Potential Energy Storage Research Articles

Experimental investigation of major rocks in Hong Kong as potential sensible thermal energy storage medium

Energy storage is considered a viable solution for managing renewable energies, and rock is recognized as an economically feasible and environmentally friendly medium for sensible heat storage. Following the principle of utilizing local resources, fifteen major rock types from Hong Kong—covering igneous, sedimentary, and metamorphic classifications—were collected and processed to required sizes for several characterization techniques, considering their heterogeneity and anisotropy. Thermophysical (thermal diffusivity/conductivity, heat capacity, and thermal expansion coefficient) and mechanical properties of the selected rocks were analyzed from room temperature to 1000 °C, along with their chemical and structural compositions. Through multidimensional evaluation, the suitability (optimal, average, poor) of these rocks from Hong Kong to serve as thermal energy storage media was assessed. The results obtained indicated that Hong Kong basalt is the optimal candidate for high-temperature thermal energy storage material, with 850 °C identified as the suitable maximum working temperature. Other igneous rocks from Hong Kong can be utilized for mid-to-low temperature range (100–500 °C) thermal energy storage engineering. However, sedimentary and metamorphic rocks from Hong Kong appear unsuitable for local thermal energy storage engineering.

Ferrocene‐Based Nickel Metal–Organic Framework Nanosheets as Efficient, Long‐Cycle Cathode Catalyst for Li‐CO2 Battery

AbstractLi‐CO2 batteries, as a novel type of secondary battery, show great potential for energy conversion and storage. However, challenges such as large electrode polarization and poor cycling performance, stemming from difficulties in decomposing discharge products, limit their practical application. Here, Ferrocene‐based nickel metal–organic framework (Ni‐Fc) nanosheets structure to act as cathode catalysts, prepared via a one‐pot solvothermal reaction. X‐ray absorption fine structure (XAFS) analysis shows that Ni metal forms abundant catalytic active centers with O coordination of carboxylic acid groups in ferrocene units. The Ni‐Fc‐based battery demonstrates a high discharge capacity of 18636 mAh g−1 and exhibits a cycle life exceeding 2000 h at a current of 200 mA g−1. Density functional theory (DFT) calculations indicate that the stronger interaction of Ni‐Fc with discharge intermediates and enhanced Li adsorption accelerate battery reaction kinetics. This study introduces novel catalyst design concepts aimed at achieving high‐performance CO2 reduction and oxidation, thereby advancing Li‐CO2 batteries toward practical application.

Multivalent Cations Substitution Accelerate Li‐Ion Diffusion in Na4Cr2Nb98O250 Defect Phase for Wide Temperature Energy Storage

AbstractNiobate materials are regarded as promising anode materials for Lithium‐ion batteries. Inspired by the design of shear‐type ReO3 materials through the multivalent cations substitution defect construction method, nonequivalent Na4M2Nb98O250 (M = Fe, Cr, NFNO, NCNO) anode materials are synthesized. The novel NCNO material exhibits a modified N‐Nb2O5 isostructural defect phase that can optimize 3D Li‐ion transport channels and enhance the electronic conductivity, leading to a superior ionic diffusion coefficient (DLi) and good structural stability. It shows balanced high performance with respect to specific capacity, rate capacity and cyclability. Furthermore, it also demonstrates outstanding wide‐temperature (−10 to 45 °C) lithiation performance, especially at low temperature (−10 °C) of a capacity exceeding 100 mAh g−1 at 5C and minimal capacity decay (0.012% per cycle) after 1000 cycles, indicating the great potential of wide temperature energy storage.

