ultrasonic mixing. We found an ammonia production rate of similar to 420 mu mol L-1 h(-1) per gram of PTFE particles for the conditions described above. This rate did not change more than 10% over an 8-h period of sustained reaction.