(289f) Atomic Layer Deposition of NiAlxOy Catalysts for Electrochemical Oxidation of Water
To study the effects of aluminum on the activity of nickel oxide based catalyst, atomic layer deposition (ALD) was used to synthesize ternary NiAlxOy films. ALD allows for the deposition of conformal thin films with angstrom-level control over thickness.Â Depositing ternary materials with ALD is shown to provide good compositional control by switching between the individual ALD chemistries. Electrochemical characterization of these synthesized thin films shows that aluminum improves the onset potential for OER and the Tafel slope when compared to nickel oxide films.
Studies of the intrinsic activity of nickel aluminum oxide catalyst are complicated by two factors: (1) nickel oxide films are prone to incidental incorporation of iron from trace impurities found in the electrolyte, (2) aluminum oxide leaches in alkaline conditions leading to changes in composition and porosity of the catalytic films. This work addresses the first issue through additional purification of the electrolyte to remove trace iron. With an iron free environment, nickel aluminum oxide catalyst is shown to outperform nickel oxide catalyst. When NiAlxOy films are allowed to age in electrolyte containing trace iron, their activity significantly improves, performing better than as-deposited NiFexOy films. The second complicating factor was further explored by comparing thin and thick films to examine the effect of porosity and its effect on performance. Though the as-deposited NiAlxOy films are initially unstable under alkaline conditions, our studies show that the films retain their high activity after aluminum leaching equilibrates with the electrolyte.
- James B. Gerken, Sarah E. Shaner, Robert C. Massé, Nicholas J. Porubsky, and Shannon S. Stahl. Energy Environ. Sci.,2014, 7, 2376