Electrochemical kinetics of the water reduction at strontium doped lanthanum chromite (SDLC)/Yttria stabilized zirconia interfaces at high temperature

Abstract

The electrochemical kinetics of the water reduction at 20% strontium doped lanthanum chromite/yttria stabilized zirconia interface at high temperature has been investigated. A two electrodes cell with porous platinum anode has been utilized to carry out several series of experiments at temperatures ranging from 650°C to 1050°C with H2/H2O ratios of the feeding mixtures from 0.18 up to 1.55.The results have been evaluated in terms of overvoltage and exchange current density and compared with those obtained previously with the Pt/YSZ cathodic interface. In both cases, at low currents, a typical behaviour which may be attributed to a charge transfer rate determining process, has been found. The activation energy of such a process was found higher in the case of SDLC (≈23 kcal/mole) than for platinum electrodes (≈14 kcal/mole).Above a certain current density the total applied voltage appears well represented by a family of straight lines in both cases, thus suggesting that in this region of high current densities the reduction process does not require any apparent additional overvoltage.The overvoltages, decreasing as temperature increases, appear higher over SDLC than over platinum. Although the faradic yield for the water splitting was still 100% in all the experiments, the oxide seems to work worse than porous platinum.