Abstract <p>In this study, CeO₂ as a carrier and Pd-loaded catalysts were prepared by mechanochemical with different treatment times, and monatomic catalysts (Pd₁-CeO₂-10&#xa0;h) were prepared by ball milling for 10&#xa0;h. The Pd₁-CeO₂-10&#xa0;h single-atom catalyst had the highest catalytic activity by fixed-bed reaction tests on toluene, benzene, and chlorobenzene, reaching 90% conversion efficiency at 173&#xa0;°C, 207&#xa0;°C and 466&#xa0;°C, respectively, based on different characterization methods to verify the results for (1) The increase in ball milling time improves the specific surface area (99.89 m² g⁻¹ to 142.96 m² g⁻¹), decreases the average pore size (4.04 to 3.26&#xa0;nm) and improves the adsorption of VOCs, and promotes the monoatomic form of Pd, which improves the utilization of the active site of Pd; (2) the promotion of Pd-Ce interaction contributes to the generation of oxygen vacancies and improves the lattice oxygen migration capacity and redox ability, increasing the number of acidic sites. During the three-stage removal process, the oxygen species involved in the catalytic reaction changed from adsorbed oxygen (<i>O</i>_ads) to lattice oxygen (<i>O</i>_latt) with increasing temperature. In addition, the removal pathway of chlorobenzene is verified by a combination of experiments and simulations, which observed the higher adsorption energy (<i>E</i>_ad) of chlorobenzene in oxygen vacancies in the reaction and the chloride species occupying oxygen vacancies and metal bonding to prevent lattice oxygen migration to cause the catalyst deactivated in the removal process. The DFT calculation also verifies the M-vK mechanism is the main pathway for the VOCs removal process during this study.</p> Graphical abstract <p></p>