Non-stoichiometric Ferrites for Solar Energy Conversion into H₂ Energy

Abstract

Abstract-Production of solar hydrogen by a novel, two-step, water splitting has been thennochemically studied using metal oxides as a redox pair MOredlMOox.Such reactive metal oxides are exemplified by a cation-excess (Ni,Mu) ferrite Nio.52(l+E}Milo51(l+EjFe2.05(1+E)04.0 with a single phase. It can be synthesized by heating the mixture of corresponding metal salts and oxide in 5% 02175% C02/20% N2 gas mixture for 18h at 1100°C. The solid product was identified by chemical analysis, Mossbauer and XRD spectrometries. The cation-excess (Ni,Mu) ferrite was reacted with water to fonn H2 gas at 700°C. The oxygen of water is quickly incorporated into the ferrite lattice. The process is completely reversible and the (Ni,Mu) ferrite can be used repeatedly. Thus, the material constitutes the reversible redox system with water. Further study will be directed towards eliminating use of low-02 content gas for activation offerrite material.

Survival of short-range order in the Ising model on negatively curved surfaces

“…The abovementioned findings led to the exploration of surface curvature effects in various kinds of statistical lattice models [27,28,29,30,31,32,33,34,35,36,37,38,39,40,41]. For instance, the q-state Potts model on the negatively curved surface exhibited a first-order phase transition when q ≥ 3 [35], and the XY model on the same surface showed the absence of Kosterlitz-Thouless transition due to strong spin-wave fluctuation [31].…”