Cyclic Voltammetry Curves Research Articles

Exploring the potential of CdSe nanostructured thin films for energy conversion and environmental remediation

Abstract The rapid thermal evaporation method was employed to prepare cadmium selenide (CdSe) nanostructured thin films with varying thicknesses on glass and FTO substrates. The films were characterized for their structural, optical, and electrochemical properties. Scanning electron microscope (SEM) analysis revealed inhomogeneous surfaces with particle sizes ranging from 18 to 46 nm. The photocatalytic performance of the CdSe films was evaluated by the degradation of methylene blue (MB) dye under visible light, with varying pH values, achieving a degradation efficiency of 100 % at pH 10 after 180 minutes. Photocurrent density measurements demonstrated the films' ability to sense visible light. We performed a cyclic voltammetry (CV) measurement and analyzed the CV curves of the CdSe nanostructured thin film electrodes. It clearly shows that the CV curves had a rectangular shape, which suggests that EDLC behavior was present and non-faradaic capacitance was the main type. The photoconversion efficiency measured is 1.4858 at a bias voltage of 0.66 V under illuminated conditions. Nonlinear optical properties were conducted for CdSe nanostructured thin films.

Constructing Co3O4 Nanowire@NiCo2O4 Nanosheet Hierarchical Array as Electrode Material for High-Performance Supercapacitor

The Co3O4 nanowire@NiCo2O4 nanosheet hierarchical array was constructed on Ni foam using hydrothermal and annealing approaches in turn, from which a NiCo2O4 nanosheet could self-assemble on the Co3O4 nanowire. The structure and morphology of the Co3O4 nanowire@NiCo2O4 nanosheet hierarchical array were characterized via XRD, EDS, SEM, and FESEM, respectively. The electrochemical performance of the composite array was measured via a cyclic voltammetry curve, galvanostatic current charge–discharge, charge–discharge cycle, and electrochemical impedance and then compared with the Co3O4 nanowire. The results show that the Co3O4 nanowire@NiCo2O4 nanosheet hierarchical array could reach a high value of 2034 F g−1 at a current density of 2.5 A g−1. After 5000 galvanostatic charge–discharge cycles, the specific capacitance of the Co3O4 nanowire@NiCo2O4 nanosheet hierarchical array could still maintain 94.7% of the original value. Therefore, the Co3O4 nanowire@NiCo2O4 nanosheet hierarchical array would be a desirable electrode material for a high-performance supercapacitor.

Fabrication of heterostructure multilayer devices through the optimization of Bi-metal sulfides for high-performance quantum dot-sensitized solar cells.

In this work, a titanium dioxide and lead sulfide (TiO2/PbS) nano-size heterostructure with tin sulfide was fabricated and coated via a two-step direct deposition process. Its microstructure, morphology, elemental composition, optical absorption, and photochemical activity were investigated. Linear sweep voltammetry and cyclic voltammetry curves substantiated its catalytic activity, indicating quantum dot effects of a well-developed space charge domain on the surface of the hybrid structure. These give rise to electron-hole recombination suppression and a high charge mobility rate. Moreover, direct stabilization was identified in current density, corresponding to the hybrid structures limiting the diffusion current process. Higher J SC values observed were substantiated by the role of quantum dot-size effects and enhanced crystalline structures, leading to a reduction in series resistance and an improved conversion efficiency of 10.05%. Overall, theoretical analyses and empirical findings indicated that the seamless migration of photoexcited electrons across the interfaces of SnS and PbS is linked to quantum dot effect synergy. This is facilitated by the space charge region, which serves as a conduit for efficient electron transfer between the respective materials.

