Supercapacitor Energy Storage Research Articles

Recent Advancements in Gel Polymer Electrolytes for Flexible Energy Storage Applications.

Since the last decade, the need for deformable electronics exponentially increased, requiring adaptive energy storage systems, especially batteries and supercapacitors. Thus, the conception and elaboration of new deformable electrolytes becomes more crucial than ever. Among diverse materials, gel polymer electrolytes (hydrogels, organogels, and ionogels) remain the most studied thanks to the ability to tune the physicochemical and mechanical properties by changing the nature of the precursors, the type of interactions, and the formulation. Nevertheless, the exploitation of this category of electrolyte as a possible commercial product is still restrained, due to different issues related to the nature of the gels (ionic conductivity, evaporation of filling solvent, toxicity, etc.). Therefore, this review aims to resume different strategies to tailor the properties of the gel polymer electrolytes as well as to provide recent advancements in the field toward the elaboration of deformable batteries and supercapacitors.

Co-precipitation Synthesis and Characterization Studies of Manganese Oxide Doped with Nickel for High-Performance Energy Storage Supercapacitor Application

The advancement in nanotechnology research has facilitated the development of eco-friendly methods for the synthesis of nanoparticles. In this work, nickel (Ni)-doped manganese oxide was synthesized using the co-precipitation method. The prepared Ni-doped manganese oxide products have been characterized by X-ray powder diffraction, scanning electron microscopy (SEM), transmission electron microscope (TEM), and energy dispersive X-ray spectroscopy (EDS). The preliminary electrochemical characteristics include charge-discharge cycling, which improves the conductivity and capacitance of the high-performance aqueous asymmetrical supercapacitor. The CV analysis of the Ni-doped manganese oxide electrode demonstrated a distinctive pseudocapacitive behavior in 1 M KOH solution. The nickel (Ni) doped electrode has a higher specific capacitance value than the pure manganese oxide electrode, with a value of 2225.07 F×g-1 at a scan rate of 5 mV×s-1. Keywords: Supercapacitor, Co-precipitation method, Nanotechnology, Synthesized, Electrochemical

Real-time energy management simulation for enhanced integration of renewable energy resources in DC microgrids

The presented work addresses the growing need for efficient and reliable DC microgrids integrating renewable energy sources. However, for the sake of practicality, implementing complex control strategies can increase system complexity. Thus, efficient methodologies are required to provide efficient energy management of microgrids while increasing the integration of renewable energy sources. The primary contribution of this work is to investigate the issues related to operating a DC microgrid with conventional control designed to power DC motors using readily available, non-advanced control strategies with the objective of achieving stable and reliable grid performance without resorting to complex control schemes. The proposed microgrid integrates a combination of uncontrollable renewable distributed generators (DGs) alongside controllable DGs and energy storage systems, including batteries and supercapacitors, connected via DC links. The Incremental Conductance (InCond) algorithm is employed for maximum power point tracking to maximize power output from the PV system. The energy management strategy prioritizes the solar system as the primary source, with the battery and supercapacitor acting as backup power sources to ensure overall system reliability and sustainability. The effectiveness of the microgrid under various operating conditions is evaluated through extensive simulations conducted using MATLAB. These simulations explore different power generation scenarios, including normal operation with varying load levels and operation under Standard Test Conditions (STC). Moreover, fault analysis of the DC microgrid is performed to examine system reliability. The system performance is evaluated using real-time simulation software (OPAL-RT) to validate the effectiveness of the approach under real-time conditions. This comprehensive approach demonstrates the efficacy of operating a DC microgrid with conventional controllers, ensuring grid stability and reliability across various operating conditions and fault scenarios while prioritizing the use of renewable energy sources. The results illustrated that system efficiency increases with load, but fault tolerance measures, can introduce trade-offs between reliability and peak efficiency.

