Electrochemical Oxide Growth on Nickel and Commercial Nickel Alloys: Influence of Chromium and Molybdenum

Abstract

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 and 0.65 V vs. Hg/HgO 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 to 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.

Environmental Stability of Actinide Oxides Mapped by Integrated and Accurate First-Principles Calculations

“…The above-mentioned unavoidable technical and physical issues encountered by experiments can be circumvented by the first-principles calculations based on density functional theory (DFT), which can yield the accurate Δ f G values for various transition-metal oxides and hydroxides if a precise enough electronic interaction potential (called as electronic density functional in DFT) is applied. ,,− The recently simulated transition-metal Poubaix diagrams not only can comprehensively explain a lot of electrochemical observations reported in previous decades but also have been widely used by many recent electrochemical experiments in the fields of, e.g., corrosion, catalysis, and clean energy to guide the design, synthesis, and characterization analysis of various transition-metal compounds. − Those new first-principles diagrams even have been used in the geological field to understand the rock weathering mechanisms in acid rains on both the ancient Earth and Mars, e.g., the dissolution of Ni oxides and the formation of magnetite (a Fe 3 O 4 -based mineral). ,, The first-principles electrochemical phase diagrams can be further used to study more complex transition-metal systems, e.g., conventional Ni–Cr alloys, multiprincipal element alloys, , complex compounds, and nanoscale passivating films, and have successfully helped precisely understand many passivation, corrosion, and precipitation behaviors, as well as their dependence on both material state and environmental condition. Such success in the thermodynamic and electrochemical calculations of transition-metal systems encourages the use of DFT to obtain reliable Δ f G data for all possible actinide oxides, which can bring the fundamental and historical contribution to the related nuclear fields.…”

Mechanical characteristics and electrochemical corrosion of NiCoCr alloys

“…Guo et al investigated the effect of chlorides on the secondary passivation film (SPF) of the laser additive manufacturing nickel-based superalloys by electrochemical machining [18]. Kretzmer et al studied the effect of chromium and molybdenum on the growth of electrochemical oxides in nickel and commercial nickel alloys [19]. Yan et al investigated the corrosion behavior of high manganese steels in a simulated marine splash zone by dry-wet cycle corrosion and electrochemical experiments [20].…”