Mechanochemical synthesis and characterization of poly[(aniline-co-N-(4-sulfophenyl) aniline] nanofibers and its nanocomposite with titanium dioxide nanoparticles and study of their efficiency in hybrid solar cell

The advantages of polyaniline for application in new generation solar cells include its cost-effectiveness, environmentally friendly synthesis, remarkable stability, and the ability to modify the bandgap through the synthesis of its nanocomposites. But a challenge for its nanostructures is the limited solubility in non-toxic solvents, including water, which limits their processability in coating techniques. We overcame this challenge by synthesizing its copolymer with diphenylamine-4-sulfonate and its nanocomposite with titanium dioxide nanoparticles (TiO2NPs). So through a solid-state and template-free technique and using sodium diphenylamine-4-sulfonate, aniline hydrochloride salt, TiO2NPs, and FeCl3∙6 H2O as an oxidant, poly(N-(sulfophenyl)aniline) nanoflowers (PSANFLs), poly [(aniline-co-N-(4-sulfophenyl) aniline] nanofibers (PAPSANFs), poly(N-(sulfophenyl)aniline) nanofibers/titanium dioxide nanoparticles (PSANFs/TiO2NPs), and poly (aniline-co-N-(4-sulfophenyl)aniline nanofibers/titanium dioxide nanoparticles (PAPSANFs/TiO2NPs) were synthesized. Characterization of the synthesized samples was carried out through field emission scanning electron microscopy (FE-SEM), Fourier-transform infrared spectra, ultraviolet-visible spectra (UV-Vis), cyclic voltammetry (CV), and elemental analysis (CHNS). The FE-SEM images clearly illustrate that the synthesized samples are of nanoscale dimensions. The band gap values of 2.23 eV for PSANFs/TiO2NPs and 1.96 eV for PAPSANFs/TiO2NPs nanocomposites were determined through electrochemical calculations based on cyclic voltammetry curves, showcasing the complementary properties of n and p semiconductors. Using doctor blade method to prepare films from synthesized materials and the architectural pattern of ITO│TiO2NPs│semiconductor sample│Al, all hybrid solar cells are fabricated. The I-V characteristics and power conversion efficiency (PCE) of the samples were examined and discussed. The PCE values for the four samples were found to be in the range of 0.20–0.82 %.

Maleic anhydride esterified potato starch as the binder in silicon nanoparticles anode for lithium-ion batteries

Potato starch is a natural carbohydrate binder. Starch has hydroxyl groups that can promote interaction with silicon particles using multifaceted hydrogen bonds. Maleic anhydride esterified potato starch can produce a binder that maintains the cycle stability of lithium-ion batteries. Fourier-transform infrared spectroscopy spectra show wavelengths of 1776 cm−1 and 1855 cm−1. Thermal gravimetric analysis curves decreased in weight percent by 80 % at 286 °C. Carbon-13 nuclear magnetic resonance spectra show high peaks at 3.37 ppm, 3.65 ppm, 4.56 ppm, 5.09 ppm, and 6.22 ppm. Scanning electron microscope images show that the morphological change in esterified starch was due to the increased length of starch and the maleic anhydride grafted onto the starch granules. The cyclic voltammetry curve shows that the reduction peak is around 0.16 V, and the oxidation peak is around 0.38 V and 0.56 V. Nyquist plots show a small half circle, indicating that the electrode's solid-electrolyte interphase layer is low. The cycling performance shows a capacity of 1950 mAh/g.

Label-free electrochemical immunosensor for rapid and highly sensitive detection of Brucella abortus in serum

Accurate and efficient detection of Brucella is crucial to control the disease and mitigate its impact on animal health and human safety. In this study, a simple and rapid label-free electrochemical immunosensor for the detection of Brucella abortus was fabricated based on the principle of current decrease after specific capture of the bacteria. A certain proportion of multi-walled carbon nanotubes (MWCNTs), dopamine hydrochloride (DA), and gold nanoparticles (AuNPs) were modified on the surface of a gold disc electrode. Then, Brucella abortus antibody and bovine serum albumin (BSA) were immobilized in sequence to complete the assembly of the sensor. The electrodes from various assembly steps were characterized by a cyclic voltammetry (CV) curve. The immunosensor exhibited high sensitivity with a wide linear range between 10 CFU/mL and 108 CFU/mL. Additionally, the sensor displayed good repeatability, stability, and interference resistance. The recovery rates for low, medium, and high concentrations of bacteria were all within the range of 90 % to 100 %, indicating a high level of accuracy. The method established in this study can provide reference and assistance for early diagnosis of Brucella abortus in clinical practice.

