Multimetallic oxygen evolution reaction (OER) electrocatalysts have recently gained significant attention due to their excellent intrinsic activity resulting from the synergistic interplay between multiple metal sites. However, in these multimetallic catalyst systems, the function of their bridging anionic ligands (e.g., O2-, S2-, and P3-/PO43-) is rarely investigated, partially due to the lack of an ideal material model system. Herein, by combining a careful electrochemical conversion of metal-organic framework (MOF) precursors with low-temperature phosphorization processes, we designed a series of NiFe-based model catalysts as a proof-of-concept platform to identify the roles of different anionic ligands in tuning the redox and electronic properties of metal sites. Our experimental and theoretical results reveal that ligands having varying electron-withdrawing/-donating ability can modulate not only the electron density of Ni2+/Fe3+ centers but also the electron transfer efficiency from Ni2+ to neighboring Fe3+ sites. Importantly, synergistically coupled ligands (e.g., S2- and PO43-) with complementary electronic properties help to optimize the chemical environments of the Ni2+/Fe3+ centers (even upon partial catalyst surface reconstruction to NiFe oxyhydroxide), thus giving rise to a remarkable OER activity. These insights open new avenues for developing highly active multimetallic OER electrocatalysts.
|Number of pages||11|
|Journal||ACS Applied Energy Materials|
|State||Published - 25 Mar 2019|
Bibliographical noteFunding Information:
We thank the Ilse Katz Institute for Nanoscale Science and Technology for the technical support in material characterization. This work was funded by the Israel Science Foundation (ISF; Grant No. 306/18). W.H. thanks the Planning and Budgeting Committee’s (PBC) fellowship program (Academic Year 2018/2019) of Israel for financial support.
© 2019 American Chemical Society.
- anionic ligands
- metal redox
- metal-organic frameworks
- oxygen evolution reaction