Effect of supercritical water on redox cycle capability of iron oxide during decomposition of formic acid

Formic acid (FA) has great potential as an in situ source of hydrogen, because it offers high energy density, and can be safely handled in aqueous solution. In the current study, decomposition of formic acid (H2+CO2←HCOOH→CO+H2O) was investigated in the supercritical water (W) medium over iron oxide nanoparticle in order to shift the conversion toward more hydrogen production through water-gas shift reaction (CO+ H2O↔ H2+ CO2). This reaction can be accelerated through the redox mechanism (Fe+3↔Fe2+) in which supercritical water has a positive effect on this cycle. The effects of parameters (temperature, water density and FA/W ratio) were investigated on the catalyst structure and gas composition. From X-ray diffraction (XRD), electron diffraction (ED) analysis of catalyst as well as gas chromatographic analysis (GC) of gas composition (CO, CO2, H2, CH4), it was revealed that water pressure has positive effect on stability of catalyst and modification of selectivity toward more H2 production. The pathway of the reaction can be seen at the following.