Effect of Cu substitution on morphological optical and electrochemical properties of Co3O4 nanoparticles by co-precipitation method

In this present study, pure Co3O4 and Cu-substituted Co3O4 nanoparticles (NPs) were prepared by a simple co-precipitation method and their structural, morphological, optical, and electrochemical aspects were assessed. X-ray diffraction (XRD) analysis indicated that the synthesized samples had a cubic structure with the formation of a secondary phase (CuO) at a higher Cu concentration. The average crystallite was decreased with increasing Cu content. Fourier transform infra-red (FT-IR) analysis revealed that the presence of vibrational bands in Cu-substituted Co3O4 NPs. The morphological study of the pure Co3O4 and Cu-substituted Co3O4 NPs revealed that the hexagonal structure with porous nature confirmed by Field emission scanning electron microscopy (FESEM). High resolution transmission electron microscope (HR-TEM) analysis with spotty diffraction rings showed that pure Co3O4 and Cu-substituted Co3O4 NPs were polycrystalline in nature. The optical properties of synthesized samples exhibited strong absorption edges, and bandgap values were found to be increased from 3.24 to 3.75 eV. Cyclic voltammetry (CV) was employed to investigate the electrochemical properties of the synthesized materials. The CV curves exhibited pseudocapacitive behavior, and the 2 % Cu-Co3O4 electrode had a high higher specific capacitance value than the pure Co3O4 electrode.

Preparation of Cu nanolayers by magnetic field-assisted electrodeposition and research on the nucleation and growth mechanism

Electrodeposition technology is widely used in the surface treatment of copper foil, and the core of this technology is roughening and curing treatment. During the electrodeposition process, the deposited layers often exhibits some problems, such as coarse grain size, uneven thickness and difficult control of crystal morphology. The magnetohydrodynamic (MHD) effect of magnetic field can obviously control the electrodeposition of Cu and improve the micro-morphology and performance of deposited layers. In this paper, Linear Sweep Voltammetry (LSV), Cyclic Voltammetry (CV) and Chronocoulometry (CC) curves were adopted to investigate the electrochemical behavior of deposited Cu in ultra-high acidity sulfate systems under different magnetic field conditions. The nucleation and growth mechanism were discussed, and the micro-morphology of deposited layers was analyzed. The results show that the electrodeposition of Cu follows the three-dimensional (3D) growth mechanism of progressive nucleation and diffusion control under the static condition, and the deposits appear cylindrical shape formed by spherical agglomerated. The magnetic field significantly improves the mass transfer rate, and the deposited layers will be more uniform and dense, following 3D growth mechanism under the electrochemical control. With the increasing of magnetic field intensity, the nucleation mechanism gradually shifts from progressive to transient nucleation. At the early stage of nucleation, the high-intensity magnetic field can significantly increase the number of grains and refine them, obtaining uniform and dense deposited nanolayers.

Marigold flower-like structured battery-type Cu2O/Co(OH)2 composite electrode material for high-performance supercapacitors

