<p>The refractory nature of cerium dioxide (CeO₂) in roasted rare earth concentrates remains a significant bottleneck for efficient extraction. This study proposes a synergistic HCl–H₂O₂ leaching system and elucidates its underlying interfacial mechanism beyond conventional process optimization. Systematic characterization reveals that roasting at 550&#xa0;°C for 2 hours triggers partial fluorination loss (10.04 pct) and atomic dissociation, creating a highly reactive surface characterized by abundant dangling bonds and high-energy states. We demonstrate that the introduction of H₂O₂ acts as a site-specific reductant, facilitating the Ce⁴⁺ to Ce³⁺ transition. This transition not only increases the density of proton-active sites but also enables the saturation of vacant bonding orbitals of surface anions by adsorbed H⁺, significantly lowering the interfacial energy barrier for mineral dissolution. Under the optimized conditions (7 mol/L HCl, 80&#xa0;°C, 40 minutes, and a liquid-to-solid ratio of 3:1), the rare earth leaching efficiency reached 83.67 pct, while achieving exceptional selectivity by suppressing fluorine co-extraction to a mere 0.21 pct. This work provides a new theoretical perspective on mineral surface state regulation, offering a robust strategy for the clean and efficient processing of complex rare earth resources.</p>