Abnormal volatile and normal stable bipolar resistive switching characteristics of hybrid nanocomposites: Morphology–defects–property ‘Relationship

Doan, Uyen Tu Thi; Phạm, Anh Tuấn; Phan, Thắng Bách; Park, Sungkyun; Luu, Anh Tuyen; Nguyen, Hung Minh; Lo, Thai Son; Tap, Tran Duy; Ohtani, Masayasu; Pham, Ngoc Kim

doi:10.1016/j.jallcom.2020.157602

Cited by 12 publications

(5 citation statements)

References 56 publications

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“…Fortunately, the positron lifetime detected from our PAL measurement is very sensitive to any small changes in the electron density and free volume of these small-size tunnels. For example, if the tunnel is filled by cations, the electron density around the tunnels increases, leading to a decrease of free volume and positron lifetime as well . Hence, we carried out the ab initio calculations by placing H + or K + with different relative ratios to Mn + in the [1 × 1] tunnels of α-MnO 2 .…”

Section: Resultssupporting

confidence: 62%

“…For example, if the tunnel is filled by cations, the electron density around the tunnels increases, leading to a decrease of free volume and positron lifetime as well. 36 Hence, we carried out the ab initio calculations by placing H + or K + with different relative ratios to Mn + in the [1 × 1] tunnels of α-MnO 2 . These cations exist in the MnO 2 synthesis, and they can be theoretically incorporated within the resultant α-MnO 2 .…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Crystallization Pathways and Evolution of Morphologies and Structural Defects of α-MnO₂ under Air Annealing

et al. 2022

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Manganese dioxide nanomaterials have wide applications in many areas from catalysis and Li−ion batteries to gas sensing. Understanding the crystallization pathways, morphologies, and formation of defects in their structure is particularly important but still a challenging issue. Herein, we employed an arsenal of X-ray diffraction (XRD), scanning electron microscopy (SEM), neutron diffraction, positron annihilation spectroscopies, and ab initio calculations to investigate the evolution of the morphology and structure of α-MnO 2 nanomaterials prepared via reduction of KMnO 4 solution with C 2 H 5 OH prior to being annealed in air at 200−600 °C. We explored a novel evolution that α-MnO 2 nucleation can be formed even at room temperature and gradually developed to α-MnO 2 nanorods at above 500 °C. We also found the existence of H + or K + ions in the [1 × 1] tunnels of α-MnO 2 and observed the simultaneous presence of Mn and O vacancies in α-MnO 2 crystals at low temperatures. Increasing the temperature removed these O vacancies, leaving only the Mn vacancies in the samples.

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Section: Resultssupporting

confidence: 62%

Section: ■ Results and Discussionmentioning

confidence: 99%

Crystallization Pathways and Evolution of Morphologies and Structural Defects of α-MnO₂ under Air Annealing

et al. 2022

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“…Looking closer into the CoS/MoS 2.46 composites, it was found that the values of τ 2 decreased while their intensities I 2 increased as the Co/Mo ratio increased (Figure c). This result can be explained by the additional contribution of the CoS/MoS 2.46 grain interface . Moreover, based on a relationship between the positron lifetime and the number of vacancies in a vacancy cluster, we found that the size of the vacancy clusters decreased from 8 (V 8 ) to 6 (V 6 ) atoms when the CoS/MoS 2.46 molar ratio increased from 0.43/1 to 7.77/1 (Figure c).…”

Section: Resultsmentioning

confidence: 69%

“…The DB and EMD measurements were performed using a HPGe detector (Ortec, USA) with an energy resolution of 1.2 keV at the 511 keV energy peak of positron annihilation. Details on the positron experiments can be found in our previous works. ,,− …”

Section: Methodsmentioning

confidence: 99%

Exploring the Sub-nanoscale Structure of Cobalt Molybdenum Sulfide and the Role of a Cobalt Promoter in Catalytic Hydrogen Evolution

