Net Charge Regulation Mechanism of Rare Earth Inclusions in Steel Adsorbed on the Surface of Carbon-Containing Refractory Materials: A DFT and AIMD Investigation

This study employs ab initio density functional calculations, combined with site projected density of states, spatial charge redistribution maps, and thermodynamic and kinetic analyses, to investigate how externally applied positive charges alter the interfacial adsorption behavior of Y, Y₂O₃, and Y₂O₂S on C(001) and C(100) crystal surfaces. The analysis results reveal that C(001) and C(100) form opposite response states under the condition of externally applied positive charges. On the C(001) surface, the increase of positive charges interferes with the charge transfer between the O-2p orbitals and Y-4d orbitals in the inclusions and graphite, thereby weakening the adsorption of inclusions on the graphite surface. Compared to the Gibbs free energy value without positive charges, it is larger, indicating a significant decrease in spontaneous deposition and reactivity tendency. The increase of positive charges leads to a lower steady-state adsorption capacity of C(001) and a gradual decrease in both the inclusion adsorption rate constant and the adsorption capacity. The dangling bonds and defect states on the C(100) surface provide additional quantum channels for charge transfer. External positive charges may promote the rehybridization of dangling bonds on the C(100) surface, which in turn reduces the energy difference between Y-4d and O-2p (or surface C-2p) orbitals, promotes orbital overlap, and strengthens the electronic coupling at the interface. The opposite responses of C(001) and C(100) to positive charges are essentially manifestations of anisotropic behavior between graphite basal planes (dominated by uniform electron distribution and electrostatic repulsion) and edge planes (dominated by abundant dangling bonds, local polarization, and orbital coupling).This discovery holds significant guiding importance for electrochemical anti-blocking technology: the inhibitory effect of impressed current on inclusion adsorption exhibits crystal face selectivity, being effective only on inert basal planes like C(001), while it may have the opposite effect on highly active edge/defect faces.