(381d) Low temperature H 2 generation from thermochemical water-splitting reaction using complex redox materials

Authors: 
Shende, R. V., South Dakota School of Mines and Technology
Amar, V. S., South Dakota School of Mines and Technology
Puzsynski, J., South Dakota School of Mines & Technology

H2 can be efficiently produced via thermochemical water-splitting process using redox materials. Among the redox materials investigated, NiFe2O4 exhibited higher H2 volume generation at water-splitting and regeneration temperatures of 900o-1100oC. High energy is typically needed to achieve higher temperatures, therefore, H2 generation via thermochemical water-splitting process is economically less attractive. To make this process cost effective, we have synthesized novel ferrite materials by using sol-gel technique and further investigated their H2 generation ability at lower temperatures. Although there are thermodynamic limitations associated with materials' regeneration abilities at lower temperatures, we believe that the materials synthesized have some merits as they exhibited H2 generation via water-splitting at lower temperatures. The H2 generation ability of these materials was investigated by performing five thermochemical cycles under isothermal condition. Solid-state diffusional parameters and charge transport properties of these redox materials were measured using EIS measurements, which were performed using GAMRY EIS 300 system by applying an A.C. voltage of 200 mV at 0.01 Hz - 300 kHz. The conductivity of the redox materials was determined from the Nyquist plots generated at the reaction temperatures. The activation energy and diffusivity of redox materials was calculated using Warburg time constant. Specific surface area (SSA) and porosity of these materials were analyzed using BET surface area analyzer. Additionally scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the grain growth.