Exploring the artificially induced nonstoichiometric effect of Li<sub>2</sub>RuO<sub>3</sub> as a reactive promoter on electrocatalytic behavior

Jang, Haeseong; Jin, Wooyoung; Nam, Gyutae; Yoo, Youngshin; Jeon, Jeong Suk; Park, Joohyuk; Kim, Min; Cho, Jaephil

doi:10.1039/d0ee00859a

Cited by 30 publications

(30 citation statements)

References 43 publications

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“…On the other hand, no significant variations were observed in M, indicating that the degree of structural distortion of a/c‐RuO 2 during the OER was negligibly low. The variations in the intensities of R and B can be attributed to the reversible Ru redox reaction arising from the insertion or removal of oxygen species [12a] . These results suggest that a/c‐RuO 2 is flexible with respect to structural distortions and the redox reaction of Ru and that this property can effectively inhibit the dissolution and over‐oxidation of Ru during the OER, resulting in high catalytic stability.…”

Section: Resultsmentioning

confidence: 92%

Sodium‐Decorated Amorphous/Crystalline RuO₂ with Rich Oxygen Vacancies: A Robust pH‐Universal Oxygen Evolution Electrocatalyst

et al. 2021

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The oxygen evolution reaction (OER) is a key reaction for many electrochemical devices. To date, many OER electrocatalysts function well in alkaline media, but exhibit poor performances in neutral and acidic media, especially the acidic stability. Herein, sodium‐decorated amorphous/crystalline RuO2 with rich oxygen vacancies (a/c‐RuO2) was developed as a pH‐universal OER electrocatalyst. The a/c‐RuO2 shows remarkable resistance to acid corrosion and oxidation during OER, which leads to an extremely high catalytic stability, as confirmed by a negligible overpotential increase after continuously catalyzing OER for 60 h at pH=1. Besides, a/c‐RuO2 also exhibits superior OER activities to commercial RuO2 and most reported OER catalysts under all pH conditions. Theoretical calculations indicated that the introduction of Na dopant and oxygen vacancy in RuO2 weakens the adsorption strength of the OER intermediates by engineering the d‐band center, thereby lowering the energy barrier for OER.

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Section: Resultsmentioning

confidence: 92%

Sodium‐Decorated Amorphous/Crystalline RuO₂ with Rich Oxygen Vacancies: A Robust pH‐Universal Oxygen Evolution Electrocatalyst

et al. 2021

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“…In stark contrast, severe disordering of the original structure of Li 2 RuO 3 occurred during prolonged cycling (Figure 2d), consistent with previous reports. [25] The STEM-HAADF image reveals a considerable number of Ru ions in the octahedral sites of the Li layer, as highlighted by the red arrows in the signal profiles. The SAED pattern reveals the emergence of additional spots, indicating the local formation of new phases.…”

Section: High Structural Stability Of LI 12 Mg 02 Ru 06 O 2 With Suppressed Structural Disordering and Restricted Cation Migrationmentioning

confidence: 98%

Selective Anionic Redox and Suppressed Structural Disordering Enabling High‐Energy and Long‐Life Li‐Rich Layered‐Oxide Cathode

Ahn

Kang

Cho

et al. 2021

Advanced Energy Materials

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phase transitions to spinel-like or rocksaltlike disordered structures caused by the irreversible migration of transition-metal (TM) ions into the Li layers during longterm battery operation. The structural evolution continuously shuffles the chemical potential of Li ions and impedes Li-ion hopping, resulting in gradual voltage decay and poor cycle life.A predominant theory of the origin of TM migration emphasizes the ability of the material to stabilize oxygen holes and inhibit oxygen release, which increases with the covalency of the TMO bond. When using a 4d TM instead of a 3d TM, the enhanced covalency between the TM and O enables the reversible anionic redox. [2,[7][8][9] For example, Li 2 RuO 3 reversibly exhibits high capacity of the cationic and anionic redox couples and releases a negligible amount of O 2 gas. [10] Nevertheless, significant voltage decay is observed for Li 2 RuO 3 , which stems from the accumulation of Ru cations in the Li layers, [11,12] indicating that the ability to hold oxygen in its lattice does not necessarily inhibit TM migration. Recently, Chueh and co-workers proposed a thermodynamic explanation for the coupling between the anionic redox and TM migration, which is that the oxidized oxygen anions favor less coordination with TM cations; this is achievable via structural Despite their high energy densities, Li-rich layered oxides suffer from low capacity retention and continuous voltage decay caused by the migration of transition-metal cations into theLi layers. The cation migration stabilizes oxidized oxygen anions through the decoordination of oxygen from the metal once the anions participate in the redox reaction. Structural disordering is thus considered inevitable in most Li-rich layered oxides. However, herein, a Mg-substituted Li-rich layered oxide, Li 1.2 Mg 0.2 Ru 0.6 O 2 , with high structural and electrochemical stability is presented. Although using both cationic and anionic redox reactions, Ru migration in Li 1.2−x Mg 0.2 Ru 0.6 O 2 is thermodynamically unfavored as a result of selectively oxidized O ions, suppressed structural disordering, and the formation of short (1.75 Å) Ru=O bonds enabled within the layered framework, which effectively decoordinate the oxidized O ions. The unprecedentedly high structural stability of Li 1.2 Mg 0.2 Ru 0.6 O 2 leads to not only a high energy density of 964 Wh kg −1 but also outstanding rate capability and cycle performance. These findings demonstrate the potential of this practical strategy for the stabilization of Li-rich layered oxides even with prolonged cycling.

