Ultralow-resistance electrochemical capacitor for integrable line filtering.

Electrochemical capacitors are expected to replace conventional electrolytic capacitors in line filtering for integrated circuits and portable electronics1-8. However, practical implementation of electrochemical capacitors into line-filtering circuits has not yet been achieved owing to the difficulty in synergistic accomplishment of fast responses, high specific capacitance, miniaturization and circuit-compatible integration1,4,5,9-12. Here we propose an electric-field enhancement strategy to promote frequency characteristics and capacitance simultaneously. By downscaling the channel width with femtosecond-laser scribing, a miniaturized narrow-channel in-plane electrochemical capacitor shows drastically reduced ionic resistances within both the electrode material and the electrolyte, leading to an ultralow series resistance of 39 mΩ cm2 at 120 Hz. As a consequence, an ultrahigh areal capacitance of up to 5.2 mF cm-2 is achieved with a phase angle of -80° at 120 Hz, twice as large as one of the highest reported previously4,13,14, and little degradation is observed over 1,000,000 cycles. Scalable integration of this electrochemical capacitor into microcircuitry shows a high integration density of 80 cells cm-2 and on-demand customization of capacitance and voltage. In light of excellent filtering performances and circuit compatibility, this work presents an important step of line-filtering electrochemical capacitors towards practical applications in integrated circuits and flexible electronics.

Unraveling the potential-dependent structure evolution in CuO for electrocatalytic biomass valorization.

Electrocatalytic oxidation of renewable biomass (such as glucose) into high-value-added chemicals provides an effective approach to achieving carbon neutrality. CuO-derived materials are among the most promising electrocatalysts for biomass electrooxidation, but the identification of their active sites under electrochemical conditions remains elusive. Herein, we report a potential-dependent structure evolution over CuO in the glucose oxidation reaction (GOR). Through systematic electrochemical and spectroscopic characterizations, we unveil that CuO undergoes Cu2+/Cu+ and Cu3+/Cu2+ redox processes at increased potentials with successive generation of Cu(OH)2 and CuOOH as the active phases. In addition, these two structures have distinct activities in the GOR, with Cu(OH)2 being favorable for aldehyde oxidation, and CuOOH showed faster kinetics in carbon-carbon cleavage and alcohol/aldehyde oxidation. This work deepens our understanding of the dynamic reconstruction of Cu-based catalysts under electrochemical conditions and may guide rational material design for biomass valorization.

Electrochemical Construction of Edge-Contacted Metal-Semiconductor Junctions with Low Contact Barrier.

2D semiconductors, such as MoS2 have emerged as promising ultrathin channel materials for the further scaling of field-effect transistors (FETs). However, the contact barrier at the metal-2D semiconductor junctions still significantly limits the device's performance. By extending the application of electrochemical deposition in 2D electronics, a distinct approach is developed for constructing metal-2D semiconductor junctions in an edge-contacted configuration through the edge-guided electrodeposition of varied metals. Both high-resolution microscopic imaging and electrical transport measurements confirm the successful creation of high-quality Pd-2D MoS2 junctions in desired geometry by combining electrodeposition with lithographic patterning. FETs are fabricated on the obtained Pd-2D MoS2 junctions and it is confirmed that these junctions exhibit a reduced contact barrier of ≈20 meV and extremely low contact resistance of 290 Ω µm and thus increase the averaged mobility of MoS2 FETs to ≈108 cm2 V -1 s-1 . This approach paves a new way for the construction of metal-semiconductor junctions and also demonstrates the great potential of the electrochemical deposition technique in 2D electronics.

Selective Electrooxidation of Biomass-Derived Alcohols to Aldehydes in a Neutral Medium: Promoted Water Dissociation over a Nickel-Oxide-Supported Ruthenium Single-Atom Catalyst.

The biomass-derived alcohol oxidation reaction (BDAOR) holds great promise for sustainable production of chemicals. However, selective electrooxidation of alcohols to value-added aldehyde compounds is still challenging. Herein, we report the electrocatalytic BDAORs to selectively produce aldehydes using single-atom ruthenium on nickel oxide (Ru1 -NiO) as a catalyst in the neutral medium. For electrooxidation of 5-hydroxymethylfurfural (HMF), Ru1 -NiO exhibits a low potential of 1.283 V at 10 mA cm-2 , and an optimal 2,5-diformylfuran (DFF) selectivity of 90 %. Experimental studies reveal that the neutral electrolyte plays a critical role in achieving a high aldehyde selectivity, and the single-atom Ru boosts HMF oxidation in the neutral medium by promoting water dissociation to afford OH*. Furthermore, Ru1 -NiO can be extended to selective electrooxidation of a series of biomass-derived alcohols to corresponding aldehydes, which are conventionally difficult to obtain in the alkaline medium.

[Investigation of phase morphology of PS/PMMA blend thin film by surface enhanced raman scattering].

Polystyrene/poly (methyl methacrylate) (PS/PMMA) was studied after the thin films were prepared on glass substrate by spin-coating from THF. Raman spectroscopy combined with microscopy was used to obtain information on the morphology and structure of the thin films. From the relative intensities of the peaks around 1 604 and 1 585 cm(-1) due to stretching of benzene rings, and 1 728 cm(-1) due to stretching of C=O for PS and PMMA respectively, the authors could define the composition of the domains in the sea-island-like phase-separated structure in the microscopic image. Furthermore, the structure evolution was followed by Raman spectroscopy during the in-situ annealing of PS/PMMA (30/70) blend thin films at 210 degrees C. And the effect of SERS on the PS thin films was also discussed.

Copper hydroxide nanoneedle and nanotube arrays fabricated by anodization of copper.

Cu(OH)2 nanoneedle and nanotube arrays were electrochemically synthesized by anodization of a copper foil in an aqueous solution of KOH. The nanoneedles and nanotubes were constructed from nanosheets of Cu(OH)2. Controlling the electrochemical conditions can qualitatively modulate the lengths, amounts, and shapes of Cu(OH)2 nanostructures. The composition of as-prepared Cu(OH)2 nanostructures has been confirmed by X-ray diffraction and select-area electron diffraction. The influences of the KOH concentration of the aqueous electrolyte, the reaction temperature, and current density on the morphology of Cu(OH)2 nanostructures were investigated, and the formation mechanism of the nanostructures is discussed. Furthermore, Cu(OH)2 nanoneedles can be successfully transformed to CuO nanoneedles with little morphology change by heating. This work developed a simple, clean, and effective route for fabrication of large area Cu(OH)2 or CuO nanostructured films.