As-grown Electrodes Research Articles

Laser-patterned boron-doped diamond electrodes with precise control of sp2/sp3 carbon lateral distribution

A thorough study on sp3 to sp2 carbon conversion in undoped and boron-doped diamond (BDD) thin (≈ 500 nm) layers leading to the desired sp2/sp3 carbon ratio and lateral distribution, which utilizes boron atom incorporation and infrared (IR) material laser processing has been performed. Polycrystalline as-grown (AG) or chem-mechanically polished (CMP) undoped diamond/BDD layers were investigated with respect to boron content and laser wavelength (800, 1030 nm). Boron incorporation leads to an increase in IR optical absorption and reduction of required energy fluence (Fth≈ 1 J cm−2) needed for sp3 to sp2 carbon conversion. Raman spectroscopy was performed to identify carbon conversion stages and to tailor the ideal parameters for other IR laser sources and required sp2/sp3 carbon ratio. Electrochemical parameters (ΔEp and IAp/ICp ratio) were obtained from cyclic voltammetry measurements of outer-([Ru(NH3)6]3＋/2＋) and inner-([Fe(CN)6]3−/4−) sphere redox markers. Values of ΔEp and IAp/ICp are mainly influenced after conversion of 10% of sp3 to sp2 carbon. This trend is most pronounced for the [Fe(CN)6]3−/4− redox marker, by decrease or increase of these parameters on AG or CMP BDD electrodes respectively. Electrochemical findings were supported by electrochemical impedance spectroscopy where Rct keeps the same trend as ΔEp values and double layer capacitance profoundly increases between 10 and 25% of surface conversion.

Porous Co3O4/VS4/rGO-SDBS@NF nanoflower as a high performance supercapacitor electrode

Maximizing the performance of supercapacitors requires the design of high-conductivity, stable, and cost-effective electrode materials. The current study presents a novel solution in the form of self-supporting binder-free hierarchical Co3O4/VS4/rGO-SDBS@NF composite electrodes. These electrodes are fabricated using a facile and efficient two-step hydrothermal process. The growth of Co3O4 particles on VS4/rGO-SDBS flower-shaped nanosheet arrays on nickel foam substrates results in a sufficient contraction and expansion space distribution during charge and discharge. The Co3O4/VS4/rGO-SDBS@NF composite shows a specific capacitance of 2620 F g−1 at 1 A g−1, which is significantly compared to the VS4/rGO-SDBS@NF composite at 284 F g−1 in a 6 M KOH solution. Furthermore, the as-grown electrode Co3O4/VS4/rGO-SDBS@NF composite displays excellent cycling stability, with 97.4 % of its initial capacitance retained after 5000 cycles. In summary, the utilization of a simple and accessible manufacturing and synthesis method, absence of binders, in-situ growth technique, achievement of a special morphology with effective electrochemistry, excellent supercapacitor capacity, and high cyclic stability demonstrate significant improvements compared to recent works. These results provide a new perspective for the selection and synthesis of materials and the design and fabrication of electrodes for supercapacitors as energy storage devices.

Chem-mechanical polishing influenced morphology, spectral and electrochemical characteristics of boron doped diamond

In this study complex characterization and comparison of as-grown and chemical-mechanical (CM) polished ultra-thin (≤500 nm) boron doped diamond (BDD) electrodes with various boron content (0.58–4.4 × 1021 cm−3, deposited with B/C 500–8000 ppm) was performed. Atomic force and scanning electron microscopy were used to compare morphological changes and confirm the reduction in roughness down to ≤2 nm. High-quality CM polishing enabled electron backscatter diffraction leading to the evaluation of grain size distribution (mean 0.3 μm) and preferred grain texture, {011}. X-ray photoelectron spectroscopy confirmed an increase in the B content on the surface of CM polished electrodes as a result of exposure of boron atoms incorporated into the bulk for highly doped BDD4000 and BDD8000 electrodes. Additionally, CM polished BDD electrodes are shown to possess uniform distribution of conductivity as proved by scanning electrochemical microscopy. This was reflected in faster heterogenous electron transfer kinetics for inner-sphere redox markers ([Fe(CN)6]3–/4– and dopamine) and higher values of double layer capacitance in comparison with as-grown electrodes. These changes were more pronounced for low doped electrodes. Finally, the improvement in electrochemical characteristics was demonstrated by superior electroanalytical performance of CM polished BDD electrodes for dopamine detection.

Optical and electrical properties of structured multilayer with tunable transparency rate

An experimental study has been carried out on structured multilayer with tunable transparency rate. In this paper, we present the optical and electrical characterization of an oxide | metal | oxide structured electrode manufactured by e-beam deposition and patterned by a lift-off process. The obtained samples are made of grids with different geometrical parameters that lead to varying surface coverage rate on glass. The electrical and optical parameters of SnOx|Ag|SnOx grids are investigated to determine the efficiency, sustainability and limitations of such structures. A linear relationship between the transmittance of the electrodes and the increase of the surface coverage rate is obtained. Coupled to an optimization process, we are able to define a high transparency in a chosen spectral range. Electrical results show a relative stability of the resistivity from 2.9 × 10 − 4 Ω.cm for an as-grown electrode to 5.6 × 10 − 4 Ω.cm for a structured electrode with a surface coverage rate of 59%.

