In-Depth Analysis of Porous Si Electrodes for Supercapacitors

Bratosin, Irina-Nicoleta; Varasteanu, Pericle; Romanițan, Cosmin; Bujor, Alexandru; Tutunaru, Oana; Radoi, Antonio; Kusko, Mihaela

doi:10.1021/acs.jpcc.0c11035

Cited by 5 publications

(1 citation statement)

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“…from 28.6 to 55.7%) obeying the following exponential law: PðÞ ¼ À29:96 expðÀ=3:92Þ þ 55:09: S4 presents a strong positive gradient from 27.8 to 76.5% that is fitted by the function PðÞ ¼ À75:97 expðÀ=2:75Þ þ 69:5: Previously, we investigated the X-ray scattering in RSMs and we found a decrease of the X-ray scattering amplitude with increasing anodization current (e.g. from 0.819 to 0.605) which can be translated into an increase of the mean porosity from 18.1 to 39.5%, in good agreement with the findings of other authors (Lascaud et al, 2017;Servidori et al, 2001;Rahmouni et al, 2018;Bratosin et al, 2021).…”

Section: Research Paperssupporting

confidence: 91%

X-ray scattering profiles: revealing the porosity gradient in porous silicon

et al. 2021

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Porous silicon layers with different porosities were prepared by adjusting the anodization current density of the electrochemical etching process, starting from highly doped p-type crystalline silicon wafers. The microstructural parameters of the porous layers were assessed by high-resolution X-ray diffraction, total external reflection, scanning electron microscopy and nitrogen adsorption–desorption analysis. Furthermore, both the surface porosity and the mean porosity for the entire volume of the samples were estimated by employing total external reflection measurements and X-ray reciprocal-space mapping, respectively. The results clearly indicate that the surface porosity is different from the mean porosity, and the presence of a depth porosity gradient is suggested. To evaluate the porosity gradient in a nondestructive way, a new laboratory method using the grazing-incidence X-ray diffraction technique is reported. It is based on the analysis of the X-ray scattering profiles of the porous layers to obtain the static Debye–Waller factors. In this way, a description of the porosity gradient in a quantitative framework becomes possible, and, as a result, it was shown that the porosity increases exponentially with the X-ray penetration depth. Moreover, a strong dependence between the porosity gradient and the anodization current was demonstrated. Thus, in the case of the lowest anodization current (e.g. 50 mA cm−2) a variation of only 15% of the porosity from the surface to the interface is found, but when applying a high anodization current of 110 mA cm−2 the porosity close to the bulk interface is almost three times higher than at the surface.

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Section: Research Paperssupporting

confidence: 91%

X-ray scattering profiles: revealing the porosity gradient in porous silicon

et al. 2021

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Fabrication of Nitrogen/Boron Highly Co‐Doped Graphene Electrode for Enhanced Electrochemical Performance

Wang

Han

et al. 2022

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A facile hydrothermal and freeze-drying approach was employed to prepare N, B co-doped graphene gel (N/BGR). Positively charged [BMIm][BF 4 ] ionic liquid as N/B source and negatively charged graphene oxide (GO) as graphene precursor are capable of combining and self-assembly by electrostatic force. The high doped concentrations of N and B elements are 8.16 at% and 6.31 at% (total 14.47 at%). The N/BGR was fabricated as electrode material in the three-electrode system. The as-prepared N/BGR-2 electrode could achieve a specific capacitance of 133.6 F/g at 0.5 A/g. The N/BGR electrode presented enhanced capacitance performance. Compared with the specific capacitance of pure GR at the same current density of 0.5 A/g, the specific capacitances of N/BGR-2 and N/BGR-1 have increased by 68.5 % and 49.4 %. The enhanced capacitance of N and B co-doped graphene could be attributed to the promotion of rapid electron migration and charge transfer and production of redox active sites that provide pseudocapacitance. In addition, N/BGR-2 electrode exhibits good cycling durability with the capacity retention of 93.2 %% after 1500 cycles at a high current density of 10 A/g. Those provide a high co-doped content fabrication strategy for high-performance supercapacitors carbon-based electrode materials.

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