A spray coated high performing metal-free onion-like carbon supercapacitor for sustainable energy storage

Supercapacitors will play a crucial role in the future energy landscape due to their high power density and extended cycle stability. However, energy density tends to be relatively low, partly because of conventional heavy current collectors, also posing sustainability issues. It is crucial to integrate lightweight, flexible current collectors and environmentally friendly active materials while maintaining the performance of the supercapacitor. Here we report on a metal-free supercapacitor using a carbon paper current collector and onion like carbon (OLC). The electrodes were fabricated through a scalable and flexible spray-coating process using onion-like carbon ink. Higher capacitances were observed for the paper-based electrode (24.1 F/g, 34.9 mF/cm2) compared to 22.5 F/g (31.5 mF/cm2) for aluminium collectors at scanrates of 2.5 mV/s over a voltage window of 2.5 V. At elevated scanrates of 100 mV/s–5 V/s, the actual operating window of a supercapacitor, the paper-based electrode offers a significantly enhanced performance. Stability tests demonstrated a capacitive retention of 98 % for both electrodes after 10,000 cycles. The utilization of onion-like carbon as the active material and a paper-based current collector enables the development of a fully carbon-based supercapacitor system, without compromising its electrochemical performance. This approach introduces a metal-free OLC supercapacitor and promotes environmental sustainability by reducing the dependence on conventional metal-based components and provides a more resource-efficient solution to address the energy storage needs.

Boosting Supercapacitor Energy Storage Using Microporous Carbon Derived from an Octavinylsilsesquioxane and Fluorenone-Linked Porous Hybrid Polymer

Boosting Supercapacitor Energy Storage Using Microporous Carbon Derived from an Octavinylsilsesquioxane and Fluorenone-Linked Porous Hybrid Polymer

Fuzzy logic-based coordinated operation strategy for an off-grid photovoltaic hydrogen production system with battery/supercapacitor hybrid energy storage

The coupling of photovoltaic power generation with water electrolyzer is advantageous for enhancing solar energy utilization and generating green hydrogen. In this work, an off-grid photovoltaic-based hydrogen production system consisting of photovoltaic, electrolyzer, battery energy storage system and supercapacitor was developed. A coordinated operation strategy is designed to manage the power of each unit in the system to avoid significant fluctuations in working power and frequent start-stop operations of the electrolyzer unit. Firstly, the coordinated operation strategy sets five operation modes for the photovoltaic-based hydrogen production system, and the fuzzy logic control algorithm is used to choose the operation mode to determine the reference power of each unit. On this basis, the state of charge feedback-based first-order low-pass filter algorithm is used to achieve the power allocation to mitigate deep charging and discharging of the supercapacitor. The proposed solution is extensively assessed through comparative simulation experiments based on three typical test days. The numerical results confirm its effectiveness and demonstrate the potential for achieving high system efficiency.

Tetraphenylanthraquinone and Dihydroxybenzene-Tethered Conjugated Microporous Polymer for Enhanced CO2 Uptake and Supercapacitive Energy Storage.

Conjugated microporous polymers (CMPs) feature extended excellent porosity properties and fully conjugated electronic systems, making them highly effective for several uses, including photocatalysis, dye adsorption, CO2 capture, supercapacitors, and so on. These polymers are known for their high specific surface area and adjustable porosity. To synthesize DHTP-CMPs (specifically TPE-DHTP CMP and Anthra-DHTP CMP) with abundant nitrogen (N) and oxygen (O) adsorption sites and spherical structures, we employed a straightforward Schiff-base [4 + 2] condensation reaction. This involved using 2,5-dihydroxyterephthalaldehyde (DHTP-2CHO) as the primary building block and phenolic OH group source, along with two distinct structures: 4,4',4″,4"'-(ethene-1,1,2,2-tetrayl)tetraaniline (TPE-4NH2) and 4,4',4″,4"'-(anthracene-9,10-diylidenebis(methanediylylidene))tetraaniline (Anthra-4Ph-4NH2). The synthesized Anthra-DHTP CMP had a remarkable BET surface area (BETSA) of 431 m2 g-1. Additionally, it exhibited outstanding thermal stability, as shown by a T d10 of 505 °C. Furthermore, for practical implementation, the Anthra-DHTP CMP demonstrates a significant capacity for capturing CO2, measuring 1.85 mmol g-1 at a temperature of 273 K and 1 bar. In a three-electrode test, the Anthra-DHTP CMP has a remarkable specific capacitance of 121 F g-1 at 0.5 A g-1. Furthermore, even after undergoing 5000 cycles, it maintains a capacitance retention rate of 79%. Due to their outstanding pore characteristics, abundant N and O, and conjugation properties, this Anthtra-DHTP CMP holds significant potential for CO2 capture and supercapacitor applications. This work will pave the way for the development of materials based on DHTP-CMPs and their postmodification with additional groups, facilitating their use in photocatalysis, photodegradation, lithium battery applications, and so on.