Addressing the limitations of individual Cu2O and Co(OH)2 components, this study aims to develop a high-performance supercapacitor electrode by synergistically combining these materials. A composite electrode material of Cu2O/Co(OH)2 was effectively synthesized on nickel foam via a facile hydrothermal method for supercapacitor applications. The as-fabricated Cu2O/Co(OH)2 composite electrode exhibits a hierarchical marigold flower-like morphology that comprises of many interspersed nanoflakes. This unique morphology offers several advantages, including increased surface area, abundant electroactive sites, and enhanced electrolyte accessibility, all of which contribute to superior electrochemical performance. The Cu2O/Co(OH)2 electrode demonstrates exceptional battery-type supercapacitor behavior, characterized by prominent redox peaks in cyclic voltammetry curves and a well-defined potential plateau during galvanostatic charge-discharge measurements. The electrode delivers an outstanding specific capacitance of 90.21 mA h g⁻1 at a current density of 1.25 A g⁻1 and retains a remarkable 81.91 % capacitance at a high current density of 12.5 A g⁻1. Furthermore, the electrode exhibits impressive cycling stability, maintaining approximately 107.84 % of its initial specific capacity value after 200 cycles at 7.5 A g⁻1. Electrochemical impedance spectroscopy measurements reveal low solution resistance and charge-transfer resistance, signifying efficient charge-transfer kinetics within the electrode. These findings highlight the potential of Cu2O/Co(OH)2 composite electrodes as promising candidates for high-performance supercapacitor applications.

An electrochemical sensor based on cobalt hydroxide/hydroxylated multiwalled carbon nanotubes for sensitively detecting 4-nitrochlorobenzene

In this work, cobalt hydroxide (Co(OH)2) is electrodeposited on glassy carbon electrode (GCE) modified by hydroxylated multiwalled carbon nanotubes (MWCNTs-OH). The obtained electrode (Co(OH)2/MWCNTs-OH/GCE) is utilized to determine 4-nitrochlorobenzene (4-NCB). The as-prepared materials are characterized through scan electron microscope, energy-dispersive spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy to analyze crystal structure, morphology, element composition and distribution. The electrochemical behaviors of 4-NCB on modified electrodes and GCE are investigated via cyclic voltammetry (CV) and AC impedance. CV curves and Nyquist plots show that the electrochemical properties of Co(OH)2/MWCNTs-OH/GCE are significantly better than the others. Differential pulse voltammetry tests demonstrate that Co(OH)2/MWCNTs-OH/GCE possesses great electrocatalytic activity for determining 4-NCB in the range of 0.01 ∼ 400 μM, and the detection limit is 6.5 nM (S/N=3). Additionally, the constructed sensor exhibits excellent reproducibility, stability and selectivity. Moreover, recovery experiment using the standard addition method is conducted on tap water, yielding satisfactory recovery rates.

The Influence of 3D Printing Methods and Materials on the Response of Printed Symmetric Carbon Supercapacitors

We compare the electrochemical response and intrinsic limitations of symmetric carbon-based supercapacitors using two 3D-printing techniques, vat polymerization (Vat-P) and fused deposition modelling (FDM). Two cell types were made in this study, one with metallized Vat-P-printed current collectors, the other with PLA (polylactic acid) FDM-printed current collectors in a similarly designed printed coin cell. Carbon-based electrode slurry (various combinations of SWCNT, GNP, Super-P, PVDF) and aqueous 6 M KOH electrolyte were used in these cells. We demonstrate the influence of internal resistance of each 3D-printing method by direct comparison of cyclic voltammetry and galvanostatic charge-discharge tests. The metallized conductive Vat-P cells display better conductivity and more ideal rectangular cyclic voltammetry response but suffer from poor cycle life in initial experiments (∼5,000 charge-discharge cycles before losing all specific capacitance). The FDM current collector cells using graphite-containing PLA materials have poorer conductivity, less ideal cyclic voltammetry curves, and are structurally less robust and partially porous, but offer very stable cycle life for supercapacitor cells retaining most of their specific capacitance after 100,000 charge-discharge cycles. The cycle life of the metallized Vat-P cells are improved by reducing the voltage window to 0.2–0.7 V to limit metal delamination and using Super-P and PVDF additives.

