High-performance supercapacitors of hydrous ruthenium oxide/mesoporous carbon composites

The amorphous hydrous ruthenium oxide/mesoporous carbon composites (denoted as RuO₂·xH₂O/MC), obtained by loading small amount of amorphous hydrous ruthenium oxide nanoparticles ranged from 0.9 to 5.4% by weight of Ru (denoted as RuO₂·xH₂O) on mesoporous carbon (MC), were investigated for the first time and were used for supercapacitors. Electrochemical measurements showed that RuO₂·xH₂O/MC composites not only have an enhanced specific capacitance but also retain the superior rate capability of MC. The RuO₂·xH₂O/MC composite with Ru loading of 3.6 wt% exhibited an increase of the specific capacitance of approximately 57% (from 115 to 181 F/g) at the scan rate of 25 mV s⁻¹ in 0.1 M H₂SO₄ aqueous electrolyte. The specific capacitance based on the mass of RuO₂ was estimated to be 1,527 F/g, by subtracting the contribution from MC in the composite. Cycle performance tests for RuO₂·xH₂O/MC composite (3.6 wt% Ru) showed that approximately 2.8% loss of the total capacitance was observed after 1,000 cycles.     

The low-temperature (5 to 310 K) heat capacity and thermodynamic functions of cesium fluoroxysulfate (CsSO4F) and the standard potential at 298.15 K for the half-reaction: SO4F−(aq) + 2H+(aq) + 2e− = HSO4−(aq) + HF(aq)

The low-temperature (5 to 310 K) heat capacity of cesium fluoroxysulfate, CsSO₄F, has been measured by adiabatic calorimetry. At T = 298.15 K, the heat capacity C_p^o(T) and standard entropy S^o(T) are (163.46±0.82) and (201.89±1.01) J · K^?1 · mol^?1, respectively. Based on an earlier measurement of the standard enthalpy of formation ΔH_f^o the Gibbs energy of formation ΔG_f^o(CsSO₄F, c, 298.15 K) is calculated to be ?(877.6±1.6) kJ · mol^?1. For the half-reaction: SO₄F^?(aq)+2H⁺(aq)+2e^? = HSO₄^?(aq)+HF(aq), the standard electrode potential E at 298.15 K, is (2.47±0.01) V.     

原位化学沉积法制备碳/聚苯胺复合材料作为超级电容器材料的研究

Polyaniline （PA） film was chemically deposited onto the surface of activated carbon （AC） uniformly. Chemical deposition was carried out in 0.1 mol/L aniline plus 0.5 mol/L H2SO4 solution adopting V2O5·nH2O coated on the surface of activated carbon as oxidant. The surface morphologies and structures of the composite materials were characterized by scanning electron microscopy and FT-IR spectra. The electrochemical properties of the composite material electrodes were studied by cyclic voltammetry and constant current charge/discharge tests in 1 molFL H2SO4 solutions. The specific capacitance of composite materials was exhibited as high as 237.5 F/g at a current density of 1.0 A/g compared with a value of 120 F/g for pure carbon electrode. Good power characteristic and good stability of composite electrodes were also demonstrated.     

Study of capacitive properties in supercapacitor for copolymer of aniline with m-phenylenediamine

The copolymers were synthesized with different molar ratios of m-phenylenediamine to aniline (R for short) by a chemical oxidation method. The products were first used as electrochemical activity materials of the supercapacitor. Capacitive behaviors of the prepared copolymers in 1 mol·L⁻¹ H₂SO₄ electrolyte were examined by electrochemical impedance spectroscopy, cyclic voltammeter, and galvanostatic charge/discharge. The relationship of molar ratios with capacitive property of the prepared products was investigated too. The results showed that the product with R of 2:98 displayed better electrochemical properties than that of the other products. Compared with the synthesized polymer in the absence of m-phenylenediamine, the polymerized copolymer with R of 2:98 exhibited the initial specific capacitance value of 475 F·g⁻¹, which increased by nearly 10.1% than that of the former at a current density of 200 mA·g⁻¹ in 1 mol·L⁻¹ H₂SO₄ electrolyte in the potential range of −0.3 to 0.7 V. The discharge specific capacitance value of the copolymer remained 300 F·g⁻¹ after 1,000 cycles, exhibiting a good cycling performance and the structure stability.     

