Gliding arc discharge in combination with Cu/Cu₂O electrocatalysis for ammonia production

Highly efficient and green ammonia production is an important demand for modern agriculture. In this study, a two-step ammonia production method is developed using a gliding arc discharge in combination with Cu/Cu₂O electrocatalysis. In this method, NO_x is provided by the gliding arc discharge and then electrolyzed by Cu/Cu₂O after alkaline absorption. The electrical characteristics, the optical characteristics and the NO_x production are investigated in discharges at different input voltage and the gas flow. The dependence of ammonia production through Cu/Cu₂O electrocatalysis on pH value and reduction potential are determined by colorimetric method. In our study, two discharge modes are observed. At high input voltage and low gas flow, the discharge is operated with a stable plasma channel which is called the steady arc gliding discharge mode (A-G mode). As lowering input voltage and raising gas flow, the plasma channel is destroyed and high frequency breakdown occurs instead, which is known as the breakdown gliding discharge mode (B-G mode). The optimal NO_x production of 7.34 mmol h⁻¹ is obtained in the transition stage of the two discharge modes. The ammonia yield reaches 0.402 mmol h⁻¹ cm⁻² at pH value of 12.7 and reduction potential of −1.0 V versus reversible hydrogen electrode (RHE).