A New 2D Layered Co(II) Complex Based on Monosubstituted Keggin Anions and its Electrocatalytic O2 Evolution

Wang, Haijuan; You, Weixiong; Meng, Bifang; Sun, Xianfeng; Cheng, Hongwei; Shan, Wenjuan

doi:10.1007/s10876-010-0346-2

Cited by 8 publications

(6 citation statements)

References 21 publications

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“…The practical advantages listed above have led to a number of publications describing polyoxometalate WOCs. − Of particular relevance to the present work is a 2010 Science paper which reported the cobalt POM Co 4 (H 2 O) 2 (PW 9 O 34 ) 2 10– (Co 4 –POM) as a highly active WOC when Ru(bpy) 3 3+ is used as the chemical oxidant . Under the specific conditions of 3.2 μM Co 4 –POM, 1.5 mM Ru(bpy) 3 3+ oxidant, and pH 8, turnover frequencies of up to 5 (mol O 2 ·s –1 ·mol Co 4 –POM –1 ) and total turnovers of >1000 (mol O 2 ·mol Co 4 –POM –1 ) were reported.…”

Section: Introductionmentioning

confidence: 91%

Water Oxidation Catalysis Beginning with 2.5 μM [Co₄(H₂O)₂(PW₉O₃₄)₂]^10–: Investigation of the True Electrochemically Driven Catalyst at ≥600 mV Overpotential at a Glassy Carbon Electrode

2013

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Evidence for the true water oxidation catalyst (WOC) when beginning with the cobalt polyoxometalate [Co4(H2O)2(PW9O34)2]10– (Co4–POM) is investigated at deliberately chosen low polyoxometalate concentrations (2.5 μM) and high electrochemical potentials (≥1.3 V vs Ag/AgCl) in pH 5.8 and 8.0 sodium phosphate electrolyte at a glassy carbon working electrodeconditions which ostensibly favor Co4–POM catalysis if present. Multiple experiments argue against the dominant catalyst being CoO x formed exclusively from Co2+ dissociated from the parent POM. Measurement of [Co2+] in the Co4–POM solution and catalytic controls with the corresponding amount of Co(NO3)2 cannot account for the O2 generated from 2.5 μM [Co4(H2O)2(PW9O34)2]10– solutions. This result contrasts with our prior investigation of Co4–POM under higher concentration and lower potential conditions (i.e., 500 μM [Co4(H2O)2(PW9O34)2]10–, 1.1 V vs Ag/AgCl, as described in Stracke, J. J.; Finke, R. G. J. Am. Chem. Soc. 2011, 133, 14872) and highlights the importance of reaction conditions in governing the identity of the true, active WOC. Although electrochemical studies are consistent with Co4–POM being oxidized at the glassy carbon electrode, it is not yet possible to distinguish a Co4–POM catalyst from a CoO x catalyst formed via decomposition of Co4–POM. Controls with authentic CoO x indicate conversion of only 3.4% or 8.3% (at pH 8.0 and 5.8) of Co4–POM into a CoO x catalyst could account for the O2-generating activity, and HPLC quantification of the Co4–POM stability shows the postreaction Co4–POM concentration decreases by 2.7 ± 7.6% and 9.4 ± 5.1% at pH 8.0 and 5.8. Additionally, the [Co2+] in a 2.5 μM Co4–POM solution increases by 0.55 μM during 3 min of electrolysisfurther evidence of the Co 4 -POM instability under oxidizing conditions. Overall, this study demonstrates the challenges of identifying the true WOC when examining micromolar amounts of a partially stable material and when nanomolar heterogeneous metal-oxide will account for the observed O2-generating activity.

