H2O-assisted O2 reduction by H2 on Pt and PtAu bimetallic nanoparticles: Influences of composition and reactant coverages on kinetic regimes, rates, and selectivities

Tomas Ricciardulli, Jason S. Adams, Marco DeRidder, Alexander P. van Bavel, Ayman M. Karim, David W. Flaherty

Research output: Contribution to journalArticlepeer-review


Hydrogen peroxide (H2O2) can replace hazardous oxidants in industrial processes but is currently too expensive for many such applications. While direct synthesis of H2O2 (H2 + O2 → H2O2) may reduce costs in comparison to incumbent technology, current catalysts lack the requisite stability and selectivity. Here, we examine the direct synthesis of H2O2 on bimetallic Pt1Aux (0 ≤ x ≤ 230) and Pt catalysts at steady-state in pure water and relate kinetic parameters for H2O2 and H2O formation to possible active site structures informed by complementary characterization methods. X-ray photoelectron spectra show significant Pt surface enrichment compared to the bulk composition. Analysis of infrared spectra of mixed monolayers of 12CO* and 13CO* indicate that Pt and Au form substitutional surface alloys. The Pt1Aux nanoparticles with the greatest mole fractions of Au predominantly expose Pt monomers (i.e., isolated Pt atoms), yet Pt atoms exposed upon all these nanoparticles possess electronic structures distinct from bulk Pt. Despite these differences, rate measurements are consistent with product formation through proton-electron transfer pathways for all Pt1Aux catalysts. In situ XAS indicate that Pt remains metallic during H2O2 synthesis. Under the most oxidizing conditions, selectivities toward H2O2 increase strongly with the Au to Pt ratio from 2% for monometallic Pt to 85% for Pt1Au170. However, selectivities are similar among all catalysts within reducing conditions. Comparisons of apparent activation enthalpies for the formation of H2O2 and H2O across these catalysts and the range of conditions suggest that Pt monomers within Au provide the greatest selectivities for H2O2 formation, because these active sites present high barriers for O-O bond rupture. Selectivities decrease with increasing ratios of H2 to O2 pressures, because Pt atoms aggregate and form oligomers that readily dissociate dioxygen intermediates. The combined use of spectroscopy, kinetics, and concepts employed in reaching these conclusions take inspiration from the legacy of Prof. Michel Boudart, and specifically his elegant methods for interrogating bimetallic catalysts.

Original languageEnglish (US)
Pages (from-to)661-678
Number of pages18
JournalJournal of Catalysis
StatePublished - Dec 2021


  • Hydrogen peroxide synthesis
  • Infrared spectroscopy
  • Oxygen reduction
  • Single atom alloys
  • X-ray absorption spectroscopy

ASJC Scopus subject areas

  • Catalysis
  • Physical and Theoretical Chemistry


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