Analysis of ammonia electro-oxidation kinetics using a rotating disk electrode

The kinetics for the electro-oxidation of ammonia in alkaline media was revisited by utilizing a rotating disk electrode (RDE) system. A well-characterized electrocatalyst for the oxidation of ammonia was developed by electrodepositing platinum over a nickel disk electrode in alkaline media at different deposition temperatures (50, 60, and 70 °C) and times (20, 40, and 80 min). The catalyst prepared by the deposition of Pt at 50 °C for 80 min over a Ni disk electrode was found to be the better electrocatalyst for the ammonia oxidation process. This electrode was used in the RDE assembly and subjected to the linear sweep voltammetry experiments to investigate the kinetics of the electro-oxidation of ammonia. The results based on the studies from varying rotational speeds (0-2000 rpm) and scan rates (1-90 mV s ^-1) indicated that the ammonia electro-oxidation was controlled by mass transfer limitations. A dimensionless analysis illustrated that the presence of an oxidation peak even at high rotational speed in the current-voltage curve could be explained by a transient current response induced by the mass transfer limitations.