Steam electrolysis using LaGaO₃ based perovskite electrolyte for recovery of unused heat energy

Application of LaGaO₃ based electrolyte for steam electrolysis was studied for the useful utilization of unused heat energy from steelmaking process. It was found that the H₂ formation rate almost obeys the Faraday's law suggesting unity of oxide ion transport number in LaGaO ₃ perovskite under an electrolysis condition up to 2.0 V applied potential. Among the examined cathode catalyst, nickel shows the smallest cathodic overpotential and the addition of Fe to Ni is highly effective for increasing the H₂ formation rate in the steam electrolysis at 873 K. The highest H₂ formation rate is obtained at the composition of Ni : Fe=9 :1. Short stack of the steam electrolysis cell consisting of 25 cells in series connection was also studied and the formation rate of H₂ was achieved as large as 70L/min at 1.8 V applied potential. Heat balance was calculated based on the developed stack level. It became clear that the heat source of 223 K level is enough for sustaining cell temperature because of large Joule heat.