Abstract
Heterogeneous catalysts are complex materials with multiple interfaces. A critical proposition in exploiting bifunctionality in alloy catalysts is to achieve surface migration across interfaces separating functionally dissimilar regions. Herein, we demonstrate the enhancement of more than 104 in the rate of molecular hydrogen reduction of a silver surface oxide in the presence of palladium oxide compared to pure silver oxide resulting from the transfer of atomic hydrogen from palladium oxide islands onto the surrounding surface formed from oxidation of a palladium–silver alloy. The palladium–silver interface also dynamically restructures during reduction, resulting in silver–palladium intermixing. This study clearly demonstrates the migration of reaction intermediates and catalyst material across surface interfacial boundaries in alloys with a significant effect on surface reactivity, having broad implications for the catalytic function of bimetallic materials.
Highlights
Heterogeneous catalysts are complex materials with multiple interfaces
We demonstrate that synergistic effects arising from interfacial energetics dramatically alter reactivity associated with hydrogen atom migration across the palladium oxide/silver oxide interface produced from oxidation of the alloy, resulting in intermixing of metal atoms at the two-dimensional bimetallic oxide interface during the reactive process at room temperature
Intermixing of palladium and silver plays a critical role in accelerating the rate of reduction of oxidized Ag(111) by molecular hydrogen because of the presence of palladium oxide islands on the silver oxide surface
Summary
Heterogeneous catalysts are complex materials with multiple interfaces. A critical proposition in exploiting bifunctionality in alloy catalysts is to achieve surface migration across interfaces separating functionally dissimilar regions. Prior studies have demonstrated that the interface between metal nanoparticles and the metal oxide support can affect chemical behavior by the creation of specific active sites[12,13,14,15,16,17,18] and direct migration or “spillover”[19] of reactive species created on one phase to a neighboring phase of differing reactivity[19,20,21,22,23,24,25]. We demonstrate that synergistic effects arising from interfacial energetics dramatically alter reactivity associated with hydrogen atom migration across the palladium oxide/silver oxide interface produced from oxidation of the alloy, resulting in intermixing of metal atoms at the two-dimensional bimetallic oxide interface during the reactive process at room temperature. The intermixing of palladium and silver that accompanies the acceleration of silver oxide reduction demonstrates the complexity of synergistic effects in catalysis, especially when reducible oxides are involved
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