First Principles Calculation Study on Surfaces and Water Interfaces of Boron-Doped Diamond

We investigated water interfaces of boron-doped diamond (BDD) terminated by hydrogen, oxygen, and hydroxyl groups by using density functional theory (DFT)-based molecular dynamics to elucidate the electrochemical behaviors of the as-grown and oxidized BDD electrodes. The reversible outer-sphere electron transfer on the as-grown electrode and the irreversibility on the oxidized electrode, observed in the experiment, are well explained by the BDD band position and subsurface band bending, which depend on the termination and interfacial dipoles. The reductive character of the H-terminated BDD is found, while the interface covered by the carbonyl oxygen is clearly oxidative. The redox character of the hydroxyl termination depends on the lateral hydrogen bonding network among the termination groups and is rather oxidative at the water interface. We also examined the preference of the boron position in the diamond and the stability of boron pairs and clusters. It is suggested that the wide distribution of the s...

Rechargeable Mg-Ion Batteries Based on WSe2 Nanowire Cathodes

The increasing interest in future energy storage technologies has generated the urgent need for alternative rechargeable magnesium ion batteries due to their innate merits in terms of raw abundance, theoretical capacity, and operational safety. Herein, we report an alternative pathway to a new energy storage regime: toward advanced rechargeable magnesium-ion batteries based on WSe2 nanowire-assembled film cathodes. The as-grown electrodes delivered efficient Mg(2+) intercalation/insertion activity, excellent cycling life, enhanced specific capacity, and excellent rate capability. We also evaluated the influence of Mg-intercalation behavior on Mg-ion batteries based on WSe2 film cathodes via the first-principles DFT computations. The results reveal the feasibility of using advanced magnesium-ion batteries based on WSe2 film as energy storage components in next-generation optoelectronic systems.

열처리된 탄소나노튜브 상대전극의 전기화학적 특성 연구

본 연구에서는 염료감응 태양전지의 상대전극으로써 다중벽 탄소나노튜브를 사용하여 전기화학적 특성에 미치는 열처리 효과에 대해 연구하였다. 다중벽 탄소나노튜브는 실리콘 기판위에 철 촉매를 사용하여 열화학 기상증착법으로 합성하였다. 직경이 다른 다중벽 탄소나노튜브를 각각 성장하여 두 개의 샘플을 준비하였고 질소 분위기의 RTA(rapid thermal annealing) system에서 <TEX>$900^{\circ}C$</TEX> 온도로 1분간 열처리 하였다. 다중벽 탄소나노튜브의 구조적, 전기적, 전기화학적 특성은 FE-SEM, Raman spectroscopy, 2-point probe station, electrochemical impedance spectroscopy (EIS)을 이용하여 측정하였다. 라만 스펙트럼 분석에서 열처리 한 다중벽 탄소나노튜브의 I(D)/I(G) ratio는 상당히 감소한 것을 확인하였으며, 다중벽 탄소나 노튜브 표면과 전해질과의 산화 환원 반응 특성에서는 열처리 전보다 열처리 후의 전해질과의 산화 환원 반응 특성이 향상된 것을 알 수 있었다. 표면에서의 반응 저항 또한 열처리 후의 다중벽 탄소나노튜브가 더 낮은 값을 나타내었다. 그 결과, 열처리 후의 다중벽 탄소나노튜브를 상대전극으로 사용하였을 때의 전기화학적 특성이 더 좋은 것을 확인하였다. We have studied the effect of heat treatment of multi-walled carbon nanotubes (MWNTs) as a counter electrode on the electro-chemical properties of dye-snsitized solar cells. MWNTs on the p-type Si substrate were synthesized by thermal chemical vapor deposition (CVD) using Fe catalysts. We prepared the two types of MWNTs samples with the different diameters. The rapid thermal annealing (RTA) treatment for the MWNTs was carried out at the growth temperature (<TEX>$900^{\circ}C$</TEX>) for 1 minute with <TEX>$N_2$</TEX> gas atmosphere. The structural, electrical and electrochemical properties of MWNTs were investigated by field-emission scanning electron microscopy (FE-SEM), Raman spectroscopy, 2-point probe station and electrochemical impedance spectroscopy (EIS). The I(D)/I(G) ratio of heat-treated MWNTs in Raman spectra was considerably decreased. It was also found that the heat-treated MWNTs showed better redox reaction of iodide at the interface between MWNTs surface and electrolyte than that of as-grown MWNTs. The redox resistance value of heat-treated electrodes was measured to be much lower than that of as-grown electrode at the interface. As a result, the counter electrode using the heat-treated MWNTs showed better electrochemical properties.

Electrochemical selectivity for redox systems at oxygen-terminated diamond electrodes

Abstract Oxygen-terminated diamond electrodes were prepared by exposing as-grown hydrogen-terminated diamond thin films to oxygen plasma. The as-grown surfaces, which were highly hydrophobic, become hydrophilic after the oxygen plasma treatment. The apparent surface conductivity was not significantly changed after the oxygen plasma treatment. However, the electrochemical responses to several redox systems became remarkably different. For example, the cyclic voltammetric anodic–cathodic peak separations for the oxygen-terminated diamond electrodes became extremely large compared to those for the as-grown electrodes. This behavior was examined in comparison with as-grown diamond and glassy carbon electrodes.