Electrochemical analysis on SnSeO3/ZnSeO3 nanocomposite

Nanocomposite SnSeO3/ZnSeO3 has been synthesized by hydrothermal method. X-ray powder diffraction confirms formation of SnSeO3/ZnSeO3 nanocomposite. It exhibits an interesting morphology of needle like nanorod structure. Thermal analysis reveals the thermal stability, decomposition behavior and critical temperatures where significant weight loss occurs. X-ray photoemission explains the role of the chemical state Sn, Zn, Se and O in SnSeO3/ZnSeO3. Electrochemical study has been made in both three electrode and two electrode system. In three electrode system, cyclic voltammetry exhibits a bell-shaped curve and the operational potential window is 0.8 V. The specific capacitance is 78.65 F/g for 5 mV scan rate. Chronopotentiometry shows quasi-triangular curves demonstrating the behavior of pseudo capacitors. Specific capacitances of 72.02 F/g was delivered at 1 A/g current density in 3M electrolyte of KOH. The plot of Nyquist for SnSeO3//ZnSeO3 confirms pseudo capacitor behavior. The series resistance Rs is low that is 0.78 Ω and charge transfer resistance is 0.42 Ω. Symmetric SnSeO3/ZnSeO3 supercapacitor device that is, two electrode system, is fabricated using 3M KOH electrolyte. Operational potential window is 1.5V. Cyclic voltammetry curves of the device show excellent capacitive behavior. The symmetric device produced specific capacitances of 39.37F/g, energy density 6.15 Wh kg-1 and power density 374.99 kW kg-1 at 1Ag-1 current density. The cell displayed 73.18% capacity retention, indicating excellent electrode stability for approximately 5000 cycles at a current density of 1 Ag-1 . Nyquist plot suggests that the system is stable and exhibits capacitive behavior.

Performances of MnO2 and SnO2 Coated MnO2 as Cathode Materials for Aqueous Rechargeable Zinc-ion Batteries

In this study, the micro-emulsion method was used to create the manganese-based cathode materials MnO2 and MnO2@SnO2. For the use as cathode materials in rechargeable zinc-ion batteries, MnO2 and SnO2 coated MnO2@SnO2 were synthesized. FT-IR, Powder X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray Spectroscopy (EDS), and UV-visible Spectroscopy were used to characterize the as-prepared materials. Electrochemical impedance spectroscopy (EIS), battery charge-discharge (BCD), and cyclic voltammetry (CV) techniques were used to investigate the electrochemical properties of the prepared cathode materials for aqueous rechargeable zinc-ion batteries (ARZIBs). The CV profiles were measured in the potential range of 2.1-1.0 V at a scan rate of 20 mV/s. A pair of redox peaks can be seen in the cycle of CV curves. Charge/discharge cycles of SnO2 coated MnO2@SnO2 electrodes are higher than those of pristine MnO2. SnO2 coated MnO2@SnO2 electrodes have better initial charge/discharge capacities than pristine MnO2 electrodes, which is a factor to take into account. In the first cycle, SnO2 coated MnO2@SnO2 electrode has a 26% higher charge capacity than the bare MnO2 electrode. The SnO2 coating on MnO2 may be the cause of the enhanced charge and discharge capabilities of MnO2@SnO2. J. of Sci. and Tech. Res. 5(1): 83-92, 2023

Symmetric two-electodes pseudosupercapacitor from trichalcogenide MoS3-MoO3-poly-O-amino-benzenethiol nanocomposite

A novel nanocomposite, MoS3-MoO3/poly-O-amino-benzenethiol (MoS3-MoO3/POABT), has been synthesized in a one-pot process and demonstrates promising applications as a material for a two-electrode configuration supercapacitor. This nanocomposite exhibits remarkable morphological characteristics, featuring uniform particles with an average diameter of 80 nm and a porous structure. The advantageous morphology contributes to the enhanced performance of the fabricated pseudo supercapacitor. The evaluation of the charge/discharge behavior and cyclic voltammetry curves of the redox reaction of the MoS3-MoO3/POABT nanocomposite reveals its efficacy as a supercapacitor material. The specific capacitance (CS) achieved for this fabricated supercapacitor is noteworthy at 152 F/g. Furthermore, the energy density (E) peaks at 12.6 W h kg−1 when operating at a current density of 0.2 A/g. This high energy density demonstrates the supercapacitor’s ability to store significant energy for practical use efficiently. Importantly, its stability remains strong, with an impressive 98% retention after 250 cycles, and even after 1000 cycles, it only slightly decreases to 95%. This remarkable stability over extended cycling periods underscores the durability of the materials in the supercapacitor. Such reliable performance establishes the MoS3-MoO3/POABT nanocomposite as a dependable choice for supercapacitor applications, ensuring longevity and consistent performance in diverse energy storage needs.

