Steam Electrolysis Cells that Can Operate at 600 °C

Steam electrolysis using proton-conducting metal oxides can potentially increase electrolyzer efficiency while reducing electrical energy demand and lowering hydrogen production costs. The present work evaluated and selected baseline cell materials and demonstrates the feasibility and operation of proton-conducting solid oxide electrolysis cells at intermediate temperature. A series of electrolyte compositions and steam electrode materials were examined using conductivity, steam stability, and electrocatalytic activity. Several cell configurations have also been evaluated. Some demonstrate excellent performance and durability (≤2.5%/1000 h in terminal voltage rise and 2.1%/1000 current efficiency reduction rate). Three and ten cell stacks were built and tested. The three cell stack reached a cell terminal voltage of 4.7 V, and the hydrogen generation rate was 42 ^NLh^-1, with a current efficiency of 83%. The cell performance stability was improved by inserting an active NiO/SZCY541 layer between the electrolyte and the cathode substrate. After 1500 h or more of durability testing, very minimal Co and Ni defused to the electrolyte layer and are not the leading cause of the minor degradation observed. The present proton-conducting solid oxide electrolysis cell design reveals a more feasible approach for realizing both highly efficient and economically viable systems.