Innovative Si@MOF-5@CNT hybrid: Tailoring energy storage and catalysis in batteries, supercapacitors, and hydrogen evolution

This work presents the silicon-doped metal-organic framework with carbon nanotube additive (Si@MOF-5/CNT) composite as a versatile and cutting-edge foundation for advanced energy storage devices. This novel work highlights the doping impact of silicon and CNT to MOF-5 structure, which improves the stability and electrochemical performance. Regarding battery applications, the Si@MOF-5/CNT composite delivers a specific capacity of 1642C/g. The asymmetric structure with Si@MOF-5/CNT and activated carbon is built for supercapacitor applications. This hybrid system (Si@MOF-5/CNT//AC) provides the specific capacity of 132C/g, an energy density of 46 Wh/kg, and a power density of 1100 W/kg. In Hydrogen Evolution Reaction (HER) applications, the Si@MOF-5/CNT composite showed a minimum overpotential of 158 mV and a Tafel slope of 59.28 mV/dec. Our findings place this composite at the forefront, demonstrating improved performance and versatility in dealing with the ever-changing environment of energy storage difficulties.

Composites of 2D Materials and Bacterial Cellulose for Sustainable Energy Storage and Environmental Remediation

AbstractThe ever‐increasing demand for sustainable energy sources and environment protection is the focus of significant scientific scrutiny worldwide. Advanced composite materials have been developed to help meet the energy demand and environmental sustainability. Researchers are drawn to the study of two‐dimensional (2D) materials/bacterial cellulose (BC) composites for energy and environmental applications due to the intriguing electrical, mechanical, electrochemical, and catalytic properties of 2D materials combined with the sustainability and biocompatibility of BC. In this review, the key strategies are explained to develop 2D materials/BC composites and highlight unique properties of such fascinating systems. The recent progress on the application of advanced 2D materials/BC composites in energy storage (supercapacitors and batteries) and environmental remediation (water treatment, antimicrobial activity, and environmental gas sensing) are explained in detail highlighting future outlooks and challenges in the field. This review is intended to serve as a valuable resource for researchers currently engaged in the study of 2D materials and/or BC for different applications and is expected to shape the upcoming research and industrial applications of emerging 2D materials/BC composites.

Performance study of high energy storage supercapacitor from waste corn husk biomass electrode materials

Waste biomass carbon materials are used as green and environmentally friendly electrode materials for supercapacitors (SCs) have great development prospects, therefore, miscellaneous elements-rich and recycled renewable porous carbon materials have important applications value in the field of energy storage device. In this paper, waste corn husk as biomass precursor to prepare corn husk porous carbon (CHPC) using two steps of high-temperature carbonization and KOH activation. The CHPC-2 optimized by KOH shows a specific surface area (SSA) of 1103 m2 g−1 and a total pore volume of 0.83 cm3 g−1, achieving a high specific capacitance of 413.4 F g−1 at 0.5 A g−1. After 10,000 cycles, only 4.17 % of the capacitance was lost. In a two-electrode system with 1 M Na2SO4 as the electrolyte, CHPC-2//CHPC-2 exhibits a specific capacitance of 333 F g−1 at a wide voltage window of 0–1.8 V, and energy density of 37.46 Wh Kg−1 when power density is 450 W kg−1, which possesses the capacitance retention rate of 85.16 % after 5000 cycles. The assembled symmetrical SCs contain capacitance of 308.79 F g−1, and 21.02 Wh kg−1 under a power density of 350 W kg−1 in PVA/KOH gel electrolyte. Consequently, CHPC materials provide a scientific and reasonable research idea for the development of SCs with inexpensive, non-polluting, and high energy density.