Assemble of porous heterostructure thin film through CuS passivation for efficient electron transport in dye-sensitized solar cells

Three different modified solar cells have been passivated with copper sulfide (CuS) on a TiO2 electrode and manganese sulfide (γ‐MnS) hexagonal as photon absorbers. The MnS were prepared using (a-c) bis(N‐Piperl‐N‐p‐anisildithiocarbamato)Manganese(II) Complexes Mn[N-Piper‐N‐p‐Anisdtc] as (MnS_1), N‐p-anisidinyldithiocarbamato Mn[N‐p-anisdtc] as (MnS_2) and N‐piperidinyldithiocarbamato Mn[N‐piperdtc] as (MnS_3). The corresponding passivated films were denoted as CM-1, CM-2, and CM-3. The influence of passivation on the structural, optical, morphological, and photochemical properties of the prepared devices has been investigated. Raman spectra show that the combination of this heterostructure is triggered by the variation in particle size and surface effect, thus resulting in good electronic conductivity. The narrow band gaps could be attributed to good interaction between the passivative materials on the TiO2 surface. CM-2 cells, stability studies show that the cell is polarized and current flows due to electron migration across the electrolyte and interfaces at this steady state. The cyclic voltammetry (CV) curve for the CM-3 with the highest current density promotes the electrocatalytic activity of the assembled solar cell. The catalytic reactions are further confirmed by the interfacial electron lifetimes in the Bode plots and the impedance spectra. The current–voltage (J–V) analysis suggests that the electrons in the conduction band of TiO2/CuS recombine with the semiconductor quantum dots (QDs) and the iodolyte HI-30 electrolyte, resulting in 5.20–6.85% photo-conversions.

Synthesis and electrochemical performance of CeO2/NiS nanocomposite for enhanced asymmetric supercapacitor device applications

A novel CeO2/NiS nanocomposite, combining the advantageous properties of transition metal sulfides (high conductivity) and rare-earth metal oxides (excellent stability), was successfully synthesized using a simple hydrothermal method. This composite leverage synergistic effects to potentially achieve superior electrochemical performance in supercapacitor applications. To evaluate its suitability for supercapacitors, the electrochemical performance of the CeO2/NiS electrode was comprehensively investigated using a series of techniques, including cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) curves, electrochemical impedance spectroscopy (EIS), and cyclic stability analysis. The results demonstrate that the as-prepared CeO2/NiS electrode exhibits significantly improved supercapacitor performance compared to the bare CeO2 electrode. The CV curves of the CeO2/NiS electrode reveal a high specific capacitance of 825.53 F/g at a low scan rate of 5 mV/s, indicating good charge storage capability. Further insights into the charge storage mechanism were obtained using the Trasatti method. This analysis revealed that the total stored capacitance of the CeO₂/NiS electrode is 1250 F/g, with contributions from both outer surface capacitance (94 F/g) and inner diffusion capacitance (1156 F/g). Notably, the dominant contribution (92.5 %) originates from capacitive processes, highlighting the efficient charge storage at the electrode surface. The CeO2/NiS electrode also demonstrates exceptional rate capability, delivering a specific capacitance (Csp) of 710 F/g at a high current density of 1 A/g. Additionally, it exhibits impressive cycling stability, retaining approximately 96.56 % of its initial capacitance even after undergoing 3000 continuous GCD cycles at a high current density of 10 A/g. These results suggest that the CeO2/NiS composite can maintain its performance during extended charge-discharge cycles, a crucial characteristic for practical supercapacitor applications. Finally, an asymmetric supercapacitor device was fabricated using the CeO2/NiS nanocomposite. This device achieved a specific capacitance of 157 F/g, demonstrating the potential of the CeO2/NiS composite for practical energy storage applications.

