Mesoporous Carbon Research Articles

Spatially Separated Cu/Ru on Ordered Mesoporous Carbon for Superior Ammonia Electrosynthesis from Nitrate over a Wide Potential Window.

Nitrate (NO3-) in wastewater poses a serious threat to human health and the ecological environment. The electrocatalytic NO3- reduction to ammonia (NH3) reaction (NO3-RR) emerges as a promising carbon-free energy route for enabling NO3- removal and sustainable NH3 synthesis. However, it remains a challenge to achieve high Faraday efficiencies at a wide potential window due to the complex multiple-electron reduction process. Herein, spatially separated dual-metal tandem electrocatalysts made of a nitrogen-doped ordered mesoporous carbon support with ultrasmall and high-content Cu nanoparticles encapsulated inside and large and low-content Ru nanoparticles dispersed on the external surface (denoted as Ru/Cu@NOMC) are designed. In electrocatalytic NO3-RR, the Cu sites can quickly convert NO3- to adsorbed NO2- (*NO2-), while the Ru sites can efficiently produce active hydrogen (*H) to enhance the kinetics of converting *NO2- to NH3 on the Cu sites. Due to the synergistic effect between the Cu and Ru sites, Ru/Cu@NOMC exhibits a maximum NH3 Faradaic efficiency (FENH3) of approximately 100% at -0.1 V vs reversible hydrogen electrode (RHE) and a high NH3 yield rate of 1267 mmol gcat-1 h-1 at -0.5 V vs RHE. Finite element method (FEM) simulation and electrochemical in situ Raman spectroscopy revealed that the mesoporous framework can enhance the intermediate concentration due to the in situ confinement effect. Thanks to the Cu-Ru synergistic effect and the mesopore confinement effect, a wide potential window of approximately 500 mV for FENH3 over 90% and a superior stability for NH3 production over 156 h can be achieved on the Ru/Cu@NOMC catalyst.

Integration of single-atom photothermal catalysts with surface-localized high temperature in peroxymonosulfate-based Fenton-like systems for enhanced antibiotics degradation

This study delves into integrating single-atom catalysts with photothermal effect in peroxymonosulfate (PMS)-based Fenton-like systems for enhanced pollutant degradation. A single-atom photothermal catalyst (Co/PMCNs) was designed using mesoporous carbon spheres as both a single-atom support and a photothermal material. Near-infrared (NIR) light was employed due to its superior thermal effect and penetration capacity in water. It was found that Co/PMCNs could generate surface-localized high temperatures for accelerating PMS activation and reducing energy gap of activation reactions, leading to improved degradation performance. Surface-localized high temperatures were demonstrated as key in distinguishing photothermal heating from external heat sources for PMS activation. Moreover, this system performed well across various operating conditions and water matrices, with Co/PMCNs showing promising recyclability. This study highlights the impact of surface-localized high temperatures on heterogeneous catalysis under NIR irradiation, and underscores the potential of integrating single-atom catalysts with photothermal effects into advanced oxidation processes for effective water pollution control.

The Polarity of Co-solvents Regulates the Charge Storage Mechanisms in Supercapacitors with Concentrated Electrolytes.

Developing better energy storage devices depends on comprehending the underlying mechanisms involved in charge storage. With the continuous conception of new electrolytes, this task becomes progressively more urgent and complex. An example is the utilization of co-solvated concentrated solutions. While these show promising electrochemical responses, their dynamic properties (especially under confinement) and their relationships with performance are not fully understood. Here, we combined modified step potential electrochemical spectroscopy and quasielastic neutron scattering to investigate systems composed of activated mesoporous carbon (AMC) and concentrated solutions of lithium bis(trifluoromethanesulfonyl)imide in acetonitrile co-solvated with either toluene or acetone. We report that acetone does not impair surface-controlled mechanisms, contrary to the case with toluene, which competes with charged species to populate the AMC's pores without contributing to charge storage. In turn, toluene promotes a greater overall capacitance owing to Faradaic processes, which may be related to changes in the solvation structures under confinement.