Advancing Electrochemical Energy Storage: The Synergistic Impact of Sulfur Nano-Confinement in Hierarchically Porous Jute-Derived Activated Carbon for Enhanced Supercapacitor Performance

The availability of energy is a cornerstone for the modernization, automation, and economic growth of nations. With the rapid depletion of fossil fuels and rising environmental concerns, such as CO2 emissions leading to global warming, there has been an intensified search for alternative, renewable energy sources like solar and wind power. However, their intermittent nature necessitates robust electric energy storage systems for effectively harnessing these resources. Electrochemical energy storage devices, particularly batteries and supercapacitors, have emerged as a focal point of recent research due to their potential to bridge this gap. While supercapacitors are known for their high power density and long cycle life, they typically exhibit limited energy density. Recent advancements have shown that composites combining carbonaceous materials with redox-active nanomaterials can significantly enhance supercapacitors' electrochemical performance. In this context, our research explores the development of hierarchically porous activated carbon nanosheets (JAC) derived from jute, an abundantly available biomass. Using a straightforward pyrolysis process, we have investigated its potential in supercapacitor applications. The prepared JAC, when employed as an electrode material in a symmetric supercapacitor with a glycerol-based bio-electrolyte, demonstrated higher specific capacitance compared to its commercial counterparts. Further innovation was achieved through the introduction of sulfur doping in JAC (S-doped JAC). This novel approach leverages the inherent porous nanosheet morphology of JAC and heteroatom modification to yield exceptional electrochemical performance. Our findings reveal that the S-doped JAC composite, particularly the variant with 25% sublimed sulfur (SJAC-25), significantly outperforms the standard JAC in terms of specific capacitance (230 F/g vs. 130 F/g at 1.0 A/g current density) in a glycerol-KOH bio-based electrolyte. Moreover, a symmetric supercapacitor assembled with SJAC-25 showcased an impressive energy density of 32 Wh/kg at a power density of 500 W/kg, maintaining 28 Wh/kg even at a heightened power density of 2500 W/kg. This demonstrates its capability to retain high energy efficiency under varying power conditions. Additionally, the SJAC-25 based supercapacitor exhibited remarkable durability, with about 94% capacitance retention and 86% Coulombic efficiency after 10,000 charge-discharge cycles. Our research not only highlights the potential of processed bio-waste as a viable material for energy storage but also introduces an advanced, scalable, and straightforward synthesis method. This method could pave the way for the preparation of highly porous and sulfur-doped nanoporous carbon, setting a new benchmark for high-performance electrochemical energy storage applications.

Architected Carbon Structures for Energy Storage

Carbon materials, owing to their excellent electrical conductivity, tailor-ability, inexpensiveness, and versatility, have been extensively studied as electrode materials for energy storage devices, including batteries and supercapacitors. In this talk, I will discuss how to combine conventional materials/chemical synthesis with 3D printing techniques to develop architected carbon electrode materials for supercapacitors. The capacitance of carbon-based supercapacitor electrodes has remained at a mediocre level between 100 and 200 F/g for decades. Until recently, a new family of carbon materials termed hierarchical porous carbons has pushed the capacitance to new benchmark values beyond 300 F/g and has revitalized the exploration of carbon materials for supercapacitors. We have recently developed some hierarchical porous carbon areogels contain different scales of pores inter-connected together and assembled in hierarchical patterns, through a combination of freeze drying, template, chemical etching and 3D printing. These porous carbons have an open porous structure, providing an extremely large and accessible surface area. They can be used as electric double layer materials that enable ultrafast charging/discharging and retain outstanding capacitive performance even at ultralow temperatures (-70 °C). They can serve as 3D conductive scaffolds/current collectors to support pseudo-capacitive materials with ultrahigh mass loadings. These findings exemplified how to use a deterministic structure to improve the rate capability of supercapacitors and their capacitances at ultrahigh current densities and mass loadings and ultralow temperatures, which are long-standing challenges for SCs.