Innovative COF@MXene composites for high performance energy applications

AbstractAs a new type of composite two-dimensional material formed by the combination of Covalent Organic Frameworks (COFs) and two- dimensional (2D) MXenes, COF/MXene heterostructures (COF@MXene) inherit the stable porous two-dimensional structure of COFs and the excellent electrochemical performance and catalytic activity of MXenes, thus attracting widespread attention. Additionally, COF@MXene possesses various elemental affinity sites, efficient ion channels, and the ability to append various functional groups, which endow them with tremendous potential in electrochemical energy storage, energy conversion, and catalysis. Currently, there is a lack of extensive literature discussing the utilization of COF@MXene. The quest for enhanced physicochemical attributes through tailored modifications and composite strategies for COF@MXene is still a noteworthy hurdle. Furthermore, discovering novel application contexts that can harness the exceptional capabilities of these materials presents a formidable task. This review initiates with an exploration of the primary methodologies for synthesizing COF and MXene composites. Subsequently, it outlines the diverse applications of COF and MXene in energy storage, energy conversion, and environmental conservation. Lastly, it discusses the primary obstacles and future trajectories within these domains.

Enhanced photocatalytic activity of BB41 and ROM2R dyes using green synthesized NiO nanoparticles: A response surface methodology approach

BackgroundNiO NPs are recognized for their potential in catalysis, energy storage, and environmental remediation. Green synthesis using plant extracts, such as Cucumis maderaspatanus L. (CmL.) leaves, offers an eco-friendly approach. This study focuses on synthesizing and analyzing the structural, optical, and photocatalytic properties of Cm-NiO NPs. MethodologyCm-NiO NPs were synthesized using CmL. leaf extract and calcinated at 300, 500, and 700 °C. XRD confirmed a face-centered cubic structure. Band gap values were 3.36 eV at 300 °C, 2.98 eV at 500 °C, and 3.15 eV at 700 °C. TEM showed spherical particles of 17.81 nm. The point of zero charge (pHpzc) was pH 7.95. The photocatalytic activity was tested on BB41 and ROM2R dyes under varying pH (4 – 10), dye concentrations (10 – 50 ppm), catalyst amounts (0.1 – 1.0 mg/mL), and light sources. Scavenger studies identified reactive compounds. Response surface methodology (RSM) optimized the degradation process. LC-MS analyzed degradation products, and ECOSAR software estimated their toxicity. Significant FindingsCm-NiO NPs showed high photocatalytic efficiency, degrading 93.60 % of BB41 and 88.76 % of ROM2R under UV light (250 W, 365 nm). The nanoparticles demonstrated a face-centered cubic structure and a pHpzc of 7.95. RSM effectively optimized the process, and toxicity analysis suggested a potential for environmental applications.

A Dual Effect Additive Modified Electrolyte Strategy to Improve the Electrochemical Performance of Zinc-Based Prussian Blue Analogs Energy Storage Device.

Prussian blue analogs (PBA) exhibit excellent potential for energy storage due to their unique three-dimensional open framework and abundant redox active sites. However, the dissolution of transition metal ions in water can compromise the structural integrity of PBAs, leading to significant issues such as low cycle life and capacity decay. To address these challenges, we proposed a dual-effect additive-modified electrolyte method to alleviate such issues, introducing sodium ferrocyanide (Na4Fe(CN)6) into aqueous alkaline electrolytes. It could not only capture Zn2+ dissolved on the surface of Na1.86Zn1.46[Fe(CN)6]0.87 (ZnHCF) electrode material during the cycling process but also conduct redox reactions on the electrode surface to provide additional capacitance. Through experiments and molecular simulation calculations, it showed that Na4Fe(CN)6 can restrict the movement of Zn dissolution into the electrolyte on the electrode surface. Based on this, an asymmetric supercapacitor based on ZnHCF//activated carbon was assembled with a modified electrolyte. The assembled supercapacitor displayed a specific capacitance of 1,329.65 mF cm-2, a power density of 2,900 mW cm-2, and an energy density of 388.28 mW h cm-2. This study provides a new idea for the design and construction of stable and efficient PBA energy storage materials by inhibiting the leaching of transition metals in PBA.

