Hydrogen production via solar‐aided water splitting thermochemical cycles with nickel ferrite: Experiments and modeling

Abstract

Water splitting -thermal reduction cyclic studies with NiFe 2 O 4 redox materials were performed in a differential fixed-bed laboratory reactor in the temperature range 700-1,400C to quantify the effects of operation temperatures and steam mole fraction on hydrogen and oxygen yields. Hydrogen yield increased drastically by an increase of the water splitting temperature from 800 to 1,000 C reaching a plateau at 1,100 C. In parallel, a simple mathematical model was formulated describing the water splitting process via the heterogeneous surface reactions of water vapor with the redox powder material, from which, in conjunction to the aforementioned experiments, the kinetic parameters of the water splitting and thermal reduction reactions were extracted. The water splitting kinetic constants exhibited weak temperature dependence between 700 and 1,100 C suggesting the existence on the redox material of more than one type of oxygen storage sites with respect to ease of exposure and accessibility to the gas phase.

Phase formations and magnetic properties of single crystal nickel ferrite (NiFe2O4) with different morphologies

“…8 However, NiFe 2 O 4 nanoparticles are found to have the mixed spinel structure together with the inverse one, [9][10][11] i.e., some Ni 2+ ions may occupy the T d sites. NiFe 2 O 4 has an inverse spinel structure with Ni 2+ ions on octahedral B sites (denoted as O h -sites) and Fe 3+ ions distributed on both the tetrahedral A (denoted as T dsite) and the O h -sites equally.…”

Hydrogen production via thermochemical water splitting

“…It has been reported that partial substitution of iron in the magnetite phase by Mn, Ni, or Zn forms mixed-metal oxides of the type MFe 2 O 4 (mixed ferrites) that are more reducible and require moderate, upper (thermal reduction) operating temperatures. A whole series of such ferrites has been tested experimentally and studied thermodynamically, including either only one divalent metal cation in the M site, such as MnFe 2 O 4 (Tamaura et al, 1999), ZnFe 2 O 4 (Aoki, Kaneko, et al, 2004;Kaneko et al, 2004), NiFe 2 O 4 (Agrafiotis, Zygogianni, Pagkoura, Kostoglou, & Konstandopoulos, 2013;Fresno, Yoshida, Gokon, FernandezSaavedra, & Kodama, 2010;Gokon, Takahashi, Yamamoto, & Kodama, 2008;Gokon, Mataga, Kondo, & Kodama, 2011), or CoFe 2 O 4 (Miller et al, 2008), or two such cations-i.e., of the type (C x D 1-x ) þ2 Fe 2 þ3 O 4 -including Ni 0.5 Mn 0.5 Fe 2 O 4 (Tamaura et al, 1998;Tamaura, Steinfeld, Kuhn, & Ehrensberger, 1995), Mn 0.5 Zn 0.5 Fe 2 O 4 (Inoue et al, 2004), and other cation stoichiometries (Allendorf, 2008;Kodama & Gokon, 2007;Kojima et al, 1996;Miller et al, 2006). However, their thermal reduction temperatures are still high (z1600e1700 K), which is an important drawback because it can cause significant sintering of the metal oxide.…”

A review on solar thermal syngas production via redox pair-based water/carbon dioxide splitting thermochemical cycles

“…Various ferrite powders synthesis techniques have been pursued from solid, liquid or gaseous precursors, among others co-precipitation [95], aerial oxidation of aqueous suspensions of Fe(II) hydroxide [96,97], sol-gel [98], atomic layer deposition [99,100], combustion synthesis [86,101] and spray pyrolysis [102]. Comparative testing of ferrite powders has identified the temperature ranges recommended for cyclic operation as well as the effects of process parameters on H 2 /O 2 yields [86,89,103]. Their TR temperatures are still high (E 1600-1700 K)-an important drawback since it can cause significant sintering of the oxide.…”