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Abstract Motivated by in silico predictions that Co, Rh, and Ir dopants would lead to low overpotentials to improve OER activity of Ni‐based hydroxides, we report here an experimental confirmation on the altered OER activities for a series of metals (Mo, W, Fe, Ru, Co, Rh, Ir) doped into γ‐NiOOH. The in situ electrical conductivity for metal doped γ‐NiOOH correlates well with the trend in enhanced OER activities. Density functional theory (DFT) calculations were used to rationalize the in situ conductivity of the key intermediate states of metal doped γ‐NiOOH during OER. The simultaneous increase of OER activity with intermediate conductivity was later rationalized by their intrinsic connections to the double exchange (DE) interaction between adjacent metal ions with variousdorbital occupancies, serving as an indicator for the key metal‐oxo radical character, and an effective descriptor for the mechanistic evaluation and theoretical guidance in design and screening of efficient OER catalysts.
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This content will become publicly available on January 1, 2027
Unveiling the role of transition-metal dopants in Ni(OH)2/NiOOH-catalyzed urea oxidation
Urea is a common waste in agriculture runoff and has also been proposed as a promising oxidizable molecule in urea electrolysis for hydrogen production from wastewater. However, the overpotential of the electrochemical urea oxidation reaction (UOR) is high due to the complicated six-electron transfer process on most metal catalysts. The competition with oxygen evolution reaction (OER) further limits catalyst options for UOR. The most promising and studied catalysts for UOR are Ni-based catalysts. Here we study the reactivity of the basal β-NiOOH(001) surface for UOR and study the effects of metal doping (Mn, Fe, Co, and Cu) on the phase transformation from β-Ni(OH)2 to β-NiOOH, UOR, and OER pathways using density functional theory (DFT) calculations. The introduction of Mn and Fe dopants facilitates the formation of catalytically active β-NiOOH phase, and also favors the adsorption of urea compared to the undoped β-NiOOH surface, thereby significantly benefitting the overall UOR. Moreover, comparison of the effect of dopants on UOR and OER provides fundamental understanding of the competition between UOR and OER and how the dopants influence the reaction selectivity and competition. This work sheds light on the structure-property relationship of Ni-catalysts in urea oxidation and provides design principles for functional Ni-based materials, which will help accelerate the development of efficient UOR catalysts.
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- Award ID(s):
- 2054933
- PAR ID:
- 10649911
- Editor(s):
- Flaherty, David W
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Journal of Catalysis
- Volume:
- 453
- Issue:
- C
- ISSN:
- 0021-9517
- Page Range / eLocation ID:
- 116503
- Subject(s) / Keyword(s):
- nickeloxohydroxide catalyst, urea oxidation, density functional theory, dopent
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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