Porous Carbon Electrodes Research Articles

Air Plasma Modification of Graphite-Based Electrode for Improved Performance of Aqueous Redox Flow Batteries

Graphite felt is widely utilized as a porous carbon electrode in aqueous redox flow batteries (RFBs). However, its inherent hydrophobic nature and limited electrochemical activity present challenges. While the correlation between RFB performance and electrode properties has been extensively studied for vanadium chemistry and other inorganic redox active materials, it remains scarce in literature for organic systems. In this study, we employ air plasma treatment, known for its controllability, solvent-free nature, and short treatment duration, to modify commercially available graphite felt for RFB applications. A comprehensive analysis is conducted to establish correlations between plasma treatment, physical properties, electrochemical characteristics, and overall cell performance in aqueous RFBs. Comparative evaluation reveals a significant enhancement, with treated graphite felt exhibiting an 85% increase in capacity at 140 mA cm−2 compared to its pristine counterpart. By intentionally utilizing authentic RFB electrodes and employing state-of-the-art ferrocyanide posolyte, this study underscores the crucial role of the interface, even for rapid (reversible) redox-active materials utilized in AORFBs.

Enhanced Redox Activity of Anthraquinone on N‐Doped Porous Carbon Electrode

AbstractAnthraquinone is one of the organic molecules that can potentially replace metal‐based electrodes due to its fast and reversible redox reaction as well as the abundance in nature. Here, we reported the redox activity of anthraquinone on N‐doped porous carbon electrodes derived from chemical activation of tea leaves with potassium carbonate. Electrochemical behavior was evaluated by cyclic voltammetry and galvanostatic charge/discharge in sulfuric acid, with X‐ray photoelectron spectroscopy providing insights into the surface chemistry of the electrodes. Anthraquinone on the composite electrode was able to achieve 97 % of its theoretical storage capacity. We found that nitrogen‐containing functional groups, especially graphitic and pyrrolic groups, had a major impact on the enhanced redox activity of anthraquinone.

Mesophase pitch-derived porous carbon constructed by template/activation synchronous pore-forming technology for electrochemical energy storage

Porous carbon materials with high specific surface area and wide pore size distribution play a crucial role in the energy storage process. In this paper, a mixed sol-gel system of carbon source, chemical activator and salt template agent was constructed using raw pitch, o-xylene soluble substance and their mesophase as carbon source, NaCl as template agent and KOH as activator. After one step process of high temperature treatment, porous carbon materials with high specific surface area (SBET 1969 m2/g) and wide nanopore distribution (0.4–6 nm) were obtained. The electrochemical properties of the prepared mesophase porous carbon materials were tested. At a charge-discharge rate of 80 mA/g, a specific capacitance of 102.5 F/g can be achieved for porous carbon materials obtained from the o-xylene soluble mesophase, indicating the feasibility of preparing porous carbon electrode materials by o-xylene soluble mesophase. The development of template/activation synchronous pore-forming technology can integrate the advantages of the two kinds of pore-forming technologies, reduce the demand for pore size control in porous carbon materials, and promote the one-step realization of porous carbon materials with high specific surface area, wide pore size distribution and controllable pore size.

Fast interfacial electrocatalytic desolvation enabling low‐temperature and long‐cycle‐life aqueous Zn batteries