Direct Observation of Reversible Surface Potential in Pseudocapacitive Electrochromic Films by Kelvin Probe Force Microscopy

High-resolution topography and local potential images together are very powerful tools for understanding the local environment of nanomaterials. In electrochemistry, there are significant changes within the electrode materials upon charging and discharging. However, the surface changes for pseudocapacitive materials in repetitive electrochemical cycling are easily being overlooked. Thanks to the advances in Atomic Force Microscopy, it becomes feasible to visualize the electrical changes in surface upon charge transfer with Kelvin Probe Force Microscopy (KPFM) equipped with a conductive tip. We report the KPFM surface potential images and profiles of NiO electrochromic films upon bleaching (charging) and coloration (discharging). The measured surface potential is about 60 times higher in bleaching state upon charging at 20mC/cm2. What is interesting is that the potential profile shows identical topographic features with the height profile of surface morphology. The surface particles further demonstrate shape entanglement in one direction (from ~100nm to ~140nm) and shrinkage in the orthogonal direction, suggesting the charge-induced electrical stress. According to the pseudocapacitive features in the cyclic voltammetry and electrochemical impedance spectroscopy, the surface-dominant redox behavior is within expectation. Though, this dynamic surface potential change is not well studied but important, and associated with work function fluctuations and various kinds of nanoscale charge-sensitive properties, especially for efficient electrochromic supercapacitor energy storage.

An optimized AC side startup strategy of E‐STATCOM for ITER pulsed power electrical network

AbstractDuring the operation of the ITER machine, hundreds of MW/Var of active and reactive power will be exchanged with the grid. The E‐STATCOM scheme composed of the Modular Multilevel Converter (MMC) and split supercapacitor energy storage has been proposed to improve the power compensation performance of the existing reactive power compensation system in the previous study. However, one of the main technical challenges which is lack of research is to precharge all submodule capacitors and supercapacitors from zero to their nominal voltage values efficiently during a startup process. As the capacitance and operating voltage of supercapacitors are much different from capacitors in each submodule, the startup of E‐STATCOM is a more complicated process. To coordinate the energy exchange between submodule capacitors and supercapacitors, submodule capacitors and the grid, this paper presents an optimized four‐stage AC side startup strategy for the E‐STATCOM. The proposed method minimizes the use of current‐limiting resistors while suppressing the surge current in the zero‐voltage startup process of supercapacitors, in addition to optimizing the energy consumption. The pulse current charging, constant current charging and constant power charging strategies of supercapacitors are adopted in different charging stages, and the detailed coordinated control scheme between submodule capacitors and supercapacitors are described and analyzed. The effectiveness and performance of the proposed method are verified by simulation results and hardware‐in‐the‐loop (HIL) experiments.

Micro/Meso-Porous Double-Shell Hollow Carbon Spheres through Spatially Confined Pyrolysis for Supercapacitors and Zinc-Ion Capacitor.

