Oxygen Electro-Reduction on C22 and C276 Nickel Metal Alloy

Abstract

The C22 and C276 alloy metal surfaces were characterized for electrochemical activity in alkaline aqueous media in the presence and absence of oxygen (O 2 ) and at 30° C. The metal was studied by electrochemical impedance spectroscopy (EIS), voltammetry with a still electrode and a specialized rotating ring-disk electrode (RRDE) technique, the cyclic potential ring measurement (CPRM) method (1). The CPRM method gave the steady state O 2 reduction kinetics. An initial study of O 2 reduction on gold yielded virtually identical results to the work of Vilambi and Taylor who first described the CPRM method. The application of the CPRM method to the study of O 2 reduction on C22 and C276 showed strong evidence for a predominantly series 2 step, 2 electron O 2 reduction pathway, where kinetic rate constants k 2 (evaluated at -0.7V versus the saturated calomel electrode) and k 3 (evaluated at -1.2V) were estimated at 30° C to be 0.001 cm/s and 0.193 cm/s respectively for C22 and 0.013 cm/s and 0.232 cm/s respectively for C276.

Effect of Oxide Film Properties on the Kinetics of O2Reduction on Alloy C-22

“…27 An electrochemical and corrosion study of Alloy C-22 in 0.5 M NaCl solution showed that open-circuit passivation of the alloy had a pronounced effect on the kinetic parameters of both the cathodic and anodic reactions involved in the corrosion process. 28 Both reactions were slower than those proceeding on the active (cathodically-reduced) alloy surface.…”

“…26 The O 2 reduction reaction on Alloys C-22 and C-276 in alkaline solutions appears to proceed via two 2-electron processes in series, with kinetic rate constants at 30 • C estimated to be in the range 0.001 to 0.232 cm/s, depending on the potential. 27 An electrochemical and corrosion study of Alloy C-22 in 0.5 M NaCl solution showed that open-circuit passivation of the alloy had a pronounced effect on the kinetic parameters of both the cathodic and anodic reactions involved in the corrosion process. 28 Both reactions were slower than those proceeding on the active (cathodically-reduced) alloy surface.…”