Charge Storage Capacity Research Articles

A microwave plasma etching strategy for preparing oxygen-vacancy-rich NiCoO2 Nanoarrays for high-rate performance supercapacitor

Supercapacitors are vital for industries like automotive and energy storage. Transition metal oxides are promising electrode materials due to their diversity and high capacity. This study uses microwave plasma etching (MPE) to synthesize oxygen-vacancy-rich NiCoO2 nanoarrays (E-NCO) for supercapacitors. The etched NiCoO2 nanoarrays exhibit remarkable performance (1360.7 F g−1 at 1 A g−1) and excellent rate performance (996.7 F g−1 at 50 A g−1) in a three-electrode system. After assembling E-NCO-15 into a hybrid supercapacitor, it demonstrated a high energy density of 48.4 Wh kg−1 at the power density of 387.4 W kg−1, and even at the ultra-high power density of 19377.1 W kg−1, the energy density remains 15.2 Wh kg−1. Through the characterization of the material and an exploration of the reaction kinetics mechanism, it was discovered that MPE as a low-cost and easily controllable material modification method can introduce oxygen vacancies into the material, thereby enhancing both the material’s electrical conductivity and charge storage capacity. In addition, nanoarrays morphology provides more active sites and faster ion transport. These results highlight E-NCO’s potential for high-performance supercapacitors.

Nano-Spheroidal MnOx/C Nanomaterial with Battery-Like and Capacitive Charge Storage for Lithium-Ion Capacitors

Nano-Spheroidal MnOx/C Nanomaterial with Battery-Like and Capacitive Charge Storage for Lithium-Ion Capacitors

Metal oxide-based nanocomposites as advanced electrode materials for enhancing electrochemical performance of Supercapacitors: A comprehensive review

In recent years, the escalating use of nonrenewable fossil fuels has emerged as a significant threat to global sustainability, prompting the need for renewable, cost-effective, and eco-friendly energy storage solutions. Supercapacitors (SCs) are notable for their high power density (PD), cycle stability, and swift charge/discharge rates, although they fall short in energy density (ED) compared to traditional batteries. The performance of SCs is greatly influenced by the electrode materials used, highlighting the importance of material innovation in tackling the challenges posed by increasing fossil fuel consumption. Transition metal oxides (TMOs), known for their redox activity in energy storage, have been thoroughly investigated for their exceptional specific capacitance, which ranges from 100 to 2000F g−1, surpassing that of electrical double-layer capacitors (EDLCs). TMOs such as ruthenium oxide (RuO2), manganese oxide (MnO2), nickel oxide (NiO), cobalt oxide (Co3O4), tin oxide (SnO2), zinc oxide (ZnO), tungsten oxide (WO3), and vanadium pentoxide (V2O5) are widely researched for their high theoretical capacitance, affordability, and longevity. This review emphasizes the groundbreaking potential of metal oxide nanocomposites (NCs) formed by combining them with graphene, carbon nanotubes (CNTs), and polymers, leading to synergistic enhancements in electrical conductivity, surface area, and charge storage capacity. This thorough review not only presents an in-depth analysis of current research but also sheds light on potential future developments, contributing to the ongoing progress in the field of advanced electrode materials for energy storage.

Fe3+-activated magnetoplumbite persistent luminescence phosphor by modulating the oxygen vacancy.

Broadband near-infrared (NIR) spectroscopy has gained significant attention due to its versatile application in various fields. In the realm of NIR phosphors, Fe3+ ion is an excellent activator known for its nontoxic and harmless nature. In this study, we prepared an Fe3+-activated SrGa12O19 (SGO) NIR phosphor and analyzed its phase and luminescence properties. Upon excitation at 326 nm, the SGO:Fe3+ phosphor exhibited a broadband emission in the range 700-1000 nm, peaking at 816 nm. The optical band gap of SGO:Fe3+ was evaluated. To enhance the long-lasting phosphorescence, an oxygen vacancy-rich SGO:Fe3+ (VO-SGO:Fe3+) sample was prepared for activation. Interestingly, the increase in the oxygen-vacancy concentration indeed contributed to the activation of persistent luminescence of Fe3+ ions. The VO-SGO:Fe3+ sample has a long duration and high charge storage capacity, allowing it to perform efficiently in various applications. This work provides the foundation for further design of Cr3+-free PersL phosphors with efficient NIR PersL.