3D Printed Symmetric Carbon Supercapacitors: A Study Comparing Electrochemical Performance and Cycle Life Depending on 3D Printing Technique and Materials

With the ongoing global energy crisis, producing reliable and efficient methods of energy storage remains an integral part of cutting-edge materials research. Within this topic, 3D-printing (also known as additive manufacturing) is evolving from a niche hobby to a reliable scientific tool for materials science research [1-3]. 3D-printing energy storage materials provides unparalleled levels of customisation [4-9] and freedom of design, while also eliminating waste material during the manufacturing process.3D-printing energy storage materials has been widely covered, but usually just focuses on one method of 3D-printing. Directly comparing more than one 3D-printing method within a single energy storage study is far more seldom researched. This work directly compares the electrochemical performances of symmetric carbon-based supercapacitor devices made using two 3D-printing techniques, SLA (stereolithography) and FDM (fused deposition modelling). Two cell types are made in this study, one with gold-sputtered SLA-printed current collectors, the other with conductive PLA (polylactic acid) FDM-printed current collectors. Carbon-based electrode (various combinations of SWCNT, GNP, Super-P, PVDF) slurries and aqueous 6M KOH electrolyte are implemented in these cells. The benefits and limitations of these 3D-printing methods are directly compared, with the electrochemical performance of the supercapacitor cells being analysed using cyclic voltammetry and galvanostatic charge-discharge tests.The sputtered conductive SLA current collector cells display better conductivity and more ideal rectangular cyclic voltammetry curves for electronic double-layer capacitors (EDLCs) but suffer from poor cycle life in initial experiments (~5,000 charge-discharge cycles before losing all specific capacitance). The FDM current collector cells have poorer conductivity, less ideal cyclic voltammetry curves, and are less structurally sound (causing some electrolyte leakage over long term cycling) but offer extremely stable cycle life for supercapacitor cells, retaining most of their specific capacitance after 100,000 charge-discharge cycles. The cycle lives of the gold-sputtered SLA current collector cells are greatly improved after several changes made during the study, such as reducing the voltage window from 0.0-1.0 V to 0.2-0.7 V, and exploring additives for the carbon-based slurry electrodes, such as Super-P and PVDF (polyvinylidene fluoride).

Date Seed-Derived Supercapacitor Electrodes in Aqueous Electrolyte: Unveiling High Capacity and Coulombic Efficiency

Date seeds, often considered byproducts of date fruit processing, represent a significant bio-waste stream. Despite their abundance, these seeds are underutilized and typically regarded as agricultural waste. Rich in carbon content, date seeds have the inherent potential to serve as precursors for hard carbon electrodes in supercapacitors. Free-standing electrodes were fabricated to enhance cyclic stability and improve Coulombic efficiency, showcasing superior electrochemical performance. The activation process with a 1:3 KOH-to-bio-char ratio yielded a specific capacitance of 204 F/g at 0.2A/g for the symmetric cell with an energy density of 6.5 Wh/kg and a power density of 47.70 W/kg, highlighting the effectiveness of this approach in advancing both structural integrity and electrochemical attributes. To elucidate the electrochemical performance of KOH-activated hard carbon, BET analysis, Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), and Raman Spectroscopy were employed. BET analyses revealed a higher surface area for the hard carbon activated with a 1:3 KOH ratio. This enhancement in structural integrity was further corroborated by cyclic voltammetry (CV) and charge-discharge curves, emphasizing the favorable electrochemical attributes of the proposed method. While previous investigations into date seed supercapacitors revealed promising results, achieving near 100% Coulombic efficiency remained challenging. In this study, the implementation of free-standing electrodes marked a significant advancement, resulting in a remarkable Coulombic efficiency of 99.97%. This nuanced approach underscores the effectiveness of our methodology in addressing and improving the Coulombic efficiency of date seed-derived supercapacitors.

