Kinetics of the ferric–ferrous couple on anodically passivated chalcopyrite (CuFeS2) electrodes

This work reports, for the first time, the kinetics of the ferric–ferrous couple on a passivated semiconductor chalcopyrite electrode. The electrode was passivated in sulfuric acid solution and, upon reaching the steady-state condition, ferric and ferrous sulfate salts were added. The registered changes in current were interpreted for kinetics. An exchange current density of 2.44 × 10− 6 A cm− 2 and anodic and cathodic transfer coefficients of 0.37 and 0.50, respectively, were obtained. The reactions were surprisingly rapid. This work demonstrates that ferric reduction on chalcopyrite is faster than the chalcopyrite oxidation reaction itself.It is expected that this method could be used as a versatile approach to measure the kinetics of redox couples on the surfaces of various mineral electrodes.

► Kinetics of the Fe3+/Fe2+ couple on a passivated chalcopyrite (CuFeS2) electrode. ► Problem rises from the interference of chalcopyrite oxidation reactions. ► The measured kinetics of the reaction were surprisingly high. ► Dissolution of chalcopyrite is mass transport-controlled. ► The reported approach can be applied to other semiconductor electrodes.