Nguyen¹,

Luu

Nguyen³

et al. 2023

ACS Appl. Mater. Interfaces

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Cobalt-promoted molybdenum sulfide (CoMoS) is known as a promising catalyst for H2 evolution reaction and hydrogen desulfurization reaction. This material exhibits superior catalytic activity as compared to its pristine molybdenum sulfide counterpart. However, revealing the actual structure of cobalt-promoted molybdenum sulfide as well as the plausible contribution of a cobalt promoter is still challenging, especially when the material has an amorphous nature. Herein, we report, for the first time, on the use of positron annihilation spectroscopy (PAS), being a nondestructive nuclear radiation-based method, to visualize the position of a Co promoter within the structure of MoS at the atomic scale, which is inaccessible by conventional characterization tools. It is found that at low concentrations, a Co atom occupies preferably the Mo-vacancies, thus generating the ternary phase CoMoS whose structure is composed of a Co-S-Mo building block. Increasing the Co concentration, e.g., a Co/Mo molar ratio of higher than 1.12/1, leads to the occupation of both Mo-vacancies and S-vacancies by Co. In this case, secondary phases such as MoS and CoS are also produced together with the CoMoS one. Combining the PAS and electrochemical analyses, we highlight the important contribution of a Co promoter to enhancing the catalytic H2 evolution activity. Having more Co promoter in the Mo-vacancies promotes the H2 evolution rate, whereas having Co in the S-vacancies causes a drop in H2 evolution ability. Furthermore, the occupation of Co to the S-vacancies leads also to the destabilization of the CoMoS catalyst, resulting in a rapid degradation of catalytic activity.

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“…The one at 529 eV can be contributed by M−O (M = Nd, Fe, Mn) bonds [ 20 , [30] , [31] , [32] ]. The peak detected at 531.3 eV could be the result of the V O occurrence inside NdMn x Fe 1-x O 3 particles [ 29 , [33] , [34] , [35] , [36] ]. In the spectra of O 1s, the estimation of the area ratio between V O and M−O showed the result of 1.98 and 1.66 for NdMn x Fe 1-x O 3 NPs with x = 0.1 and x = 0.3, respectively.…”

Section: Resultsmentioning

confidence: 99%

Tailored synthesis of NdMnxFe1-xO3 perovskite nanoparticles with oxygen-vacancy defects for lithium-ion battery anodes

Nguyen,

Mittova

et al. 2023

Heliyon

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Abnormal volatile and normal stable bipolar resistive switching characteristics of hybrid nanocomposites: Morphology–defects–property ‘Relationship

Cited by 12 publications

References 56 publications

Crystallization Pathways and Evolution of Morphologies and Structural Defects of α-MnO₂ under Air Annealing

Crystallization Pathways and Evolution of Morphologies and Structural Defects of α-MnO₂ under Air Annealing

Exploring the Sub-nanoscale Structure of Cobalt Molybdenum Sulfide and the Role of a Cobalt Promoter in Catalytic Hydrogen Evolution

Tailored synthesis of NdMnxFe1-xO3 perovskite nanoparticles with oxygen-vacancy defects for lithium-ion battery anodes

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Abnormal volatile and normal stable bipolar resistive switching characteristics of hybrid nanocomposites: Morphology–defects–property ‘Relationship

Cited by 12 publications

References 56 publications

Crystallization Pathways and Evolution of Morphologies and Structural Defects of α-MnO2 under Air Annealing

Crystallization Pathways and Evolution of Morphologies and Structural Defects of α-MnO2 under Air Annealing

Exploring the Sub-nanoscale Structure of Cobalt Molybdenum Sulfide and the Role of a Cobalt Promoter in Catalytic Hydrogen Evolution

Tailored synthesis of NdMnxFe1-xO3 perovskite nanoparticles with oxygen-vacancy defects for lithium-ion battery anodes

Contact Info

Product

Resources

About

Crystallization Pathways and Evolution of Morphologies and Structural Defects of α-MnO₂ under Air Annealing

Crystallization Pathways and Evolution of Morphologies and Structural Defects of α-MnO₂ under Air Annealing