Molecular Iron Oxide Clusters Boost the Oxygen Reduction Reaction of Platinum Electrocatalysts at Near‐Neutral pH

Lv, Jiaqi; Lang, Zhongling; Fu, Jiaqi; Lan, Qiao; Liu, Rongji; Zang, Hong‐Ying; Li, Yangguang; Ye, Dingding; Streb, Carsten

doi:10.1002/anie.202202650

Cited by 19 publications

(8 citation statements)

References 52 publications

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“…Alternatively, the use of water soluble polyoxometalate (POM) anions as ligand scaffold remains quite successful to isolate a wide variety of iron oxo clusters (Fe 2 À Fe 30 ) which are stable in acidic to moderately basic pH (~8). [12,13] Some of these clusters are even able to split water, [14,15] reduce oxygen, [16] oxidize organic compounds and degrade dyes under suitable photo and/or electrochemical condition. [17,18] Nevertheless, the electrocatalytic water oxidation with POM catalysts is preferred in neutral [19,20] and/or acidic medium [21,22] as because of hydrolytic degradation of POM based water oxidation catalysts under neutral to alkaline pH and electrochemical condition predominantly leads to evolve the most reactive metal oxide as heterogeneous catalyst.…”

Section: Introductionmentioning

confidence: 99%

Ionic γ‐FeO(OH) Nanocrystal Stabilized by Small Isopolymolybdate Clusters as Reactive Core for Water Oxidation

Mallick

Chakraborty

2022

Chemistry A European J

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At near neutral to basic pH, hydrolysis-induced aggregation to insoluble bulk iron-oxide is often regarded as the pitfalls of molecular iron clusters. Iron-oxide nanocrystals are encouragingly active over the molecular clusters and/or bulk oxides albeit, stabilizing such nanostructures in aqueous pH and under turnover condition remain a perdurable challenge. Herein, an Anderson-type [Mo 7 O 24 ] 6À isopolyanion, a small (dimension ca. 0.85 nm) isolable polyoxometalate (POM) possessing only {31} atoms, has been introduced for the first time as a covalent linker to stabilize an infinitely stable and aqueous-soluble γ-FeO(OH) nanocore. During the hydrothermal isolation of the material, a partial dissociation of the parent [Mo 7 O 24 ] 6À may lead to the in situ generation of few analogous [Mo x O y ] nÀ clusters, proved by Raman study, which can also participate in stabilizing the γ-FeO(OH) nanocore, Mo x O y @FeO(OH). However, due to high ionic charge on {Mo=O} terminals of the [Mo x O y ] nÀ , they are covalently linked via Mo VI -μ 2 O-Fe III bridging to γ-FeO(OH) core in Mo x O y @FeO(OH), established by numerous spectroscopic and microscopic evidence. Such bonding mode is more likely as precedent from the coordination motif documented in the transition metal clusters stabilized by this POM. The γ-FeO(OH) nanocore of Mo x O y @FeO(OH) behaves as potent active center for electrochemical water oxidation with a overpotential, 263 mV @ 10 mA cm À 2 , lower than that observed for bare γ-FeO(OH). Despite of some molybdenum dissolution from the POM ligands to the electrolyte, residual anionic POM fragments covalently bound to the OER active γ-FeO(OH) core of the Mo x O y @FeO(OH) makes the surface predominantly ionic that results in an ordered electrical double layer to promote a better charge transport across the electrode-electrolyte junction, less likely in bulk γ-FeO(OH).

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Section: Introductionmentioning

confidence: 99%

Ionic γ‐FeO(OH) Nanocrystal Stabilized by Small Isopolymolybdate Clusters as Reactive Core for Water Oxidation

Mallick

Chakraborty

2022

Chemistry A European J

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“…The elemental survey scan confirmed the presence of Fe, Mo, Ni, and O that appeared at the respective binding energy values (Figure S12). In the core-level XP spectrum of Fe 2p, two spin–orbit components, Fe 2p 3/2 and Fe 2p 1/2 , appeared at the binding energy values of 710 and 723.9 eV, respectively, indicating the Fe III valence state (Figure i). , The satellite peaks at 717.5 eV (red arrow) for the Fe 2p 3/2 component and those at 732.3 eV (black arrow) for the Fe 2p 1/2 component further confirmed the presence of the Fe III valence state (Figure i) . The core-level XPS spectrum of Mo 3d indicates the presence of both Mo VI and Mo IV (Figure j).…”

Section: Resultsmentioning

confidence: 68%

Stabilization of Nickel-Doped Iron-oxy-hydroxide Core in Water by Heptamolybdate Ions to Improve the Electrochemical Oxygen Evolution Reaction

Samanta,

Mallick,

Chakraborty

2023

ACS Appl. Energy Mater.

