Structure and Capacitive Performance of Porous Carbons Derived from Terephthalic Acid–Zinc Complex via a Template Carbonization Process

High-performance porous carbons as supercapacitor electrode materials have been prepared by a simple but efficient template carbonization process, in which commercially available terephthalic acid–zinc complex is used as a carbon source. It reveals that the carbonization temperature plays a crucial role in determining the structure and capacitive performance of carbons. The <b>carbon-1000</b> sample has high surface area of 1138 m² g^–1 and large pore volume of 1.44 cm³ g^–1 as well as rationally hierarchical pore size distribution. In a three-electrode system, the <b>carbon-1000</b> sample possesses high specific capacitances of 266.0 F g^–1 at 0.5 A g^–1 and good cycling stability. In a two-electrode system, the operation temperature (25/50/80 °C) can greatly influence the electrochemical performance of the <b>carbon-1000</b> sample, especially with an extended voltage window (∼ 3 V). The temperature-dependent operation makes it possible for the application of supercapacitors under extreme conditions

Nitrogen-Doped Porous Carbon Spheres Derived from Polyacrylamide

Spherical nitrogen-doped porous carbons have been prepared through a template carbonization method, in which polyacrylamide (PAM) serves as carbon and nitrogen sources, and calcium acetate as hard template. It reveals that the mass ratio of polyacrylamide and calcium acetate and the carbonization temperature have crucial impacts upon the pore structures and the correlative capacitive performance. The <b>PAM-Ca-650-1:3</b> sample displays the best capacitance performance. It is amorphous with low-graphitization degree, possessing a total BET surface area of 648 m² g^–1 and total pore volume of 0.59 cm³ g^–1. At a current density of 0.5 A g^–1, the resultant specific capacitance is 194.7 F g^–1. It exhibits high capacitance retention of 97.8% after charging–discharging 5000 times. The polyacrylamide used is cheap and commercially available, making it promising for large-scale production of porous carbons containing nitrogen as an excellent electrode material for supercapacitor

Polyvinylidene Fluoride-Based Carbon Supercapacitors: Notable Capacitive Improvement of Nanoporous Carbon by the Redox Additive Electrolyte of 4‑(4-Nitrophenylazo)-1-naphthol

The nanoporous graphitic carbon materials (NGCM) have been prepared by a synchronous carbonization and graphitization process, using waste polyvinylidene fluoride (PVDF) as carbon precursor and Ni­(NO₃)₂·6H₂O as the graphitic catalyst. It reveals that the carbonization temperature plays a crucial role in determining the pore structures as well as their electrochemical performances. Increasing the carbonization temperature from 800 to 1200 °C, the corresponding porosity has slightly decreased, accompanied by an increase of graphitization degree. Next, to further improve the electrochemical performance of the sample prepared at 800 °C, a novel redox additive of 4-(4-nitrophenylazo)-1-naphthol (NPN) with different amounts has been introduced in 2 mol L^–1 KOH electrolyte. Therein, the specific capacitance by adding 4 mmol L^–1 of NPN can reach 2.98 times higher than the pristine value. Apparently, the mixed electrolytes have largely enhanced the electrochemical performance, which is expected to be applied in the field of high performance supercapacitors

Temperature-Dependent Conversion of Magnesium Citrate into Nanoporous Carbon Materials for Superior Supercapacitor Application by a Multitemplate Carbonization Method

A straightforward multitemplate carbonization method for producing nanoporous carbons has been implemented using magnesium citrate as the carbon source and magnesium powder as the template. Notably, the crystallinities of the carbon materials were greatly enhanced with increasing carbonization temperatures. Sample C-4:1–900 obtained by carbonizing the mixture of magnesium citrate and Mg powder (in a mass ratio of 4:1) at 900 °C exhibited a large BET surface area of 1972.1 m² g^–1 and a high pore volume of 4.78 cm³ g^–1, thereby resulting in the best electrochemical behaviors. It delivered a large specific capacitance of 236.5 F g^–1 at 1 A g^–1 when measured in a three-electrode system. Additionally, in a two-electrode system, the energy density was 15 Wh kg^–1 for a power density of 0.5 W kg^–1, when measured at an operating temperature of 80 °C

Nitrogen-Doped Porous Carbon Prepared from Urea Formaldehyde Resins by Template Carbonization Method for Supercapacitors

Through a simple and convenient template carbonization method, nitrogen-doped porous carbon has been successfully achieved by heating urea formaldehyde (UF) resin and magnesium citrate at 800 °C, where the magnesium citrate serves as a template. The mass ratio between the UF resin and magnesium citrate plays a crucial impact on the surface areas, pore structures, and the correlative capacitive behaviors of the final porous carbons, denoted as samples UF-Mg-1:1, -1:3, and -1:5. All present porous carbons exhibited amorphous features with low graphitization degrees. Sample UF-Mg-1:3 displayed the best capacitive performance with a large specific capacitance of 239.7 F g^–1 at a current density of 0.5 A g^–1 and a high energy density of 33.3 Wh kg^–1 at a power density of 0.25 kW kg^–1. More importantly, it exhibited a high capacitance retention of 94.4% after 5000 charge/discharge cycles, clearly indicating good cycling durability

Integration of Redox Additive in H₂SO₄ Solution and the Adjustment of Potential Windows for Improving the Capacitive Performances of Supercapacitors

