Kinetic studies of the electrochemical nitrogen reduction and incorporation into yttria stabilized zirconia

The kinetics of the electrochemical reduction of molecular nitrogen at gold micro electrodes on yttria stabilized zirconia (YSZ) solid oxide electrolyte is studied by steady state polarization measurements. From the η / lg i plot for both cathodic and anodic polarization the apparent transfer coefficients αa and αc are evaluated. The sum of αa + αc exceeds unity and thus a multistep electron transfer process is suggested. The concept of the stoichiometric number is applied to the electrode reaction N2 + 6e− = 2N3− supposing that the overall process involves at least two intermediate species. On the basis of the evaluation of the experimental results the reaction N2− + e− ⇌ N22− is suggested as the rate determining reaction step for the cathodic nitrogen reduction and nitride formation.