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Section: Introductionmentioning

confidence: 91%

Water Oxidation Catalysis Beginning with 2.5 μM [Co₄(H₂O)₂(PW₉O₃₄)₂]^10–: Investigation of the True Electrochemically Driven Catalyst at ≥600 mV Overpotential at a Glassy Carbon Electrode

2013

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“…Lai O 39 ]}. 149 The starting POM was characterized by X-ray crystallography, IR spectroscopy, and elemental analysis. Although the authors claim catalytic water oxidation by the POM, the only evidence provided is cyclic voltammetry showing an irreversible oxidation wave at ∼1300 mV versus Ag/AgCl.…”

Section: Acs Catalysismentioning

confidence: 99%

“…A final cobalt-based example of electrocatalytic water oxidation uses a carbon-paste-supported [Hpy] 2 {[Co(4,4′-Hbpy) 2 (H 2 O) 2 ][SiCoW 11 O 39 ]} . The starting POM was characterized by X-ray crystallography, IR spectroscopy, and elemental analysis.…”

Section: Water Oxidation Catalysis Studies Beginning With Polyoxometa...mentioning

confidence: 99%

“…After catalysis, the islands contain 1.1% and 9.0% cobalt and phosphorus, and the interstitial space between the island contains 8.24% and 4.81%consistent with in situ formed CoO x . [Hpy] 2 {[Co(4,4′-Hbpy) 2 (H 2 O) 2 ][SiCoW 11 O 39 ]}electrochem. carbon paste in pH 4.5, NaOAcN/A [Ru 4 (μ-O) 4 (μ- OH) 2 (H 2 O) 4 (γ-SiW 10 O 36 ) 2 ] 10– Ce(IV) in pH 0.6UV–vis shows reversible protonation of POM over pH range of 0.6–2.0 (p K a = 3.62). This protonation/deprotonation is concentration independent, and the FTIR spectrum is unchanged during this titration.…”

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confidence: 99%

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Distinguishing Homogeneous from Heterogeneous Water Oxidation Catalysis when Beginning with Polyoxometalates

2014

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Polyoxometalates (POMs) have been proposed to be excellent homogeneous water oxidation catalysts (WOCs) due to their oxidative stability and activity. However, recent literature indicates that even these relatively robust compounds can be transformed into heterogeneous, metal-oxide WOCs under the oxidizing reaction conditions needed to drive O 2 evolution. This review covers the experimental methodology for distinguishing homogeneous and heterogeneous WOCs; it then addresses the "what is the true catalyst?" problem for POMs used as precatalysts in the oxidation of water to O 2 . These results are also compared to the broader WOC literature. The primary findings in this review are the following: (1) Multiple, complementary experiments are needed to determine the true catalyst, including determination of catalyst stability, speciation, and kinetics under operating conditions. (2) Controls with hypothetical heterogeneous metal-oxide catalysts are required to determine their kinetic competence in the reaction and support the conclusion of either a homogeneous or heterogeneous catalyst. (3) Although many studies observe qualitative stability of the starting POM under the reaction conditions, there is a lack of quantitative stability studies; if one does not know where the (pre)catalyst mass lies, then it is very difficult to rule out the possibility of an alternative species as the true catalyst. (4) The stability of POMs is dependent on the polyoxometalate, the metal center, and the reaction conditions. And, (5) as a result of the variable stability of POMs under different reaction conditions, those different conditions can influence the dominant catalyst identity. Overall, knowledge of which POMs (or other starting materials) tend to transform into heterogeneous WOCs, and how they do so, is therefore critical to developing the next generation of higher stability, higher activity, and truly long-lived POM and other water oxidation catalysts.

