Electrochemical oxygen reduction on layered mixed metal oxides: Effect of B-site substitution

Samira, Samji; Camayang, John Carl A.; Nacy, Ayad M.; Díaz, Montserrat López; Meira, Suzana Matsumura; Nikolla, Eranda

doi:10.1016/j.jelechem.2018.12.023

Cited by 19 publications

(23 citation statements)

References 54 publications

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“…As-received Vulcan XC-72R carbon was treated with concentrated HNO 3 via refluxing at 80 °C for 12 h to remove all traces of metal impurities present in the carbon during its seeded growth synthesis. 65 Acid treatment of the carbon was followed by washing it with copious amounts of Millipore water (∼7–8 L) to neutralize the acidity.…”

Section: Methodsmentioning

confidence: 99%

Dynamic Surface Reconstruction Unifies the Electrocatalytic Oxygen Evolution Performance of Nonstoichiometric Mixed Metal Oxides

Samira

Hong

Camayang

et al. 2021

JACS Au

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Compositionally versatile, nonstoichiometric, mixed ionic–electronic conducting metal oxides of the form A n +1 B n O 3 n +1 ( n = 1 → ∞; A = rare-earth-/alkaline-earth-metal cation; B = transition-metal (TM) cation) remain a highly attractive class of electrocatalysts for catalyzing the energy-intensive oxygen evolution reaction (OER). The current design strategies for describing their OER activities are largely derived assuming a static, unchanged view of their surfaces, despite reports of dynamic structural changes to 3d TM-based perovskites during OER. Herein, through variations in the A- and B-site compositions of A n +1 B n O 3 n +1 oxides ( n = 1 (A 2 BO 4 ) or n = ∞ (ABO 3 ); A = La, Sr, Ca; B = Mn, Fe, Co, Ni), we show that, in the absence of electrolyte impurities, surface restructuring is universally the source of high OER activity in these oxides and is dependent on the initial oxide composition. Oxide surface restructuring is induced by irreversible A-site cation dissolution, resulting in in situ formation of a TM oxyhydroxide shell on top of the parent oxide core that serves as the active surface for OER. The rate of surface restructuring is found to depend on (i) composition of A-site cations, with alkaline-earth-metal cations dominating lanthanide cation dissolution, (ii) oxide crystal phase, with n = 1 A 2 BO 4 oxides exhibiting higher rates of A-site dissolution in comparison to n = ∞ ABO 3 perovskites, (iii) lattice strain in the oxide induced by mixed rare-earth- and alkaline-earth-metal cations in the A-site, and (iv) oxide reducibility. Among the in situ generated 3d TM oxyhydroxide structures from A n +1 B n O 3 n +1 oxides, Co-based structures are characterized by superior OER activity and stability, even in comparison to as-synthesized Co-oxyhydroxide, pointing to the generation of high active surface area structures through oxide restructuring. These insights are critical toward the development of revised design criteria to include surface dynamics for effectively describing the OER activity of nonstoichiometric mixed-metal oxides.

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Section: Methodsmentioning

confidence: 99%

Dynamic Surface Reconstruction Unifies the Electrocatalytic Oxygen Evolution Performance of Nonstoichiometric Mixed Metal Oxides

Samira

Hong

Camayang

et al. 2021

JACS Au

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“…These structures identified ligand effects and strain as levers to tune the surface electronic structure and the adsorption behavior of oxygenated intermediates during ORR. Along with Pt-based NCs, efforts for the development of Pt-free catalysts via various binary and ternary combinations of Pd, Au, Ag, with 3d transition metal, − carbon complexes, , metal oxides, − and nitrides are also underway. These studies provide opportunities to tune the electronic and chemical properties of metallic surface and laid the indispensable foundation for further research of Pt-free electrocatalysts.…”

Section: Introductionmentioning

confidence: 99%

Heterogeneous NiO₂-to-Pd Epitaxial Structure Performs Outstanding Oxygen Reduction Reaction Activity