Solid-Liquid-Solid Growth of Doped Silicon Nanowires for High-Performance Lithium-Ion Battery Anode

Silicon nanowires (SiNWs) have great potential in electronic devices, sensors, energy storage, and conversion devices. Despite various ways to synthesize SiNWs, however, the growth of SiNWs directly from stable, abundant, sustainable silica sources has yet to be achieved. Herein, we report a modified alumino-reduction process of the silica to produce tin (Sn)-doped SiNWs that can be initiated at low temperature (250 °C) based on a solid-liquid-solid growth mechanism in analogy to the well-known vapor-liquid-solid (VLS). In this growth process, the reduced silicon atoms migrate freely in the molten salt and alloy with pre-reduced Sn. The supersaturation of silicon in the Sn-Si alloy leads to the precipitation of single-crystal SiNWs. The prepared SiNWs are of excellent crystallinity and doped with high non-equilibrium concentration (~3.0at.%) of Sn. This process with the solid-liquid-solid mechanism can also be extended to produce other group IV elements-based nanowires such as germanium. In addition, the prepared Sn-doped SiNWs as the anode material in lithium-ion batteries exhibit excellent performance with a high initial Coulombic efficiency of 85.4%, and a substantial reversible capacity of 1133 mAh g-1 even after 500 cycles at 4Ag-1. By utilizing the solid-liquid-solid mechanism, this modified alumino-reduction process offers a novel route for synthesizing doped SiNWs, holding promise for diverse applications.

Deciphering the multi-electron redox chemistry of metal-sulfide electrode toward advanced aqueous Cu ion storage

While neutral aqueous metal batteries, featuring cost-effectiveness and non-flammability, hold significant potential for large-scale energy storage, their practical application is hampered by the limited specific capacity of cathode materials (less than 500 mAh g−1). Herein, capacity-oriented CoS2 and rate-optimized Co9S8 cathodes are developed based on the aqueous copper ion system. The charge-storage mechanism is systematically investigated through a series of ex-situ tests and density functional theory calculations, focusing on the reversible transitions of Co9S8→Cu7S4→Cu9S5/Cu1.8S and CoS2→Cu7S4→Cu2S, which are associated with the redox reactions of Cu2+/Cu+‖Co2+/Co and Cu2+/Cu+‖S22−/S2−, respectively. The electrochemical results show that CoS2 can exhibit a superior capacity of 619 mAh g−1 at 1 A g−1 after 400 cycles, while Co9S8 maintains an outstanding rate performance of 497 mAh g−1 at 10 A g−1 (the retention rate is 95% compared to 521 mAh g−1 at 1 A g−1). As a proof of concept, an advanced CoS2//Zn hybrid aqueous battery demonstrates a working voltage of 1.20 V and a specific energy of 663 Wh kgcathode−1. This work provides an alternative direction for developing sulfide cathodes in energetic aqueous metal batteries.

Modulating Electrolyte Solvation Structure for High‐Voltage and Low‐Temperature Magnesium‐ion Supercapacitors

Aqueous electrolytes supercapacitors have great potential in energy storage devices due to their high‐power density and safety. However, due to the water hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), the electrochemical stabilization window of aqueous electrolytes needs to be widened. Moreover, the application of aqueous electrolyte at low temperature is often limited by the freezing point of water. In this paper, we modulate the solvation structure of aqueous magnesium‐ion supercapacitors by using sulfolane as a co‐solvent. The modulated low salt concentration hybrid electrolyte extends the electrochemical stability window of the electrolyte to 2.9V and enhances the stability of the electrolyte at extreme temperatures, as well as provides safe and non‐flammable properties. Based on the hybrid electrolyte, the water‐organic hybrid magnesium‐ion supercapacitors (HMSCs) are able to operate within an enlarged voltage range of 0 – 2.2 V at a low temperature of ‐30°C. The HMSC shows a specific capacitance of up to 58 F/g at room temperature and retains a specific capacitance of 39 F/g at a current density of 15 A/g. Furthermore, it has an outstanding cycling performance at ‐30 °C, maintaining a specific capacitance of more than 92% after 20,000 cycles.

