Comparative study of α-, β-, γ- and δ-MnO2 on toluene oxidation: Oxygen vacancies and reaction intermediates

Su, Ziang; Xu, Zhenghao; Yang, Wenhao; Peng, Yue; Li, Junhua

doi:10.1016/j.apcatb.2019.118150

Cited by 487 publications

(232 citation statements)

References 58 publications

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“…IrO 2 /δ-MnO 2 had the similar structure with IrO 2 / γ-MnO 2 . What is more, α-MnO 2 generally has a higher BET surface areas and pore volume than other phases, [13,31] which is beneficial for the diffusion of the produced gas from the catalyst and prevented the produced oxygen to hinder the continuous reaction, and finally enhanced the electrochemical performance. The mass activity for each sample was also determined.…”

Section: Resultsmentioning

confidence: 99%

Influence of the MnO₂ Phase on Oxygen Evolution Reaction Performance for Low‐Loading Iridium Electrocatalysts

Wang

Gao

et al. 2021

ChemElectroChem

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Developing high-performance, low-loading, Ir-based electrocatalysts for the oxygen evolution reaction (OER) in acidic media is still a great challenge. Herein, we fabricated an iridium manganese catalyst with only 5 % iridium. The influence of the manganese dioxide phase states (α-, β-, γand δ-MnO 2) on the OER performance of IrO 2 /MnO 2 catalysts was investigated. α-MnO 2 , as the substrate, can generate smaller iridium particles and more high-valence-state iridium to promote OER performance. Therefore, the 5 % IrO 2 /α-MnO 2 electrocatalyst exhibits excellent electrocatalytic OER performance with a high mass activity of 216.67 A/g Ir and 655.33 A/g Ir at 1.53 V in acidic and alkaline media, respectively, significantly outperforming commercial IrO 2 .

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Section: Resultsmentioning

confidence: 99%

Influence of the MnO₂ Phase on Oxygen Evolution Reaction Performance for Low‐Loading Iridium Electrocatalysts

Wang

Gao

et al. 2021

ChemElectroChem

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“…It was found that the ratios of (Mn 2+ +Mn 3+ )/Mn total varied with the change of crystal phase of manganese oxides. The highest (Mn 2+ +Mn 3+ )/Mn total ratio of 0.58 was achieved on the surface of α‐MnO 2 , implying more surface oxygen vacancies existed in α‐MnO 2 , which was beneficial for the catalytic toluene oxidation.…”

Section: Resultsmentioning

confidence: 99%

“…It was believed that the tunnel structure and active lattice oxygen species were the main factors that determined the excellent performance of δ‐MnO 2 . Li et al . verified the important promoting effect of oxygen vacancies for the remarkable low‐temperature catalytic activity in toluene oxidation through a comparative study of δ‐ and β‐MnO 2 .…”

Section: Introductionmentioning

confidence: 96%

Transient in‐situ DRIFTS Investigation of Catalytic Oxidation of Toluene over α‐, γ‐ and β‐MnO₂

Fan

Ren

et al. 2020

ChemCatChem

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Manganese oxides with different crystal phases (i. e. α‐MnO2, γ‐MnO2 and β‐MnO2) were synthesized for catalytic oxidation of toluene. The catalytic activity was strongly influenced by the crystal phases of MnO2. α‐MnO2 exhibited the highest catalytic activity with a 50 % toluene conversion (T50) at 229 °C and a 90 % toluene conversion (T90) at 238 °C, followed by γ‐MnO2 (T90=252 °C) and β‐MnO2 (T90=278 °C). The remarkable catalytic activity of α‐MnO2 was attributed to its superior redox property and lattice oxygen mobility. Different intermediates were detected on the surfaces of α‐, γ‐ and β‐MnO2 by in situ diffuse reflectance infrared Fourier transform spectroscopy (in‐situ DRIFTS). Benzoate species were found to be the key intermediates on α‐MnO2 at 240 °C, while benzoyl oxide species and benzoate were the major intermediates on γ‐MnO2 at 260 °C. The surface of β‐MnO2 was mainly covered by carbonate and benzoate species after the adsorption of toluene at 280 °C.

