Electrochemical oxidation of sulphite in neutral media on graphite

In this paper, electrochemical behavior of sulphite ions on graphite electrode in neutral solution (1 mol L −1 Na 2 SO 4 ) has been studied in order to identify the relationship between the sulphite concentration in the electrolyte solution (10 −3, 10 −2, 10 −1, 5·10 −1 and 1 mol L −1 ) and kinetic parameters of the anodic process. Electrochemical behavior of sulphite in the test solutions has been studied by square wave voltammetry (SWV) and differential pulse voltammetry (DPV), as well as by linear (LV) and cyclic voltammetry (CV). Tafel slopes between 167 and 191 mV dec −1 have been obtained, corresponding to an anionic transfer coefficient in the range of 0.31–0.34. Exchange current density values up to 0.80 A m −2 reveals that the rate of the electrochemical oxidation of sulphite in the neutral media is at the same order of magnitude as in the alkaline solution. The general aim of these studies is to obtain new anodes with electrocatalytic properties for sulphite oxidation in SO 3 2− /O 2 alkaline fuel cells.