Atomistic insight into the interfacial reaction and evolution between FeCr alloys and supercritical CO2 with impurities

The supercritical CO₂ cycle offers high thermal efficiency and flexibility, enhancing energy conversion efficiency and utilization. As the commercialization of supercritical CO₂ cycles advances, the stability of the metal-CO₂ interface is the key to ensure the safety of this power cycle. In this paper the interfacial reactions between FeCr alloys and CO₂ with impurities were investigated using the oxidation thermodynamics and molecular dynamics. With the increase of Cr content in FeCr alloy, the adsorption stability of SO₂ and CO₂ molecules on the surface of FeCr alloy became stronger, in which CO₂ molecules were adsorbed and decomposed in two ways. When the C-O bond was broken, the detached O atom was in a free state or reorganized into O₂ molecule, while the CO molecule would be separated from the CO₂ molecule. In the initial oxidation stage, adding appropriate amount of H₂S in CO₂ environment could reduce the diffusion of O atoms from the CO₂ molecule to Fe20Cr alloy, and the stress in the oxide film would not increase. The early oxidation behavior of Fe20Cr alloy in CO₂ with H₂S impurity gas may prove to be an effective method for enhancing its oxidation resistance of Fe20Cr alloy.