Intermediate temperature steam electrolysis using doped lanthanum gallate solid electrolyte (2) effects of CeO₂ interlayer on activity

Steam electrolysis is attracting much interest method to produce hydrogen and also the new energy recovery process of wasted heat energy. Up to now, Y₂O₃ stabilized ZrO₂ (YSZ) has been used for a solid electrolyte and so the operating temperature is limited down to 1273K. This study is focused on increasing the performance of steam electrolysis by using LaGaO₃ based oxide for electrolyte at intermediate temperature of 873 K, which is upper limit of the obtainable wasted heat. It was found that the formation amount of H₂ is almost obeyed the Faraday law up to 1.8 V suggesting that the ionic transport number of oxide ion in LaGaO₃ was kept to be 1 under the steam electrolysis condition. The electrolyzing current is improved as following order; La_0.6Sr_0.4CoO ₃<Sm_0.5Sr_0.5CO₃≪ Ba _0.6La_0.4CoO₃ for anode and Pt<Ni<Ni-Fe for cathode, respectively. Hydrogen production rate higher than 100 umol ml ^-1 min^-1 at 873 K and 300 mA cm^-2 were successfully demonstrated at 1.8 V in this study. Electrolysis reaction under various reaction conditions are also presented. The H₂ formation rate increased with increasing total flow rate due to the diffusion resistance.