Electrochemical charge storage performance of (Mn, Ni, Mo, Co, Fe)3O4 high entropy oxide nanoparticles produced via thermal plasma route

Highly complex high entropy metal oxides (HEOs) have several unique characteristics, such as more active sites and material stability that improve the electrochemical charge storage capacity. In this study, HEOs (Mn, Ni, Mo, Co, Fe)3O4 nanoparticles were synthesized using a thermal plasma route and its electrochemical energy storage performance was studied with two distinct electrolytes such as 1 M KOH and NaOH. The X-ray diffraction analysis revealed the phase pure spinel structured HEOs with crystalline size ranging from 13 to 29 nm. Scanning electron microscopy and electron dispersive X-ray spectroscopy results revealed the quasi-spherical morphology and uniform distribution of constitutional cations in the as-synthesized HEOs. The X-ray photoelectron spectroscopy results identified the oxidation states of cations in spinel HEOs. The charge/discharge studies of as-synthesized HEOs showed a specific capacitance of 215 F g-1 /26.9 mAh g-1 at a current density of 2 A g-1 in 1 M KOH electrolyte which is 156 % greater than 1 M NaOH electrolyte. Furthermore, a high capacitance retention of 91 % was achieved after completing 3000 cycles at 10 A g-1 current density which indicates that the HEOs have excellent charge/discharge reversibility. Electrochemical impedance spectroscopy revealed that the solution and charge transfer resistances of HEOs electrodes were 1.04 and 3.2 Ω, respectively. This novel synthesis strategy attempts to overcome the difficulties experienced by established methods for bulk manufacture of phase pure HEOs since thermal plasma method is a rapid and a single-step approach for the bulk production of nanomaterial.

High Capacitance Based on Vacancy Defective Porous Carbon in Ionic Liquid

AbstractPorous carbons have been extensively studied in electrochemical capacitors (ECs). However, low capacitance remains a limitation due to the electrical double layer (EDL) storage mechanism when porous carbons are used in ionic liquids (ILs) based ECs. Herein, the nitrogen‐derived vacancy defects in porous carbon nanospheres are found which can boost capacitive charge storage and present reversible high capacitance of 427 F g−1 in pure IL electrolyte, equal to a normalized area capacitance (CA) of 16 µF cm−2, surpassing the theoretical EDL CA (≈11 µF cm−2). When used as capacitive cathode, the assembled Lithium hybrid capacitor express high energy density of 635 Wh kg−1 based on active material under much high‐power density of 14.5 kW kg−1. A combination of control experiments and density functional theory investigation indicate that the EC's performance improvement mostly stems from strong interactions at vacancy defects, triggering extraordinary faradaic capacitance. The results shed light on defect engineering for realizing extra faradaic capacitance of carbon materials, and open up new opportunities for improving EC's energy density.

Unlocking the Potential of Bismuth‐Based Materials in Supercapacitor Technology: A Comprehensive Review

AbstractSupercapacitors (SCs) have attracted significant attention in the realm of energy storage devices due to their exceptional features, such as enhanced charge storage capacity, fast charge‐discharge rates, and high power density. The emergence of cost‐effective and highly productive SCs is a topic of interest among industrial and scientific communities. Ferrites with a perovskite crystal structure are often considered excellent electrode materials due to their intrinsic properties, affordability, low environmental impact, and widespread availability. An in‐depth investigation of perovskite ferrites in the context of SCs is necessary to advance the understanding of these materials. The techniques used in the synthesis of ABO3‐type perovskite bismuth ferrite materials are comprehensively reviewed in this review. The review starts by analyzing various types of SCs classified based on their electrode materials. The review provides a comprehensive understanding of the design and functionality of these devices, serving as an important source of inspiration for new methods of synthesis and fabrication methodologies that aim to produce environmentally friendly SCs.

