Journal article
Engineering metal-metal oxide surfaces for high-performance oxygen reduction on Ag-Mn electrocatalysts
Understanding fundamental material-property relationships in mixed-element catalyst systems is crucial to advancing the viability of renewable electrochemical energy technologies, an important part of creating a more sustainable future. Herein, we report our insight on the nature and dynamics of highly active silver-manganese oxide (Ag-MnOx) catalyst surfaces for the oxygen reduction reaction (ORR) via a combined experimental-theoretical approach.
Experimentally, we synthesize well-mixed Ag-Mn co-deposited thin films that are measurably flat and smooth, despite Mn surface migration and oxidation upon air exposure and electrochemical measurements. Cyclic voltammetry in 0.1 M KOH demonstrates up to 10-fold specific activity enhancements over pure Ag at 0.8 V vs.
RHE for Ag-rich films (70-95% Ag in bulk). To further understand the Ag-Mn system, separate samples were synthesized with small amounts of Mn sequentially deposited onto the surface of a pure Ag thin film (Mn@Ag), ranging from partial to full surface coverage (down to 0.3 nmMn cm−2geo ∼ 0.2 μgMn cm−2geo).
These sequentially deposited Mn@Ag films show analogous performance to their co-deposited counterparts indicating similar enhanced active sites. With density functional theory (DFT), we calculate that this enhancement arises from the tuned d-band of these material surfaces owing to the optimal hybridization of the electronic structures in specific Ag and MnOx geometries.
Together, electrochemical measurements, DFT calculations, X-ray absorption spectroscopy, and valence-band X-ray photoelectron spectroscopy suggest synergistic electronic interactions between Ag and MnOx yield enhanced oxygen adsorption, and thus ORR activity, with DFT highlighting the Ag-MnOx interface sites as the most enhanced.
This work demonstrates how combined experimental-theoretical methods can help design electrocatalysts with enhanced electrocatalytic properties and understand the nature of complex mixed metal-metal oxide surfaces.
Language: | English |
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Publisher: | The Royal Society of Chemistry |
Year: | 2022 |
Pages: | 1611-1629 |
ISSN: | 17545706 and 17545692 |
Types: | Journal article |
DOI: | 10.1039/d2ee00047d |
ORCIDs: | 0000-0002-2205-0303 , Gunasooriya, G. T.Kasun Kalhara , 0000-0002-7122-6870 , 0000-0003-1750-6860 , 0000-0001-6087-7662 , 0000-0002-9987-0748 , 0000-0002-2259-1935 , Nørskov, Jens K. , 0000-0003-3584-0600 and 0000-0001-9900-0622 |