Accelerated Fe2+ regeneration for efficient electro-Fenton oxidation of refractory pollutants through pore structure engineering

Electro-Fenton (EF) is efficient in decontaminating refractory pollutants but high consumption of Fe2+ as a hydrogen peroxide (H2O2) activator increases its operation cost. Designing EF system with accelerated Fe2+/Fe3+ cycling is crucial for both hydroxyl radical generation and Fe2+ dosage reduction. Here, we employed pore structure tailoring engineering to optimize pore size of mesoporous hollow carbon spheres (MHCS), achieving an improved H2O2 electro-synthesis and Fe2+ regeneration. MHCS with 8 nm surface pores yielded 81.33 mmol gcatalyst−1h−1 H2O2 and realized 51.2 % Fe2+ regeneration efficiency, enabling complete removal of sulfamethazine with a low energy consumption of just 0.87 kWh g−1 total organic carbon. Finite element simulation revealed that MHCS with 8 nm surface pores favored mass transfer, facilitating solute diffusion to the electrode’s active layer for reaction. In addition, EF system maintained a degradation efficiency of 90 % after five cycles of operation and was effective in removing various types of pollutants, which implies its application potential. This work demonstrated a novel catalyst structure optimization strategy to both enhance Fe2+ regeneration and improve EF performance, offering an energy-efficient water purification solution.

Pseudocapacitance-Enhanced Mesoporous Carbon Produced by Stepwise Pyrolysis of Discarded Oil-Absorbing Aerogels

Pseudocapacitance-Enhanced Mesoporous Carbon Produced by Stepwise Pyrolysis of Discarded Oil-Absorbing Aerogels

Electronic regulation of hcp-Ru by d-d orbital coupling for robust electrocatalytic hydrogen oxidation in alkaline electrolytes

Bimetallic alloys hold exceptional promise as candidate materials because they offer a diverse parameter space for optimizing electronic structures and catalytic sites. Herein, we fabricate ruthenium-cobalt alloy nanoparticles uniformly dispersed within hollow mesoporous carbon spheres (hcp-RuCo@C) via impregnation and pyrolysis strategies. The intriguing hollow mesopore structure of hcp-RuCo@C facilitates efficient contact between active sites and reactants, thereby accelerating hydrogen oxidation reaction (HOR) kinetics. As anticipated, the hcp-RuCo@C showcases remarkable exchange current density and mass activity of 3.73 mA cm−2 and 2.8 mA μgRu-1, respectively, surpassing those of commercial Pt/C and documented Ru-based electrocatalysts. Notably, hcp-RuCo@C demonstrates robust resistance to 1000 ppm CO, a trait lacking in Pt/C catalysts. Comprehensive experimental results reveal that the alloying-induced d-d electronic interactions between Ru and Co species significantly optimizes hydrogen binding energy (HBE) and hydroxide binding energy (OHBE). This optimization promotes the vital Volmer step, ameliorating the alkaline HOR properties of hcp-RuCo@C.

Architecture of interconnected cubic NiCo2S4 decorated mesoporous carbon with self-doped nitrogen based-hydrogel for high performance hybrid supercapacitor

Although the transition metal sulfides have shown persuasive proof and stellar traits for energy storage applications, their real applications still possess some obstacles such as prolonged ionic and electronic transport. Hence, NiCo2S4 decorated a pyrolyzed hydrogel (NiCo2S4@PHG) via facile synthesis is considered a promising electrocatalyst for energy storage devices. The prepared electrode materials were characterized utilizing different analysis techniques like XPS, XRD, FT-IR, TGA, SEM, TEM, elemental mapping and EDX that reveal the crucial role of the hydrogel pyrolysis in creating a homogenous nitrogen-doped carbon matrix. The as-fabricated 0.5 NiCo2S4@PHG nanocomposite was electrochemically examined in a sealed workstation cell and showed a clear battery-type supercapacitor behavior attributed to various redox reactions, porosity, and conductivity that was enhanced by self-doped nitrogen. In contrast, composites based on nickel and cobalt sulfides individually with pure hydrogel demonstrated the superiority of binary metal composites. The 0.5 NiCo2S4@PHG electrode exposed a marvelous specific capacity of 317.9 mAh g−1 and capacitance of 2728.5 F g−1 at a current density of 1 A g−1. A hybrid asymmetric supercapacitor was established by 0.5 NiCo2S4@PHG (cathode) and activated carbon (AC, anode), which brought large energy and power densities of 32.8 Wh kg−1 and 750 W kg−1, respectively. The fabricated cell manifests ultra-high retention of 82.6% at a current density of 20 A g−1 after 10,000 cycles. These outstanding accomplishments hold significant potential for practical energy storage and conversion applications.