AbstractLow‐temperature zinc batteries (LT‐ZIBs) based on aqueous electrolytes show great promise for practical applications owing to their natural resource abundance and low cost. However, they suffer from sluggish kinetics with elevated energy barriers due to the dissociation of bulky Zn(H2O)62+ solvation structure and free Zn2+ diffusion, resulting in unsatisfactory lifespan and performance. Herein, dissimilar to solvation shell tuning or layer spacing enlargement engineering, delocalized electrons in cathode through constructing intrinsic defect engineering is proposed to achieve a rapid electrocatalytic desolvation to obtain free Zn2+ for insertion/extraction. As revealed by density functional theory calculations and interfacial spectroscopic characterizations, the intrinsic delocalized electron distribution propels the Zn(H2O)62+ dissociation, forming a reversible interphase and facilitating Zn2+ diffusion across the electrolyte/cathode interface. The as‐fabricated oxygen defect‐rich V2O5 on hierarchical porous carbon (ODVO@HPC) electrode exhibits high capacity robustness from 25 to −20°C. Operating at −20°C, the ODVO@HPC delivers 191 mAh g−1 at 50 A g−1 and lasts for 50 000 cycles at 10 A g−1, significantly enhancing the power density and lifespan under low‐temperature environments in comparison to previous reports. Even with areal mass loading of ~13 mg cm−2, both coin cells and pouch batteries maintain excellent stability and areal capacities, realizing practical high‐performance LT‐ZIBs.

Laser-induced nitrogen and phosphorus-doped spongy carbon with graphene wings derived from lignin for significantly enhanced capacitance deionization performance

Efficient capacitive deionization (CDI) technology puts forward higher requirements for electrode materials. However, the traditional process of preparing porous carbon (PC) electrodes by alkaline chemical activation is polluting and energy-consuming. In this work, the N/P co-doped biocarbon material (H-AL/APP) was prepared by using alkali lignin (AL) and ammonium polyphosphate (APP) as carbon precursors based on laser-induced carbonization and hydrothermal activation technology. The as-prepared carbon material shows a three-dimensional (3D) structure with a hierarchical porous structure, large specific surface area of 405.98 m2/g (SSA), excellent pore volume, and outstanding mesoporosity. Compared with commercial YP80 activated carbon, The H-AL/APP electrode exhibits a higher specific capacitance of 210F/g with excellent rate performance and cycle stability. When assembled for desalination, H-AL/APP shows the highest removal rate of 23 mg/g/min with an outstanding desalination capacity of 34.6 mg/g than those of YP80 activated carbon. Furthermore, reasonable cycle stability and reproducibility highlight their promising application prospects. In summary, this work provides a green, efficient, and economical method for preparing high-performance heteroatom-doped PCs for efficient CDI desalination.

Biomass waste derived from cassia fistula into value-added porous carbon electrode for aqueous symmetric supercapacitors

Activated carbon derived from biomass sources has been renowned as one of the key materials and economical precursors for numerous energy conversion and storage applications. Herein, we utilized a less explored Cassia fistula (Pulp and seed) biomass as the carbon source for supercapacitor application. Further, a less toxic and low activation method has been implemented to activate the biomass-derived carbon. The highly dense seed resulted in better porous compared to the pulp source. The electrochemical performances of the bio-carbon electrodes have been examined by CV, GCD, and EIS studies. The activated carbon derived from the Cassia fistula seed (CFSA) electrode achieved a specific capacitance value of 136.5 Fg−1 at 0.5 Ag−1 in 3 M KOH. Moreover, the electrode demonstrates an extremely long stability by sustaining 98 % of initial capacitance after 10,000 cycles, which signifies the robust electrochemical stability behavior of the obtained electrode. Further, the aqueous symmetric supercapacitor achieved a maximum energy and power density of 7.2 WhKg−1 and 3488.1 WKg−1, respectively. Likewise, after 10,000 stability cycles, the cell retains 96.4 % capacitance at 5 Ag−1 which denotes the noteworthy capacitive behaviour of the CFSA electrode. Thus, the present work suggests an eco-friendly resource for developing an effectual carbon electrode for energy storage applications.

Briefing: Selective laser sintering technology to print walnut shell/phenolic resin new biomass-based porous electrode

In this paper, porous carbon electrodes were prepared by using walnut shell and phenolic resin as matrix materials, combined with selective laser sintering (SLS) technology and carbonization process. The effects of different ratios and temperatures on the macroscopic morphology, graphitization degree, electrical conductivity and pore structure of the carbonized parts were investigated. The results show that the lower proportion of walnut shell and the higher carbonization temperature increase the degree of graphitization. High temperature has a significant effect on the conductivity. The conductivity at 1000 °C is 7.5197 S·cm−1, which is 752 % higher than that at 600 °C, while the conductivity at 30 % walnut shell content is only 75.4 % higher than that at 50 %. This study provides a new reference for the preparation of carbon electrodes with complex shape and structure by biomass consumables.

