THERMOCHEMICAL WATER-SPLITTING BY A CARBON-BEARING NI(II) FERRITE AT 300-DEGREES-C

A tailor made carbon-bearing Ni(II) ferrite (CBNF) represented by Ni0. 382Fe2.618O4-deltaCtau was studied for two-step water-splitting at 300 degrees C. It was activated in Ar gas with low O-2-content (<50 ppm) to give a CBNF with a larger delta value. The activated CBNF was react ed with water to form H-2 gas. The water-splitting reactivity depends on the delta and tau values, longer activation time being required for larger delta values. The rate of water splitting was dependent on the activation time and mode. Typically it was 5.4 cm(3) H-2 g(-1) h(-1) under conditions of 5 min cyclic activation mode on a CBNF with tau 0. 280. This is much larger than that of a typical photochemical water-sp litting, 0.016 cm(3) H-2 cm(-3) h(-1). Mossbauer spectroscopy revealed that iron rearrangement in the CBNF occurred at the first water-split ting cycle and was retained through the subsequent water-splitting cyc les, and that the water-splitting occurs through the CIO layer represe nted by (Ni0.632+Fe2.372+O32-)(x)C-tau. Copyright (C) 1996 Internation al Association for Hydrogen Energy