The integrity of the solid electrolyte interphase (SEI) formed on the negative electrode of lithium‐ion batteries (LIB) is especially critical for the performance of next‐generation LIBs comprising silicon‐carbon based electrode materials. The protecting character of the SEI is compromised due to volume expansion and shrinking during de/intercalation of Li ions leading to irreversible changes upon long‐term cycling. Scanning electrochemical microscopy (SECM) is proposed as local electrochemical technique to investigate the degradation mechanisms of advanced negative electrodes. The impact of charge/discharge cycling on the SEI properties on Si−C electrodes was investigated, and the sensitivity of SECM successfully reveals inhomogeneities at an early stage of the cycling already at about 5 cycles. Macroscopic EIS measurements and evaluation of the coulombic efficiency may result in misleading interpretations of degradation. SECM is demonstrated to be a powerful and complementary technique for revealing μm‐heterogeneities in the SEI surface reactivity after a few charge/discharge cycles.
This work reports an electrochemical sensor with a modified glassy carbon electrode for the detection of kaempferol. The method was tailored by the immobilization of multiwalled carbon nanotubes (MWCNTs) assimilated with Fe 2 O 3 nanoparticles (NPs) onto the electrode surface to detect kaempferol using differential pulse voltammetry.Thermogravimetric, transmission electron microscopic, cyclic, and differential voltammetric techniques were employed to characterize the developed electrochemical sensor. The kaempferol produces an anodic quasireversible peak at pH 6.6 in phosphate buffer with Fe 2 O 3 NPs/MWCNTs/GCE. The current of the anodic peak at 0.32 V increases linearly upon addition of kaempferol standard, resulting in Ip( µ A) = 1.577( µ M) + 1.347 (R 2 = 0.9930). The limits of detection and limits of quantification were found to be 0.53 µ M and 1.73 µ M, respectively. Upon quantitative analysis of kaempferol in broccoli samples, it was found to be 3.78 µ g g −1 with an average percent recovery of 99.55%. The findings of this study identify the efficient catalytic property as a major contributor in the electron-transferring capacity from the electrode surface to the analyte, with promising possibilities of designing a highly sensitive electrochemical sensor for food industry applications.
This work describes a simple method for the fabrication of an enzymatic electrode with high sensitivity to oxygen and good performance when applied as biocathode. Pencil graphite electrodes (PGE) were chosen as disposable transducers given their availability and good electrochemical response. After electrochemical characterization regarding hardness and surface pre-treatment suited modification with carbon-based nanostructures, namely with reduced graphene, MWCNT and carbon black for optimal performance was proceeded. The bioelectrode was finally assembled through immobilization of bilirubin oxidase (BOx) lashed on the modified surface of MWCNT via π–π stacking and amide bond functionalization. The high sensitivity towards dissolved oxygen of 648 ± 51 µA mM−1 cm−2, and a LOD of 1.7 µM, was achieved for the PGE with surface previously modified with reduced graphene (rGO), almost the double registered for direct anchorage on the bare PGE surface. Polarization curves resulted in an open circuit potential (OCP) of 1.68 V (vs Zn electrode) and generated a maximum current density of about 650 μA cm−2 in O2 saturated solution.
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