The First Application of Palladium–Phosphorus Catalysts in the Direct Synthesis of Hydrogen Peroxide: Reasons for the Promoting Action of Phosphorus

The main reasons for the promoting effect of phosphorus on the properties of Pd–P/ZSM-5 catalysts during direct synthesis of H₂O₂ from H₂ and O₂ under mild conditions are considered based on the data obtained by X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and inductively coupled plasma mass spectrometry (ICP MS). The introduction of phosphorus in the catalyst affects the particle size and the electronic state of palladium in the surface layer, as well as the surface concentration of the phosphate and phosphite ions. The yield of H₂O₂ increases when the particle size of the Pd–P catalysts decreases, when the side process of H₂O₂ decomposition is inhibited by the phosphate and phosphite surface ions, and when the hydrogen solubility in the solid solutions of phosphorus in palladium decreases.