Thermochemical two-step water splitting by internally circulating fluidized bed of NiFe2O4 particles: Successive reaction of thermal-reduction and water-decomposition steps

Modelling of solar thermochemical reaction systems

“…These calculations can provide great insight into mechanisms of the reaction pathway and the material properties that can limit or enhance active material performance. Recent works using DFT calculations to elucidate design principles for improved solar thermochemical cycle active materials have suggested that the thermodynamics of forming oxygen vacancies in a metal oxide lattice and the kinetics of conducting those vacancies (Kodama et al, 2008;Gokon et al, 2011;Kodama et al, 2005;Rydén et al, 2011;Alvani et al, 2005;Tamaura et al, 1998;Hwang et al, 2004;Miller et al, 2008;Fresno et al, 2009;Fresno et al, 2010;Arifin et al, 2012;Gokon et al, 2008b;Agrafiotis et al, 2015;Agrafiotis et al, 2012;Goikoetxea et al, 2016;Lorentzou et al, 2014;Cha et al, 2007;Kodama et al, 2002) to and from the surface are important in assessing material activity (Michalsky et al, 2015a,b;Ezbiri et al, 2015). Indeed, a study data mining first principles data from doped ceria studies identified surface oxygen vacancy formation energy as the primary descriptor that correlates with enhanced water splitting ability (Botu et al, 2016).…”

“…The studies on ferrite-based systems have shown that required reduction temperatures can be lowered by substituting metals such as manganese or nickel into ferrite based mixed metal oxides of the type M x Fe 3-x O 4 (Steinfeld, 2005). Co, Ni, Zn, Cu, and Mn substitutions into ferrite spinel structures have recently been used in successful hightemperature H 2 O/CO 2 splitting, suggesting that the M x Fe 3-x O 4 form of these mixed oxides is particularly active (Kodama et al, 2008;Gokon et al, 2011;Kodama et al, 2005;Rydén et al, 2011;Alvani et al, 2005;Tamaura et al, 1998;Hwang et al, 2004;Miller et al, 2008;Fresno et al, 2009;Fresno et al, 2010;Arifin et al, 2012;Gokon et al, 2008b;Agrafiotis et al, 2015;Goikoetxea et al, 2016;Lorentzou et al, 2014;Cha et al, 2007;Kodama et al, 2002). Other spinel structures are also of interest, such as the ''hercynite cycle" (Muhich et al, 2013 (Haussener et al, 2010c).…”

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.…”

“…Researchers from the University of Tokyo, Japan, introduced a rotary-type reactor in which a cylindrical rotor coated with redox pair of materials such as CeO 2 and mixed ferrites (Ni 0.5 Mn 0.5 Fe 2 O 4 ) rotates between two chambers, one in which the water-splitting reaction is performed and one where thermal regeneration is performed (Kaneko, Fuse, Miura, Ishihara, & Tamaura, 2006). The research group at Niigata University in Japan proposed a spouted bed-type reactor in which redox powders of NiFe 2 O 4 /ZrO 2 are irradiated by concentrating solar irradiation (Gokon et al, , 2011Gokon, Yamamoto, Kondo, & Kodama, 2010). In the United States, the research group at Sandia National Laboratories developed (a) (b) Figure 11.6 Actual dual-chamber, HYDROSOL reactor, and concept demonstration at the Plataforma Solar de Almería, Spain.…”

Magnetic separation for a continuous solar-two-step thermochemical cycle for solar hydrogen/CO production using ferrites

“…systems based on transporting metal oxide particles in the form of fluidized beds or moving beds [12][13][14], where particles are conveyed from hotter sections of the reactors where thermal reduction takes place to colder sections to allow water oxidation to take place, and returned after completion; 2. designs suggesting achieving this by using monolithic porous structures made of the active metal oxides and turning or moving them, such that they alternately move through the hot and cold sections [15,16]; and 3. designs suggesting fixing the metal oxide and raising/ lowering the solar heat flux by focusing/defocusing the mirrors [17,18].…”