Synthesis of ultra-high nitrogen doped hollow mesoporous carbon nanospheres via a universal solid–liquid interface self-assembly strategy

Functional mesoporous polymers, particularly their derived hollow mesoporous carbon spheres (HMCS), have introduced new opportunities in the field of energy storage. Traditional synthesis methods for HMCS typically rely on chemical etching, which often results in uniform chemical properties and structural control, thereby limiting their application in large-scale production and diverse fields. Therefore, in this study, we report a novel strategy for obtaining HMCS through the direct pyrolysis of a core matrix, melamine–formaldehyde resin (MF), to achieve hollow structures and ultra-high nitrogen doping (approximately 14.8 wt%). This new solid–liquid interfacial self-assembly approach enables the production of HMCS with remarkable electrochemical performance and practical application prospects in sodium-ion half-cells and full cells, thanks to the high nitrogen doping and unique structure. Notably, this strategy has been validated for its general applicability across 1D, 2D, and 3D solid matrices. Additionally, by adjusting the calcination temperature, this method allows for precise control over both the core size and nitrogen content of the egg yolk-shell structure mesoporous carbon spheres. In summary, the mesoporous materials developed in this study demonstrate flexibility, simplicity, versatility, and structural diversity, offering significant insights for future applications in energy storage and other fields.

Nanoporous Carbon Materials as Solid Contacts for Microneedle Ion-Selective Sensors.

Continuous sensing of biomarkers, such as potassium ions or pH, in wearable patches requires miniaturization of ion-selective sensor electrodes. Such miniaturization can be achieved by using nanostructured carbon materials as solid contacts in microneedle-based ion-selective and reference electrodes. Here we compare three carbon materials as solid contacts: colloid-imprinted mesoporous (CIM) carbon microparticles with ∼24-28 nm mesopores, mesoporous carbon nanospheres with 3-9 nm mesopores, and Super P carbon black nanoparticles without internal porosity but with textural mesoporosity in particle aggregates. We compare the effects of carbon architecture and composition on specific capacitance of the material, on the ability to incorporate ion-selective membrane components in the pores, and on sensor performance. Functioning K+ and H+ ion-selective electrodes and reference electrodes were obtained with gold-coated stainless-steel microneedles using all three types of carbon. The sensors gave near-Nernstian responses in clinically relevant concentration ranges, were free of potentially detrimental water layers, and showed no response to O2. They all exhibited sufficiently low long-term potential drift values to permit calibration-free, continuous operation for close to 1 day. In spite of the different specific capacitances and pore architecture of the three types of carbon, no significant difference in potential stability for K+ ion sensing was observed between electrodes that used each material. In the observed drift values, factors other than the carbon solid contact are likely to play a role, too. However, for pH sensing, electrodes with CIM as a carbon solid contact, which had the highest specific capacitance and best access to the pores, exhibited better long-term stability than electrodes with the other carbon materials.