Recent development in addressing challenges and implementing strategies for manganese dioxide cathodes in aqueous zinc ion batteries

Safety issues of energy storage devices in daily life are receiving growing attention, together with resources and environmental concerns. Aqueous zinc ion batteries (AZIBs) have emerged as promising alternatives for extensive energy storage due to their ultra-high capacity, safety, and eco-friendliness. Manganese-based compounds are key to the functioning of AZIBs as the cathode materials thanks to their high operating voltage, substantial charge storage capacity, and eco-friendly characteristics. Despite these advantages, the development of high-performance Mn-based cathodes still faces the critical challenges of structural instability, manganese dissolution, and the relatively low conductivity. Primarily, the charge storage mechanism of manganese-based AZIBs is complex and subject to debate. In view of the above, this review focuses on the mostly investigated MnO2-based cathodes and comprehensively outlines the charge storage mechanisms of MnO2-based AZIBs. Current optimization strategies are systematically summarized and discussed. At last, the perspectives on elucidating advancing MnO2 cathodes are provided from the mechanistic, synthetic, and application-oriented aspects.

Towards the fabrication of fully printed flexible P(VDF-TrFE)-based piezoelectric sensors

The emergent Internet of Things (IoT) market has increased the need of sensors, actuators and nanogenerators, demanding cost-effective and large-scale manufacturing methods to fabricate these devices. Printed electronics (PE), which consists of the application printing and coating technologies in the deposition of functional materials, is one of the ways to process low-cost lightweight, semi-transparent, and flexible devices, usually employing polymers as functional materials. In this work we present the fabrication of poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) copolymer-based printed piezoelectric devices applying different semi-transparent flexible conductive substrates as bottom electrodes. The screen-printing process was chosen as a large-scale cost-effective fabrication method at low-temperature processing. Printing and the laser scribing parameters were established, and the effectively use of silver and PEDOT:PSS as top electrodes was demonstrated. The final devices were electrically poled and characterized by Electrochemical Impedance Spectroscopy (EIS) and correlations among the device’ performance regarding the different bottom and top electrodes were set up, leading to processing recommendations. Employing a cycle olefin polymer coated with silver nanowires (AgNW) as substrate, P(VDF-TrFE) as active material and silver as top electrode, a 223 µF/m2 capacitance was obtained when compressing at 2.37 KPa, demonstrating the devices charge storage capacity by the application of a mechanical stress. All the employed processing conditions can be easily integrated in a R2R pilot line, allowing high throughput, low-cost and large-area manufacturing. Additionally, the use of the polymer substrates enables the fabrication of flexible and lightweight devices.

N, O self-doped porous carbon derived from distiller's grains for high performance supercapacitors

Improving the charge storage capacity of carbon materials derived from biomass waste is an important aspect for their practical applications as supercapacitor electrodes. A reasonable design of heteroatom-doped carbon materials derived from industrial distiller 's grains can significantly enhance the efficacy of the supercapacitor. Therefore, a distiller's grain-derived (DG) N/O self-doped activated carbon (DG-5-X) was developed for use in supercapacitors. The incorporation of heteroatoms into porous carbon materials can facilitate enhanced electrode-to-electrolyte interaction resulting in improved pseudo-capacitance, thereby enhancing the electrochemical performance. A remarkable 345.2 F g−1 specific capacitance was demonstrated in a three-electrode system employing DG-5–6 (with N and O heteroatom contents of 1.62 % and 19.27 %, respectively) as the electrode in a 6 M KOH electrolyte solution (at 1 A g−1). In addition, a symmetric coin-type supercapacitor (SSC) device was developed, which demonstrated excellent cyclic stability and a competitive energy density of 12.2 Wh kg−1 (at a 348.8 W kg−1 power density). SSC retained 95.6 % of the capacitance after 5000 cycles at 5 A g−1. In summary, the distiller’s grains as a raw material show great potential in the development of carbon-based energy storage materials that display outstanding electrochemical performance.

