Solar Energy Conversion into H2 Energy Using Ferrites

Abstract

Abstract: A cation-excess (Ni,Mn) ferrite N~o.~zMno.51Fe2.0504.0 with a single phase was synthesized by heating the mixture of corresponding metal salts and oxide in 5% 02175% C02120% N2 gas mixture for 18h at 1100C. It could be thermochemically activated to form a cation-excess ferrite Nio,5z~l+s~Mno.51~l+6~Fe2~05~1+6~0440 in N2 gas at elevated temperature: The ( value was 0.03 1 at 1100C. The activated (Ni,Mn) femte was reacted with water to form Hz gas at 700C. The process was reversible and could be carried out repeatedly. 1. INTRODUCTION Solar thermal production of hydrogen by single-step (direct) thermal water dissociztion, although conceptually simple, still lacks of an effective technique for separating hydrogen and oxygen at high temperatures. Two-step water-splitting cycle, based upon metal oxides redox system, bypasses the separation obstacle. A novel two-step water-splitting cycle is presented which, in contrast to previously proposed cycles that require upper operating temperatures above 2300K, can be conducted at a much moderate (and workable) temperature. In the first, endothermic step, Nio.5Mno,5Fe204 is thermally activated at above 1073 K to form an oxygen-deficient ferrite. In the second step, activated femte is reacted with water at below 1073 K to form hydrogen; the ferrite product is recycled to the first step. H2 and