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Abstract Fe-containing transition-metal (oxy)hydroxides are highly active oxygen-evolution reaction (OER) electrocatalysts in alkaline media and ubiquitously form across many materials systems. The complexity and dynamics of the Fe sites within the (oxy)hydroxide have slowed understanding of how and where the Fe-based active sites form—information critical for designing catalysts and electrolytes with higher activity and stability. We show that where/how Fe species in the electrolyte incorporate into host Ni or Co (oxy)hydroxides depends on the electrochemical history and structural properties of the host material. Substantially less Fe is incorporated from Fe-spiked electrolyte into Ni (oxy)hydroxide at anodic potentials, past the nominally Ni2+/3+redox wave, compared to during potential cycling. The Fe adsorbed under constant anodic potentials leads to impressively high per-Fe OER turn-over frequency (TOFFe) of ~40 s−1at 350 mV overpotential which we attribute to under-coordinated “surface” Fe. By systematically controlling the concentration of surface Fe, we find TOFFeincreases linearly with the Fe concentration. This suggests a changing OER mechanism with increased Fe concentration, consistent with a mechanism involving cooperative Fe sites in FeOxclusters.
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Dynamic evolution and reversibility of single-atom Ni(II) active site in 1T-MoS2 electrocatalysts for hydrogen evolution
Abstract 1T-MoS2and single-atom modified analogues represent a highly promising class of low-cost catalysts for hydrogen evolution reaction (HER). However, the role of single atoms, either as active species or promoters, remains vague despite its essentiality toward more efficient HER. In this work, we report the unambiguous identification of Ni single atom as key active sites in the basal plane of 1T-MoS2(Ni@1T-MoS2) that result in efficient HER performance. The intermediate structure of this Ni active site under catalytic conditions was captured by in situ X-ray absorption spectroscopy, where a reversible metallic Ni species (Ni0) is observed in alkaline conditions whereas Ni remains in its local structure under acidic conditions. These insights provide crucial mechanistic understanding of Ni@1T-MoS2HER electrocatalysts and suggest that the understanding gained from such in situ studies is necessary toward the development of highly efficient single-atom decorated 1T-MoS2electrocatalysts.
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- Award ID(s):
- 1654140
- PAR ID:
- 10184444
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- Nature Communications
- Volume:
- 11
- Issue:
- 1
- ISSN:
- 2041-1723
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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