Bhalothia¹,

Chen

Yan³

et al. 2019

J. Phys. Chem. C

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A novel nanocatalyst (NC) with an epitaxial structure of Ni oxide adjacent to a metallic Pd nanocrystal is developed for oxygen reduction reaction (ORR). We demonstrate that, by formation of an ordered local structure both in Ni oxide and Pd regions, the ORR performance of such an NC can be substantially enhanced eightfold as compared to that of NiO x /Pd nanocomposites (control sample) without a local ordering structure. By cross-referencing results of physical and electrochemical inspections, we revealed that the control sample has a complex cluster-in-cluster structure of Ni oxides/NiPd alloy/Pd nanocrystals when Ni ions are deposited on the carbon support (acid-treated carbon nanotubes) at 25 °C and then turns to a highly mismatched Pd to NiO2 epitaxial structure by increasing the deposition temperature to 70 °C. In this event, a strong lattice mismatch and electronegative difference preserve the metallic characteristics of Pd. Such a scenario reduces the energy barrier and kinetics for O2-splitting, therefore boosting the ORR activity. With such a unique structure, the mass activity (MA) is 231.2 mA mg–1 and specific activity is 0.492 mA cm–2 for the NiO2/Pd epitaxial structure. Those properties are 3.5- and 2-times improved as compared to that of commercial Johnson Matthey [J.M.-Pt/C (20 wt % Pt)], which shines light on Ni-based catalysts to be potential candidates against expensive and limited Pt-based catalysts in fuel-cell applications.

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“…For example, oxygen vacancies have been shown to directly affect kinetics of both OER and ORR in these materials, and oxygen hyperstoichiometry influences catalytic activity by providing access to high valent oxidation states of transition metals within the lattice . The high ionic conductivity with respect to O 2− anions has also made RPOs a central focus in solid oxide fuel cells, resulting in the synthesis and structural characterization of a large selection of ternary and quaternary compositions . The comprehensive electrochemical behavior of RPO materials is not typically explored in detail.…”

Section: Introductionmentioning

confidence: 99%

Electrochemically Induced Phase Changes in La₂CuO₄ During Cathodic Electrocatalysis

Whittingham

Smith

2019

ChemElectroChem

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The ability of layered perovskites to accommodate both oxygen vacancies and hyperstoichiometry provides a dimension of tunability that makes them appealing for electrocatalytic applications, but the resulting ionic conductivity enables electron transfer reactions within bulk crystals. We report on the stability of La 2 CuO 4 in the voltage regimes relevant to oxygen reduction, hydrogen evolution and CO 2 reduction. Voltammetric experiments, X-ray photoelectron spectroscopy and X-ray diffraction reveal both surface and bulk electron transfer reactions. Application of anodic voltages results in expansion in the crystal c-axis, while cathodic voltages induce contraction. The ability to catalyze each of the three cathodic reactions is confirmed, but X-ray diffraction and electron microscopy reveal amorphization of the electrocatalyst at voltages below À 0.4 V that affects both the oxygen reduction and CO 2 reduction reactions. While the ionic conductivity of Ruddlesden Popper oxides introduces intriguing properties, it simultaneously introduces the risk of structural instability in catalytically relevant voltages.[a] A.

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Electrochemical oxygen reduction on layered mixed metal oxides: Effect of B-site substitution

Cited by 19 publications

References 54 publications

Dynamic Surface Reconstruction Unifies the Electrocatalytic Oxygen Evolution Performance of Nonstoichiometric Mixed Metal Oxides

Dynamic Surface Reconstruction Unifies the Electrocatalytic Oxygen Evolution Performance of Nonstoichiometric Mixed Metal Oxides

Heterogeneous NiO₂-to-Pd Epitaxial Structure Performs Outstanding Oxygen Reduction Reaction Activity

Electrochemically Induced Phase Changes in La₂CuO₄ During Cathodic Electrocatalysis

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Electrochemical oxygen reduction on layered mixed metal oxides: Effect of B-site substitution

Cited by 19 publications

References 54 publications

Dynamic Surface Reconstruction Unifies the Electrocatalytic Oxygen Evolution Performance of Nonstoichiometric Mixed Metal Oxides

Dynamic Surface Reconstruction Unifies the Electrocatalytic Oxygen Evolution Performance of Nonstoichiometric Mixed Metal Oxides

Heterogeneous NiO2-to-Pd Epitaxial Structure Performs Outstanding Oxygen Reduction Reaction Activity

Electrochemically Induced Phase Changes in La2CuO4 During Cathodic Electrocatalysis

Contact Info

Product

Resources

About

Heterogeneous NiO₂-to-Pd Epitaxial Structure Performs Outstanding Oxygen Reduction Reaction Activity

Electrochemically Induced Phase Changes in La₂CuO₄ During Cathodic Electrocatalysis