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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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Redox-Induced Microstructure and Phase Dynamics in Nickel: Insights from In Situ Synchrotron X-ray Diffraction
Using in situ synchrotron X-ray diffraction, we interrogate the microstructural and phase evolution of polycrystalline nickel (Ni) during redox cycling in O2, H2, and H2O environments. Oxidation in O2 promotes strong (111) texturing in both the NiO overlayer and the underlying Ni substrate. However, this crystallographic alignment is lost following reduction in H2 and subsequent reoxidation, demonstrating irreversible microstructural changes. H2 exposure leads to proton dissolution into the Ni lattice, triggering a localized phase transition from face-centered cubic (FCC) to hexagonal close-packed (HCP) Ni in hydrogen-saturated regions. In H2O-containing atmospheres, dissociative H2O adsorption produces protons that permeate the NiO layer, forming γ-NiOOH within the NiO lattice and HCP Ni beneath the NiO overlayer as protons accumulate. Kinetic analysis via the Johnson-Mehl-Avrami–Kolmogorov model uncovers distinct growth mechanisms: preoxidized Ni surfaces follow one-dimensional (1D) kinetics for NiO, γ-NiOOH, and HCP growth, whereas pristine Ni exhibits three-dimensional (3D) kinetics due to island-like nucleation and growth of NiO. These results highlight the critical interplay between H2O dissociation, hydrogen permeation, and redox-driven phase transformations, with practical implications in engineering nickel-based catalysts and hydrogen storage systems through controlled microstructural and phase evolution.
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- Award ID(s):
- 2303712
- PAR ID:
- 10680962
- Publisher / Repository:
- American Chemical Society
- Date Published:
- Journal Name:
- Journal of the American Chemical Society
- Volume:
- 147
- Issue:
- 31
- ISSN:
- 0002-7863
- Page Range / eLocation ID:
- 27651 to 27663
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1021/jacs.5c06066
