Rational design of active sites in alumina-based catalysts to optimize antibonding-orbital occupancy for tetrafluoromethane decomposition

Abstract

Tetrafluoromethane (CF₄) is a potent greenhouse gas with high stability, thus its effective decomposition is crucial for mitigating its environmental impact. However, the lack of chemical understanding and efficient catalysts impedes the development of CF₄ decomposition reactions. Herein, this work elucidates the fundamental interactions between the active center and CF₄ by density functional theory (DFT). Our research reveals that the key to activating CF₄ lies in the antibonding-orbital occupancy of the active center, particularly within the context of the commonly used Al₂O₃ catalyst. A comprehensive theoretical calculation was undertaken to optimize the antibonding-orbital occupancy, revealing that Zr and Hf could potentially function as novel active sites, thereby augmenting the antibonding-orbital occupancy on the Al₂O₃ surface. This augmentation effectively enhances the electronic interaction between CF₄ and the active sites, paving the way for subsequent reaction dynamics. Accordingly, we synthesized Al₂O₃, Zr–Al₂O₃ and Hf–Al₂O₃ catalysts, and observed CF₄ conversions of 34.8%, 54.5%, and 100% at 650 °C, respectively, which is consistent with the theoretical results. This result aligns with the theoretical findings, demonstrating the practical applicability of our research. These findings provide a basis for rational catalyst design towards efficient CF₄ decomposition, and can be extended to other robust molecules.