Enhancing power and energy densities of supercapacitors with slit porous carbon electrodes by playing with pore width and ion shapes

The energy and power performances of double-layer supercapacitors can be affected by pore size, the nature of the electrolyte, and electrode–electrolyte interaction. We performed molecular dynamics simulations of mixtures of ionic liquids confined into slit-shaped carbon electrodes with pores of 0.75 and 1.5nm under applied voltage to investigate the interplay of pore size, and ion shape to the performance of supercapacitor. Inside the pores of 1.5nm the ions are organized into two layers, and a single layer inside the pore of 0.75nm. The tetramethylammonium cations ([TMA]+) is steric hindered to fill the pores of 0.75nm that can be only filled by 1-ethyl-3-methyl-imidazolium cations ([EMIM]+) and bis(trifluoromethanesulfonyl)imide anions ([NTf2]−). The increase of [TMA][NTf2] in the mixtures results in small pores with a decreased density of ions or empty at the non-charged state of the electrode. Upon the application of voltage, these empty or partially filled pores have only the adsorption of counter ions, which are responsible for the best performance of mixtures with mole fraction of [TMA]+ equals to 0.25 and 0.75.

Iodine intercalation-assisted alkali activation constructs coal-based porous carbon for high-performance supercapacitors

Supercapacitors have the advantages of fast charging and discharging speeds, high power density, long cycle life, and wide operating temperature range. They are widely used in portable electronic equipment, rail transit, industry, military, aerospace, and other fields. The design and preparation of low-cost, high-performance electrode materials still pose a bottleneck that hinders the development of supercapacitors. In this paper, coal was used as the raw material, and the coal-based porous carbon electrode material was constructed using the iodine intercalation-assisted activation method and used for supercapacitors. The CK-700 electrode exhibits excellent charge storage performance in a 6 M potassium hydroxide (KOH) electrolyte, with a maximum specific capacitance of 350 F/g at a current density of 0.5 A/g. In addition, it has an excellent rate performance (310 F/g at 1 A/g) and cycle stability (capacitance retention up to 91.7 % after 30000 cycles). This work provides a method for realizing high-quality, high-yield and low-cost preparation of coal-based porous carbon, and an idea for improving the performance of supercapacitors.

ZIF-8-derived N-doped porous carbon electrodes enabled with in situ embedded ZrO2 nanoparticles for phosphorus removal

Excessive phosphorus discharges are not favorable to the normal functioning of water ecosystems. Although some treatments have been implemented to control phosphorus concentrations in sewage, several challenges remain for them. Capacitive deionization technology (CDI) possesses excellent potential for phosphorus removal, and the electrode material is the key to CDI. Herein, a novel ZIF-8-derived N-doped porous carbon electrode enabled with in situ embedded ZrO2 nanoparticles (ZNPC) was fabricated through a simple in-situ growth approach. The experimental results demonstrate that ZrO2 embedded in ZNPC can improve the electrochemical performance and provide suitable affinity sites for phosphorus, thus enhancing the electrode performance in capturing phosphorus. Isothermal and kinetic models were adopted to investigate the phosphorus uptake process. Mechanism analysis reveals that the phosphorus removal behavior is associated with the electric field, ligand exchange, and electrostatic attraction. This study provides a promising approach for facile constructing Zr-based N-doped porous carbon and expands its potential utility for phosphorus removal from aqueous solutions.

