Understanding the Enhancement of the Catalytic Properties of Goethite by Transition Metal Doping: Critical Role of O* Formation Energy Relative to OH* and OOH*

Lee, Tae Hyung; Lee, Sol A; Park, Hoonkee; Choi, Min‐Ju; Lee, Donghwa; Jang, Ho Won

doi:10.1021/acsaem.9b02140

Cited by 19 publications

(7 citation statements)

References 67 publications

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“…It is now well established that mixed-metal oxyhydroxides of Fe and first-row transition metals such as Mn, Cr, Co, and Ni are dramatically more rapid and efficient electrocatalysts for water oxidation than any of the single-metal materials alone. − Moreover, detailed investigations identify Fe(III) as the active site at which O–O bond formation occurs. ,− Despite this intriguing and potentially important role of Fe, less is known about the catalytic properties of the iron oxyhydroxides, FeOOH, themselves. ,,− …”

Section: Introductionmentioning

confidence: 99%

Solution-State Catalysis of Visible Light-Driven Water Oxidation by Macroanion-Like Inorganic Complexes of γ-FeOOH Nanocrystals

et al. 2021

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Recent investigations reveal that by providing active sites for O−O bond formation, Fe(III) oxyhydroxides (FeOOH) dramatically enhance the oxygen evolution activities of iron-containing abundant-earth CoO x H y and NiO x H y electrocatalysts. In contrast to α-Fe 2 O 3 (hematite), however, little detailed information is available concerning fundamental reactivities of the Fe(III) oxyhydroxides themselves. We here report a macroanion-like polyoxometalate cluster-anion complex of 2.6 nm γ-FeOOH nanocrystals, 1, that not only catalyzes visible light-driven water oxidation with no need for added photosensitizers but also whose unique stability and solubility facilitate investigation of oxygen evolution using the toolbox of solution-state methods typically reserved for molecular catalysis. The γ-FeOOH active centers of 1 are comprised of ca. 250 Fe atoms and coordinated by an average of six oxo-donor ligands, [α-PW 11 O 39 Fe III ] 4− -μ-O − , each with a formal charge of 5−, giving freely diffusing macroanion-like hexacoordinate complexes readily observed in their native, vitreous water solution state by cryogenic TEM. With a bandgap energy of 2.3 eV and valence-and conduction-band (VB and CB) energies of 2.34 and 0.04 V vs NHE, 1 catalyzes visible light-driven water oxidation by orthoperiodate {H 3 I VII O 6 } 2− at pH 8, at a rate similar to that documented for hematite nanocrystals. Kinetic data show the reaction to be one-half order in concentrations of both 1 and {H 3 I VII O 6 } 2− , indicative of a chain mechanism. A solvent kinetic isotope effect (KIE), k H /k D , of 1.32 was assigned to the rate-limiting trapping of photoexcited electrons by {H 3 I VII O 6 } 2− , which initiates a radical-chain process inhibited by added iodate [I V O 3 ] − . In contrast to the rate-determining O−O bond formation typical of metal-oxide electrocatalysts and of many molecular catalysts, chain mechanisms initiated by the rate-limiting trapping of excited-state electrons may prove a general feature of water oxidation by freely diffusing photoactive nanocrystals.

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Section: Introductionmentioning

confidence: 99%

Solution-State Catalysis of Visible Light-Driven Water Oxidation by Macroanion-Like Inorganic Complexes of γ-FeOOH Nanocrystals

et al. 2021

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“…The smaller half-circle in the Nyquist plot shows that the charge transfer resistance drops distinctively when applied doping and H 2 annealing. Based on the previous studies about the relationship between the oxygen vacancy and water and hydroxyl group adsorption, the oxygen vacancies at the surface promote the fast and easy water and hydroxyl group adsorption, boosting the oxygen evolution reaction at the interface [ 56 – 58 ].…”

Section: Resultsmentioning

confidence: 99%

“…The parameters for interfacial free energy calculation are stated in Table 2 . H 2 annealing at TiO 2 thin film could stimulate the adsorption of H 2 O molecules and hydroxyl ions, which is verified by lowered interfacial free energy [ 56 – 58 , 61 ]. Furthermore, when applying the H 2 annealing, the interfacial free energy of 1 M NaOH solution changes further compared to the distilled water.…”

Section: Resultsmentioning

confidence: 99%

Regulating the surface of anion-doped TiO2 nanorods by hydrogen annealing for superior photoelectrochemical water oxidation