High-performance pseudo-capacitance supercapacitor with highly mesoporous fluorine doped polymeric carbon nitride nanosheets as electrode material

In this study, graphitic carbon nitride (GCN) material obtained from urea was hydrothermally doped with fluorine atoms (F-doped GCN). The resulting F-doped GCN material was designed as an electrode material for supercapacitors. Characterization of these samples was carried out by XRD, EDS, SEM, nitrogen adsorption and FTIR analyses. EDS and FTIR analyses confirmed the doping of fluorine atoms onto GCN. Nitrogen adsorption analyses supported the formation of a significant mesoporous structure with fluoride doping on GCN. The specific capacitance values of the GCN and F-doped GCN supercapacitors were calculated as 39.75 F/g and 305.72 F/g at a frequency of 0.01 Hz. A significant increase of about 7-fold in capacitance value was obtained by fluorine doping on GCN. Cycling trials of the F-doped GCN supercapacitor for up to 1000 cycles at a current density of 0.4 A/g maintain an efficiency of 86.72 %. For the supercapacitor designed from F-doped GCN material, the maximum energy density and power density were calculated as 4.26 Wh/kg and 1792 Wh/kg, respectively.

Tuning Internal Accessibility via Nanochannel Orientation of Mesoporous Carbon Spheres for High‐Rate Potassium‐Ion Storage in Hybrid Supercapacitors

AbstractEnhancing the accessibility and utilization of active sites through mesopores in carbon anode materials is crucial for developing high‐power potassium‐ion hybrid supercapacitors (PIHCs). Here, a multiscale phase separation method combining block copolymer (BCP) microphase‐ and homopolymer (HP) macrophase‐separation is utilized to produce two model carbon materials with controlled mesopore orientation: open‐end (oe‐MCS) and closed‐end mesoporous carbon sphere (ce‐MCS). BCPs form identical cylindrical micelles, and HPs encapsulate these cylindrical micelles within spheres and control their orientations relative to the interface. This approach manipulates only the degree of mesopore openings in the MCS materials while maintaining all other factors at similar levels. Opening mesopores in carbon anode materials primarily enhances K+ adsorption capacity, reduces K+ diffusion length, and improves ion transport. Thus, oe‐MCS anode exhibits a higher specific capacity with a significant capacitive‐controlled contribution. The resulting PIHC device displays maximum energy and power densities of 103 Wh kg−1 and 12 300 W kg−1, respectively, along with capacity retention of 86.1% after 20 000 cycles at 2.0 A g−1. This study significantly advances the understanding of mesopore design to improve capacitive K+ storage in hard carbon materials, paving the way for the development of high‐power PIHCs.

Enhanced Capacitive Deionization of Hollow Mesoporous Carbon Spheres/MOFs Derived Nanocomposites by Interface-Coating and Space-Encapsulating Design.

Exploring new carbon-based electrode materials is quite necessary for enhancing capacitive deionization (CDI). Here, hollow mesoporous carbon spheres (HMCSs)/metal-organic frameworks (MOFs) derived carbon materials (NC(M)/HMCSs and NC(M)@HMCSs) are successfully prepared by interface-coating and space-encapsulating design, respectively. The obtained NC(M)/HMCSs and NC(M)@HMCSs possess a hierarchical hollow nanoarchitecture with abundant nitrogen doping, high specific surface area, and abundant meso-/microporous pores. These merits are conducive to rapid ion diffusion and charge transfer during the adsorption process. Compared to NC(M)/HMCSs, NC(M)@HMCSs exhibit superior electrochemical performance due to their better utilization of the internal space of hollow carbon, forming an interconnected 3D framework. In addition, the introduction of Ni ions is more conducive to the synergistic effect between ZIF(M)-derived carbon and N-doped carbon shell compared with other ions (Mn, Co, Cu ions). The resultant Ni-1-800-based CDI device exhibits excellent salt adsorption capacity (SAC, 37.82mg g-1) and good recyclability. This will provide a new direction for the MOF nanoparticle-driven assembly strategy and the application of hierarchical hollow carbon nanoarchitecture to CDI.

