Realizing the high loading amount of active Cu on Al₂O₃ to boost its CO catalytic oxidation

Catalytic oxidation of carbon monoxide (CO) by Cu/Al₂O₃ has garnered increasing interest in recent years due to its promising application prospects. Numerous investigations conducted on the Cu/Al₂O₃ system, but its catalytic performance for CO oxidation is still not as promising as that of precious metal catalysts. Increasing the loading amount of the active Cu on Al₂O₃ surface is a feasible method for improving its activity. However, with the increase of Cu loading, the agglomeration and enlargement of Cu particles is inevitable, which reduces the active Cu amount. Therefore, the utilization rate of Cu atoms is not high and the catalytic performance often can not further rise. Enhancing active Cu loading amount as high as possible is a prerequisite to further enlarge the activity of Cu/Al₂O₃ catalyst. Herein, self-synthesized Al₂O₃ nanofibers (Al₂O₃-nf) with high specific surface area and abundant penta-coordinated aluminum (Al_V) are used as the support to maximize the Cu loading amount by chemical vapor deposition (CVD). And commercially available α-Al₂O₃ is used for comparative experiment. The high specific surface area could make Cu high dispersion on Al₂O₃, even at 20 wt% Cu loads, which is beneficial to high concentration load of active Cu. The catalytic activity of Cu/Al₂O₃-nf-CVD gradually increases with the increase of Cu loading from 2 wt% to 20 wt%, exhibiting a clear linear correlation with the surface content of Cu⁰ on the catalyst. Meanwhile, this result confirms that Cu⁰ plays a crucial role in CO oxidation of Cu/Al₂O₃. However, commercial α-Al₂O₃ reaches its highest activity when the Cu load is 5%, and then its activity begins to decrease due to the agglomeration of particles. Moreover, Cu/Al₂O₃-nf-CVD also exhibits remarkable thermal stability for CO oxidation. This work highlights a new strategy to synthesis of high Cu loading amount, high activity and thermostable Cu/Al₂O₃ catalyst for low-temperature oxidation of CO.