CryoEXAFS: X-ray absorption spectroscopy station with cryogenic or in-beam operando electrochemistry sample conditions at BESSY II

Improving the stability of electrocatalysts for the oxygen evolution reaction (OER) through materials design has received less attention than improving their catalytic activity. We explored the effects of Mn addition to a cobalt oxide for stabilizing the catalyst by comparing single phase CoO x and (Co 0.7 Mn 0.3 )O x films electrodeposited in alkaline solution. The obtained disordered films were classified as layered oxides using X-ray absorption spectroscopy (XAS). The CoO x films showed a constant decrease in the catalytic activity during cycling, confirmed by oxygen detection, while that of (Co 0.7 Mn 0.3 )O x remained constant within error as measured by electrochemical metrics. These trends were rationalized based on XAS analysis of the metal oxidation states, which were Co 2.7 + and Mn 3.7 + in the bulk and similar near the surface of (Co 0.7 Mn 0.3 )O x , before and after cycling. Thus, Mn in (Co 0.7 Mn 0.3 )O x successfully stabilized the bulk catalyst material and its surface activity during OER cycling. The development of stabilization approaches is essential to extend the durability of OER catalysts.

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“…Hard XAS measurements were performed at the KMC‐2 or KMC‐3 beamlines [146,147] . Co−K and Mn−K edge references were collected at KMC‐3.…”

Section: Methodsmentioning

confidence: 99%

“…Hard XAS measurements were performed at the KMC-2 or KMC-3 beamlines. [146,147] CoÀ K and MnÀ K edge references were collected at KMC-3. Samples at CoÀ K edge and MnÀ K edge as well as a few references were collected at KMC-2.…”

Section: X-ray Absorption Spectroscopy (Xas)mentioning

confidence: 99%

Stabilization of a Mn−Co Oxide During Oxygen Evolution in Alkaline Media

et al. 2022

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“…Hard XAS spectra at Co‐ K edge were collected at the KMC‐3 beamline [ 68 ] at Helmholtz–Zentrum Berlin. Spectra were recorded in fluorescence mode using a 13 element silicon drift detector (SDD) from RaySpec.…”

Section: Methodsmentioning

confidence: 99%

Requirements for Beneficial Electrochemical Restructuring: A Model Study on a Cobalt Oxide in Selected Electrolytes

Villalobos

González-Flores

Urcuyo

et al. 2021

Advanced Energy Materials

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The requirements for beneficial materials restructuring into a higher performance oxygen evolution reaction (OER) electrocatalyst are still a largely open question. Here erythrite (Co3(AsO4)2·8H2O) is used as a Co‐based OER electrocatalyst to evaluate its catalytic properties during in situ restructuring into an amorphous Co‐based catalyst in four different electrolytes at pH 7. Using diffraction, microscopy, and spectroscopy, a strong effect in the restructuring behavior is observed depending of the anions in the electrolyte. Only carbonate electrolyte can activate the catalyst material, which is related to its slow restructuring process. While the catalyst turnover frequency (TOF) undesirably reduces by a factor of 28, the number of redox active sites continuously increases to a factor of 56, which results in an overall twofold increase in current of the restructured catalyst after 800 cycles. The activation is attributed to an adequate local order, a high Co oxidation state close to 3+, and a high number of redox‐active Co ions. These three requirements for beneficial restructuring provide new insights into the rational design of high‐performance OER catalysts by electrochemical restructuring.

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“…Hard XAS measurements were performed at the KMC-2 or KMC-3 beamlines. [116,117] Co-K and Mn-K edge references were collected at KMC-3. Samples at Co-K edge and Mn-K edge as well as a few references were collected at KMC-2.…”

Section: X-ray Absorption Spectroscopy (Xas)mentioning

confidence: 99%

Stabilization of Co oxide during oxygen evolution in alkaline media by the introduction of Mn oxide

Villalobos

Morales

Antipin

et al. 2022

Preprint

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Improving the stability of electrocatalysts for the oxygen evolution reaction (OER) through materials design has received less attention than improving their catalytic activity. We explored the effect of Mn addition to a cobalt oxide for stabilizing the catalyst by comparing Na-containing CoOx and (Co0.7Mn0.3)Ox films electrodeposited in alkaline solution. The obtained disordered films were classified as layered oxides using X-ray absorption spectroscopy (XAS). The CoOx films showed a constant decrease in the catalytic activity during cycling, confirmed by oxygen detection, while that of (Co0.7Mn0.3)Ox slightly increased as measured by electrochemical metrics. These trends were rationalized based on XAS analysis of the metal oxidation states, which were Co2.8+ and Mn3.7+ near the surface after cycling. Thus, adding Mn to CoOx successfully stabilized the catalyst material and its activity during OER cycling. The development of stabilization approaches is essential to extend the durability of OER catalysts.

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CryoEXAFS: X-ray absorption spectroscopy station with cryogenic or in-beam operando electrochemistry sample conditions at BESSY II

Cited by 12 publications

References 5 publications

Stabilization of a Mn−Co Oxide During Oxygen Evolution in Alkaline Media

Stabilization of a Mn−Co Oxide During Oxygen Evolution in Alkaline Media

Requirements for Beneficial Electrochemical Restructuring: A Model Study on a Cobalt Oxide in Selected Electrolytes

Stabilization of Co oxide during oxygen evolution in alkaline media by the introduction of Mn oxide

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