Zinc-ion hybrid supercapacitors with hierarchically N-doped porous carbon electrodes and ZnSO4/ZnI2 redox electrolyte exhibit boosted energy density

Zinc-ion hybrid capacitors (ZIHCs) with high energy density is commercial need as energy storing devices, but facile preparation is still a challenge. Herein, we proposed a combined strategy for preparation of ZIHCs with high performance. For this purpose, a nanoemulsion assembly approach with Pluronic F127 as structure-directing agent, 1, 3, 5-trimethylbenzene as pore-expanding agent, polydopamine as carbon and nitrogen source, was used to synthesize hierarchically N-doped porous carbon spheres (N-HNCSs). The optimized sample of N-HNCS-1 exhibited uniform size of 150 nm, hierarchically porous structure, large surface area (705.46 m2 g−1), and N-doping amount of 6.51 %. These properties were beneficial for the transportation of the electrolyte ions resulted in that the N-HNCS-1 electrode displayed superior electrochemical performance with specific capacity of 142 mAh g−1. Furthermore, the Zn//ZnSO4 + ZnI2//N-HNCS-1 ZIHCs achieves an exceptionally high energy density of 347.7 Wh kg−1, which is 3-fold higher than that of Zn//ZnSO4//N-HNCS-1 ZIHCs. To elucidate this outstanding performance, we investigate the mechanisms involved, including Zn2+ deposition/stripping, SO42-/I- adsorption/desorption, Zn4SO4(OH)6⋅0.5 H2O precipitation/dissolution, and redox reactions relating to iodine ions. The incorporation of ZnI2 redox-electrolyte significantly enhanced the energy density by providing prominent pseudocapacitance via the faradaic reaction. Therefore, the high performance of Zn//ZnSO4 + ZnI2//N-HNCS-1 ZIHCs is attributed to the introduction of nitrogen (N) species, advantageous 3D carbonaceous framework, and redox reactions triggered by adding zinc iodide (ZnI2) into the aqueous zinc sulfate (ZnSO4) electrolyte. This groundbreaking research opens up possibilities for the development of high-energy ZIHCs, and advancements in energy storage technology.

Surprising Route to a Monoazaporphyrin and Full Characterization of Its Complexes with Five Different 3d Metals.

In the search for mild agents for the oxidative cyclization of tetrapyrromethane to the corresponding corrole, we discovered a route that leads to a monoazaporphyrin with three meso-CF3 groups. Optimization studies that allowed access to appreciable amounts of this new macrocycle paved the way for the preparation of its cobalt, copper, nickel, zinc, and iron complexes. All complexes were fully characterized by various spectroscopic methods and X-ray crystallography. Their photophysical and electrochemical properties were determined and compared to those of analogous porphyrins in order to deduce the effect of the peripheral N atom. Considering the global efforts for designing efficient alternatives to platinum group metal (PGM) catalysts, they were also absorbed onto a porous carbon electrode material and studied as electrocatalysts for the oxygen reduction reaction (ORR). The cobalt complex was found to be operative at a quite positive catalytic onset potential and with good selectivity for the desirable 4-electrons/4-protons pathway.

Double-kill contribution of high-roughness high-density porous carbon electrodes to mechanically self-sensing supercapacitors

Double-kill contribution of high-roughness high-density porous carbon electrodes to mechanically self-sensing supercapacitors

A green potassium citrate activation strategy via one-step synthesis of 3D porous carbon for capacitive deionization

Capacitive deionization (CDI) shows potential for desalination whereas exploring green and low-cost porous carbon electrodes exhibiting good desalination performance is still challenging. Herein, a green one-step carbonization-activation strategy was developed with carboxymethyl cellulose (CMC) as precursor and potassium citrate as activator to prepare CA(K)/CMC for CDI desalination. Owing to the introduction of potassium citrate, CA(K)/CMC exhibited larger specific surface area, better porous structure, more defects, and richer oxygen content. These improvements effectively accelerated charge transfer and ion transport process in CA(K)/CMC, which significantly increased the specific capacitance of CA(K)/CMC. Owing to the synergistic effect of these above properties, the optimized CA(K)/CMC-1-2 demonstrated high salt adsorption capacity (17.21 mg g−1, 1.2 V, 200 mg/L) and desalination rate (0.023 mg g−1 s−1, 1.2 V, 200 mg/L), and good cycling stability. Density functional theory (DFT) calculations further verified the advantageous characteristics of CA(K)/CMC-1-2 indeed improved ions adsorption. This finding offers new insights for designing green and economical carbon-based electrodes for desalination by CDI.

