Unified structural motifs of the catalytically active state of Co(oxyhydr)oxides during the electrochemical oxygen evolution reaction

Bergmann, Arno; Jones, Travis E.; Moreno, Elías Martínez; Teschner, Detre; Chernev, Petko; Gliech, Manuel; Reier, Tobias; Dau, Holger; Strasser, Peter

doi:10.1038/s41929-018-0141-2

Cited by 493 publications

(618 citation statements)

References 69 publications

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“…However, after catalysis, the XPS analysis indicates the true electronic states, in which along with the Co 2+ , the appearance of a new peak at slightly higher energy (782.2 eV) can be attributed to 2p 3/2 of Co 3+ (Figure S14 in the Supporting Information). In addition, the absence of a peak for Co 0 , and the relative decrease in the intensity of Co 2+ , strongly support the potential‐induced conversion of NCs to (oxy)hydroxide (Co III O x ‐OH), which may further ameliorate the oxophilicity of the material by imparting electronic flexibility in accordance with a previous report . These results further support our calculations of the slight increase in the number of active sites and thus surface area after catalysis.…”

Section: Resultssupporting

confidence: 91%

Ultrasmall Co@Co(OH)₂ Nanoclusters Embedded in N‐Enriched Mesoporous Carbon Networks as Efficient Electrocatalysts for Water Oxidation

et al. 2019

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Metal nanoclusters (NCs, size ≤2 nm) are emerging materials in catalysis owing to their unique catalytic and electronic properties such as high surface/volume ratio, high redox potential, plethora of surface active sites, and dynamic behavior on a suitable support during catalysis. Herein, in situ growth of ultrasmall and robust Co@β‐Co(OH)2 NCs (≈2 nm) hosted in a honeycomb‐like 3D N‐enriched carbon network was developed for water‐oxidation catalysis with extremely small onset potential (1.44 V). Overpotentials of 220 and 270 mV were required to achieve a current density of 10 mA cm−2 and 100 mA cm−2, respectively, in alkaline medium (1 m KOH). More promisingly, at η10=240 mV, the prolonged oxygen evolution process (>130 h) with faradaic efficiency >95 % at a reaction rate of 22 s−1 at 1.46 V further substantiated the key role of the ultrasmall supported NCs, which outperformed the benchmark electrocatalysts (RuO2/IrO2) and NCs reported so far. It is anticipated that the high redox potential of NCs with regeneratable active sites and their concerted synergistic effects with the N‐enriched porous/flexible carbon network are inherently worth considering to enhance the mass/charge transport owing to the nanoscale interfacial collaboration across the electrode/electrolyte boundary, thereby efficiently energizing the sluggish/challenging oxygen evolution process.

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Section: Resultssupporting

confidence: 91%

Ultrasmall Co@Co(OH)₂ Nanoclusters Embedded in N‐Enriched Mesoporous Carbon Networks as Efficient Electrocatalysts for Water Oxidation

et al. 2019

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“…Therefore, 5 cyclic voltammograms at each scan rate (10,20,30,40,50,60,80, and 100 mV s −1 ) were measured in the non-Faradaic region, which was a 100 mV potential window around the open circuit voltage of the system. Therefore, 5 cyclic voltammograms at each scan rate (10,20,30,40,50,60,80, and 100 mV s −1 ) were measured in the non-Faradaic region, which was a 100 mV potential window around the open circuit voltage of the system.…”

Section: Methodsmentioning

confidence: 99%

“…[10,11,52] The leaching of Zn 2+ in alkaline media leads to increased metal vacancies in the material, as proven by the EXAFS analysis of the sample after electrochemical reaction. For all those samples, it is agreed that the OER activity arises from adjacent Co (III-IV) O(H) groups connected by µ 2 -O-bridges.…”

Section: Is An Important Intermediate In the Electrochemical Formatiomentioning

confidence: 96%

Zn_0.35Co_0.65O – A Stable and Highly Active Oxygen Evolution Catalyst Formed by Zinc Leaching and Tetrahedral Coordinated Cobalt in Wurtzite Structure

Wahl

El-Refaei

Buzanich

et al. 2019

Advanced Energy Materials

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To arrive to sustainable hydrogen‐based energy solutions, the understanding of water‐splitting catalysts plays the most crucial role. Herein, state‐of‐the‐art hypotheses are combined on electrocatalytic active metal sites toward the oxygen evolution reaction (OER) to develop a highly efficient catalyst based on Earth‐abundant cobalt and zinc oxides. The precursor catalyst Zn0.35Co0.65O is synthesized via a fast microwave‐assisted approach at low temperatures. Subsequently, it transforms in situ from the wurtzite structure to the layered γ‐Co(O)OH, while most of its zinc leaches out. This material shows outstanding catalytic performance and stability toward the OER in 1 m KOH (overpotential at 10 mA cm−2 ηinitial = 306 mV, η98 h = 318 mV). By comparing the electrochemical results and ex situ analyses to today's literature, clear structure‐activity correlations are able to be identified. The findings suggest that coordinately unsaturated cobalt octahedra on the surface are indeed the active centers for the OER.