(Invited) Probing Local Ion Insertion through Operando AFM

Electrode volume change during ion insertion or intercalation has been one of the main failure mechanisms for several energy storage devices, especially Li-based batteries. Fundamental understanding of the relationship between the amount of the ions/charge stored and the induced volume changes of the hosting electrodes, and how this relationship impact the materials’ performance are necessary to develop the next generation batteries. However, most of the studies on the volume change were based on bulk techniques, which study the entire electrode including binders and additives. Here, we use operando atomic force microscopy (AFM), which allows tracking local volume changes and other mechanical responses with sub-nanometer spatial resolution under the conditions close to the device operation.In this work, we monitored electrode volume change via operando AFM and demonstrated the electro-chemo-mechanical coupling behaviors during proton insertion into WO3 materials. The concept of mechanical cyclic voltammetry (mCV) curves was developed, and the relationship between electrochemical current and strain was investigated with simplified models. The results revealed multiple ion-intercalation processes with different mechanical responses are involved during electrode cycling. Local heterogeneity was investigated via mCV mapping, confirming that the charging mechanisms varied across the electrode. These local variations could be further correlated to local morphology, crystal orientations, or chemical compositions. We further demonstrate that the mCV approach is applicable to a variety of energy storage materials (e.g., birnessite, MXene and metal nitrides) with the increasing complexity of current-deformation relationships.

Electrochemical Performance and Characterisation of Chemically Treated Conductive PLA Fused Deposition Modelling (FDM) Current Collectors within Additively Manufactured (3D-Printed) Symmetric Carbon Supercapacitors

Within the fields of materials science, producing reliable, long-lasting, and efficient energy storage devices to meet the world’s energy needs remains a foremost research goal. 3D-printing (also known as Additive Manufacturing) provides many benefits to this research [1-8], allowing for excellent customization and freedom of design, while eliminating waste material in the manufacturing process. Wearable electronics, medical implants, and the Internet of Things will doubtless benefit from the advantages provided by additive manufacturing.Our previous work compared the electrochemical performances of symmetric carbon-based supercapacitor devices made using two 3D-printing techniques, SLA (stereolithography) and FDM (fused deposition modelling). Though possessing excellent cycle life, the conductive polylactic acid (PLA) FDM printed current collectors suffered from relatively high resistance and poor cyclic voltammetry curves (far from the rectangular shape of ideal electronic double-layer capacitors). This study aims to improve the conductivity of the FDM current collectors via chemically induced surface modification [9]. Both dimethylformamide (DMF) and aqueous potassium hydroxide (KOH) treatments are used for this purpose. The untreated, DMF-treated, and KOH-treated FDM current collectors are loaded with 1:1 by mass single-walled carbon nanotubes and graphene nanoplatelets carbon slurry, placed within stereolithography (SLA) 3D-printed casings [10], and assembled as supercapacitor cells (separated by glass microfiber filter separators soaked in 6 M aqueous KOH electrolyte).This works shows how DMF treatment method results in little change in electrochemical performance compared to the untreated FDM current collector cells, but pre-treatment in a solution of KOH identical to the cell electrolyte markedly improves the current collector conductivity. The KOH treatment provides a tenfold decrease in the FDM current collector resistance, which correlates with the improved cyclic voltammetric response. Galvanostatic charge-discharge tests reveal the effect of these treatments on specific capacitance, charge-discharge response, efficiency, and rate capability for these printed cells. The pre-treatment confirms that the cell electrolyte does not limited long term performance by interacting with the PLA current collector in 3D printed supercapacitor cells and tests using other inorganic active materials will also be shown.