Characterization of green-synthesized carbon quantum dots from spent coffee grounds for EDLC electrode applications

This study investigates the green synthesis of carbon quantum dots (CQDs) from spent coffee grounds using a hydrothermal method, offering an eco-friendly, cost-effective, and straightforward approach to nanomaterial production. The synthesized CQDs, with particle sizes ranging from 1.6 to 4.4 nm, exhibited notable fluorescence, achieving quantum yields of 37.0 %, 54.3 %, and 63.3 % depending on the coffee source. Characterization technique, including XRD, FTIR, SEM, TEM, and BET, confirmed their structural suitability of these CQDs for energy storage applications. Their electrochemical performance was evaluated through cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). Among the CQDs tested, those derived from spent Liberica coffee ground (medium roasted) demonstrated superior performance, with a discharging specific capacitance of 97.5 F/g, an energy density of 4.3 Wh/kg, and a power density of 130.6 W/kg at a current density of 0.5 A/g. Additionally, they exhibited acceptable internal resistance (Ra = 0.01 kΩ and Rab = 16.9 kΩ), indicating favourable charge transfer characteristics. These results underscore the enhanced energy storage potential of CQDs derived from spent coffee grounds. The findings not only highlight the excellent electrochemical performance but also support the viability of biomass waste as a valuable resource for advanced energy storage applications, promoting sustainable, eco-friendly technologies.

Modification and Functionalization of Separators for High Performance Lithium-Sulfur Batteries.

Lithium-sulfur batteries (LSB) have been recognized as a prominent potential next-generation energy storage system, owing to their substantial theoretical specific capacity (1675 mAh g-1) and high energy density (2600 Wh kg-1). In addition, sulfur's abundance, low cost, and environmental friendliness make commercializing LSB feasible. However, challenges such as poor cycling stability and reduced capacity, stemming from the formation and diffusion of lithium polysulfides (LiPSs), hinder LSB's practical application. Introducing functional separators represents an effective strategy to surmount these obstacles and enhance the electrochemical performance of LSBs. Here, we have conducted a comprehensive review of recent advancements in functional separators for LSBs about various (i) carbon and metal compound materials, (ii) polymer materials, and (iii) novel separators in recent years. The detailed preparation process, morphology and performance characterization, and advantages and disadvantages are summarized, aiming to fundamentally understand the mechanisms of improving battery performance. Additionally, the development potential and future prospects of advanced separators are also discussed.

A Feasible Strategy for High-Performance Aqueous Zinc-Ion Batteries: Introducing Conducting Polymer.

Aqueous zinc ion batteries (AZIBs) offer great potential for large-scale energy storage because of their high safety, low cost and acceptable energy density. However, the cycle life of AZIBs is inevitably affected by parasitic reactions and dendritic growth caused by multiple factors such as electrode, electrolyte and separator, which pose significant obstacles to the practical application of AZIBs. To address these challenges, conducting polymer (CP) based materials have gained widespread attention in the realm of rechargeable batteries due to the adjustable band gap, controllable morphology, and excellent flexibility of CPs. In particular, CPs exhibit remarkable conductivity, low dimensionality, and doping characteristics, making them highly promising for integration into the AZIB system. In this review, the problems associated with the cathode, anode, electrolyte, and separator of AZIBs are discussed, and the application of CPs for their modification is summarized. The review provides a comprehensive analysis of the action mechanisms involved in the CP modification process and offers valuable insights for the design and development of CPs that can be effectively utilized in AZIBs. Additionally, the review presents a promising outlook of this research field, aiming to further advance the application of low-cost and high-performance CPs and their composites in AZIBs.

Enhanced nonlinear optical properties of MXene (Ti3C2Tx) via surface-covalent functionalization with porphyrin

