Investigation of the electrocatalytic activity of nickel for ammonia oxidation

The electrocatalytic activity of nickel for ammonia oxidation was investigated and analyzed by cyclic voltammetry and semiconductor electrochemistry theory. A layer of oxide is always formed on the nickel electrode surface in the various alkaline solutions to disable the adsorption of ammonia on electrode based on valence bond theory. Furthermore, nickel oxide is a p-type semiconductor with the main charge carriers of cation vacancies. Upon ionization, the cation vacancies are charged negatively, causing electro-migration and then adsorption of NH4+ ions in the solutions. However, the sequential discharging processes of NH4+ are inhibited by the negatively charged cation vacancies in the oxide that reverse the electron generation. Therefore, the semiconducting properties of nickel oxide deactivate the capability of nickel as an electrocatalyst for ammonia oxidation.