Ru-based multifunctional mesoporous catalyst for low-pressure and non-thermal plasma synthesis of ammonia

The non-thermal plasma (NTP) allows the synthesis of ammonia, one of the major hydrogen carriers, at a lower temperature and pressure than the traditional Haber-Bosch process. In this study, we report the synthesis of ammonia using NTP, and a Ru-based, multifunctional catalytic system deposited on mesoporous Si-MCM-41. Various surface characterization methods were used to analyze the catalyst. For the ammonia synthesis results, we determined that the synthesis efficiency increased in the high frequency zone (>20,000 Hz). The effects of different experimental parameters were studied and the highest ammonia synthesis efficiency achieved was 1.7 g/kWh at 5000 V and 26,000 Hz. Results were analyzed in the context of several synergetic effects including the plasma forming mechanism, discharge effects of the catalysts, plasma shielding effects of the mesoporous structure, and other plasma-catalyst interactions. Lastly, a new concept of a two-step non-thermal plasma ammonia synthesis method was also proposed.