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“…Shan and coworkers entrapped a cobalt-based monosubstituted Keggin-type POM, [Hpy] 2 [Co(4,40-Hbpy) 2 (H 2 O) 2 ][SiCoW 11 O 39 ], in carbon paste to investigate electrocatalytic water oxidation activity. [102] There are some POM architectures that incorporate a transition metal atom as their central atom in the framework such as , where Lacunary units stabilize the whole architecture and establish a Bronsted acid-base chemistry to provide multiple proton-transfer sites to facilitate water oxidation. Reproduced with permission.…”

Section: Pom-based Oer Electrocatalystsmentioning

confidence: 99%

Electron‐Sponge Nature of Polyoxometalates for Next‐Generation Electrocatalytic Water Splitting and Nonvolatile Neuromorphic Devices

Ahmad,

Wang

et al. 2023

Advanced Science

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Designing next‐generation molecular devices typically necessitates plentiful oxygen‐bearing sites to facilitate multiple‐electron transfers. However, the theoretical limits of existing materials for energy conversion and information storage devices make it inevitable to hunt for new competitors. Polyoxometalates (POMs), a unique class of metal‐oxide clusters, have been investigated exponentially due to their structural diversity and tunable redox properties. POMs behave as electron‐sponges owing to their intrinsic ability of reversible uptake‐release of multiple electrons. In this review, numerous POM‐frameworks together with desired features of a contender material and inherited properties of POMs are systematically discussed to demonstrate how and why the electron‐sponge‐like nature of POMs is beneficial to design next‐generation water oxidation/reduction electrocatalysts, and neuromorphic nonvolatile resistance‐switching random‐access memory devices. The aim is to converge the attention of scientists who are working separately on electrocatalysts and memory devices, on a point that, although the application types are different, they all hunt for a material that could exhibit electron‐sponge‐like feature to realize boosted performances and thus, encouraging the scientists of two completely different fields to explore POMs as imperious contenders to design next‐generation nanodevices. Finally, challenges and promising prospects in this research field are also highlighted.

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A New 2D Layered Co(II) Complex Based on Monosubstituted Keggin Anions and its Electrocatalytic O2 Evolution

Cited by 8 publications

References 21 publications

Water Oxidation Catalysis Beginning with 2.5 μM [Co₄(H₂O)₂(PW₉O₃₄)₂]^10–: Investigation of the True Electrochemically Driven Catalyst at ≥600 mV Overpotential at a Glassy Carbon Electrode

Water Oxidation Catalysis Beginning with 2.5 μM [Co₄(H₂O)₂(PW₉O₃₄)₂]^10–: Investigation of the True Electrochemically Driven Catalyst at ≥600 mV Overpotential at a Glassy Carbon Electrode

Distinguishing Homogeneous from Heterogeneous Water Oxidation Catalysis when Beginning with Polyoxometalates

Electron‐Sponge Nature of Polyoxometalates for Next‐Generation Electrocatalytic Water Splitting and Nonvolatile Neuromorphic Devices

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A New 2D Layered Co(II) Complex Based on Monosubstituted Keggin Anions and its Electrocatalytic O2 Evolution

Cited by 8 publications

References 21 publications

Water Oxidation Catalysis Beginning with 2.5 μM [Co4(H2O)2(PW9O34)2]10–: Investigation of the True Electrochemically Driven Catalyst at ≥600 mV Overpotential at a Glassy Carbon Electrode

Water Oxidation Catalysis Beginning with 2.5 μM [Co4(H2O)2(PW9O34)2]10–: Investigation of the True Electrochemically Driven Catalyst at ≥600 mV Overpotential at a Glassy Carbon Electrode

Distinguishing Homogeneous from Heterogeneous Water Oxidation Catalysis when Beginning with Polyoxometalates

Electron‐Sponge Nature of Polyoxometalates for Next‐Generation Electrocatalytic Water Splitting and Nonvolatile Neuromorphic Devices

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Resources

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Water Oxidation Catalysis Beginning with 2.5 μM [Co₄(H₂O)₂(PW₉O₃₄)₂]^10–: Investigation of the True Electrochemically Driven Catalyst at ≥600 mV Overpotential at a Glassy Carbon Electrode

Water Oxidation Catalysis Beginning with 2.5 μM [Co₄(H₂O)₂(PW₉O₃₄)₂]^10–: Investigation of the True Electrochemically Driven Catalyst at ≥600 mV Overpotential at a Glassy Carbon Electrode