Bimetallic palladium and copper single atoms catalyst boosting direct oxidation of methane to formaldehyde with 100 % selectivity at room temperature

Abstract

Direct oxidation of methane (DOM) to sole value-added products (such as HCHO, etc.) at room temperature is of great importance for synthesis of commodity chemicals but still remains challenging. Herein, we design and construct ZSM-5 supported bimetallic palladium and copper single atoms catalysts (Pd₁-Cu₁/ZSM-5) via modified co-adsorption strategy to promote the DOM by using molecular oxygen (O₂) with the assistance of hydrogen (H₂) at room temperature. The Pd₁-Cu₁/ZSM-5 achieves a remarkable formaldehyde selectivity of 100 % (yield of 22.7 μmol·g_cat⁻¹·h⁻¹) at room temperature and the reaction atmosphere is out of the explosive limits of CH₄/H₂/O₂ systems. The characterization results demonstrate that the synergistic effect between palladium and copper facilitates the formation of highly reactive surface hydroxyl species to activate C-H bonds of CH₄, which is the key for the high performance of DOM over Pd₁-Cu₁/ZSM-5 compared with that of sole Pd and Cu single atom catalysts (Pd₁/ZSM-5 and Cu₁/ZSM-5). This work provides a new direction for DOM to sole value-added products with O₂ at room temperature via designing single atom center catalysts.