Petroleum residue-based ultrathin-wall graphitized mesoporous carbon and its high-efficiency adsorption mechanism

Creating petroleum residue-based new functional materials are vital for the sustainable development of petroleum residues. This study developed a method to prepare a petroleum residue-based ultrathin-wall graphitized mesoporous carbon (PGMC) with high specific surface area by the carbonization of a composite of the petroleum residue uniformly mixed with aluminium isopropoxide. Results show that the PGMC possesses a highly fluffy ultrathin-wall mesoporous structure with a high degree of graphitization. It had a high specific surface area of 1174 m2 g−1 with a high pore volume of 4.57 cm3 g−1 and a narrow pore size distribution at 8.09 nm. These unique features endow the PGMC with excellent adsorption properties for Congo red, Malachite green, and Methylene blue removal. The experimental data were better described with Freundlich isotherm and Quasi-second-order kinetic models. Thermodynamic analysis indicated a spontaneous and endothermic adsorption process. The adsorption mechanisms proposed that pore-filling effect, π-π conjugation, and electrostatic interaction were the main interactions between the PGMC and dyestuff, followed by functional groups and hydrogen bonding. Moreover, the PGMC could maintain good adsorption rates after five cycles, proving that it is an effective adsorbent with good adsorption ability and cycling stability.

A smartphone-based tunable tyrosinase functional mimic modulated portable amperometric sensor for the rapid and real-time monitoring of catechol

A smartphone-based electrochemical sensor for rapid detection of catechol (CC) was designed. The system contained a smartphone, a hand-held detector, and tyrosinase enzyme mimicking material modified screen-printed carbon electrode (SPCE). Metal nanoparticles confined in porous carbon have been widely used as enzyme mimics owing to their enhanced electrochemical activity. However, the fabrication of enzyme-mimicking catalysts in a scalable and tunable manner is challenging. A two-step synthesis strategy was followed: carbonization of the silica template to form cubic-structured mesoporous carbon (CMC) and high-temperature calcination for copper confinement into CMC (Cu–CMC). The non-covalent interactions enable the Cu precursors to coordinate with the carbon atoms in the face-centered cubic lattice of CMC. The uncalcined material is the as-synthesized (As–Cu–CMC), while the 900 °C calcined are stage 1 (Cu–CMCS1) and stage 2 (Cu–CMCS2) materials with different Cu loadings. The Cu–CMCS2 possess a large pore volume (0.224 cm3g−1) and high surface area (104.2 m2/g). The Cu–CMCS2 modulated sensors enable rapid and real-time detection of CC. Under optimized conditions, the linear range of 1.0–1000 µM (0.0 V vs. integrated Ag/AgCl reference electrode) with the sensitivity and lower detection limit of 10.21 µA µM−1 cm−2 and 0.099 μM (S/N=3) was achieved. The excellent sensor performance is attributed to the increased number of Cu vacancies that mimic the native tyrosinase enzyme. The sensor connected to a portable potentiostat enable high-throughput real-time testing of the CC without sophisticated equipment. Furthermore, the sensor detected CC in green tea and water samples, and the results were validated using UV–visible spectrophotometry and high-performance liquid chromatography.Abbreviations: CMC, cubic-structured mesoporous carbon; Cu–CMCS2, copper loaded stage 2 material; CC, catechol; CMS, cubic mesoporous silica; SPCE, screen-printed carbon electrode; HF, hydrofluoric acid; P123, Pluronic 123; TEOS, Tetraethyl orthosilicate; AA, ascorbic acid; Glu, glucose; HQ, hydroquinone; 4-NP, 4-nitrophenol; CA, caffeic acid; RS, resorcinol; Cu–CMCS1, copper loaded stage 1 material; UV–Vis, UV–visible spectrophotometry; FE-SEM, field-–emission scanning electron microscopy; EDS, energy–dispersive X–-ray spectroscopy; Si, silica; TEM, transmission electron microscopy; NPs, nanoparticles; SAED, selected area electron diffraction; FT-IR, Fourier-Transform Infrared Spectroscopy; BET, Brunauer–Emmett–Teller; BJH, Barrett–Joyner–Halenda; TGA, Thermogravimetric analysis; CV, cyclic voltammetry; ipa, anodic peak current; ECSA, electrochemically active surface area; EIS, electrochemical impedance spectroscopy; Rct, charge-transfer resistance; CA, chronoamperometry; LOD, limit of detection.

