气候变化领域集成服务门户(CCPortal): Microkinetic model for pH- And potential-dependent oxygen evolution during water splitting on Fe-doped β-NiOOH

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DOI	10.1039/d0ee02292f
	Microkinetic model for pH- And potential-dependent oxygen evolution during water splitting on Fe-doped β-NiOOH
	Govind Rajan A.; Carter E.A.
发表日期	2020
ISSN	17545692
起始页码	4962
结束页码	4976
卷号	13 期号:12
英文摘要	Electrochemical water splitting using excess renewable electricity is a CO2-free synthesis route for sustainable hydrogen production and a renewable-energy storage strategy. Electrolyte pH and electrode potential are key reactor operating conditions used to tune water-splitting kinetics whose influence remains incompletely understood. Here, we develop a microkinetic model, based on the Marcus theory of electron transfer, to predict the anodic oxygen-evolution-reaction (OER) current density (water-splitting rate) as a function of solution pH and electrode potential. Our model offers startling new insights into OER kinetics on Fe-doped β-nickel oxyhydroxide (β-NiOOH), a promising, inexpensive candidate for electrocatalyzing the OER, under alkaline solution conditions. Only four fitting parameters with clearly defined physical meaning-reorganization free energies (λ) for H+- and OH--based reactions and work terms (w) for transporting H+/OH- ions and water from the bulk solution to the electrocatalyst surface-are required to reproduce experimental polarization curves (i.e., current-density vs. potential plots) at multiple alkaline pHs. The inclusion of work terms renders multiple steps rate-determining for the OER. The predicted λH+ = 0.744 eV is much smaller than λOH- = 2.474 eV, and wions = 0.607 eV is much larger than wwater = 0.065 eV, suggesting that the OER occurs primarily but not exclusively via water oxidation, rather than hydroxide oxidation, even under alkaline conditions. We show unequivocally that hydroxide oxidation also must occur as a minor channel, as accurate reproduction of polarization curves is impossible without it. We conclusively demonstrate the need to use the reversible, rather than the standard, hydrogen electrode as a reference in microkinetic models. Moreover, we deduce that the electrocatalyst surface is positively charged, contrary to inferences made in previous reports. Finally, we predict the following properties for the OER under high overpotential (≳0.3 V) conditions on Fe-doped β-NiOOH: a Tafel slope of ∼76 mV per decade, an effective charge transfer coefficient of 0.77, and an exchange current density of 3.5 μA cm-2 rivaling that of RuO2, one of the best noble-metal-containing water-splitting electrocatalysts. Our work substantially deepens the mechanistic understanding of water-splitting kinetics on inexpensive iron/nickel-oxyhydroxide-based electrocatalysts, which may help optimize operating conditions for their widespread deployment. This journal is © The Royal Society of Chemistry.
英文关键词	Alkalinity; Cell proliferation; Charge transfer; Current density; Curve fitting; Electric energy storage; Electrocatalysts; Electrodes; Electrolysis; Electrolytes; Electron transport properties; Hydrogen storage; Iron compounds; Kinetics; Nickel compounds; Oxidation; Oxygen; Oxygen evolution reaction; Polarization; Precious metals; Ruthenium compounds; Electrode potentials; Exchange current densities; Microkinetic modeling; Nickel oxyhydroxides; Oxygen evolution reaction (oer); Potential-dependent; Renewable electricity; Renewable energy storages; Hydrogen production; chemical reaction; inorganic compound; model; oxygen; pH; reaction kinetics; water treatment
语种	英语
来源期刊	Energy & Environmental Science
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/189461
作者单位	Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544-5263, United States; Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, Los Angeles, CA 90095-1592, United States; Office of the Chancellor, University of California, Los Angeles, Box 951405, Los Angeles, CA 90095-1405, United States
推荐引用方式 GB/T 7714	Govind Rajan A.,Carter E.A.. Microkinetic model for pH- And potential-dependent oxygen evolution during water splitting on Fe-doped β-NiOOH[J],2020,13(12).
APA	Govind Rajan A.,&Carter E.A..(2020).Microkinetic model for pH- And potential-dependent oxygen evolution during water splitting on Fe-doped β-NiOOH.Energy & Environmental Science,13(12).
MLA	Govind Rajan A.,et al."Microkinetic model for pH- And potential-dependent oxygen evolution during water splitting on Fe-doped β-NiOOH".Energy & Environmental Science 13.12(2020).