Energy storage in supercapacitors and hybrid zinc ion capacitors (ZIC) using porous carbon materials offers a promising alternative method for clean energy solutions. The unique combination of hierarchical porous structure and nitrogen doping in these materials has demonstrated significant capacity for energy storage. Nevertheless, the full potential of these materials, particularly the relationship between pore structure configuration and performance, remains underexplored. Herein, a confined pyrolysis strategy based on the polymerization characteristics of polydopamine (PDA) was developed to construction of hollow carbon spheres with microporous/mesoporous dual shell structure. The depth of micropores and cavity can be controlled by adjusting the duration of heat treatment and hydrothermal treatment, in accordance with the decomposition and polymerization characteristics of PDA. Due to the elasticity of this structure, the relationship between the micro/mesoporous depth of the prepared carbon spheres and the energy storage performance in supercapacitors and ZIC is established. Through optimizing the ion transport capacity of carbon spheres and considering the influence of its internal cavity structure on energy storage, the resulting carbon spheres exhibit high specific capacitance of 389 F g-1 in supercapacitor and specific capacitance of 260 F g-1 and excellent stability with 99.3 % retention after 30000 chare/discharge cycles in ZIC.

Phytogenic Cu2OBi2O3ZrO2 nanomaterial for supercapacitor and water splitting: Synthesis, characterization, and energy applications

Copper-based nanocomposites are regarded as sustainable energy materials having tremendous potential for energy storage supercapacitors and energy generation water splitting applications. Herein, a facile Cu-based ternary Cu2OBi2O3ZrO2 nanocomposite is prepared by a sustainable, lower-cost, and simple hydrothermal-based phyto-synthesis route by using Amaranthus Viridis L. amaranthaceae plant (abbreviated as AVL.A). The synthesized AVL.A-Cu2OBi2O3ZrO2 nanocomposite is characterized by powder-X-ray diffraction and FE-Scanning electron microscopy for its phase composition and surface morphology. The electrochemical efficiency of AVL.A-Cu2OBi2O3ZrO2 nanocomposite is investigated for supercapacitors and overall water splitting. The fabricated Cu2OBi2O3ZrO2 nanocomposite-based Nickel foam (NF) electrode shows superior performance with a specific capacitance of 524.5 F/g at 2 mV/s and 400 F/g at 1 A/g. The excellent rate capability is observed at scan rates from 2 mv/s to 300 mV/s and at current densities from 0.5 A/g to 30 A/g for AVL.A-Cu2OBi2O3ZrO2–NF. Furthermore, fabricated AVL.A-Cu2OBi2O3ZrO2–NF shows excellent electrochemical stability with 100% Coulombic efficiency till 5000 charge-discharge cycles. As bifunctional electrocatalyst AVL.A-Cu2OBi2O3ZrO2–NF electrode exhibits 117 mV overpotential at 10 mA/cm2 current density for HER kinetics along with 112 mV/dec Tafel slope values. The same Tafel slope value is also observed for OER measurements. These values of overpotential and Tafel slope for AVL.A-Cu2OBi2O3ZrO2–NF suggest a rapid and efficient electrochemical process of AVL.A-Cu2OBi2O3ZrO2–NF bifunctional electrocatalyst for energy generation. Overall study highly proposed AVL.A-Cu2OBi2O3ZrO2–NF as the potential electrode for energy storage supercapacitor and energy generation overall water splitting.

Evaluating the electrochemical boost and antimicrobial power of biogenic zinc oxide-polyaniline nanocomposite

Bio-based materials from bark, wood, leaves, and fruits have several uses in nanotechnology. Anthocephalus Cadamba is a biological reducing agent in nanocomposites. The fruit of Anthocephalus Cadamba is used to synthesize ZnO nanoparticles and polyaniline to make a ZnO-PANI nanocomposite. We describe UV–visible, FTIR, XRD, and SEM data to support synthesis. The dielectric constant is highest in the ZnO-PANI nanocomposite compared to pure ZnO nanoparticles. The Nyquist plot semicircular arc confirms temperature-induced conductivity improvement in nanocomposites. Nanocomposites have 1.3 ×10−2 S/m higher conductivity than nanoparticles. The ZnO-PANI nanocomposite has the greatest specific capacitance (Csp) of 1.3 × 10−2. This work suggests that ZnO-PANI nanocomposite electrodes might be useful supercapacitors in energy storage devices with antibacterial properties. XTT assay and biofilm formation assay using CLSM (Confocal laser scanning microscope) indicated that Integration of ZnO-PANI nanocomposites onto biofilm-prone surfaces like medical devices or implants inhibited bacteria adhesion and biofilm growth in antimicrobial investigations.

