The absolute value of the LSF-30Fe-Pec-P normalised solids conversion
was higher than the average during both the reduction and
oxidation. This seems to indicate that the reactivity of this material
did not correspond just to the simple additive model proposed (Eq.
(8)). This improvement in reactivity could be due to the inhibition
of sintering and agglomeration of the iron oxide when well dispersed
within the LSF731 matrix. It would be possible to construct
an average normalised solids conversion using the results from the
first reduction (shown in Fig. 4) with sub-micron iron oxide powder;
sintering being yet to occur to a high extent. Regardless of if
the average is calculated from first or third cycle conversions, or
if sub-micron powder, FeP, or particles, Fe80-160, of iron oxide
are used, the composite material, LSF-30Fe-Pec-P, always performs
better than any average model. This improvement must be due to a
synergetic effect. It is suggested that the structure of the composite
material enhanced the availability of oxygen and, therefore, the
hydrogen production, as shown below.