Mechanochemical activation drives non-chemisorbed oxygen-dependent Hg⁰ oxidation across wide temperature

Cerium oxide has emerged as a promising catalyst for Hg⁰ purification in flue gas, yet strategically modulating non‑oxygen active sites and strengthening its oxidation activity on CeO₂ to mitigate the formation of unstable HgO remains challenging. Here we pioneered a one-step mechanochemical strategy for simultaneous CuCl₂ activation and heterojunction engineering of highly crystalline CeO₂, fabricated one novel CuCe/CN-m catalyst with multiple-metal dominated active sites and enhanced oxidation activity, achieving exceptional Hg⁰ removal efficiency across a broad temperature range (80-280 °C). The optimized Cu₆Ce/CN-m₆ achieved Hg⁰ removal efficiency of 97.32 % and 87.30 % at 200 °C under N₂ and simulated flue gas conditions, respectively, and delivered a record Hg⁰ removal capacity of 26.44 mg·g^-1 under continuous O₂ supplementation, demonstrating superior environmental adaptability. Hg-TPD analysis confirmed that catalytic oxidation predominates, and the residual absorbed Hg species showed exceptional thermal stability with desorption peaks at 367.08-528.17 °C. Mechanistic studies revealed that heterojunction construction optimized interfacial charge transfer, while CuCl₂ activation introduced novel active sites stronger than oxygen and modulated the d-band center of CuCe/CN heterojunction, which synergistically strengthened the non-chemisorbed oxygen-preferential Hg⁰ oxidation pathway of CuCe/CN. The mercury oxidation activity hierarchy followed Ce-top>Cu-top>O-top, supported by d-p orbital coupling at the Fermi level between Hg/Ce atom and s-d hybridization near -4 eV between Hg/Cu atom. The scalable synthesis pathway, broad-temperature Hg⁰ removal activity, enhanced metallic active sites, and non-chemisorbed oxygen-dependent oxidation pathways collectively establish CuCe/CN as an industrially viable catalyst for sustainable mercury control from industrial waste gas.