Electrochemical-catalytic NH 3 synthesis from H 2 O and N 2 using an electrochemical cell with a Ru catalyst, Pd–Ag membrane cathode, and NaOH–KOH molten salt electrolyte at 250 °C

Using sustainable energy-based electricity to synthesize NH 3 from H 2 O and N 2 to release O 2 not only contributes to making chemical fertilizer production carbon neutral, but also holds promise for the use of NH 3 as a fuel. NH 3 synthesis from water and nitrogen was conducted at around 250 °C and below 1.0 MPa by combining a molten salt electrolyte of NaOH–KOH, a Pd alloy hydrogen-permeable membrane cathode, a Ni anode, and a Ru-based catalyst on the cathode backside. The rate and current efficiency for NH 3 formation were obtained as 11 nmol s −1 cm −2 (38 μmol h −1 cm −2 ) and 25%, respectively, at 30 mA cm −2 , 1.0 MPa, and 250 °C. It was confirmed that the remaining percentage from the 100% current efficiency for NH 3 production was attributed to the current efficiency for H 2 production. The cell voltage was as low as 1.47 V at 30 mA cm −2 and increased to 1.95 V at 100 mA cm −2 . The potential of this electrochemical system is discussed.