The surface terminations (=O, -OH, and -F) play a key role in determining the physical and chemical properties of MXenes, which have been demonstrated with significant potential in field-effect transistors, humidity sensors, energy storage, and photocatalysis, etc. It is therefore crucial to modify these active functional groups on the surface of MXenes in order to optimize the applicability of these materials. In this study, we introduce a covalent modification strategy to successfully construct a porphyrin-functionalized Ti3C2Tx organic-inorganic nanohybrid (TPP-Ti3C2Tx) by covalently attaching porphyrin molecules to the surface groups on Ti3C2Tx nanosheets for the first time. As revealed by steady-state fluorescence spectra, transient fluorescence spectra, and DFT calculations, the robust covalent bonds between TPP and Ti3C2Tx can effectively promote the photon-induced electron and/or energy transfer within the TPP-Ti3C2Tx nanohybrid. The investigation on the nonlinear optical (NLO) properties of TPP-Ti3C2Tx nanohybrid as well as its precursors, reveals that the TPP-Ti3C2Tx nanohybrid exhibits the highest nonlinear absorption coefficient and the lowest optical limiting threshold among the tested samples at both 532 and 1064 nm, indicating its great potential as a broadband optical limiter for visible and near-infrared wavelengths. This work not only demonstrates the significant promise of covalently-linked TPP-Ti3C2Tx nanohybrid in optical limiting applications but also provides a paradigm for engineering high-performance NLO MXenes-based materials through the covalent modification strategy.

In Situ Molecular Reconfiguration of Pyrene Redox-Active Molecules for High-Performance Aqueous Organic Flow Batteries.

Aqueous organic flow batteries (AOFBs) hold great potential for large-scale energy storage, however, scalable, green, and economical synthetic methods for stable organic redox-active molecules (ORAMs) are still required for their practical applications. Herein, pyrene-based ORAMs are obtained via an in situ organic electrolysis strategy in a flow cell. It is revealed that the water attacking pyrenes restructured molecules to produce a variety of isomers and dimers during the electrolysis, which can be modulated by regulating the local electron cloud density and steric hindrance of pyrene precursors. As a result, the molecularly reconfigured pyrene-based catholytes, even without any further purification, achieved a high electrolyte utilization of ≈96% and volumetric capacity above 50AhL-1. Inspiringly, remarkable cell stability with almost no capacity decay for ≈70 days is achieved, benefiting from the robust aromatic structure of the pyrene cores. The insights into the in situ electrosynthesis of pyrene-based ORAMs provided in the work will provide guidance for designing ultra-stable ORAMs for AOFB applications.

ALd of Metal Fluorides–Potential Applications and Current State

AbstractMetal fluoride thin films are important materials in a multitude of applications. Currently, they are mostly used in optics, but their potential in energy harvesting and storage is recognized as well. Atomic layer deposition (ALD) is an advanced thin film deposition method that has an ever‐increasing role in microelectronics. The assets of ALD are its capability to produce uniform, stoichiometric, and pure films with precise thickness control even on top of complicated structures, such as high aspect ratio trenches. These characteristics can be beneficial in applications of metal fluoride thin films but so far ALD of metal fluorides has remained much less studied and used than ALD of metal oxides, nitrides, sulfides, and pure metals. This review aims to motivate research on ALD of metal fluorides by surveying potential applications for ALD metal fluoride thin films and coatings. The basics of luminescent applications, antireflection coatings, and lithium‐ion batteries will be discussed. Next, the fundamentals of ALD will be presented followed by a comprehensive summary of the metal fluoride ALD processes published so far.

Covalent Organic Framework Derived Oxygen/Sulfur-Doped Porous Carbon for Robust High-Capacitance Symmetric Supercapacitors.

Heteroatom-doped porous carbons (HPCs) have been considered promising electrode materials for supercapacitors due to their improvement of energy density by providing extra pseudocapacity. Covalent organic frameworks (COFs) are obtaining great importance in energy storage because of their designable structure and versatile functionality. Herein, we designed and fabricated oxygen and sulfur dual-doped covalent organic framework (COF) derived HPCs with very high heteroatoms content (up to 25.76 atom%) via a facile coupling reaction. The optimized HPCs exhibit a porous structure with high specific surface area (up to 2835 m2 g-1) along with a high specific capacitance (430 F g-1 at 0.5 A g-1), excellent capacitance retention (96.9%), and high coulombic efficiency (98.5%) after 10000 cycles at 5 A g-1. As electrodes for aqueous symmetric supercapacitors, the HPCs exhibits a high energy density of 60 Wh kg-1 at a 250 W kg-1 power density, excellent cycling stability of capacity retention (82.2%) and a high coulombic efficiency (92.3%) after 10000 cycles at 10 A g-1, indicating attractive application potential in chemical energy storage. This work establishes a promising strategy for preparation of high heteroatom content HPCs using COFs and demonstrates great potential for energy storage/conversion devices.