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“…Notably, the Co K‐edge of Co 0.75 Fe 0.25 BO/CP after OER displayed a decreased intensity of the white line compared with standard CoOOH, demonstrating the apparent change in the electronic structure of the Co surrounding structure owing to the intense interaction between Co and Fe . The length of Co−O decreases after OER (from pink curve to black curve), as observed in the corresponding Fourier transform spectra (see Figure e), which also indicated the formation of a new phase of Co 3+ . Moreover, the EXAFS curve of Co 0.75 Fe 0.25 BO/CP after OER exhibits an analogous coordination environment with the CoOOH sample, and the slight difference was ascribed to the coordination number and doping of heteroatoms (Figure e).…”

Section: Resultsmentioning

confidence: 81%

“…[45] The length of CoÀOd ecreases after OER( from pink curve to black curve), as observed in the corresponding Fouriert ransform spectra (see Figure 5e), which also indicated the formation of an ew phase of Co 3 + . [46] Moreover,t he EXAFS curve of Co 0.75 Fe 0.25 BO/CP after OER exhibits an analogousc oordination environment with the CoOOH sample, and the slight differencew as ascribed to the coordination number and doping of heteroatoms (Figure 5e). The coordination number (N)o fC o ÀOi nt he standard CoOOH is 6, clearlyi ndicating a CoO 6 octahedral structure.…”

Section: Resultsmentioning

confidence: 86%

Amorphous Cobalt Iron Borate Grown on Carbon Paper as a Precatalyst for Water Oxidation

Liu

Qiao

et al. 2019

ChemSusChem

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The key to improving water oxidation is to develop efficient and earth‐abundant catalysts for the oxygen evolution reaction (OER). Herein, a new amorphous cobalt iron borate supported on 3D carbon paper integrated electrode is reported as a precatalyst for the OER, which was synthesized by using a one‐pot hydrothermal method. An optimum OER activity was obtained at 25 % Fe doping by screening the compositions of the Co and Fe. The best synthesized catalyst needs an overpotential of 227 mV to deliver a current density of 10 mA cm−2 and also exhibits a long‐term durability of 24 h. Impressively, we find that CoFe oxyhydroxide was formed in situ in the OER process, which serves as the real catalytic active species for OER. Moreover, the direct conversion from CoFe borate to CoFe oxyhydroxide is reported for the first time in metal borate OER catalysts. The discovery in this work, that is, that metal borate as a precursor can efficiently catalyze the OER in alkaline media, significantly widens the family of OER catalysts.

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Unified structural motifs of the catalytically active state of Co(oxyhydr)oxides during the electrochemical oxygen evolution reaction

Cited by 493 publications

References 69 publications

Ultrasmall Co@Co(OH)₂ Nanoclusters Embedded in N‐Enriched Mesoporous Carbon Networks as Efficient Electrocatalysts for Water Oxidation

Ultrasmall Co@Co(OH)₂ Nanoclusters Embedded in N‐Enriched Mesoporous Carbon Networks as Efficient Electrocatalysts for Water Oxidation

Zn_0.35Co_0.65O – A Stable and Highly Active Oxygen Evolution Catalyst Formed by Zinc Leaching and Tetrahedral Coordinated Cobalt in Wurtzite Structure

Amorphous Cobalt Iron Borate Grown on Carbon Paper as a Precatalyst for Water Oxidation

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Unified structural motifs of the catalytically active state of Co(oxyhydr)oxides during the electrochemical oxygen evolution reaction

Cited by 493 publications

References 69 publications

Ultrasmall Co@Co(OH)2 Nanoclusters Embedded in N‐Enriched Mesoporous Carbon Networks as Efficient Electrocatalysts for Water Oxidation

Ultrasmall Co@Co(OH)2 Nanoclusters Embedded in N‐Enriched Mesoporous Carbon Networks as Efficient Electrocatalysts for Water Oxidation

Zn0.35Co0.65O – A Stable and Highly Active Oxygen Evolution Catalyst Formed by Zinc Leaching and Tetrahedral Coordinated Cobalt in Wurtzite Structure

Amorphous Cobalt Iron Borate Grown on Carbon Paper as a Precatalyst for Water Oxidation

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Ultrasmall Co@Co(OH)₂ Nanoclusters Embedded in N‐Enriched Mesoporous Carbon Networks as Efficient Electrocatalysts for Water Oxidation

Ultrasmall Co@Co(OH)₂ Nanoclusters Embedded in N‐Enriched Mesoporous Carbon Networks as Efficient Electrocatalysts for Water Oxidation

Zn_0.35Co_0.65O – A Stable and Highly Active Oxygen Evolution Catalyst Formed by Zinc Leaching and Tetrahedral Coordinated Cobalt in Wurtzite Structure