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“…[ 15 ] Its functional activity depends on the types of elements and distances between atoms on the surface, which, in case of tunnel‐structured MnO 2 nanowires ( Figure ), can be tuned with the angstrom‐level precision if open tunnel spaces appear on the lateral facet with tunnel‐driven insertion/adsorption/transport of associated molecules/radicals/ions. [ 16,17 ] Therefore, it is critical to understand the atomic arrangement patterns on the surface of MnO 2 particles before they can be accurately reconstructed for computer‐assisted modeling and/or efficiently engineered for physicochemical property enhancement.…”

Section: Introductionmentioning

confidence: 99%

Revealing the Atomic Structures of Exposed Lateral Surfaces for Polymorphic Manganese Dioxide Nanowires

et al. 2020

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Polymorphic 1D MnO2 nanostructures are widely applied in fields such as catalysis, sensing, and energy storage with the functionality mainly determined by the atomic patterns of their laterally exposed facets, which largely remain unclear so far. Herein, by high‐resolution transmission electron microscopy (HRTEM) imaging directly along their axial directions, the atomic structures of the outmost lateral facets of polymorphic MnO2 nanowires are disclosed. To generalize the findings, four most commonly seen phases with characteristic tunnel structures are targeted, i.e., β‐, γ‐, α‐, and todorokite(t)‐MnO2, which are synthesized conventionally using a hydrothermal method reported in the literature. Axially imaging these MnO2 nanowires via HRTEM, the {hkl} facets covering the lateral surfaces are accurately indexed, the atomic pattern of each {hkl} facet is revealed, and it is further coupled with the outmost tunnel configuration that can significantly affect the physicochemical property of MnO2 materials via tunnel‐driven mass adsorption/transport. This work provides a reliable reference for atomic modeling of MnO2 to benefit the pursuit of its structure–property relationship; in addition, it can benefit surface engineering strategies to better rationalize the facet growth control with optimized functionality.

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Comparative study of α-, β-, γ- and δ-MnO2 on toluene oxidation: Oxygen vacancies and reaction intermediates

Cited by 487 publications

References 58 publications

Influence of the MnO₂ Phase on Oxygen Evolution Reaction Performance for Low‐Loading Iridium Electrocatalysts

Influence of the MnO₂ Phase on Oxygen Evolution Reaction Performance for Low‐Loading Iridium Electrocatalysts

Transient in‐situ DRIFTS Investigation of Catalytic Oxidation of Toluene over α‐, γ‐ and β‐MnO₂

Revealing the Atomic Structures of Exposed Lateral Surfaces for Polymorphic Manganese Dioxide Nanowires

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Comparative study of α-, β-, γ- and δ-MnO2 on toluene oxidation: Oxygen vacancies and reaction intermediates

Cited by 487 publications

References 58 publications

Influence of the MnO2 Phase on Oxygen Evolution Reaction Performance for Low‐Loading Iridium Electrocatalysts

Influence of the MnO2 Phase on Oxygen Evolution Reaction Performance for Low‐Loading Iridium Electrocatalysts

Transient in‐situ DRIFTS Investigation of Catalytic Oxidation of Toluene over α‐, γ‐ and β‐MnO2

Revealing the Atomic Structures of Exposed Lateral Surfaces for Polymorphic Manganese Dioxide Nanowires

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Resources

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Influence of the MnO₂ Phase on Oxygen Evolution Reaction Performance for Low‐Loading Iridium Electrocatalysts

Influence of the MnO₂ Phase on Oxygen Evolution Reaction Performance for Low‐Loading Iridium Electrocatalysts

Transient in‐situ DRIFTS Investigation of Catalytic Oxidation of Toluene over α‐, γ‐ and β‐MnO₂