<p>In the smelting process of metallurgical-grade silicon (MG-Si), silicon carbide (SiC) serves as a critical intermediate product, and its formation efficiency directly influences both MG-Si yield and energy consumption. Based on diffusion couple experiments between silica and bituminous coal, this study explores how K₂CO₃-induced structural evolution in bituminous coal influences interfacial SiC formation. The results indicate that the loading of K₂CO₃ increases the diffusion depth of Si elements into the bituminous coal by 173 pct and enhances the SiC yield by 9.0 pct. This improvement is primarily attributed to the physicochemical structural transformations of the coal under K₂CO₃ treatment. In terms of physical structure, the specific surface area and pore volume increased from 1.55 m²/g and 0.0036 cm³/g to 10.55 m²/g and 0.0113 cm³/g, respectively; for the chemical structure, the degree of disorder in the carbon matrix increased by 44 pct and the binding energy of the C–C bond decreased by 0.37 eV. The physical structure changes led to a higher density of surface cracks and a more uniform pore distribution in the bituminous coal. The chemical structure changes resulted in an increase of the number of active sites on the coal surface by 148 pct. This work reveals the mechanism of K₂CO₃ in enhancing the smelting efficiency of MG-Si, and provides theoretical support for the optimization of the smelting process based on alkali metal catalysis.</p>