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Nickel-chromium-molybdenum (NiCrMo) alloys are well-known for having exceptional corrosion resistance, but their electrocatalytic properties have not been extensively studied. In this paper, the development of electro-active nickel-oxyhydroxide (NiOOH) phases and kinetics of the oxygen evolution reaction (OER) have been examined on alloys G35, B3, and C276 in alkaline electrolyte at 25 °C. Reproducible oxide layers were grown by potential cycling between 0.85 and 1.52 V vs RHE up to 600 cycles, and the transition between Ni(OH) 2 and NiOOH was monitored by cyclic voltammetry throughout. Onset potentials, Tafel slopes, and turnover frequencies (TOF) were measured at OER overpotentials between 270 and 390 mV. Alloys with dissimilar Cr:Mo ratios had significantly higher electrochemical surface area and increased γ -NiOOH formation, suggesting higher metal dissolution rates. The equal Cr:Mo concentration alloy and pure Ni developed a primarily β -NiOOH surface, and had 1.8–2.0 times larger TOF values than those containing significant γ -NiOOH. The NiCrMo alloys required smaller overpotentials (54–80 mV) to produce 10 mA cm −2 of OER current, and had comparable Tafel slopes to pure Ni. The findings here indicate a β -NiOOH-developed surface to be more OER-active than a γ -NiOOH-developed surface, and suggest certain NiCrMo alloys have promise as OER electrocatalysts.
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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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