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Heterometal-doped nickel-oxy-hydroxides or high-entropy multimetallic oxides show notable electrocatalytic activity. Herein, a readily available Anderson-type polyoxometalate (POM) anion, heptamolybdate ([Mo 7 O 24 ] 6− ), is taken as an inorganic ligand to stabilize the nickel(II)-doped iron-oxy-hydroxide nanocore. [Mo 7 O 24 ] 6−ligated Ni x Fe 1−x O(OH) nanomaterials with different ratios of Ni(II) and Fe(III) in the core (1−3) are prepared via a hydrothermal route. ICP−MS and the subsequent PXRD study of the materials have found out that approximately 1.5−2% nickel is incorporated into the γ-FeO(OH) core without altering its two-dimensional-layered lattice structure. The presence of numerous POMs covalently linked on the surface of 4−5 nm highly crystalline Ni x Fe 1−x O(OH) core is proven by multiple spectroscopic and microscopic techniques. Negative zeta potential of 1−3 infers the ionic surface of the materials due to the presence of negatively charged POMs which makes them highly dispersed and stable in water. Using 1−3 as electrocatalysts, oxygen evolution reaction (OER) is studied under alkaline condition. For catalytic OER, 1−3 on the nickel foam (NF) electrode require almost 20 mV less overpotential compared to the undoped core material Mo x O y @FeO(OH) and the POM-free bare FeO(OH) and Ni x Fe 1−x O(OH). The better OER activity can be correlated to better electrokinetics, realized from the Tafel slope and charge-transfer resistance (R ct ). The fabricated electrode 1@NF not only shows a long-term stability under the OER condition but also can be fabricated to a watersplitting electrolyzer using a graphite rod as the cathode to produce green hydrogen with Faradaic efficiency of ca. 72%. In this study, Anderson-type POM is used as a potential ligand to derive the quantum-dot-sized Ni x Fe 1−x O(OH) core as a reactive electrocatalyst for OER. In a broad context, this strategy, i.e., the use of POM as a pure inorganic ligand to stabilize a reactive metal oxide nanocore, can further be adapted to design a variety of multimetallic or mixed-valence metal oxide materials.

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“…Electrocatalytic ORR is an essential process in a variety of energy conversion technologies, such as fuel cells and metal‐air batteries [12–16] . Developing energy‐efficient electrocatalysts for the 4e − ORR with considerable rates under potentials close to 1.23 V versus RHE is of vital importance and has attracted increasing interests [15–39] . To improve ORR electrocatalysis, we consider to mimic the biological heme/Cu site by placing a redox‐active metal ion at the second‐sphere of the ORR metal site.…”

Section: Figurementioning

confidence: 99%

Adapting Synthetic Models of Heme/Cu Sites to Energy‐Efficient Electrocatalytic Oxygen Reduction Reaction

Meng,

Qin,

Lei

et al. 2023

Angew Chem Int Ed

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In nature, cytochrome c oxidases catalyze the 4e− oxygen reduction reaction (ORR) at the heme/Cu site, in which CuI is used to assist O2 activation. Because of the thermodynamic barrier to generate CuI, synthetic Fe‐porphyrin/Cu complexes usually show moderate electrocatalytic ORR activity. We herein report on a Co‐corrole/Co complex 1‐Co for energy‐efficient electrocatalytic ORR. By hanging a CoII ion over Co corrole, 1‐Co realizes electrocatalytic 4e− ORR with a half‐wave potential of 0.89 V versus RHE, which is outstanding among corrole‐based electrocatalysts. Notably, 1‐Co outperforms Co corrole hanged with CuII or ZnII. We revealed that the hanging CoII ion can provide an electron to improve O2 binding thermodynamically and dynamically, a function represented by the biological CuI ion of the heme/Cu site. This work is significant to present a remarkable ORR electrocatalyst and to show the vital role of a second‐sphere redox‐active metal ion in promoting O2 binding and activation.

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Molecular Iron Oxide Clusters Boost the Oxygen Reduction Reaction of Platinum Electrocatalysts at Near‐Neutral pH

Cited by 19 publications

References 52 publications

Ionic γ‐FeO(OH) Nanocrystal Stabilized by Small Isopolymolybdate Clusters as Reactive Core for Water Oxidation

Ionic γ‐FeO(OH) Nanocrystal Stabilized by Small Isopolymolybdate Clusters as Reactive Core for Water Oxidation

Stabilization of Nickel-Doped Iron-oxy-hydroxide Core in Water by Heptamolybdate Ions to Improve the Electrochemical Oxygen Evolution Reaction

Adapting Synthetic Models of Heme/Cu Sites to Energy‐Efficient Electrocatalytic Oxygen Reduction Reaction

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