High-performance electrosorption of lanthanum ion by Mn3O4-loaded phosphorus-doped porous carbon electrodes via capacitive deionization

Transition-metal-oxide@heteroatom doped porous carbon composites have attracted considerable research interest because of their large theoretical adsorption capacity, excellent electrical conductivity and well-developed pore structure. Herein, Mn3O4-loaded phosphorus-doped porous carbon composites (Mn3O4@PC-900) were designed and fabricated for the electrosorption of La3+ in aqueous solutions. Due to the synergistic effect between Mn3O4 and PC-900, and the active sites provided by Mn–O–Mn, C/PO, C–P–O and Mn–OH, Mn3O4@PC-900 exhibits high electrosorption performance. The electrosorption value of Mn3O4@PC-900 was 45.34% higher than that of PC-900, reaching 93.02 mg g−1. Moreover, the adsorption selectivity reached 87.93% and 89.27% in La3+/Ca2+ and La3+/Na+ coexistence system, respectively. After 15 adsorption-desorption cycles, its adsorption capacity and retention rate were 50.34 mg g−1 and 54.12%, respectively. The electrosorption process is that La3+ first accesses the pores of Mn3O4@PC-900 to generate an electric double layer (EDL), and then undergoes further Faradaic reaction with Mn3O4 and phosphorus-containing functional groups through intercalation, surface adsorption and complexation. This work is hoped to offer a new idea for exploring transition-metal-oxide @ heteroatom doped porous carbon composites for separation and recovery of rare earth elements (REEs) by capacitive deionization.

Soft Actuator with Biomass Porous Electrode: A Strategy for Lowering Voltage and Enhancing Durability.

Electroactive artificial muscles with deformability have attracted widespread interest in the field of soft robotics. However, the design of artificial muscles with low-driven voltage and operational durability remains challenging. Herein, novel biomass porous carbon (BPC) electrodes are proposed. The nanoporous BPC enables the electrode to provide exposed active surfaces for charge transfer and unimpeded channels for ion migration, thus decreasing the driving voltage, enhancing time durability, and maintaining the actuation performances simultaneously. The proposed actuator exhibits a high displacement of 13.6 mm (bending strain of 0.54%) under 0.5 V and long-term durability of 99.3% retention after 550,000 cycles (∼13 days) without breaks. Further, the actuators are integrated to perform soft touch on a smartphone and demonstrated as bioinspired robots, including a bionic butterfly and a crawling robot (moving speed = 0.08 BL s-1). This strategy provides new insight into the design and fabrication of high-performance electroactive soft actuators with great application potential.

Pore-structure control of porous carbon electrode materials and energy-storage performance in water-in-salt electrolytes

The pore structure of carbon-based materials and the voltage window of the electrolyte are two key factors affecting the energy density of carbon-based supercapacitors (SCs). In this paper, activated carbon materials of different pore sizes is successfully synthesized by chemical activation method by adjusting the mass ratio of ZnCl2 to sucrose, and successfully applied to construct SCs based on different electrolyte systems. As the specific surface area of the prepared porous carbon materials shows a tendency to increase and then decrease, reaching a maximum in the presence of micropores. Further summarizing the constitutive relationship between pore structure-electrochemical performance in the high-concentration electrolyte system, it is found that the normalized specific capacity is larger at smaller pore sizes, and with the increase of mesoporous proportion, the normalized specific capacity decreases and tends to be stable. In addition, the different strengths of solvation of anions and cations in the electrolyte, with the cations contributing more to the contrast, and the presence of mesopores providing ion transport channels to improve the efficiency of ion transport in porous materials, which provide directions for designing a suitable pore structure for highly concentrated salt electrolytes, as well as another way of optimizing the properties of carbon-based materials for SCs.

