Tuning oxidation level, electrical conductance and band gap structure on graphene sheets by a cyclic atomic layer reduction technique

Gu, Siyong; Hsieh, Chien Te; Lin, Tzu Wei; Chang, Jeng‐Kuei; Li, Jianlin; Gandomi, Yasser Ashraf

doi:10.1016/j.carbon.2018.05.024

Cited by 11 publications

(5 citation statements)

References 47 publications

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“…[19] For the CNS and CNT samples, distinct peaks appear at ~26°and ~42°, corresponding to the (002) and (100) plane diffraction of the graphitic structure, respectively. [20] The (002) interplane distances of CNSs and CNTs calculated using Bragg's law are ~0.345 and ~0.338 nm, respectively, which are close to that of ideal ChemSusChem graphite (i.e., 0.335 nm). [21] Figure S2 shows the Raman spectra of the carbon materials.…”

Section: Resultsmentioning

confidence: 60%

“…According to the XRD data, AC exhibits a featureless pattern, indicating low crystallinity [19] . For the CNS and CNT samples, distinct peaks appear at ∼26° and ∼42°, corresponding to the (002) and (100) plane diffraction of the graphitic structure, respectively [20] . The (002) interplane distances of CNSs and CNTs calculated using Bragg's law are ∼0.345 and ∼0.338 nm, respectively, which are close to that of ideal graphite (i.e., 0.335 nm) [21] .…”

Section: Resultsmentioning

confidence: 99%

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Hierarchical Carbon Composites for High‐Energy/Power‐Density and High‐Reliability Supercapacitors with Low Aging Rate

et al. 2022

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A facile method for preparing hierarchical carbon composites that contain activated carbon (AC), carbon nanospheres (CNSs), and carbon nanotubes (CNTs) for use as the electrode material in supercapacitors (SCs) was developed. The CNS/CNT network enabled the formation of three-dimensional conducting pathways within the highly porous AC matrix, effectively reducing the internal resistance of an SC electrode. The specific capacitance, cyclability, voltage window, temperature profile during charging/discharging, leakage current, gas evolution, and self-discharge of the fabricated SCs were systematically investigated and the optimal CNS/CNT ratio was determined. A 2.5 V floating aging test at 70 °C was performed on SCs made with various hierarchical carbon electrodes. Electrochemical impedance spectroscopy, postmortem electron microscopy, Raman spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy analyses were conducted to examine the electrode aging behavior. A hierarchical carbon architecture with an appropriate AC/CNS/CNT constituent ratio could significantly improve charge-discharge performance, increase cell reliability, and decrease the aging-related degradation rate.

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Section: Resultsmentioning

confidence: 60%

Section: Resultsmentioning

confidence: 99%

Hierarchical Carbon Composites for High‐Energy/Power‐Density and High‐Reliability Supercapacitors with Low Aging Rate

et al. 2022

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“…Additionally, an energy band gap ( E g ) was used to evaluate the electronic conductivity of the catalytic electrodes. [ 48 ] As shown in Figure S28, Supporting Information, the CoNiCH (0.663 eV) exhibited a lower E g than the Cu(OH) 2 (0.899 eV), CoCH (1.623 eV), and NiCH (1.352 eV), displaying an essence of optimal electron transfer in the CoNiCH. Therefore, the DFT analysis provided an essential comprehension of the CoNiCH as a high‐performance electrocatalyst for OER.…”

Section: Resultsmentioning

confidence: 99%

3D Printing of Multiscale Ti64‐Based Lattice Electrocatalysts for Robust Oxygen Evolution Reaction

et al. 2022

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Electrically assisted water splitting is an endurable strategy for hydrogen production, but the sluggish kinetics of oxygen evolution reaction (OER) extremely restrict the large-scale production of hydrogen. Developing highly efficient and non-precious catalytic materials is essential to accelerate the sluggish kinetics of OER. However, currently used catalyst supports, such as copper foam, suffer from inferior corrosion resistance and structural stability, resulting in the disabled functionality of 3D conductive networks. To this end, a novel 3D freestanding electrode with corrosion-resistant and robust Ti-6Al-4V titanium alloy lattice as the catalyst support is designed via a 3D printing technology of selective laser melting. After the coating of core-shell Cu(OH)2@CoNi carbonate hydroxides (CoNiCH) on the designed lattice, a unique micro/nano-sized hierarchical porous structure is formed, which endows the electrocatalyst with a promising electrocatalytic activity (a low overpotential of 355 mV at 30 mA cm −2 and Tafel slope of 125.3 mV dec −1 ). Computational results indicate that the CoNiCH exhibits optimized electron transfer and the catalytic activity of the Ni site is higher than that of the Co site in the CoNiCH. Therefore, the integration of robust catalyst supports and highly active materials opens up an avenue for reliable and high-performance OER electrocatalysts.

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“…Functionalization using the chemical rationale may help fine-tune the nature and magnitude of the gap required for various electronic, optical, and catalytic applications. With the advent of atomic layer deposition (ALD) processes , that help engineer nanoscale chemisorption and desorption, tactful disruption of π-electron delocalization by saturating a few sp 2 carbon atoms appears to be more promising.…”

Section: Introductionmentioning

confidence: 99%

Topological Impact of Delocalization on the Stability and Band Gap of Partially Oxidized Graphene

2023

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Strategic perturbations on the graphene framework to inflict a tunable energy band gap promises intelligent electronics that are smaller, faster, flexible, and much more efficient than silicon. Despite different chemical schemes, a clear scalable strategy for micromanaging the band gap is lagging. Since conductivity arises from the delocalized π-electrons, chemical intuition suggests that selective saturation of some sp 2 carbons will allow strategic control over the band gap. However, the logical cognition of different 2D π-delocalization topologies is complex. Their impact on the thermodynamic stability and band gap remains unknown. Using partially oxidized graphene with its facile and reversible epoxides, we show that delocalization overwhelmingly influences the nature of the frontier bands. Organic electronic effects like hyperconjugation, conjugation, aromaticity, etc. can be used effectively to understand the impact of delocalization. By keeping a constant C 4 O stoichiometry, the relative stability of various πdelocalization topologies is directly assessed without resorting to resonance energy concepts. Our results demonstrate that >C�C< and aromatic sextets are the two fundamental blocks resulting in a large band gap in isolation. Extending the delocalization across these units will increase the stability at the expense of the band gap. The band gap is directly related to the extent of bond alternation within the π-framework, with forced single/double bonds causing the large gap. Furthermore, it also establishes the ground rules for the thermodynamic stability associated with the π-delocalization in 2D systems. We anticipate that our findings will provide the heuristic guidance for designing partially saturated graphene with the desired band gap and stability using chemical intuition.

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Tuning oxidation level, electrical conductance and band gap structure on graphene sheets by a cyclic atomic layer reduction technique

Cited by 11 publications

References 47 publications

Hierarchical Carbon Composites for High‐Energy/Power‐Density and High‐Reliability Supercapacitors with Low Aging Rate

Hierarchical Carbon Composites for High‐Energy/Power‐Density and High‐Reliability Supercapacitors with Low Aging Rate

3D Printing of Multiscale Ti64‐Based Lattice Electrocatalysts for Robust Oxygen Evolution Reaction

Topological Impact of Delocalization on the Stability and Band Gap of Partially Oxidized Graphene

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