Electrokinetics of Nitrite to Ammonia Conversion in the Neutral Medium Over A Platinum Surface

Polycrystalline Pt electrode was employed to selectively convert nitrite ions ( $$ ) into useful nitrogenous compound through electrochemical reduction reaction in neutral medium. According to adsorptive stripping analysis, the reduction process produced nitric oxide (NO) on the surface of Pt electrode. The spectroscopic test and gas chromatographic studies discovered the presence of ammonia (NH₃) in the electrolyzed solution, suggesting the transformation of adsorbed NO into NH₃ during the reverse scan. Scan rate dependent investigation was performed to elucidate kinetic information relating to this reaction on Pt surface. From E_p vs scan rate (υ) and j_p vs υ (logarithmic plot), it was found that the conversion of $$ ion into NO is an irreversible reaction which relies on the diffusion of $$ ions to electrode surface. The Tafel analysis unveiled that the first electron transfer sets the overall reaction rate, having formal reduction potential, E⁰'=-0.46 V and standard heterogeneous rate constant, k⁰= $$ cm s^-1. Reductive transfer coefficient (α) is another kinetics parameter, which was found to be approximate 0.77 from the difference between E_p and E_p/2 of the voltammograms obtained over scan rate range 0.005 V s^-1 to 0.250 V s^-1, indicating a stepwise process. According to temperature-dependent voltammograms, the nitrite reduction reaction on Pt had a calculated activation energy of about 19.8 kJ mol^-1 and a pre-exponential factor of about 8.39×10³ mA cm^-2.