Polycrystalline phases engineered in-situ in polyaniline-graphene composite evoluting an exceptional stability and high charge storage capacity: An EIS investigative approach to evaluate material's stability

Development of electroactive materials exhibiting high performance with superior stability is crucial in the field of supercapacitors and battery research. We report on synthesis of highly stable composite of semi-polycrystalline polyaniline and graphene (SPani-graphene) and its application in supercapacitor electrodes. The electrochemical behavior and device performance of the electrodes were investigated through cyclic voltammetry (CV), galvanostatic charge-discharge GCD) and electrochemical impedance spectroscopy (EIS) in a 3-electrode and a 2-electrode (device) cell configurations, repectively. The cell specific capacitance (Cell Csp) achieved from the 2-electrode symmetric cell configuration was 525.5 F g−1 at 0.1 A g−1 using polymer gel electrolyte (PGE). The PGE in this work is xanthan gum jellied in 1 M aq. Na2SO4. The maximum energy density and power density achieved from the device was 46.7 Wh kg−1 and 16.16 kW kg−1, respectively, at 0.4 A g−1. Furthermore, the device exhibits an excellent retention of cell specific capacitance and coulombic efficiency of 97 % and 94 %, respectively, over 10,000 continuous GCD cycles, indicating an excellent rate capability as well as a promising power management. To investigate the material's electrochemical durability, a detailed EIS study has been carried out using both, 3-electrode, and 2-electrode cell configurations, before and after long cycling test (over 10,000 continuous GCD cycles). Our thorough experimentation delivers satisfactory results and has been explained in detail in the manuscript. Hereby, we propose that the EIS technique can be adopted for investigating materials' electrochemical stability, in addition to long CV and GCD cycles in the field of supercapacitors and battery research.

Identifying the plateau sodium storage behavior of hard carbon through the spin state

Hard carbon has emerged as a promising anode material for rechargeable sodium-ion batteries, owing to its abundant precursor sources and remarkable reversible charge storage capacity. The key to achieving an extended sodium storage capacity lies in the plateau capacity largely associated with the closed-pore structure, yet a comprehensive understanding in this area remains incomplete. In our study, we utilized electron paramagnetic resonance (EPR) spectra to discern the spin state of unpaired electrons within hard carbon materials, enabling the identification of sodium storage plateau regions. Hard carbon anodes with plateau capacity predominantly exhibit delocalized spins, evident in the EPR spectrum by limited spin density and a linewidth exceeding 100 G. These spins originate from the extended aromatic structure within small-sized but curved nano-graphite and the closed-pore walls, which are crucial for plateau capacity. Conversely, hard carbon anodes exclusively possessing slope capacity are characterized by localized spins, presenting a typical narrow and intense Lorentzian EPR signal. These localized spins arise from the edge defects of the nano-graphite structure, serving as favourable sites for sodium adsorption. Our development of a methodology to discern hard carbon plateau capacity behavior based on EPR spectra presents a facile and rapid approach for advancing high-performance hard carbon materials.

Unveiling the non-innocence of vanadium dopant in TiO2 nanocrystals for advanced energy storage and smart windows

Vanadium doped TiO2 NCs stand out as a promising candidate for energy storage applications due to its high electrical conductivity and redox properties. However, the thermodynamical behavior of the material under working conditions has not been explored and the reasons for its superior performance remain unlocked. This study explores the use of a combination of advanced in situ spectroscopy techniques, including x-ray absorption spectroscopy (XAS), spectro-electrochemistry (SEC), and electrochemical impedance spectroscopy (EIS) to provide unprecedented insights into the intricate electrochemical reaction mechanisms within these nanocrystals. Density functional theory calculations and EIS reveal the active role of substitutional V ions in the TiO2 anatase network as electron donors, enhancing surface charge and carrier density and improving pseudocapacitive properties. Cyclic voltammetry and in situ SEC reveal that V-doped TiO2 NCs exhibit significantly improved charge storage capacities, particularly in the pseudo-capacitance storage mechanism. In situ SEC and XAS analyses indicate that a more effective reduction of Ti4+ ions occurs during the electrochemical process in doped NCs, leading to higher charge capacitance and faster processes. Furthermore, in situ XAS measurements of the V K-edge revealed that the vanadium ions, beyond improving the redox behavior of the host, also actively participate in the reduction process. The significant changes in the V K-edge XANES and extended x-ray absorption fine structure spectra observed under reduction conditions can be ascribed to a change in the structure and oxidation state of the vanadium ions during the electrochemical reaction.

