Highly active, selective, and stable direct H₂O₂ generation by monodispersive Pd–Ag nanoalloy

Abstract

Hydrogen peroxide (H₂O₂), a green oxidant, has wide applications in various chemical syntheses and is also a promising candidate to replace the traditional toxic oxidants. The direct synthesis of H₂O₂ from H₂ and O₂ is a potential approach, as it is a green and atomically economic reaction. However, the most previous systems are notorious in complicated post-purification procedures, high energy cost, and low selectivity because of the uncontrollable O-O bond cleavage. We have solved this challenge by tuning the chemical state of Pd with high H₂O₂ productivity of 80.4 mol kgcat-1 h-1 and high H₂O₂ selectivity of 82.1% via the design of Pd-Ag nanoalloys with flexibly tuned size and composition. The created Pd-Ag nanoalloy also exhibits excellent stability with limited performance decay over recycles. The X-ray photoelectron spectroscopy analysis confirms the electron transfer from Ag to Pd, which generates more Pd⁰ and enables improved H₂O₂ productivity. The theoretical calculation shows that the incorporation of Ag into Pd is beneficial for the stabilization of O₂²⁻ and the cleavage of H₂ for the enhanced H₂O₂ generation. In addition, the enhanced H₂O₂ desorption on Pd-Ag nanoalloy is beneficial for releasing H₂O₂, which results in the increased H₂O₂ selectivity.