Constructing highly active zeolite encapsulated PdAg alloy catalysts for typical VOCs deep oxidation: The role of electron-structure interaction

Benzene series volatile organic compounds (VOCs) are extremely toxic and hazardous to human beings and the environment, and their efficient degradation at low temperatures has attracted much attention. Precious metal catalysts are generally recognized as highly active for VOCs removal. Currently, encapsulation of precious metals is an effective strategy to address the lack of long-term stable performance and activity of supported precious metal catalysts. In this work, a PdAg alloy catalyst was successfully constructed inside Slicalite-1 (S-1) zeolite (PdAg@S-1) and applied to toluene degradation. The PdAg@S-1 exhibits excellent toluene degradation activity (T90 = 179 °C) and favorable long-term stability and resistance. The XPS and XAFS results reveal the existence of electronic interactions between Pd and Ag, and the transfer of electrons from Ag to Pd created electron-rich Pd sites. Furthermore, the DFT calculations corroborate that the unique electronic-structural interactions between the PdAg alloys favor the dissociation of the C-H bond and the strong adsorption of gas-phase oxygen, which is the key to the deep oxidation of toluene. The in situ DRIFTS results demonstrate that the reaction followed the Langmuir-Hinshelwood (L-H) mechanism and gas-phase oxygen participates in the redox reaction as an active oxygen species. The construction of high-performance PdAg alloy catalysts by a simple and feasible method inspires the development of catalysts for the efficient degradation of VOCs.