Defect chemistry of La1-xSrxMnO3 +/-delta under cathodic polarization

Cyclic voltammetry and potentiometric chrono method were conducted on yttria-stabilized zirconia (YSZ)-supported La(1-chi)SrchiMnO(3+delta) (LSM) electrode to elucidate the kinetics of electrochemical redox of Mn ions at the LSM/YSZ interface and its effect on the performance of LSM electrode under cathodic polarization. Three electrochemical processes were detected under cathodic polarization, which correspond to the reduction of adsorbed oxygen, Mn-Mn(.) to Mn-Mn(X) and Mn-Mn(X) to Mn'(Mn). The electrochemical activation of LSM electrode at the first stage of the cathodic polarization is attributed mainly to the reduction of Mn-Mn(.) to Mn-Mn(X) with the concomitant removal of the metal vacancies at the LSM/YSZ interface. When the cathodic polarization is negative enough, the oxygen vacancies at the LSM/YSZ interface may be generated with further reduction of Mn-Mn(X) to Mn'(Mn). However, this may disturb the thermodynamic equilibrium between YSZ electrolyte and the LSM electrode, causing defects at the LSM/ YSZ interface if under long-time operation. (C) 2004 The Electrochemical Society.