Cobalt-catalyzed carbonization from polyacrylonitrile for preparing nitrogen-containing ordered mesoporous carbon CMK-1 electrode with high electric double-layer capacitance

Ordered mesoporous carbon CMK-1 was prepared via carbonization at a relatively low temperature (the first step) followed by partial graphitization (the second step of carbonization at higher temperature) inside the ordered mesopores of cobalt-loaded mesoporous silica MCM-48 using polyacrylonitrile (PAN) as a carbon/nitrogen source. This first step of the carbonization is called “infusibilization”, and the resultant material is denoted as PANinf. In an advanced temperature-programmed desorption analysis of the PANinf/MCM-48 composite, the temperature of the observed HCN signal indicated that carbonization was reduced from 550 to 450 °C by a Co catalyst. The amount of typical N2 formation associated with the selective removal of pyridinic N species, resulting in the graphitic surface formation, also increased at a relatively high temperature (approximately 1000 °C) with the aid of the Co catalyst. The CMK-1 prepared through cobalt-catalyzed carbonization exhibited a higher electric double-layer capacitance with an Et4N+BF4–/propylene carbonate electrolyte, and higher electrical conductivity than CMK-1 prepared without a catalyst. This also implied the progress of graphitization within the carbonaceous wall. These results suggest that the edge planes of the graphitic domains in CMK-1 are predominantly exposed on the surfaces of the carbonaceous walls, resulting in an increase in the number of adsorptive sites for the electrolyte during capacitance measurements.

Valorization and Upcycling of Acid Mine Drainage and Plastic Waste via the Preparation of Magnetic Sorbents for Adsorption of Emerging Contaminants.

Plastic waste poses a serious environmental risk, but it can be recycled to produce a variety of nanomaterials for water treatment. In this study, poly(ethylene terephthalate) (PET) waste and acid mine drainage were used in the preparation of magnetic mesoporous carbon (MMC) nanocomposites for the adsorptive removal of pharmaceuticals and personal care products (PPCPs) from water samples. The latter were then characterized using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), and ζ potential. The results of Brunauer-Emmett-Teller isotherms revealed high specific surface areas of 404, 664, and 936 m2/g with corresponding pore sizes 2.51, 2.28, and 2.26 nm for MMC, MMAC-25%, and MMAC-50% adsorbents, respectively. Under optimized conditions, the equilibrium studies were best described by the Langmuir and Freundlich models and kinetics by the pseudo-second-order model. The maximum adsorption capacity for monolayer adsorption from the Langmuir model was 112, 102, and 106 mg/g for acetaminophen, caffeine, and carbamazepine, respectively. The composites could be reused for up to six cycles without losing their adsorption efficiency. Furthermore, prepared adsorbents were used to remove acetaminophen, caffeine, and carbamazepine from wastewater samples, and up to a 95% removal efficiency was attained.

Preparation of functionalized porous chitin carbon to enhance the H2O2 production and Fe3+ reduction properties of Electro-Fenton cathodes for efficient degradation of RhB

The performance of Electro-Fenton (EF) cathode materials is primarily assessed by H2O2 yield and Fe3+ reduction efficiency. This study explores the impact of pore structure in chitin-based porous carbon on EF cathode effectiveness. We fabricated mesoporous carbon (CPC-700-2) and microporous carbon (ZPC-700-3) using template and activation methods, retaining nitrogen from the precursors. CPC-700-2, with mesopores (3–5 nm), enhanced O2 diffusion and oxygen reduction, producing up to 778 mg/L of H2O2 in 90 min. ZPC-700-3, with a specific surface area of 1059.83 m2/g, facilitated electron transport and ion diffusion, achieving a Fe2+/Fe3+ conversion rate of 79.9%. EF systems employing CPC-700-2 or ZPC-700-3 as the cathode exhibited superior degradation performance, achieving 99% degradation of Rhodamine B, efficient degradation, and noticeable decolorization. This study provides a reference for the preparation of functionalized carbon cathode materials for efficient H2O2 production and effective Fe3+ reduction in EF systems.