Unveiling Phenoxazine's Unique Reversible Two‐Electron Transfer Process and Stable Redox Intermediates for High‐Performance Aqueous Zinc‐ion Batteries

AbstractThe low specific capacity determined by the limited electron transfer of p‐type cathode materials is the main obstruction to their application towards high‐performance aqueous zinc‐ion batteries (ZIBs). To overcome this challenge, boosting multi‐electron transfer is essential for improving the charge storage capacity. Here, as a typical heteroaromatic p‐type material, we unveil the unique reversible two‐electron redox properties of phenoxazine in the aqueous electrolytes for the first time. The second oxidation process is stabilized in the aqueous electrolytes, a notable contrast to its less reversibility in the non‐aqueous electrolytes. A comprehensive investigation of the redox chemistry mechanism demonstrates remarkably stable redox intermediates, including a stable cation radical PNO⋅+ characterized by effective electron delocalization and a closed‐shell state dication PNO2+. Meanwhile, the heightened aromaticity contributes to superior structural stability during the redox process, distinguishing it from phenazine, which features a non‐equivalent hybridized sp2‐N motif. Leveraging these synergistic advantages, the PNO electrodes deliver a high capacity of 215 mAh g−1 compared to other p‐type materials, and impressive long cycling stability with 100 % capacity retention over 3500 cycles. This work marks a crucial step forward in advanced organic electrodes based on multi‐electron transfer phenoxazine moieties for high‐performance aqueous ZIBs.

Unveiling Phenoxazine's Unique Reversible Two-Electron Transfer Process and Stable Redox Intermediates for High-Performance Aqueous Zinc-ion Batteries.

The low specific capacity determined by the limited electron transfer of p-type cathode materials is the main obstruction to their application towards high-performance aqueous zinc-ion batteries (ZIBs). To overcome this challenge, boosting multi-electron transfer is essential for improving the charge storage capacity. Here, as a typical heteroaromatic p-type material, we unveil the unique reversible two-electron redox properties of phenoxazine in the aqueous electrolytes for the first time. The second oxidation process is stabilized in the aqueous electrolytes, a notable contrast to its less reversibility in the non-aqueous electrolytes. A comprehensive investigation of the redox chemistry mechanism demonstrates remarkably stable redox intermediates, including a stable cation radical PNO⋅+ characterized by effective electron delocalization and a closed-shell state dication PNO2+. Meanwhile, the heightened aromaticity contributes to superior structural stability during the redox process, distinguishing it from phenazine, which features a non-equivalent hybridized sp2-N motif. Leveraging these synergistic advantages, the PNO electrodes deliver a high capacity of 215 mAh g-1 compared to other p-type materials, and impressive long cycling stability with 100 % capacity retention over 3500 cycles. This work marks a crucial step forward in advanced organic electrodes based on multi-electron transfer phenoxazine moieties for high-performance aqueous ZIBs.

Ultraflexible PEDOT:PSS/IrOx-Modified Electrodes: Applications in Behavioral Modulation and Neural Signal Recording in Mice.

