Modular Design of Noble‐Metal‐Free Mixed Metal Oxide Electrocatalysts for Complete Water Splitting

Gao, Dandan; Liu, Rongji; Biskupek, Johannes; Kaiser, Ute; Song, Yu‐Fei; Streb, Carsten

doi:10.1002/anie.201900428

Cited by 189 publications

(88 citation statements)

References 45 publications

(12 reference statements)

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“…Metal foam support: For technological applications, high surface area metal electrodes, e.g., commercially available metal foams, are ideal catalyst supports. However, the chemically and mechanically stable linkage between POM-WOC and metal surface is still challenging [86]. Streb, Song and co-workers have explored a facile one-step hydrothermal reaction to deposit microcrystals of a O 40 ] and Co 2+ as molecular precursors [87].…”

Section: Heterogeneous Electrocatalytic Water Oxidation By Pomsmentioning

confidence: 99%

“…To this end, synthetic routes are being researched which enable the controlled conversion of the molecular POMs into active solid-state catalysts together with their stable deposition on suitable conductive substrates. Pioneering studies have, for example, explored the use of Keggin tungstates to deposit mixed cobalt copper tungsten oxides on metal electrodes, resulting in composites capable of oxygen evolution and hydrogen evolution [86]. Related studies have deposited POM-based metal oxides on carbon-based electrode materials; e.g., graphene for water oxidation catalysis [107].…”

Section: Outlook and Future Directionsmentioning

confidence: 99%

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The Reactivity and Stability of Polyoxometalate Water Oxidation Electrocatalysts

et al. 2019

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This review describes major advances in the use of functionalized molecular metal oxides (polyoxometalates, POMs) as water oxidation catalysts under electrochemical conditions. The fundamentals of POM-based water oxidation are described, together with a brief overview of general approaches to designing POM water oxidation catalysts. Next, the use of POMs for homogeneous, solution-phase water oxidation is described together with a summary of theoretical studies shedding light on the POM-WOC mechanism. This is followed by a discussion of heterogenization of POMs on electrically conductive substrates for technologically more relevant application studies. The stability of POM water oxidation catalysts is discussed, using select examples where detailed data is already available. The review finishes with an outlook on future perspectives and emerging themes in electrocatalytic polyoxometalate-based water oxidation research.

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Section: Heterogeneous Electrocatalytic Water Oxidation By Pomsmentioning

confidence: 99%

Section: Outlook and Future Directionsmentioning

confidence: 99%

The Reactivity and Stability of Polyoxometalate Water Oxidation Electrocatalysts

et al. 2019

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“…The traditional noble metal based electrocatalysts in which iridium and ruthenium oxides for the OER and platinum for the HER indeed show high catalytic performance; however, they commonly suffer from the expensive cost and scarce reserves. [3] Correspondingly, enormous research efforts have been devoted to seeking earth-abundant, cost-effective, and life-stable electrocatalysts. [4,5] Despite these endeavors, how to design and construct an efficient and durable noble-metal-free bifunctional catalyst for both OER and HER is challenging.…”

Section: Introductionmentioning

confidence: 99%

Alkali‐Etched Ni(II)‐Based Metal–Organic Framework Nanosheet Arrays for Electrocatalytic Overall Water Splitting