Single-atom decorated hollow mesoporous carbon spheres composited with free-standing carbon cloth supported cobalt sulfide nanowire arrays as high-performance sulfur host for lithium-sulfur batteries

BackgroundLithium-sulfur batteries (LSBs) are a promising next generation electrochemical energy storage device. Its commercialization however is hindered by several technical challenges, particularly shuttling of polysulfides. MethodsA composite sulfur host, coupled with a porous current collector, was developed to mitigate the shuttling problem. Iron single atom (SAFe) decorated hollow mesoporous carbon spheres (HMCS), composited with cobalt sulfide nanowire arrays supported on free-standing carbon cloth (S-Co@CC), were fabricated as a high-performance sulfur host for LSBs. The sulfur host combines the high electrical conductivity and physical confinement capability of HMCS, the excellent polysulfides chemisorption capability of cobalt sulfide nanowire arrays, and the high catalytic efficiency of iron single atoms toward polysulfide conversion reactions, to achieve a high-performance LSB. Significant findingsThe S-Co@CC/SAFe-HMCS based LSB exhibited a high initial specific capacity of 1430 mAh g−1 at 0.1 C. For cycling stability, a specific capacity of 578 mAh g−1 was maintained after a 600-cycle operation at 1 C, achieving an ultralow average capacity decay rate of 0.029 % per cycle. The design of composite sulfur hosts, combining all functional components in one, proves to be an effective strategy to advance the development of high-performance LSBs.

Mesoporous Carbons Produced from Tannin Biomass for Lithium-Sulfur Batteries

Lithium-sulfur batteries (LSBs) are promising alternatives since sulfur can provide a theoretical specific capacity of 1675 mA h g-1 when combined with lithium [1]. Thus, LSBs can achieve a theoretical energy density (2500 W h kg-1) that is much greater than that of conventional lithium-ion batteries [1]. However, several problems must be resolved to enable commercial production on a large scale, such as the formation of soluble species of lithium polysulfides [2]. Various approaches have been used to minimize this problem, including the development of carbon-based hosts capable of retaining these polysulfides. Among these, the development of cathodes based on carbon‒sulfur composites using carbon from biomass is an alternative that benefits from the possibility of obtaining materials with a modifiable surface area and porosity at low cost [2]. On this basis, this work reports the synthesis of mesoporous carbons (MCs) from tannin biomass, the incorporation of sulfur and the development of lithium-sulfur batteries. The MC sample was produced using the solvent-free method [3] and was named C. The incorporation of sulfur into mesoporous carbons was carried out using melt diffusion methodology [4]. Two quantities of sulfur were added to the carbon host by mass, and the materials were named CS1 and CS2 at ratios of 1:1 and 2:1, respectively, in relation to sulfur:MC. Coin cells (CR 2032) were assembled using the produced materials on the cathode, metallic Li on the anode and the electrolyte 1 M LiTFSI and 1% (w/v) LiNO3 in 1,2-dimethoxyethane/1,3-dioxolane (DME/DOL) and characterized by cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) cycling. The mesoporous carbon C presented a type IV isotherm characteristic of mesoporous materials, with a BET surface area of 539 m2g-1, average pore size of 7.7 nm and total pore volume of 0.747 cm3g-1. There was a decrease in the area and pore volume of the materials after sulfur incorporation, reaching 70 m2g-1 and 0.195 cm3g-1 for CS1 and 3 m2g-1 and 0.012 cm3g-1 for CS2, respectively. The sulfur contents were determined by thermogravimetric analysis (TGA) and were 39% and 61% for CS1 and CS2, respectively. The sulfur contents determined by TGA were close to those obtained by elemental analysis (CHNS), which were 45% and 63% for CS1 and CS2, respectively. The CV data showed that both cells presented cathodic and anodic potentials typical of Li-S batteries. The GCD data show that the cell containing the cathode with the material with a higher elemental sulfur content (CS 2) is stable and maintains specific capacities on the order of 550 mA h g-1 after 45 galvanostatic cycles at different current densities. However, this cell showed a more abrupt decrease in capacity at the highest rates (2C and 4C), Figure 1. Most likely, the higher sulfur content used in this sample did not result in total impregnation of the porous structure, resulting in sulfur deposition on the surface of the particles. As a result, the interparticle contact resistance in the electrodes increases, which limits the performance at higher current demands. For the cell built with the sample containing 39% S (CS1), excellent performance is obtained at high C rates. At 0.1 C, the cathode operates above 900 mA h g-1 in the initial cycles and above 550 mA h g-1 at 0.5 C, and no significant capacity drop is observed between 1 C and 2 C (≈500 mA h g-1). At 4C, a decrease in the specific capacity is noted, but the specific capacity remains above 350 mA h g-1. These results demonstrate the potential of carbon materials obtained from biomass for building high-performance Li-S batteries.Acknowledgments: The authors thank the financial support from the Rota 2030 Program at Fundep – Brazil.

