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Double-Atom Catalysts Provide a Molecular Platform for Oxygen Evolution

preprint
submitted on 09.12.2019, 14:40 and posted on 17.12.2019, 11:16 by Lichen Bai, Chia-Shuo Hsu, Duncan Alexander, Hao Ming Chen, Xile Hu
The oxygen evolution reaction (OER) is an essential anode reaction for the generation of solar and electric fuels through water splitting or CO2 electroreduction. Mixed metal oxides containing Co, Fe, or Ni prove to be the most promising OER electrocatalysts in alkaline medium. However, the active sites and reaction mechanisms of these catalysts are difficult to study due to their heterogeneous nature. Here we describe a general synthesis of Co, Fe, and Ni-containing double-atom catalysts from their single-atom precursors via in-situ electrochemical transformation. Atomic-resolution microscopy and operando X-ray absorption spectroscopy (XAS) reveal molecule-like bimetallic active sites for these supported catalysts. Based on electrokinetic and XAS data, we propose a complete catalytic cycle for each catalyst. These mechanisms follow a similar O-O bond forming step and all exhibit bimetallic cooperation. However, the mechanisms diverge in the site and source of OH- for O-O bond formation as well as the order of proton and electron transfer. Our work demonstrates double-atom catalysts as an attractive platform for fundamental studies of heterogeneous OER electrocatalysts.

History

Email Address of Submitting Author

xile.hu@epfl.ch

Institution

EPFL

Country

Switzerland

ORCID For Submitting Author

0000-0001-8335-1196

Declaration of Conflict of Interest

none

Version Notes

First pre-print

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