Solid-State Reaction of Ferrocene Controlled by Co-Precursor and Reaction Atmosphere Leading to Hematite and Cohenite Nanomaterials: A Reaction Kinetic Study

The present article investigates the thermal decomposition of ferrocene in the presence of oxalic acid dihydrate in oxidative and inert atmospheres. A mixture of ferrocene and oxalic acid dihydrate on thermal decomposition in O-2 and N-2 atmospheres produces hematite and cohenite nanomaterials, respectively. These decompositions are complex and reflected through multiple overlapped reaction steps in the thermogravimetry profiles, and peak deconvolution method is adopted to separate the reaction steps involved. It is found that the synthesis of hematite is a two-step process, while that of cohenite is a one-step process. Model-free integral isoconversional methods are adopted to estimate the values of activation energy for these thermal reactions. The most probable reaction mechanism and the reaction rate of thermal decomposition are determined by an intercept-based model fitting method. The reaction mechanism is found to be different for different steps. To verify the suitability of the adopted kinetic models, the experimental conversion curves are compared with the reversely constructed ones and the agreement is quite reasonable. The conversion dependence of thermodynamic parameters is obtained using the estimated kinetic parameters. Comparing the estimated values of the kinetic and thermodynamic parameters, the effect of the reaction atmosphere on the thermal decomposition process of ferrocene is realized. Utilizing the kinetic and thermodynamic parameters conversion-dependent nucleation rates of the reaction steps have been estimated. The present study describes how different nanomaterials of iron can be synthesized starting with the same precursor material, how the reaction (solid and gaseous) atmosphere affects the reaction profile and the residual material, and finally, how kinetic calculations help in understanding the solid state reaction process involved. This study suggests the use suitable combination of precursor, co-precursor, and gaseous reaction atmosphere for the solid-state thermal synthesis of iron-based nanoparticles using organo-iron compounds. The study also highlights the successful application of the peak-deconvolution method.