(246e) “Herycnite Cycle” Materials for Pseudo-Isothermal Solarthermal Water Splitting

Solar thermal water splitting (STWS) is a promising technology for producing hydrogen gas economically, efficiently and cleanly. Two-step, metal oxide based STWS cycles generate H₂ by a metal oxide undergoing sequential high temperature reduction and water re-oxidation. The “hercynite cycle”, which is based on iron reduction in a spinel structure, relies on intimate contact between CoFe₂O₄ and Al₂O₃ phases in order to form the Co_0.33Fe_0.66Al₂O₄ structure needed for STWS redox cycling. In this work we used atomic layer deposition of CoFe₂O₄ on a nano-scale alumina support to produce the 85% active “hercynite cycle” material. Using this material we carried STWS operating under pseudo-isothermal water splitting (PITWS), where the reduction and oxidation temperatures differed less than 150°C. By combining ALD fabricated “hercynite cycle” materials and PITWS we were able to produce H₂ of approximately  400 μmol H₂/total g.