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Unraveling Nanoscale Cobalt Oxide Catalysts for the Oxygen Evolution Reaction: Maximum Performance, Minimum Effort


Reith, Lukas; Triana, Carlos A; Pazoki, Faezeh; Amiri, Mehran; Nyman, May; Patzke, Greta R (2021). Unraveling Nanoscale Cobalt Oxide Catalysts for the Oxygen Evolution Reaction: Maximum Performance, Minimum Effort. Journal of the American Chemical Society, 143(37):15022-15038.

Abstract

The oxygen evolution reaction (OER) is a key bottleneck step of artificial photosynthesis and an essential topic in renewable energy research. Therefore, stable, efficient, and economical water oxidation catalysts (WOCs) are in high demand and cobalt-based nanomaterials are promising targets. Herein, we tackle two key open questions after decades of research into cobalt-assisted visible-light-driven water oxidation: What makes simple cobalt-based precipitates so highly active—and to what extent do we need Co-WOC design? Hence, we started from Co(NO3)2 to generate a precursor precipitate, which transforms into a highly active WOC during the photocatalytic process with a [Ru(bpy)3]2+/S2O82–/borate buffer standard assay that outperforms state of the art cobalt catalysts. The structural transformations of these nanosized Co catalysts were monitored with a wide range of characterization techniques. The results reveal that the precipitated catalyst does not fully change into an amorphous CoOx material but develops some crystalline features. The transition from the precipitate into a disordered Co3O4 material proceeds within ca. 1 min, followed by further transformation into highly active disordered CoOOH within the first 10 min. Furthermore, under noncatalytic conditions, the precursor directly transforms into CoOOH. Moreover, fast precipitation and isolation afford a highly active precatalyst with an exceptional O2 yield of 91% for water oxidation with the visible-light-driven [Ru(bpy)3]2+/S2O82– assay, which outperforms a wide range of carefully designed Co-containing WOCs. We thus demonstrate that high-performance cobalt-based OER catalysts indeed emerge effortlessly from a self-optimization process favoring the formation of Co(III) centers in all-octahedral environments. This paves the way to new low-maintenance flow chemistry OER processes.

Abstract

The oxygen evolution reaction (OER) is a key bottleneck step of artificial photosynthesis and an essential topic in renewable energy research. Therefore, stable, efficient, and economical water oxidation catalysts (WOCs) are in high demand and cobalt-based nanomaterials are promising targets. Herein, we tackle two key open questions after decades of research into cobalt-assisted visible-light-driven water oxidation: What makes simple cobalt-based precipitates so highly active—and to what extent do we need Co-WOC design? Hence, we started from Co(NO3)2 to generate a precursor precipitate, which transforms into a highly active WOC during the photocatalytic process with a [Ru(bpy)3]2+/S2O82–/borate buffer standard assay that outperforms state of the art cobalt catalysts. The structural transformations of these nanosized Co catalysts were monitored with a wide range of characterization techniques. The results reveal that the precipitated catalyst does not fully change into an amorphous CoOx material but develops some crystalline features. The transition from the precipitate into a disordered Co3O4 material proceeds within ca. 1 min, followed by further transformation into highly active disordered CoOOH within the first 10 min. Furthermore, under noncatalytic conditions, the precursor directly transforms into CoOOH. Moreover, fast precipitation and isolation afford a highly active precatalyst with an exceptional O2 yield of 91% for water oxidation with the visible-light-driven [Ru(bpy)3]2+/S2O82– assay, which outperforms a wide range of carefully designed Co-containing WOCs. We thus demonstrate that high-performance cobalt-based OER catalysts indeed emerge effortlessly from a self-optimization process favoring the formation of Co(III) centers in all-octahedral environments. This paves the way to new low-maintenance flow chemistry OER processes.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
08 Research Priority Programs > Solar Light to Chemical Energy Conversion
Dewey Decimal Classification:540 Chemistry
Scopus Subject Areas:Physical Sciences > Catalysis
Physical Sciences > General Chemistry
Life Sciences > Biochemistry
Physical Sciences > Colloid and Surface Chemistry
Uncontrolled Keywords:Colloid and Surface Chemistry, Biochemistry, General Chemistry, Catalysis
Language:English
Date:22 September 2021
Deposited On:14 Feb 2022 11:56
Last Modified:27 May 2024 01:53
Publisher:American Chemical Society (ACS)
ISSN:0002-7863
OA Status:Green
Publisher DOI:https://doi.org/10.1021/jacs.1c03375
Project Information:
  • : FunderSNSF
  • : Grant IDCRSII2_160801
  • : Project TitlePhotocatalytic Processes at Solvated Interfaces
  • Content: Accepted Version