The Application of Ultrasound Pre-Treatment in Low-Temperature Synthesis of Zinc Oxide Nanorods

Zinc oxide, due to its unique physicochemical properties, including dual piezoelectric and semiconductive ones, demonstrates a high application potential in various fields, with a particular focus on nanotechnology. Among ZnO nanoforms, nanorods are gaining particular interest. Due to their ability to efficiently transport charge carriers and photoelectric properties, they demonstrate significant potential in energy storage and conversion, as well as photovoltaics. They can be prepared via various methods; however, most of them require large energy inputs, long reaction times, or high-cost equipment. Hence, new methods of ZnO nanorod fabrication are currently being sought out. In this paper, an ultrasound-supported synthesis of ZnO nanorods with zinc acetate as a zinc precursor has been described. The fabrication of nanorods included the treatment of the precursor solution with ultrasounds, wherein various sonication times were employed to verify the impact of the sonication process on the effectiveness of ZnO nanorod synthesis and the sizes of the obtained nanostructures. The morphology of the obtained ZnO nanorods was imaged via a scanning electron microscope (SEM) analysis, while the particle size distribution within the precursor suspensions was determined by means of dynamic light scattering (DLS). Additionally, the dynamic viscosity of precursor suspensions was also verified. It was demonstrated that ultrasounds positively affect ZnO nanorod synthesis, yielding longer nanostructures through even reactant distribution. Longer nanorods were obtained as a result of short sonication (1–3 min), wherein prolonged treatment with ultrasounds (4–5 min) resulted in obtaining shorter nanorods. Importantly, the application of ultrasounds increased particle homogeneity within the precursor suspension by disintegrating particle agglomerates. Moreover, it was demonstrated that ultrasonic treatment reduces the dynamic viscosity of precursor suspension, facilitating faster particle diffusion and promoting a more uniform growth of longer ZnO nanorods. Hence, it can be concluded that ultrasounds constitute a promising solution in obtaining homogeneous ZnO nanorods, which is in line with the principles of green chemistry.

ZnO-NaNO3 nanocomposites for solar thermal energy storage systems

High-temperature phase change materials (PCMs) with good energy storage density and thermal conductivity are needed to utilize solar thermal energy effectively to meet industrial thermal energy demands. Composite PCMs containing a material of higher thermal conductivity and an inorganic high-temperature PCM can be explored to meet these requirements. Accordingly, a high-temperature, composite inorganic PCM (ZnO-NaNO3) with enhanced thermophysical properties was prepared, and its energy storage potential was investigated experimentally. A maximum thermal conductivity enhancement of 22.7% was achieved at 200 °C for 2 wt% ZnO-NaNO3 nanocomposite. The increase in thermal conductivity at higher temperatures may be attributed to the formation of ordered sodium nitrate layers on the nanoparticle surfaces. The increase in surface area and surface energy due to the addition of ZnO nanoparticles increased the specific heat of the nanocomposite in both the solid and liquid phases (43.5% in the liquid phase for 2 wt% ZnO-NaNO3). Thus, the addition of ZnO nanoparticles to NaNO3 increased its energy storage capacity. The addition of ZnO nanoparticles to NaNO3 did not affect the onset, peak or endset temperature during melting and freezing. Moreover, 2 wt% ZnO-NaNO3 exhibited cyclic stability even after 500 cycles and thus has potential as an energy storage medium.

