Temperature effect on the synthesis of iron–cobalt nano-particles using catalytic chemical vapor deposition of CO2 in thermo-gravimetric analyzer: Analytical and thermodynamic studies

Abstract

Fe–Co catalysts were prepared by conventional precipitation (co-precipitation for Fe–Co) method for the synthesis of nano-particles, using CO 2 as the carbon precursor by catalytic chemical vapor deposition. Synthesis was done in a thermo gravimetric analyzer at different temperatures ranging from 450 °C to 1000 °C particularly for Fe–Co nano particles. Products were then evaluated using the FESEM, TEM, XRD and EDS analyses. Nano-particles of pebble-like shapes with some of conjoined shapes were observed at different temperatures for Fe, Co and Fe–Co. It was also observed that increase in temperature not only enhanced the size of the nanoparticles but it also led to a greater sphericity and crystallinity of the nanoparticles. For Fe–Co alloy, the dimensions of nanoparticles were found using FESEM to be 51 ± 1 nm, 54 ± 1 nm, 72 ± 1 nm and 165 ± 1 nm at 500, 600, 700, and 800 °C, respectively. TEM also shows similar results to that of FESEM. XRD results show that at lower temperature (500 °C), products are amorphous in nature but at higher temperature (800 °C), the peaks became much longer and sharper indicating the crystalline nature of Fe–Co nanoparticles. CO disproportionation reaction was discussed and equations for equilibrium constant and mole fraction (y CO and y CO 2 ) were developed. It was observed that CO decomposition is thermodynamically limited from 520 to 800 °C which led to carbon deposition on the catalyst as observed by the carbon presence in EDS, XRD and TEM images i.e. the encapsulation of thin layer of carbon on the Fe–Co particles.