(Invited) Low Temperature Plasma Synthesis and Functionalisation of Carbon Nanostructures for Energy Conversion and Storage

Low-temperature plasmas are nowadays widely developed and used for synthesis and functionalization of various materials with applications in areas ranging from microelectronics and aeronautical industry to energy conversion and storage. The focus of the research and applications has lately shifted towards carbon and carbon-based materials synthesis. The materials of interest vary from nanoparticles, nanotubes, nanowalls, free standing graphene flakes, vertical graphene rods, sponge structures, nanostructured surfaces, to composites (with conductive or non-conductive polymers, or MoS2, to mention some of the examples that will be presented herein). The interest for direct applications of plasma processes as well as nanostructures in the field of energy conversion and storage has been present since a long time. Recently, however, several interesting fundamental breakthroughs have been observed in terms of better control of processes, diagnostics and several other benefits that are attracting more and more attention: lower temperatures of surfaces needed for synthesis and functionalization (due to active plasma species interacting with surfaces), dry processes (diluted precurors or liquid monomers introduced in processes, without use of solvents), decreased overall pollution, fast processes, to mention just some of the advantages. However, our work must not forget the disadvantages and problems that can occur during application tests, such as stability, adhesion, loss of conductivity, reproducibility, general ageing or recyclability.Different factors can affect the function of the final setup (from photocatalytic elements, to batteries or fuel cells/HER systems, in our case) – from production of the starting materials to the assembly. Therefore, careful synthesis and control of the process (including the chamber and surface conditions for example) is necessary. We present herein several examples of carbon materials developed or in development (as mentioned 1D-3D carbons, carbon in organic and inorganic composits, mesoporous carbons). These materials were synthesized at surface temperatures between room temperature and up to 550°C.We emphasize, for example, the importance of in-situ control of processes, the importance of precise process conditions, the control of the synthesized materials with regard to their electrical conductivity, adhesion, thermal stability or sensitivity to photon irradiation.Acknowledgments:Authors acknowledge the EU Graphene Flagship FLAG-ERA III JTC 2021 project VEGA (PR-11938) and the project PEGASUS (funded by the European Union's Horizon research and innovation programme under grant agreement No 766894. UC and NMS acknowledge the Slovenian Research Agency for the program ARRS No. P1-0417 and project Z2-4467. TS, EK and JB want to thank HZB for the allocation of synchrotron radiation beamtime at the HE-SGM beamline of BESSY II. Thanks goes also to Prof. Wöll from KIT for providing the HE-SGM endstation used for the XPS and NEXAFS measurements. This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 730872 (Nr. 18207084-ST and 18207393- ST). EK and JB acknowledge also support obtained via ARD MATEX Region Centre.