Recent advancements in neural probe technology have become pivotal in both neuroscience research and the clinical management of neurological disorders. State-of-the-art developments have led to the advent of multichannel, high-density bidirectional neural interfaces that are adept at both recording and modulating neuronal activity within the central nervous system. Despite this progress, extant bidirectional probes designed for simultaneous recording and stimulation are beset with limitations, including elicitation of inflammatory responses and insufficient charge injection capacity. In this paper, we delineate the design and application of an innovative ultraflexible bidirectional neural probe engineered from polyimide. This probe is distinguished by its ability to facilitate high-resolution recordings and precise stimulation control in deep brain regions. Electrodes enhanced with a PEDOT:PSS/IrOx composite exhibit a substantial increase in charge storage capacity, escalating from 0.14 ± 0.01 mC/cm2 to an impressive 24.75 ± 0.18 mC/cm2. This augmentation significantly bolsters the electrodes' charge transfer efficacy. In tandem, we observed a notable reduction in electrode impedance, from 3.47 ± 1.77 MΩ to a mere 41.88 ± 4.04 kΩ, while the phase angle exhibited a positive shift from -72.61 ± 1.84° to -34.17 ± 0.42°. To substantiate the electrodes' functional prowess, we conducted in vivo experiments, where the probes were surgically implanted into the bilateral motor cortex of mice. These experiments involved the synchronous recording and meticulous analysis of neural signal fluctuations during stimulation and an assessment of the probes' proficiency in modulating directional turning behaviors in the subjects. The empirical evidence corroborates that targeted stimulation within the bilateral motor cortex of mice can modulate the intensity of neural signals in the stimulated locale, enabling the directional control of the mice's turning behavior to the contralateral side of the stimulation site.

Planar amorphous silicon carbide microelectrode arrays for chronic recording in rat motor cortex

Chronic implantation of intracortical microelectrode arrays (MEAs) capable of recording from individual neurons can be used for the development of brain-machine interfaces. However, these devices show reduced recording capabilities under chronic conditions due, at least in part, to the brain's foreign body response (FBR). This creates a need for MEAs that can minimize the FBR to possibly enable long-term recording. A potential approach to reduce the FBR is the use of MEAs with reduced cross-sectional geometries. Here, we fabricated 4-shank amorphous silicon carbide (a-SiC) MEAs and implanted them into the motor cortex of seven female Sprague-Dawley rats. Each a-SiC MEA shank was 8 μm thick by 20 μm wide and had sixteen sputtered iridium oxide film (SIROF) electrodes (4 per shank). A-SiC was chosen as the fabrication base for its high chemical stability, good electrical insulation properties, and amenability to thin film fabrication. Electrochemical analysis and neural recordings were performed weekly for 4 months. MEAs were characterized pre-implantation in buffered saline and in vivo using electrochemical impedance spectroscopy and cyclic voltammetry at 50 mV/s and 50,000 mV/s. Neural recordings were analyzed for single unit activity. At the end of the study, animals were sacrificed for immunohistochemical analysis. We observed statistically significant, but small, increases in 1 and 30 kHz impedance values and 50,000 mV/s charge storage capacity over the 16-week implantation period. Slow sweep 50 mV/s CV and 1 Hz impedance did not significantly change over time. Impedance values increased from 11.6 MΩ to 13.5 MΩ at 1 Hz, 1.2 MΩ–2.9 MΩ at 1 kHz, and 0.11 MΩ–0.13 MΩ at 30 kHz over 16 weeks. The median charge storage capacity of the implanted electrodes at 50 mV/s was 58.1 mC/cm2 on week 1 and 55.9 mC/cm2 on week 16, and at 50,000 mV/s, 4.27 mC/cm2 on week 1 and 5.93 mC/cm2 on week 16. Devices were able to record neural activity from 92% of all active channels at the beginning of the study, At the study endpoint, a-SiC devices were still recording single-unit activity on 51% of electrochemically active electrode channels. In addition, we observed that the signal-to-noise ratio experienced a small decline of −0.19 per week. We also classified observed units as fast and slow repolarizing based on the trough-to-peak time. Although the overall presence of single units declined, fast and slow repolarizing units declined at a similar rate. At recording electrode depth, immunohistochemistry showed minimal tissue response to the a-SiC devices, as indicated by statistically insignificant differences in activated glial cell response between implanted brains slices and contralateral sham slices at 150 μm away from the implant location, as evidenced by GFAP staining. NeuN staining revealed the presence of neuronal cell bodies close to the implantation site, again statistically not different from a contralateral sham slice. These results warrant further investigation of a-SiC MEAs for future long-term implantation neural recording studies.