Park

Lee

et al. 2022

Nano Convergence

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Dedications to achieve the highly efficient metal oxide semiconductor for the photoelectrochemical water splitting system have been persisted to utilize the TiO2 as the promising photoanode material. Herein, we report notable progress for nanostructured TiO2 photoanodes using facile sequential one-pot hydrothermal synthesis and annealing in hydrogen. A photocurrent density of 3.04 mA·cm−2 at 1.23 V vs. reversible hydrogen electrode was achieved in TiO2 nanorod arrays annealed in hydrogen ambient, which is approximately 4.25 times higher than that of pristine TiO2 annealed in ambient air. 79.2% of incident photon-to-current efficiency at 380 nm wavelength demonstrates the prominence of the material at the near-UV spectral range region and 100 h chronoamperometric test exhibits the stability of the photoanode. Detailed studies regarding crystallinity, bandgap, and elemental analysis provide the importance of the optimized annealing condition for the TiO2-based photoanodes. Water contact angle measurement displays the effect of hydrogen annealing on the hydrophilicity of the material. This study clearly demonstrates the marked improvement using the optimized hydrogen annealing, providing the promising methodologies for eco-friendly mass production of water splitting photoelectrodes. Graphical Abstract

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“…The OER activities of FeOOH substituted by other transition metals including Cr, Mn, and Ni are evaluated and the substituted dopants are all confirmed to be the active sites for OER. [ 184 ] Although all these dopants can improve the activity of FeOOH, Co‐doped FeOOH exhibits best due to the most optimal intermediate binding energy. β‐FeOOH nanorods can gradually convert into Fe 2 O 3 nanorods during a simple thermal treatment.…”

Section: Transition Metal‐based Oer Electrocatalystsmentioning

confidence: 99%

Advanced Transition Metal‐Based OER Electrocatalysts: Current Status, Opportunities, and Challenges

Zhang

Zou

2021

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and sustainable energy sources, which have been considered as an encouraging solution to significantly reduce the dependency on traditional fossil fuels. Hydrogen is a promising clean energy carrier by virtue of zero-carbon content and the highest gravimetric energy density. [1] In this scenario, hydrogen production through electricity-driven water splitting represents a promising strategy for renewable energy conversion.Water electrolysis involves hydrogen evolution reaction (HER) on cathode and oxygen evolution reaction (OER) on anode. Theoretically, it requires a potential difference of 1.23 V between anode and cathode for driving the overall reaction. [2] But actually, a much higher voltage is needed in a practical water electrolyzer due to the overpotentials on both electrodes. HER is a relatively simple two-electron transport process involving electrochemical H + adsorption and desorption of H 2 . In contrast, OER is an inherently more complex process and has sluggish oxygen evolution kinetics, since it needs to transfer four electrons through multi-step reactions with single-electron transfer at each step. [3] As a result, the accumulation of energy at each step makes OER kinetically hindered and a large overpotential is needed to overcome the kinetic energy barrier. On the other hand, OER is an important half reaction involved in rechargeable metal-air batteries which are also regarded as the emerging sustainable energy conversion technology. Nevertheless, the bottlenecks such as low lifetimes, inferior energy conversion efficiency, and limited stability of metal-air batteries mainly originate from the intrinsically sluggish kinetics of OER. [4] Hence, developing effective and stable OER electrocatalysts by improving oxygen electrokinetics can significantly contribute to improving energy-conversion efficiency.To date, transition metal-based OER catalysts have been extensively studied by virtue of their excellent OER catalytic activities. [5] Noble-metal-based electrocatalysts have been considered as the most powerful electrocatalysts for OER in spite of their high prices. Among them, Ru and Ir have been verified to outperform Pt, Pd, and Rh. [6] Considering the high potential applied during OER, noble-metal oxides such as IrO 2 and RuO 2 are widely chosen as the state-of-the-art electrocatalysts. Nevertheless, RuO 2 is highly unstable in both acidic and alkaline electrolytes under high anodic potential. [7] Although IrO 2 Oxygen evolution reaction (OER) is an important half-reaction involved in many electrochemical applications, such as water splitting and rechargeable metal-air batteries. However, the sluggish kinetics of its four-electron transfer process becomes a bottleneck to the performance enhancement. Thus, rational design of electrocatalysts for OER based on thorough understanding of mechanisms and structure-activity relationship is of vital significance. This review begins with the introduction of OER mechanisms which include conventional adsorbate evolution mechanism and lattice-oxygen-mediated...

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Understanding the Enhancement of the Catalytic Properties of Goethite by Transition Metal Doping: Critical Role of O* Formation Energy Relative to OH* and OOH*

Cited by 19 publications

References 67 publications

Solution-State Catalysis of Visible Light-Driven Water Oxidation by Macroanion-Like Inorganic Complexes of γ-FeOOH Nanocrystals

Solution-State Catalysis of Visible Light-Driven Water Oxidation by Macroanion-Like Inorganic Complexes of γ-FeOOH Nanocrystals

Regulating the surface of anion-doped TiO2 nanorods by hydrogen annealing for superior photoelectrochemical water oxidation

Advanced Transition Metal‐Based OER Electrocatalysts: Current Status, Opportunities, and Challenges

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