THE OBJECTIVE OF THIS PROPOSAL IS TO DEMONSTRATE LOW-TEMPERATURE HYDROGEN PRODUCTION FROM PROTON CONDUCTING SOLID OXIDE ELECTROLYSIS CELL (P-SOEC) TECHNOLOGY WITH ENHANCED ACTIVITY, EFFICIENCY, AND DURABILITY THROUGH A SERIES OF WORK IN MATERIALS DEVELOPMENT, INTERFACE ENGINEERING, MANUFACTURING IMPROVEMENT, DEGRADATION STUDY, AND FARADAIC EFFICIENCY. BY THE END OF BUDGET PERIOD 1, THE TEAM WILL 1) DEMONSTRATE THE ACTIVE AND DURABLE P-SOEC MATERIAL SYSTEM BASED ON TRIPLE CONDUCTING OXYGEN ELECTRODE AND BARIUM-ZIRCONATE ELECTROLYTE WITH COMPATIBLE THERMAL AND CHEMICAL PROPERTIES, 2) IDENTIFY SURFACE CHEMISTRY AND ELECTRODE DEGRADATION MECHANISMS ON SURFACE, 3) DEMONSTRATE LARGE-SCALE SINGLE-CELL CELL MANUFACTURING WITH OPTIMAL PROTOCOLS. BY THE END OF BUDGET PERIOD 2, THE TEAM WILL 1) DEMONSTRATE ENHANCED MECHANICAL STRENGTH, INTERFACIAL BONDING, AND POLARIZATION RESISTANCE FOR OPTIMIZED ELECTROCHEMICAL ACTIVITY, 2) DELIVER DEEP UNDERSTANDING ON THE PHASE EVOLUTION DURING ELECTROLYSIS FOR SUPPRESSING INTERFACIAL DEGRADATION, 3) IMPROVE MANUFACTURING READINESS AND DEMONSTRATE A P-SOEC SHORT STACK FOR ELECTROLYSIS OPERATION. BY THE END OF BUDGET PERIOD 3, THE TEAM WILL 1) DEMONSTRATE THE IMPROVEMENT OF FARADAIC EFFICIENCY BY INTERFACE ENGINEERING TO ELIMINATE ELECTRONIC LEAKAGE, 2) SUCCESSFULLY DESIGN AN INTERFACE FOR ELIMINATING LONG-TERM DEGRADATION BY UNDERSTANDING THE FAILURE MECHANISM AND PROVIDING COST-EFFECTIVE APPROACH, 3) DELIVER 500-W P-SOEC STACK FOR ELECTROLYSIS OPERATION.