Polyaniline and water pre-intercalated V2O5 cathodes for high-performance planar zinc-ion micro-batteries

The imperative development of high-performance planar micro-batteries featuring high-capacity electrodes and environmentally safer, cost-effective systems is crucial for powering forthcoming smart, miniaturized portable electronic devices. In alignment with this necessity, this study centers on achieving high-capacity cathode materials. This involves the pre-intercalation of polyaniline and water into V2O5 nanowires to enhance capacity, applied in conjunction with Zn anodes within a planar device structure to boost charge storage performance. The presented straightforward strategy is demonstrated to not only effectively increase charge storage capacities from 235 mAh/g to 384 mAh/g at 200 mA/g but also reduce the pre-activation process. Consequently, the Zn-ion micro-batteries obtained, featuring high-capacity cathodes, not only provide a substantial areal capacity of 409 μAh/cm2 but also exhibit notable peak areal energy density and power density at 306.7 μWh/cm2 and 3.44 mW/cm2, respectively. Additionally, the micro-battery demonstrates a slow self-discharge voltage response, with approximately 80 % retention even after 200 h. This work proposes an effective strategy to enhance the electrochemical performance of planar micro-batteries, a critical advancement for the development of advanced portable electronics.

Trap-induced hydro-charging polylactic acid nonwovens with high charge storage capability for stable and efficient air filtration

Under the background of carbon neutrality, eco-friendly biodegradable polylactic acid (PLA) melt-blown nonwovens have been developed in air filtration. Nevertheless, the filtration performance of existing PLA melt-blown nonwovens is in an embarrassing situation and fails to meet the requirement of high efficiency air filters. Here, with controllable doping of N, N′-ethylene bis-stearamide (EBS), and barium titanate (BaTiO3) into PLA, through the melt-blown process, the charge-storage capacity of PLA nonwovens enhanced significantly. By utilizing the hydro-charging technology thereafter, we have prepared hydro-charged PLA/EBS/BaTiO3 nonwovens (HCP-EB) with excellent filtration performances. The doped EBS and BaTiO3 could improve the crystallization and charge storage capacity of PLA during the melt-blown process, thus constructing a large number of interfacial traps between crystalline and amorphous regions, leading to more electric charges captured during the hydro-charging process. The HCP-EB exhibited a high filtration efficiency (99.69 %) for PM0.3, a low pressure drop (27.44 Pa), and superior charge storage stability. Furthermore, the HCP-EB, remained at 99.18 % filtration efficiency after 48 h of treatment at 90 % relative humidity. After 3 months of storage, it still possessed an excellent filtration efficiency (99.02 %). Our work will contribute to the practical application of PLA melt-blown nonwovens in air filters and masks, and inspire the research of next-generation biodegradable electret air filtration materials.

Iron-doped cross-linked puffed carbon as capacitive anode for the enhancement of bioelectron storage capacity in microbial fuel cells

Microbial fuel cell (MFC) can utilize the metabolism of electroactive microorganisms to remove organic pollutants from wastewater, and the application of capacitive anodes can enhance the power generation capacity of MFC and the energy storage capacity of bioelectronics. This research aimed to create a capacitive anode with a large specific surface area and excellent electrical conductivity. To achieve this aim, iron-doped cross-linked puffed carbon (CPC–Fe) was prepared for the modification of carbon cloth (CC) substrates by a simple one-step expansion carbonization method using FeCl3·6H2O and maltose as raw materials. The surface structure characterization confirms the successful incorporation of Fe atoms, with Fe3O4 accounting for 79.61%. Fe3O4 exhibits excellent specific capacitance characteristics and can also serve as a good conductor for the transmission or reception of electrons generated by electroactive bacteria. Furthermore, the mesoporous volume of CPC-Fe significantly increases, which contributes to the enhancement of the specific capacitance of material and the improvement of charge storage capacity. Based on these advantages, the maximum power density of MFC equipped with CPC-Fe/CC anode reaches 1850.50 mW m−2. The CPC-Fe/CC bioanode has a cumulative total charge of 1076.02 C m−2, showing good capacitive behaviour and exhibiting a significant enrichment effect on Geobacter species. This study demonstrates that the regulation of extracellular electron transfer (EET) process based on bioelectronic reception steps can not only enhance the power generation performance of MFC, but also effectively improve the energy storage capacity of MFC, which offers significant knowledge for the development of electrode design in other bioelectrochemical systems.