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“…The metal dopants cover almost all the metal elements, such as alkali metals, [45] alkaline-earth metals, [46,47] transition metals, [48][49][50][51][52] and noble metals, [53,54] while nonmetal dopants include boron, [55] carbon, [56] pnictogens, [57][58][59][60][61] chalcogens, [62] and halogens. [63,64] Depending on the doped materials, metal doping can be realized through solid-state, [50,65,66] co-precipitation, [67,68] hydro/solvothermal, [48,69] electrodeposition, [70,71] and sol-gel [72] methods. For example, by mixing Li 2 CO 3 , Na 2 CO 3 , and Mg(OH) 2 with MnO 2 precursor for high-temperature solid-phase sintering, Liu et al successfully synthesized Na/Mg co-doped LiMn 2 O 4 electrode material.…”

Section: Heteroatom Dopingmentioning

confidence: 99%

mentioning

confidence: 99%

Multidimensional Nonstoichiometric Electrode Materials for Electrochemical Energy Conversion and Storage

Liu

Jinhan

et al. 2021

Advanced Energy Materials

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number of compounds deviate from definite composite. For example, Wüstite type FeO was found to occur in varied Fe/O ratios with Fe vacancies over a narrow limit in nature, [2,3] while stoichiometric form of FeO was obtained only under high pressure. [4] With the discovery of more chemical compounds with compositions deviating from their stoichiometric counterparts, a new family of materials, which is now recognized as nonstoichiometric material (NMs) or berthollides in honor of Berthollet, has drawn increasing research interest in materials chemistry.Structurally, nonstoichiometry can be induced from defect engineering, element doping, or substitution. [5,6] Although the resulting composition and elemental ratio are allowed to vary in a wide range, the phase and space group of nonstoichiometric compounds are generally identical to the parent stoichiometric counterparts. The type of nonstoichiometry is multidimensional, ranging from point defects (vacancy, substitution or interstitial), local defect (Frenkel pair or cation mixing), linear substitution (typically in layered compounds) to surface defect, bulk composition variation, and spatially dependent concentration gradient. [7] Thermodynamically, deviation from stoichiometry is always accompanied by the change in the system Gibbs free energy and/or redox of characteristic ions, which would endow the materials with multiple physicochemical features in modulating electronic structures, chemical valence, charge storage, carrier diffusion, and stability. [8][9][10][11] Since nonstoichiometry widely exists in many types of compounds including oxides, nitrides, carbides, sulfides, and alloys, it is desirable to develop deep understanding over the fundamental origin, related features, and their contributions to practical functionality.In the context of developing renewable energy conversion and storage, functional electrode materials are crucial to determine the electrochemical performance, stability, and cost. [11,12] In electrocatalysis, exploring highly active electrode materials for hydrogen evolution reaction (HER), oxygen reduction reaction (ORR), and oxygen evolution reaction (OER) is a key to boost the performance of water splitting, fuel cell, and metalair battery. [13][14][15] Meanwhile, electrochemical nitrogen reduction reaction (NRR) under ambient conditions provides a promising pathway of ammonia synthesis from N 2 and H 2 O alternative to the traditional contaminative Haber-Bosch process. [16] For batteries, the cell voltage, reversible capacity, and cycling Nonstoichiometry plays an important role in determining physicochemical properties such as conductivity, activity, and stability due to the compositioninduced change in phase, local atomic environment, and electronic structure. A variety of materials with nonstoichiometry have emerged in electrochemical energy conversion and storage, which necessitates a solid understanding of their formation mechanism and structure-function relationship. This review presents a summary of the progress made in this ...

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Exploring the artificially induced nonstoichiometric effect of Li₂RuO₃ as a reactive promoter on electrocatalytic behavior

Abstract: We have explored the independent effect of mixed valence and oxygen defects on the catalytic origin by artificially engineering the stoichiometry of Li2RuO3.

Cited by 30 publications

References 43 publications

Sodium‐Decorated Amorphous/Crystalline RuO₂ with Rich Oxygen Vacancies: A Robust pH‐Universal Oxygen Evolution Electrocatalyst

Sodium‐Decorated Amorphous/Crystalline RuO₂ with Rich Oxygen Vacancies: A Robust pH‐Universal Oxygen Evolution Electrocatalyst

Selective Anionic Redox and Suppressed Structural Disordering Enabling High‐Energy and Long‐Life Li‐Rich Layered‐Oxide Cathode

Multidimensional Nonstoichiometric Electrode Materials for Electrochemical Energy Conversion and Storage

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Exploring the artificially induced nonstoichiometric effect of Li2RuO3 as a reactive promoter on electrocatalytic behavior

Abstract: We have explored the independent effect of mixed valence and oxygen defects on the catalytic origin by artificially engineering the stoichiometry of Li2RuO3.

Cited by 30 publications

References 43 publications

Sodium‐Decorated Amorphous/Crystalline RuO2 with Rich Oxygen Vacancies: A Robust pH‐Universal Oxygen Evolution Electrocatalyst

Sodium‐Decorated Amorphous/Crystalline RuO2 with Rich Oxygen Vacancies: A Robust pH‐Universal Oxygen Evolution Electrocatalyst

Selective Anionic Redox and Suppressed Structural Disordering Enabling High‐Energy and Long‐Life Li‐Rich Layered‐Oxide Cathode

Multidimensional Nonstoichiometric Electrode Materials for Electrochemical Energy Conversion and Storage

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Exploring the artificially induced nonstoichiometric effect of Li₂RuO₃ as a reactive promoter on electrocatalytic behavior

Sodium‐Decorated Amorphous/Crystalline RuO₂ with Rich Oxygen Vacancies: A Robust pH‐Universal Oxygen Evolution Electrocatalyst

Sodium‐Decorated Amorphous/Crystalline RuO₂ with Rich Oxygen Vacancies: A Robust pH‐Universal Oxygen Evolution Electrocatalyst