Abstract
Despite numerous studies, the origin of the enhanced catalytic performance of bimetallic nanoparticles (NPs) remains elusive because of the ever-changing surface structures, compositions, and oxidation states of NPs under reaction conditions. An effective strategy for obtaining critical clues for the phenomenon is real-time quantitative detection of hot electrons induced by a chemical reaction on the catalysts. Here, we investigate hot electrons excited on PtCo bimetallic NPs during H2 oxidation by measuring the chemicurrent on a catalytic nanodiode while changing the Pt composition of the NPs. We reveal that the presence of a CoO/Pt interface enables efficient transport of electrons and higher catalytic activity for PtCo NPs. These results are consistent with theoretical calculations suggesting that lower activation energy and higher exothermicity are required for the reaction at the CoO/Pt interface.
Highlights
Despite numerous studies, the origin of the enhanced catalytic performance of bimetallic nanoparticles (NPs) remains elusive because of the ever-changing surface structures, compositions, and oxidation states of NPs under reaction conditions
Extensive experimental studies demonstrate that hot electrons are crucial for explaining the kinetics of catalytic surface reactions because the transport of hot electrons facilitates the formation of a transient state in the molecules[4,5,6]
In a previous study on Pt nanoparticle (NP)/Au/TiO2 catalytic nanodiodes, we showed that the size-dependent catalytic activity of Pt NPs was quantitatively described by the chemicurrent, which is the flow of hot electrons generated on the Pt NPs during a chemical reaction[9]
Summary
The origin of the enhanced catalytic performance of bimetallic nanoparticles (NPs) remains elusive because of the ever-changing surface structures, compositions, and oxidation states of NPs under reaction conditions. To investigate the dynamics of hot electrons on nanocatalysts, we use catalytic NP/Au/TiO2 nanodiodes composed of stoichiometric PtCo bimetallic NPs prepared via the co-reduction method using two metals In both chemicurrent and turnover rate measurements, we observe that the catalytic activity of the bimetallic PtCo NPs is significantly enhanced compared with monometallic Co or Pt NPs. Through X-ray photoelectron spectroscopy (XPS) analysis, transmission electron microscopy (TEM), and densityfunctional theory (DFT) calculations, we confirm that this improvement is attributed to the presence of a CoO/Pt interface stabilized on the PtCo NP surface under reaction conditions. By estimating the chemicurrent yield, we conclude that the catalytic properties of the bimetallic NPs are strongly governed by the oxide–metal interface, which facilitates hot electron transfer on the NPs
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