Operando Identification of Hydrangea-like and Amorphous Cobalt Oxyhydroxide Supported by Thin-Layer Copper for Oxygen Evolution Reaction

Chen, Hsueh-Yu; Chang, Yu‐Chung; Lee, Jyh‐Fu; Pao, Chih‐Wen; Huang, Hsin‐Chih; Wang, Chenhao

doi:10.1021/acssuschemeng.1c03936

Cited by 27 publications

(14 citation statements)

References 65 publications

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“…This is in perfect agreement with the nominal Co oxidation state in CoOOH and excludes the presence of O vacancies. These findings differ from other studies where an average oxidation state significantly lower than 3 was found on the as-prepared samples. , In the case of Co 3 O 4 , α = 2.54 in air, which departs from the expected 2.66 value. After immersion in the electrolyte, α = 2.62.…”

Section: Resultscontrasting

confidence: 99%

Unraveling the Cobalt Oxidation State at the Surface of Epitaxial Cobalt Oxide Films during the Oxygen Evolution Reaction by Operando X-ray Absorption Spectroscopy/Surface X-ray Diffraction

Bouvier,

Pacheco Bubi,

Wiegmann

et al. 2023

ACS Appl. Energy Mater.

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Better understanding of the oxygen evolution reaction on cobalt oxides requires insights into the oxide−solution interface structure and composition under reaction conditions. We here present operando studies of electrodeposited epitaxial thin films with planar surface morphology that couple X-ray absorption spectroscopy, surface X-ray diffraction, and electrochemical measurements. This enabled us to disentangle bulk and surface contributions of the XAS signal and to correlate the cobalt oxidation state with the surface structure of cobalt oxide films. In the case of Co 3 O 4 (111) films, we show a one-to-one correlation between the Co oxidation state increase in the pre-OER potential range and the potential-dependent thickness of the reversibly formed amorphous layer on the oxide surface. From this correlation, we conclude that this amorphous layer is exclusively composed of Co 3+ . In the case of CoOOH(001) films, we show that no such surface amorphization takes place and that the small oxidation state change with potential may be attributed to the progressive deprotonation of the surface Co-OH groups. For both oxides, the amount of Co 4+ remains below the detection limit.

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Section: Resultscontrasting

confidence: 99%

Unraveling the Cobalt Oxidation State at the Surface of Epitaxial Cobalt Oxide Films during the Oxygen Evolution Reaction by Operando X-ray Absorption Spectroscopy/Surface X-ray Diffraction

Bouvier,

Pacheco Bubi,

Wiegmann

et al. 2023

ACS Appl. Energy Mater.

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“…An increase in the cell temperature makes the kinetics faster as well as diminishes the thermodynamic potential. , Moreover, an alkaline pH is necessarily chosen due to the minimum water oxidation potential. Although a majority of the transition-metal-based catalysts outperform under alkaline conditions, they behave as electro(pre)catalysts and transform into metal-oxy-hydroxides in situ. − As a result of the high alkaline stability of transition-metal-oxy-hydroxides such as NiO(OH), FeO(OH), and CoO(OH), they are often studied as efficient OER electrocatalysts. ,− However, the inferior conductivity of these oxides or oxyhydroxides is the potential bottleneck to achieve the highest activity. Second, metal doping is found to be effective to improve conductivity as well as activity. , For instance, Fe x Ni 1– x O(OH) is found to be the most reactive transition-metal-based catalyst. − Detailed studies have found that the incorporation of Fe into NiO(OH) or CoO(OH) leads to a higher OER activity, and this is due to the improved conductivity by the Ni/Co centers, while Fe is considered as the active site .…”

Section: Introductionmentioning

confidence: 99%

Slow O–H Dissociation in the First-Order Oxygen Evolution Reaction Kinetics on Polycrystalline γ-FeO(OH)

et al. 2023

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To unravel the reaction mechanism of the electrochemical oxygen evolution reaction (OER), analysis of the intrinsic activity parameters obtained via electrokinetic investigation remains effective. In this study, polycrystalline γ-FeO(OH), synthesized at room temperature, was used as a stable, albeit reactive, anode for OER, and electrokinetic studies were performed to unravel the oxygen evolution reaction pathway. The cell temperature, hydroxyl ion concentration, and the cation of the supporting electrolyte were varied, and the influence of external bias on the OER activity was recorded. Changes in the cell temperature from 30 to 65 °C lead to an enhanced OER activity due to small overpotential, Tafel slope, and charge-transfer resistance (R ct ) values at high temperatures, which unambiguously highlights the influence of the thermodynamic barrier and electron-transfer kinetics. The calculated anodic charge-transfer coefficient (α a ) and specific exchange current density (j 0,s ) values are 0.65 and 2.24 × 10 −5 mA cm −2 , respectively. The faster OER kinetics on polycrystalline γ-FeO(OH) can also be attributed to an appreciably low activation energy of 8.26 ± 2 kJ mol −1 , where variation of the electrolyte concentration indicated a first-order dependence on [OH] − . Experimentally obtained intrinsic kinetic parameters such as the Tafel slope, anodic chargetransfer coefficient, exchange current density, activation energy (E a ), reaction order (m), and deuterium isotope effect implicate the dissociation of hydroxyl ions on the polycrystalline γ-FeO(OH) as the rate-determining step. The direct effect of cations such as Li + , Na + , and K + of the electrolyte on OER highlights a weak interaction of the cations with the surface-active [Fe III -OH] species. A change in the electrode substance from three-dimensional highly conductive nickel foam (NF) to two-dimensional less conductive carbon cloth (CC) resulted in a change in the slow step, leading to the formation of a high-valency iron oxo intermediate from the iron hydroxy species.

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“…Together, the XANES features in the post-reaction sample resemble reported profiles of CoOOH, consistent with reports of Co-based electrocatalysts in alkaline solutions. 69,70…”

Section: Resultsmentioning

confidence: 99%

Identification of catalytic activity descriptors for selective 5-hydroxymethyl furfural electrooxidation to 2,5-furandicarboxylic acid

et al. 2023

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Operando Identification of Hydrangea-like and Amorphous Cobalt Oxyhydroxide Supported by Thin-Layer Copper for Oxygen Evolution Reaction

Cited by 27 publications

References 65 publications

Unraveling the Cobalt Oxidation State at the Surface of Epitaxial Cobalt Oxide Films during the Oxygen Evolution Reaction by Operando X-ray Absorption Spectroscopy/Surface X-ray Diffraction

Unraveling the Cobalt Oxidation State at the Surface of Epitaxial Cobalt Oxide Films during the Oxygen Evolution Reaction by Operando X-ray Absorption Spectroscopy/Surface X-ray Diffraction

Slow O–H Dissociation in the First-Order Oxygen Evolution Reaction Kinetics on Polycrystalline γ-FeO(OH)

Identification of catalytic activity descriptors for selective 5-hydroxymethyl furfural electrooxidation to 2,5-furandicarboxylic acid

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