Nanoporous carbon material with large specific surface area (2208 m² g^–1) and high pore volume (4.15 cm³ g^–1) has been synthesized by the template carbonization method, using a glucose–zinc nitrate complex as the precursor. Moreover, adding redox-mediated ferrous ammonium sulfate (FAS) to an H₂SO₄ electrolyte and regulating the potential windows in a two-electrode system can result in an ultrahigh specific capacitance of 1499 F g^–1 at 10 A g^–1 and a high energy density of 58.70 Wh kg^–1, which are higher than those of the pristine one without any FAS. These remarkable improvements are attributed to Faradaic pseudocapacitances by the reversible Faradaic reactions of FAS as well as the edge active carbons showing excellent electrosorption toward Fe^2+/3+, NH₄⁺, and H⁺. Furthermore, regulating the potential windows also exerts crucial roles in the capacitive performances. It is revealed that the potential of the −0.5–0.5 V window can lead to optimum capacitance and energy efficiency

Two-Dimensional Carbon Nanosheets for High-Performance Supercapacitors: Large-Scale Synthesis and Codoping with Nitrogen and Phosphorus

Two-dimensional carbon nanosheets codoped with N and P species have been successfully synthesized by a template carbonization method coupled with nitrogenization and phosphorylation processes using trisodium citrate dihydrate, melamine, and NH₄H₂PO₄ as C, N, and P sources, respectively. Dopants of N and P species play crucial roles in the determination of carbon porosities and electrochemical performance; notably, increasing the P content can lead to a decrease in the BET surface area together with a corresponding decrease in the electrochemical performance. For instance, regulating the mass ratio between the C source and the N and P sources to 2:1 results in the maximum BET surface area of 1340 m² g^–1, whereas a ratio of 1:2 results in a decreased value of only 47 m² g^–1. Moreover, the mass ratio of 1:1 results in superior electrochemical behaviors, with a maximum energy density that can reach up to 13.3 Wh kg^–1. The present synthesis method provides an alternative route for producing N- and P-containing carbon nanostructures with two-dimensional features, serving as excellent electrode materials for energy propagation and storage

Microporous Carbon Materials by Hydrogen Treatment: The Balance of Porosity and Graphitization upon the Capacitive Performance

The balance of porosity and graphitization toward carbon materials plays acrucial role in determining the capacitive performance. In this work, this purpose has been successfully implemented by adjusting the carbonization temperature and hydrogen gas treatment. Oxygen containing functional groups have conspicuously reduced by the coeffects of hydrogen gas and high temperature on carbon materials. Besides, by treatment at a temperature of 800 °C with hydrogen, the electrochemical performances have been greatly improved. The electrode treated at the temperature of 800 °C with hydrogen displays higher specific capacitances of 171 F g^–1 compared with that of bare carbon electrode of 145 F g^–1, owing to enlarged BET surface area and pore volume and reduced resistance. At the same time, the electrode treated at the temperature of 800 °C with hydrogen exhibits a higher cycling stability of 96.3% of primary specific capacitances after 5000 cycles and energy density of 8.36 Wh kg^–1, respectively

Generalized Conversion of Halogen-Containing Plastic Waste into Nanoporous Carbon by a Template Carbonization Method

Halogen-containing plastic materials have been converted into nanoporous carbon by a template carbonization method, using zinc powder as an efficient hard template. The mass ratio between plastics and zinc powder as well as carbonization temperature plays a crucial role in determining the carbon structures and resultant electrochemical performances. The <b>PTFE-1:3-700</b> sample that is obtained by carbonizing polytetrafluoroethene and zinc powder (the mass ratio of 1:3) at 700 °C has a large BET surface area of 800.5 m² g^–1 and a high total pore volume of 1.59 cm³ g^–1, also delivering excellent specific capacitance of 313.7 F g^–1 at 0.5 A g^–1. Moreover, it exhibits a superior cycling stability with high capacitance retention of 93.10% after cycling for 5000 times. More importantly, it can be extended to produce nanoporous carbon derived from other halogen-containing plastic materials such as poly­(vinylidene fluoride) and poly­(vinyl chloride), revealing the generality of the synthesis method

Mechanistic Insights into the Intermolecular Interaction and Li⁺ Solvation Structure in Small-Molecule Crowding Electrolytes for High-Voltage Aqueous Supercapacitors

The introduction of a small-molecule crowding agent with low viscosity to expand the operating voltage of aqueous electrolytes is an effective strategy to achieving low-cost and high-voltage aqueous carbon-based supercapacitors (SCs). Herein, the electrochemical stable window (ESW) of a lithium nitrate electrolyte (2 M LiNO3) is expanded to 3.65 V after adding the water-miscible dimethyl sulfoxide (DMSO) with high Gutmann donor number (29.8 kcal mol–1) as the crowding agent. The small-molecule crowding electrolyte (SMCE) has the advantages of low viscosity (3.87 mPa·s), wide temperature flexibility (−40 to 80 °C), better wettability to activated carbon (AC), and nonflammability. The reorganization of the Li+ solvation structure and the regulation of hydrogen bonds (H-bonds) of water in a DMSO-induced highly crowded environment suppress the water decomposition on the charged electrode. In situ differential electrochemical mass spectrometry (DEMS) shows that the detrimental hydrogen and oxygen evolution reactions (HER and OER) in SMCE are substantially inhibited. Molecular dynamics simulations (MDSs) indicate that the formation of a 1H2O-2DMSO molecular aggregate in SMCE destroys the H-bond network of water molecules. The SMCE enables symmetric SCs to deliver a high operating voltage of 2.4 V and an energy density of 44 Wh kg–1 at 1.2 kW kg–1