(631e) H2 Generation From Water-Splitting Using Novel Ferrite Foam Materials

Thermochemical water-splitting, which utilizes metal oxide (MO) - based redox reactions, has significant commercial potential due to lower water-splitting temperature as compared to thermolysis. Among several materials investigated so far, ferrites such as (A_xB_y)Fe_zO₄ (doped spinel) or (A_xB_y)Fe_1-x-yO (doped wustite) or their mixtures, where A and B being bivalent metal cations such as Mn, Ni or Zn, were reported to be most active materials for hydrogen generation from water-splitting. These ferrites have been used primarily in the form of powder material for water-splitting reaction. In this investigation, ferrite foam material was synthesized using modified sol-gel method. Specifically to synthesize Ni ferrites, Ni⁺² and Fe⁺³ salts were dissolved in ethanol by sonication and the gel formation was accomplished by adding propylene oxide. To this gel 10% (w/w) polymer microspheres were added and homogeneous mixture was fired rapidly in a quartz tubular furnace at 1000^oC and quenched in air. The scanning electron microscopic (SEM) images of this ferrite foam material are presented in Figures 1a&b and the energy dispersive X-ray (EDX) mapping are shown in Figures 1c&d. Foam-like morphology with pore size of 1-20 mm was observed from the SEM images whereas EDX structure indicated the presence of Fe and Ni throughout the sample matrix. The BET surface area of this ferrite foam was 156 m²/g, which is higher than for Mn-Ni-ferrites reported in the literature. In preliminary experiments, H₂ was generated by water-splitting reaction using Ni ferrite at 1000^oC. Synthesis method, characterization, and transient H₂ profiles obtained at various experimental conditions will be presented in detail.

 
Figure 1a) SEM image of Ni_xFe_yO_z foam prepared by rapid firing in a tubular furnace and quenching, b) Ni_xFe_yO_z foam at higher resolution, and c &d) x-ray mapping indicating Fe and Ni.