Chen-Chi M. Ma

The electrochemical activation is a common technique enhancing the capacitive performances of carbons in high-voltage supercapacitors while volume expansion during the activation process often makes the active materials detachment, dropping the capacitance. In this work, the KOH-neutralized polyurethane-crosslinked-polyacrylic acid (PUPAH_10-xK_x) polymers are proposed to replace the polyvinylidene fluoride (PVDF) as a binder for expanded mesocarbon microbead (EMCMB) electrodes to buffer the volume expansion. The effects of binder rheology, morphology and neutralization degree on the capacitive performance of EMCMB are investigated. Introducing PUPAH₆K₄ with moderate viscoelasticity to EMCMB forms an expansion-buffering electrode and promotes the electrochemical activation process.

This paper presents a geopolymer-based battery that has good potential as a solid-state battery owing to fast ionic conduction at room temperature, reduced battery leakage, and a non-flammable nature. The geopolymer was synthesized by alkali activation (10 M KOH) of ground granulated blast furnace slag (GGBFS), and has a similar mechanical behavior to cement, in addition to rapid hardening and a high ionic conductivity. Some researchers have used cement as an electrolyte to produce a sufficient, sustainable electrical output, but the operation voltage and discharge life are low. The experimental results showed that the geopolymer-based battery had a better electrochemical performance than cement-based batteries. Relationships between the age and polymerization of the geopolymer and the power density and operating voltage it produced were noted. The minimum bulk resistance and electrical resisivty of the geopolymer were 1.9Ω and 65Ω⋅cm on day 1, respectively. The discharge voltage, current density, and power density of the battery was investigated using a geopolymer electrolyte, a copper plate cathode, and an aluminum plate anode. Under a constant current density of 0.13 mAcm⁻², the operating voltage was maintained at 0.97 V and remained stable for 600 s. The maximum current density was 1173 μAcm⁻² at 0.4 V, and the maximum power density was 507μWcm⁻².

The lithium-ion capacitor (LIC), combining the advantages of lithium-ion batteries and supercapacitors, has gained significant attention as a new class of energy storage system. Typically, the LIC consists of graphite as the negative electrode and activated carbon (AC) as the positive electrode, while the energy density is limited by the low capacitance of the positive electrode. In this study, an innovative composite material of nitrogen-doped reduced graphene oxide (NrGO) chemically bonded with carbon nanotubes (CNTs), denoted [NrGO-CNT], is designed to circumvent this issue. The [NrGO-CNT] composite possesses not only high electrical conductivity but also high specific surface area and well-distributed mesopores and micropores. The LIC employing [NrGO-CNT] composite shows a cell capacitance retention of 93.5% after 1000 cycles at a scan rate of 200 mV s⁻¹, revealing high cycling stability. This LIC delivers a high specific energy of 124.9 Wh kg⁻¹ at a specific power of 1.26 kW kg⁻¹ at the cell voltages between 1.5 and 4.5 V. Consequently, the [NrGO-CNT] composite is a promising electrode material for high-performance LICs.

Amyloid-beta peptide 1–42 (Aβ42) is considered as a reliable biomarker for the early diagnosis of Alzheimer’s disease (AD). Thus, it is urgent to develop a simple and efficient method for the detection of Aβ42. In this work, a reusable biosensor based on magnetic nitrogen-doped graphene (MNG) modified Au electrode for the detection of Aβ42 has been developed. The antibodies of Aβ 1–28 (Aβ_ab) are used as the specific biorecognition element for Aβ42 that were conjugated on the surface of MNG. In the presence of magnetic nanoparticles on MNG, the electrode coating material, the biosensor can be quickly constructed, without requiring an electrode drying process, which reduce the analysis time and is convenient for proceeding to detection. The reusable biosensor with good reproducibility and stability was linear within the range from 5 pg mL⁻¹ to 800 pg mL⁻¹, covering the cut-off level of Aβ42 and a detection limit of 5 pg mL⁻¹ had been achieved. Furthermore, the fabricated biosensor for Aβ42 detection not only improves the detection performance but also reduces the cost and shortens the response time, demonstrating its potential in diagnosing applications.

In this study, we reported the synthesis of the two-dimensional (2D) nanocomposite of molybdenum disulfide and nitrogen-doped graphene oxide (MoS2/nGO) as a platinum-free counter electrode (CE) for dye-sensitized solar cells (DSSCs). X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), and Raman spectroscopy were used to examine the characteristics of the 2D nanocomposite of MoS2/nGO. The cyclic voltammetry (CV), electrochemical impedance spectra (EIS), and the Tafel polarization measurements were carried out to examine the electrocatalytic abilities. XPS and Raman results showed the 2D behaviors of the prepared nanomaterials. HRTEM micrographs showed the direct evidence of the 2D nanocomposite of MoS2/nGO. The results of electrocatalytic examinations indicated the MoS2/nGO owning the low charge transfer resistance, high electrocatalytic activity, and fast reaction kinetics for the reduction of triiodide to iodide on the electrolyte–electrode interface. The 2D nanocomposite of MoS2/nGO combined the advantages of the high specific surface of nGO and the plenty edge sites of MoS2 and showed the promoted properties different from those of their individual constituents to create a new outstanding property. The DSSC with MoS2/nGO nanocomposite CE showed a photovoltaic conversion efficiency (PCE) of 5.95 % under an illumination of AM 1.5 (100 mW/cm2), which was up to 92.2 % of the DSSC with the conventional platinum (Pt) CE (PCE = 6.43 %). These results reveal the potential of the MoS2/nGO nanocomposite in the use of low-cost, scalable, and efficient Pt-free CEs for DSSCs.

Platinum nanocubes (PtNCs) were deposited onto a fluorine-doped tin oxide glass by electrochemical deposition (ECD) method and utilized as a counter electrode (CE) for dye-sensitized solar cells (DSSCs). In this study, we controlled the growth of the crystalline plane to synthesize the single-crystal PtNCs at room temperature. The morphologies and crystalline nanostructure of the ECD PtNCs were examined by field emission scanning electron microscopy and high-resolution transmission electron microscopy. The surface roughness of the ECD PtNCs was examined by atomic force microscopy. The electrochemical properties of the ECD PtNCs were analyzed by cyclic voltammetry, Tafel polarization, and electrochemical impedance spectra. The Pt loading was examined by inductively coupled plasma mass spectrometry. The DSSCs were assembled via an N719 dye-sensitized titanium dioxide working electrode, an iodine-based electrolyte, and a CE. The photoelectric conversion efficiency (PCE) of the DSSCs with the ECD PtNC CE was examined under the illumination of AM 1.5 (100 mWcm−2). The PtNCs in this study presented a single-crystal nanostructure that can raise the electron mobility to let up the charge-transfer impedance and promote the charge-transfer rate. In this work, the electrocatalytic mass activity (MA) of the Pt film and PtNCs was 1.508 and 4.088 mAmg−1, respectively, and the MA of PtNCs was 2.71 times than that of the Pt film. The DSSCs with the pulse-ECD PtNC CE showed a PCE of 6.48 %, which is higher than the cell using the conventional Pt film CE (a PCE of 6.18 %). In contrast to the conventional Pt film CE which is fabricated by electron beam evaporation method, our pulse-ECD PtNCs maximized the Pt catalytic properties as a CE in DSSCs. The results demonstrated that the PtNCs played a good catalyst for iodide/triiodide redox couple reactions in the DSSCs and provided a potential strategy for electrochemical catalytic applications.