Effect of puffing on electrochemical properties of sorghum seed based porous carbon materials in supercapacitors

Biomass-based carbon materials are renewable, affordable and environmentally friendly, possessing great potential in electrochemical energy storage as electrode materials in supercapacitors due to their large specific surface area and self-doped heteroatoms. However, the electrochemical properties of these carbon materials may be influenced to some extent by pretreatment procedures of carbon precursors. For this research, a range of porous carbon materials based on unpuffed and puffed sorghum seeds were synthesized under various pre‑carbonization and activation temperatures. Among them, the puffed sorghum seed-based porous carbon (PH-R6A7), prepared through pre‑carbonization at 600 °C and KOH activation at 700 °C, exhibits a higher graphitization degree, increased N and O content, as well as a greater variety of nitrogen-containing groups and significant increasing graphite nitrogen compared to unpuffed sorghum seed-based porous carbon (PC-R6A7) fabricated under similar conditions. These improvements result in enhanced conductivity and wettability of electrode materials, thereby boosting their electrochemical properties. In a three-electrode setup employing a 6 M solution of KOH, PH-R6A7 demonstrates an exceptional specific capacitance of 523.84 F g−1 at 1 A g−1 compared with PC-R6A7 of 366.00 F g−1; even at a high current density of 20 A g−1 it maintains a high level of capacitance at 387.94 F g−1. When employed in a double-electrode configuration at the same current density (i.e., 1 A g−1), PH-R6A7 also achieves higher specific capacitance of 357.83 F g−1 than PC-R6A7 (286.89 F g−1), accompanied by an increased energy density of 12.35 Wh kg−1 and 8.85 Wh kg−1 at a power density of 249.97 W kg−1 and 4.98 kW kg−1, respectively. Furthermore, after undergoing 10,000 cycles at 2 A g−1, PH-R6A7 demonstrates a superior capacitance retention of 99.68 % and coulomb efficiency of 99.91 %. PH-R6A7 fabricated through the combination method of puffing pretreatment and carbonization activation merits acknowledgment as an electrode material of superior performance and notable practical importance.

Statistics design for the synthesis optimization of lignin-sulfonate sulfur-doped mesoporous carbon materials: promising candidates as adsorbents and supercapacitors materials

This study employed lignin-sulfonated (LS) to develop biobased carbon materials (LS-Cs) through a sulfur-doping approach to enhance their physicochemical properties, adsorption capabilities, and energy storage potentials. Various characterization techniques, including BET surface area analysis, SEM imaging, XPS, Raman spectroscopy, and elemental composition (CHNS), were employed to assess the quality of the LS-Cs adsorbent and electrode samples. Response Surface Methodology (RSM) was utilized for optimizing the two main properties (specific surface area, ABET, and mesopore area, AMESO) by evaluating three independent factors (i.e., activation temperature, ZnCl2:LS ratio, and sulfur content). According to the statistical analysis, ABET and AMESO were affected by ZnCl2 and sulfur content, while the pyrolysis temperature did not affect the responses in the studied conditions. It was found that increasing the ZnCl2 and sulfur contents led to an increment of the ABET and AMESO values. The LS-C materials exhibited very high ABETvalues up to 1993 m2 g−1 and with predominantly mesoporous features. The S-doping resulted in LS-Cs with high sulfur contents in their microstructures up to 15% (wt%). The LS-C materials were tested as adsorbents for sodium diclofenac (DCF) adsorption and reactive orange 16 dye (RO-16) and as electrodes for supercapacitors. The LS-Cs exhibited excellent adsorption capacity values for both molecules (197–372 mg g−1) for DCF, and (223–466 mg g−1) for RO-16. When tested as electrodes for supercapacitors, notably, LS-C3, which is a doped sample with sulfur, exhibited the best electrochemical performance, e.g. high specific capacitance (156 F/g at 50 mV/s), and delivered an excellent capacitance after 1000 cycles (63 F/g at 1 A/g), which denotes the noteworthy capacitive behavior of the S-doped electrode. Thus, the present work suggests an eco-friendly resource for developing effective, productive carbon materials for adsorbent and electrodes for SC application. However, further studies on the complete application of these materials as adsorbents and electrodes are needed for a deeper understanding of their behavior in environmental and energy storage applications.