Direct synthesis of hydrogen peroxide from hydrogen and oxygen over activated-carbon-supported Pd–Ag alloy catalysts

Abstract

A series of bimetallic PdAg catalysts on an activated carbon support were prepared and assessed for the direct synthesis of hydrogen peroxide from hydrogen and oxygen. The ensemble effect and electronic effect between Pd and Ag were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), and temperature-programmed desorption of H₂/O₂ (H₂-/O₂-TPD), etc. Our results showed that the Ag additive increased the monomeric Pd sites which were the primary active sites for H₂O₂ formation. In addition, the content of Pd²⁺ was increased via the electronic interaction between Pd and Ag, which prevented the decomposition and hydrogenation of H₂O₂ to some extent. Therefore, the selectivity of this reaction was increased using bimetallic PdAg catalysts, as compared with the monometallic Pd catalyst. The optimal PdAg-40 catalyst achieved a H₂O₂ productivity of 7022 mol kg_Pd⁻¹ h⁻¹ and a high selectivity of 70.9%, which were superior to those of the Pd/C catalyst.