Sizing of Energy Storage Systems in Electric Vehicles based on Battery-Supercapacitor Technology

The purpose of this research is to determine the ideal hybrid energy storage system (HESS) size with the goal to improve the effectiveness and efficiency of combined battery and supercapacitor energy storage in electric vehicles. The research uses Mixed Integer Linear Programming (MILP) to determine the most suitable configurations using simulation data from a modeled electric vehicle. The results show that MILP works at identifying the specific capacity needs of the storage system, which change based on the vehicle's power and energy capacity. The innovation provides a paradigm for the development of sustainable and highly efficient electric vehicles in the future, while also enhancing the functionality of current electric vehicles.

Solar powered membrane bioreactor (MBR) treating wastewater for reuse at a hospital in Kampala, Uganda – Results of pilot-scale trials

A robust and cost-effective pilot solar-powered membrane bioreactor (MBR) with downstream granular activated carbon (GAC) filter hospital wastewater treatment was developed for the Lubaga hospital in Kampala, Uganda. The MBR-GAC pilot included a 25 m2 ultrafiltration (UF) module, a 100 kg GAC filter, 20 photovoltaic panels totaling 7 kWp and a 3.55 kWh supercapacitor energy storage unit to produce non-potable and reusable water for toilet flushing, cleaning and irrigation. The pilot operated with 43% clean energy autonomy with grid and diesel generator backup for power outages of more than 1 hour. The MBR pilot produced an average flux of 10–15 L m–2 h–1 with 50% total organic carbon (TOC) removal. The nitrification, denitrification and filtration tanks were separated to achieve a nitrification of 80% and denitrification of 20%. The removal of typical hospital pharmaceutical residues that could not be reduced by the MBR increased to approximately 90% after the downstream GAC filter was upgraded. The removal efficiency of the GAC decreased to approximately 25% at 4,290 bed volume (BV). The significant increase of 75% in the removal efficiency of diclofenac in the MBR was attributed to the acclimation of the activated sludge. The quality of the treated wastewater from the pilot plant was sufficient for reuse by irrigation of the hospital garden, toilet flushing and cleaning. Finally, the study discussed ways to optimize the design and operation of the plant. The pilot is scalable to be replicated elsewhere and adapted in an efficient and cost-effective manner in sub-Saharan countries in Africa.

Harnessing true capacitive activity of nitrogen-doped MXene through hydrogel assembly and theoretical understanding of the role of dopant sites

Heteroatom nitrogen (N) doping in MXene can significantly push its energy storage metric. However, translating the intrinsic improvement of individual sheets into macroscopic electrodes is challenging due to the blockage of dopant sites by restacking. Here, we report the development of restack-controlled N-doped MXene hydrogel through speedy interfacial assembly methods to keep the dopant sites electrochemically accessible. Application of a small voltage between two zinc plates in an aqueous dispersion of N-doped MXene leads to the rapid development of doped hydrogel over the positive zinc plate via electrophoretic drag and linking by interfacial released zinc ions. As-developed hydrogels having continuous porosity and quasi-oriented sheet arrangement preserve ion transporting channels, thus allowing the surface dopant sites to participate in the supercapacitive energy storage actively. N-doped hydrogel displays a high capacitance of 488 F g−1 at 5 mV s−1 much higher as compared to compact film. The N-doped MXene hydrogels display excellent rate performance with retention over 88 % at 1000 mV s−1 and cyclic stability of 87 % over 10000 cycles. The detailed density functional theory (DFT) calculation reveals a major pseudocapacitive contribution from the surface adsorption and functional group substitution type N dopant sites as compared to another dopant site, namely, lattice substitution.