Design of a Na-Doped Amorphous Aluminum Catalyst for CF ₄ Decomposition at Room Temperature under Nonthermal Plasma

Tetrafluoromethane (CF4) is a potent and persistent greenhouse gas, but the robust C–F bond and highly symmetric structure pose significant challenges in CF4 decomposition. Herein, we designed a Na-doped amorphous aluminum catalyst that could decompose a high concentration of CF4 (10%) at room temperature by coupling with nonthermal plasma. The unsaturated Al and Na sites associated with strong Lewis acids as well as the −OH groups are active centers for CF4 decomposition. The Na doping elevates greatly the amounts of strong acidic and basic sites, thereby improving the activity and longevity of the catalyst. Particularly, the Na provides additional active sites for adsorbing F-containing intermediates, which increases the amount of F fixed on the catalyst, thus benefiting the recovery of F from CF4. The F is present on the catalyst surface in the form of AlF3 and NaF. During the reaction, the −OH groups donate H to CF4 and then can be converted into unsaturated oxygen (O2) species. The presence of O2 under plasma will destroy the Al sites and −OH groups and exhibits a negative effect on CF4 decomposition. The Na doping enhances the stability of these active centers, thereby altering the effect of O2 on CF4 decomposition from inhibition to promotion. This work provides new insight into the CF4 decomposition reaction and gives an effective method to remove the CF4 at room temperature.