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Rapid solvent-evaporation strategy for three-dimensional cobalt-based complex hierarchical architectures as catalysts for water oxidation.

ABSTRACT: It is a challenging task to seek a highly-efficient electrocatalyst for oxygen evolution reaction (OER) of water splitting. Non-noble Co-based nanomaterials are considered as earth-abundant and effective catalysts to lower overpotential and increase polarization current density of OER. In this work, we reported, for the first time, a "rapid solvent-evaporation" strategy for the synthesis of three-dimensional (3D) cobalt complex hierarchical architectures constructed by two-dimensional (2D) nanosheets. The 3D structured cobalt complexes have excellent performances in catalyzing OER with lower onset potential, overpotential, Tafel slope and better stability than commercial IrO₂. Superior electrochemical performances would be beneficial from the unique 3D structure. This extremely simple method for 3D Co complex with good OER activities makes the complex be promising commercial OER catalyst to replace earth-rare and expensive IrO₂.

SUBMITTER: Jiang H

PROVIDER: S-EPMC6821758 | biostudies-literature | 2019 Oct

REPOSITORIES: biostudies-literature

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Rapid solvent-evaporation strategy for three-dimensional cobalt-based complex hierarchical architectures as catalysts for water oxidation.

Jiang Hong H Zhang Hao H Kang Qiaoling Q Ma Haifeng H Tong Yinlin Y Gao Feng F Lu Qingyi Q

Scientific reports 20191030 1

It is a challenging task to seek a highly-efficient electrocatalyst for oxygen evolution reaction (OER) of water splitting. Non-noble Co-based nanomaterials are considered as earth-abundant and effective catalysts to lower overpotential and increase polarization current density of OER. In this work, we reported, for the first time, a "rapid solvent-evaporation" strategy for the synthesis of three-dimensional (3D) cobalt complex hierarchical architectures constructed by two-dimensional (2D) nanos ...[more]

PMID: 31666571

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Project description:Cobalt polyoxometalates (Co-POMs) have emerged as promising water oxidation catalysts (WOCs), with the added advantage of their molecular nature despite being metal oxide fragments. In comparison with metal oxides, that do not offer well-defined active surfaces, POMs have a controlled, discrete structure that allows for precise correlations between experiment and computational analyses. Thus, beyond highly active WOCs, POMs are also model systems to gain deeper mechanistic understanding on the oxygen evolution reaction (OER). The tetracobalt Weakley sandwich [CoII 4(H2O)2(B-α-PW9O34)2]10- (Co4-WS) has been one of the most extensively studied. We have compared its activity with that of the iron analog [FeIII 4(H2O)2(B-α-PW9O34)2]6- (Fe4-WS) looking for the electronic effects determining their activity. Furthermore, the effect of POM nuclearity was also investigated by comparison with the iron- and cobalt-monosubstituted Keggin clusters. Electrocatalytic experiments employing solid state electrodes containing the POMs and the corresponding computational calculations demonstrate that CoII-POMs display better WOC activity than the FeIII derivatives. Moreover, the activity of POMs is less influenced by their nuclearity, thus Weakley sandwich moieties show slightly improved WOC characteristics than Keggin clusters. In good agreement with the experimental data, computational methods, including pK a values, confirm that the resting state for Fe-POMs in neutral media corresponds to the S1 (FeIII-OH) species. Overall, the proposed reaction mechanism for Fe4-WS is analogous to that found for Co4-WS, despite their electronic differences. The potential limiting step is a proton-coupled electron transfer event yielding the active S2 (FeIV[double bond, length as m-dash]O) species, which receives a water nucleophilic attack to form the O-O bond. The latter has activation energies slightly higher than those computed for the Co-POMs, in good agreement with experimental observations. These results provide new insights for the accurate understanding of the structure-reactivity relationships of polyoxometalates in particular, and or metal oxides in general, which are of utmost importance for the development of new bottom-up synthetic approaches to design efficient, robust and non-expensive earth-abundant water oxidation catalysts.

Dataset Information

Rapid solvent-evaporation strategy for three-dimensional cobalt-based complex hierarchical architectures as catalysts for water oxidation.

Publications

Rapid solvent-evaporation strategy for three-dimensional cobalt-based complex hierarchical architectures as catalysts for water oxidation.

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