Direct Synthesis of H2O2on AgPt Octahedra: The Importance of Ag–Pt Coordination for High H2O2Selectivity

Abstract

H2O2 production by direct synthesis (H2 + O2 → H2O2) is a promising alternative to the energy-intensive anthraquinone oxidation process and to the use of chlorine for oxidation chemistry. Steady-state H2O2 selectivities are approximately 10-fold greater on AgPt octahedra (50%) than on Pt nanoparticles of similar size (6%). Moreover, the initial H2O2 formation rates and selectivities are sensitive to the fractional coverage of Pt atoms and their location on the surfaces of AgPt octahedra, which can be controlled by exposing these catalysts to either CO or inert gases at 373 K to produce Pt-rich (16% initial H2O2 selectivity) or Pt-poor (36% initial H2O2 selectivity) surfaces. Increasing the coordination of Pt to Ag significantly modifies the electronic structure of Pt active sites, which is reflected by a shift in the ν(C=O) singleton frequency in 13CO from 2016 cm–1 on Pt to ∼1975 cm–1 on AgPt. These bimetallic AgPt catalysts present lower activation enthalpies (ΔH⧧) for H2O2 formation (29 kJ mol–1 on Pt ...