Hot electron chemistry on bimetal catalysts

Tailoring composition of PtCo bimetallic nanoparticles gives rise to the control of hot electron generation and catalytic activity

Go to the profile of Jeong Y. Park
Jun 10, 2018
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The paper in Nature Communications is here:

In the field of heterogeneous catalysis, there is much interest in understanding how hot electrons, which are associated with energy dissipation and conversion processes during surface reactions, affect catalytic activity and selectivity. In order to understand the electronic origin of catalytic reactions, metal–semiconductor catalytic nanodiodes have been developed as a powerful tool for detecting and utilizing hot electrons generated on nanocatalysts under various surface reactions. The architecture of these devices allows for the quick extraction of hot electrons across the metal–semiconductor interface before thermalization, thereby providing key evidence of non-adiabatic charge transfer during surface reactions.

Bimetallic materials have opened a new pathway that could control the electronic structure and binding energy in catalysts, resulting in superior catalytic performance. Despite considerable focus on various catalytic reaction studies, there are still questions about the underlying causes of improved performance because the structure, chemical composition, and oxidation state of bimetallic materials can change under reaction conditions. Recently, the presence of oxide–metal interfacial sites formed by surface segregation of bimetallic nanoparticles were specifically suggested to be responsible for increased catalytic activity. However, the physical nature and fundamental role of oxide–metal interfaces are still elusive because of a lack of definitive evidence.

Here, we report the real-time detection of hot electrons generated on bimetallic PtCo nanoparticles during exothermic hydrogen oxidation and clarify the origin of the synergistic catalytic activity of PtCo nanoparticles with corresponding chemicurrent values. To investigate the dynamics of hot electrons on nanocatalysts, we utilized PtCo bimetallic nanoparticles deposited on Au/TiO2 nanodiodes. The surprising finding for us was that in both chemicurrent and turnover rate measurements, the catalytic activity of the bimetallic nanoparticles is significantly enhanced compared with monometallic Co or Pt nanoparticles. Our in-situ transmission electron microscopy measurement and theoretical calculation using density functional theory, we confirm that this improvement is attributed to the presence of a CoO/Pt interface stabilized on the PtCo nanoparticles surface under reaction conditions. By estimating the chemicurrent yield, we conclude that the catalytic properties of the bimetallic nanoparticles are strongly governed by the oxide–metal interface, which facilitates hot electron transfer.

We feel that the precise measurements of hot electrons on the catalysts give insight on the mechanism of heterogeneous catalysis, which can help the smart design of highly reactive materials. The next challenges we plan to tackle include the operando surface characterizations of bimetal surfaces under catalytic conditions, using spectroscopic and microscopic methods. Furthermore, the control of catalytic activity via electronic engineering of catalysts would be a promising prospect that may open the door to the new field of combining catalysis with electronics, called “catalytronics”.

Go to the profile of Jeong Y. Park

Jeong Y. Park

Professor, KAIST and IBS

Surface science and catalysis

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