Enhancing Energy Storage Capacity of 3D Carbon Electrodes Using Soft Landing of Molecular Redox Mediators.

The incorporation of redox-active species into the electric double layer is a powerful strategy for enhancing the energy density of supercapacitors. Polyoxometalates (POM) are a class of stable, redox-active species with multielectron activity, which is often used to tailor the properties of electrochemical interfaces. Traditional synthetic methods often result in interfaces containing a mixture of POM anions, unreactive counter ions, and neutral species. This leads to degradation in electrochemical performance due to aggregation and increased interfacial resistance. Another significant challenge is achieving the uniform and stable anchoring of POM anions on substrates to ensure the long-term stability of the electrochemical interface. These challenges are addressed by developing a mass spectrometry-based subambient deposition strategy for the selective deposition of POM anions onto engineered 3D porous carbon electrodes. Furthermore, positively charged functional groups are introducedon the electrode surface for efficient trapping of POM anions. This approach enables the deposition of purified POM anions uniformly through the pores of the 3D porous carbon electrode, resulting in unprecedented increase in the energy storage capacity of the electrodes. The study highlights the critical role of well-defined electrochemical interfaces in energy storage applications and offers a powerful method to achieve this through selective ion deposition.

Heteroatom doping carbon film derived from hyphae as a self-supporting cathode for advanced lithium sulfur batteries

Much attention has been paid to lithium sulfur battery due to its high energy density. However, low S loading and poor cycling stability have hindered their commercialization. In this work, a porous carbon film with rich heteroatom doping was prepared from the Penicillium chrysogenum hyphae film by freezing drying and high-temperature carbonization. Then the carbon film loaded polysulfide solution was utilized as a self-supporting cathode for Li-S batteries. The self-supporting cathode exhibited good rate performance (513.1 mAh/g at 1C) and improved cycling stability (more than 400 cycles) under a high current density (0.5C). This is mainly attributed to the abundant heteroatoms that provided active sites with superior adsorption ability for lithium polysulfide, which not only enhanced the cycling stability but also facilitated the conversion kinetics. Besides, the fibrous network morphology with affluent porous structures inherited from hyphae provided a large specific surface area and sufficient space for accommodating active substances. This work shows the great potential of hyphae derived porous carbon electrodes for high-performance energy storage applications.

One‐Step Preparation Pitch‐Based Porous Carbon via Carbonization and Co‐Activation for High‐Performance Supercapacitors

AbstractHierarchical porous carbon (HPC) materials for supercapacitor (SC) application are synthesized via a one‐step carbonization and activation method, using a novel composite activating agent with synergistic activation effect from mesophase pitch (MP) as precursor. The prepared mesophase pitch‐based porous carbon (MPPC) exhibits an ultra‐high specific surface area (SSA) of 2955.0 m2 g−1, well‐controlled pore size distribution (PSD), and exceptional electrochemical performance. The specific capacitance of MPPC‐4 attains up to 338.1 F g−1 at 1 A g−1 and 250.1 F g−1 at 20 A g−1, demonstrating remarkable rate capability. Furthermore, the assembled symmetric SC achieves a high energy density of 29.83 Wh kg−1 at a power density of 999.93 W kg−1 and still maintains 6.56 Wh kg−1 at a high power density of 19.89 kW kg−1. Furthermore, the SC exhibits advantageous cyclic stability, as evidenced by its remarkable capacitance retention rate of 88.55 % even after 5000 cycles. The utilization of this novel composite activating agent in the synthesis of pitch‐derived porous carbon (PC) electrode materials is an exceptionally effective and inventive process.