Zhou

Dou

et al. 2020

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However, only limited MOFs were explored for electrocatalytic water splitting, mainly due to the poor structure stability of most MOFs in water system, especially under acidic/alkaline conditions. [11-13] Most importantly, metal nodes in most MOFs are coordinately saturated with ligand/ solvent molecules, [14,15] which are inert in electrocatalysis, even if these metal sites are highly exposed by rich pores. [16] For instance, Zhang and co-workers reported a new metal azolate framework [Co 2 (µ-Cl) 2 (bbta)], [12] but showing poor OER activity. The metal sites became active only on the functionalization by hydroxide ligands, and then exhibited efficient electrocatalysis performance. In addition, the low electrical conductivity for most MOFs also affects the electrocatalytic activity. [17] The principal reason is that the larger inner impedance of most organic ligands and rigid pore structures are not conducive to long-range charge transport. [18,19] Despite few of efforts including synthesis of ultrathin 2D layers or introduction of conductive materials in channels for exposing more active sites or improving their conductivity, the electrocatalytic activity enhancement is still not prominent. [20,21] Thus, it is desired to rationally design or optimize the structure and composition of MOFs to improve water spitting activity. Herein, we propose that the construction of defects into MOFs could be a feasible strategy to create highly active sites and improve conductivity for optimizing electrocatalytic properties. As a proof of concept, a Ni(II)-based MOF [Ni 2 (OH) 2 (BDC); BDC = 1,4-benzenedicarboxylate] with intrinsic 2D metal-oxide layers connected by BDC ligands [22] was selected and its defectrich nanosheet array (as D-Ni-MOF NSA) was prepared via a simply alkali-etched strategy (Figure 1). The intrusion of KOH leads to partial breaking of NiO bonds in the MOF, accompanied with the generation of open unsaturated Ni sites and the introduction of extra-framework K cations. Subsequently, the unsaturated Ni sites were attacked by the OH − ions, leading to the exposed active site NiO(OH), while the original framework topology is still well maintained. Theoretical/experimental results reveal that the above features could endow the D-Ni-MOF with richer active sites and largely improved conductivity, compared with pristine Ni-MOF. Finally, the assembled D-Ni-MOF||D-Ni-MOF electrolyte cell could achieve comparable electrocatalytic performance with that of the noble metal-based benchmark catalysts, demonstrating a promising bifunctional electrocatalyst for overall water splitting. The exploration of efficient electrocatalysts is the central issue for boosting the overall efficiency of water splitting. Herein, pertinently creating active sites and improving conductivity for metal-organic frameworks (MOFs) is proposed to tailor electrocatalytic properties for overall water splitting. An Ni(II)-MOF nanosheet array is presented as an ideal material model and a facile alkali-etched strategy is developed to break its NiO b...

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“…[19][20][21][22] More importantly,t he electrocatalytic efficiency can be tuned by adjusting the chemical compositiona nd microenvironment of POMs. [23][24][25][26] In terms of POMs applicationinHER, several POM-based electrocatalysts for HER in acidic solution were reporteds of ar.F or example, Zhang etal. presented the P 8 W 48 /rGO nanomaterial as an efficient electrocatalyst for the HER in acidic aqueous solution.…”

Section: Introductionmentioning

confidence: 99%

Devisable POM/Ni Foam Composite: Precisely Control Synthesis toward Enhanced Hydrogen Evolution Reaction at High pH

Jia

Streb

Song

2019

Chemistry A European J

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Polyoxometalates (POMs) are promising catalysts for the electrochemical hydrogen production from water owing to their high intrinsic catalytic activity and chemical tunability.H owever,p oor electrical conductivity and easy detachment of the POMs from the electrode cause significant challenges under operating condition. Herein, as imple onestep hydrothermal methodi sr eportedt os ynthesize as eries of Dexter-Silverton POM/Ni foam composites (denoted as NiM-POM/Ni; M = Co, Zn, Mn), in which the stable linkage between the POM catalysts and the Ni foam electrodes lead to high activity for the hydrogen evolution reaction (HER).Amongthem, the highest HER performance can be observed in the NiCo-POM/Ni, featuring an overpotential of 64 mV (at 10 mA cm À2 ,v s. reversible hydrogen electrode), and aT afel slope of 75 mV dec À1 in 1.0 m aqueous KOH. Moreover, the NiCo-POM/Ni catalyst showedahigh faradaic efficiency % 97 %f or HER. Post-catalytic of NiCo-POM/Ni analyses showedv irtually no mechanical or chemical degradation. The findings propose af acile and inexpensivem ethodt o designs table and effective POM-based catalysts for HER in alkaline water electrolysis.

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Modular Design of Noble‐Metal‐Free Mixed Metal Oxide Electrocatalysts for Complete Water Splitting

Cited by 189 publications

References 45 publications

The Reactivity and Stability of Polyoxometalate Water Oxidation Electrocatalysts

The Reactivity and Stability of Polyoxometalate Water Oxidation Electrocatalysts

Alkali‐Etched Ni(II)‐Based Metal–Organic Framework Nanosheet Arrays for Electrocatalytic Overall Water Splitting

Devisable POM/Ni Foam Composite: Precisely Control Synthesis toward Enhanced Hydrogen Evolution Reaction at High pH

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