Hydrogen-oxygen Generation with Intermediate Temperature Steam Electrolysis Using LaGaO3 Based Perovskite Electrolyte for Recovery of Unused Heat Energy

Application of LaGaO3 based electrolyte for steam electrolysis at intermediate temperature was studied for the generation of hydrogen and oxygen by using the unused heat energy from steelmaking process. It was found that H-2 formation rate was much improved by combination of oxygen ion conducting oxide with NiFe (9:1) bimetallic alloy. In particular, combination with La0.6Sr0.4Fe0.9Mn0.1O3 (LSFM) or Ce0.8Sm0.2O2 (SDC) is highly effective for increasing current density. Impedance plots for cathode were consisted of two semicircles, which could be assigned to a diffusion and an activation overpotential in low and high frequency region, respectively. Comparing with NiFe, mixing with SDC is much effective for decreasing the diffusion overpotential. This might be assigned to increase in three phase boundary and porosity of cathode. Effects of steam partial pressure was further studied and because of slow diffusivity of water in porous cathode, increase in humidity pressure decreased H-2 formation rate. Humidity utilization of 56% was achieved by using 81 ml/min (29% P-H2O) steam flow rate.