Asymmetric supercapacitors based on stabilized α-Ni(OH)2 and activated carbon

In this work, stabilized Al-substituted α-Ni(OH)₂ materials were successfully synthesized by a chemical coprecipitation method. The experimental results showed that the 7.5% Al-substituted α-Ni(OH)₂ materials exhibited high specific capacitance (2.08?×?10³ F/g) and excellent rate capability due to the high stability of Al-substituted α-Ni(OH)₂ structures in alkaline media, suggesting its potential application in electrode material for supercapacitors. To enhance energy density, an asymmetric type pseudo/electric double-layer capacitor was considered where α-Ni(OH)₂ materials and activated carbon act as the positive and negative electrodes, respectively. Values for the maximum specific capacitance of 127 F/g and specific energy of 42 W·h/kg were demonstrated for a cell voltage between 0.4 and 1.6 V. By using the α-Ni(OH)₂ electrode, the asymmetric supercapacitor exhibited high energy density and stable power characteristics. The hybrid supercapacitor also exhibited a good electrochemical stability with 82% of the initial capacitance over consecutive 1,000 cycle numbers.     

A High-Performance Asymmetric Supercapacitor Based on Tungsten Oxide Nanoplates and Highly Reduced Graphene Oxide Electrodes

Tungsten oxide/graphene hybrid materials are attractive semiconductors for energy-related applications. Herein, we report an asymmetric supercapacitor (ASC, HRG//m-WO₃ ASC), fabricated from monoclinic tungsten oxide (m-WO₃) nanoplates as a negative electrode and highly reduced graphene oxide (HRG) as a positive electrode material. The supercapacitor performance of the prepared electrodes was evaluated in an aqueous electrolyte (1 m H₂SO₄) using three- and two-electrode systems. The HRG//m-WO₃ ASC exhibits a maximum specific capacitance of 389 F g⁻¹ at a current density of 0.5 A g⁻¹, with an associated high energy density of 93 Wh kg⁻¹ at a power density of 500 W kg⁻¹ in a wide 1.6 V operating potential window. In addition, the HRG//m-WO₃ ASC displays long-term cycling stability, maintaining 92 % of the original specific capacitance after 5000 galvanostatic charge–discharge cycles. The m-WO₃ nanoplates were prepared hydrothermally while HRG was synthesized by a modified Hummers method.     

The effect of the polyaniline morphology on the performance of polyaniline supercapacitors

The polyaniline (PANI) prepared by the pulse galvanostatic method (PGM) or the galvanostatic method on a stainless steel substrate from an aqueous solution of 0.5 mol/l H₂SO₄ with 0.2 mol/l aniline has been studied as an electroactive material in supercapacitors. The electrochemical performance of the PANI supercapacitor is characterized by cyclic voltammetry, a galvanostatic charge–discharge test and electrochemical impedance spectroscopy in NaClO₄ and HClO₄ mixed electrolyte. The results show that PANI films with different morphology and hence different capacitance are synthesized by controlling the synthesis methods and conditions. Owing to the double-layer capacitance and pseudocapacitance increase with increasing real surface area of PANI, the capacitive performances of PANI were enhanced with increasing real surface area of PANI. The highest capacitance is obtained for the PANI film with nanofibrous morphology. From charge–discharge studies of a nanofibrous PANI capacitor, a specific capacitance of 609 F/g and a specific energy density of 26.8 Wh/kg have been obtained at a discharge current density of 1.5 mA/cm². The PANI capacitor also shows little degradation of capacitance after 1,000 cycles. The effects of discharge current density and deposited charge of PANI on capacitance are investigated. The results indicate that the nanofibrous PANI prepared by the PGM is promising for supercapacitors.     

石墨烯-氧化钌纳米复合材料的水热法合成及电化学电容性能

通过水热法制备了石墨烯-氧化钌(G-RuO₂)纳米复合材料。对样品进行了X射线衍射(XRD),扫描电子显微镜(SEM),透射电子显微镜(TEM)和能量色散谱(EDS)表征。SEM结果表明氧化钌粒子均匀地分散在石墨烯层片上。TEM结果显示氧化钌纳米粒子的平均粒径约为3 nm。对样品进行了循环伏安和充放电性能测试,结果表明在1 A·g^-1的电流密度下,样品在H₂SO₄(1 mol·L^-1)溶液中具有219.7 F·g^-1的比电容。     

V2O5·0.6H2O nanoribbons as cathode material for asymmetric supercapacitor in K2SO4 solution

V₂O₅·0.6H₂O nanoribbons were prepared and their electrochemical behaviors in K₂SO₄ aqueous solution were investigated. Results show for the first time that K⁺ ions could intercalate/deintercalate reversibly in the V₂O₅·0.6H₂O lattice. An asymmetric supercapacitor activated carbon/0.5 mol/l K₂SO₄/V₂O₅·0.6H₂O was successfully assembled, which could be cycled reversibly in the voltage region of 0–1.8 V. This supercapacitor presents an energy density of 29.0 Wh/kg based on the total mass of the active electrode materials, a very good rate behavior with energy density of 20.3 Wh/kg at power density of 2 kW/kg, and also a rather good cycling performance.     

Organic salt-derived phosphorus-doped mesoporous carbon for high performance supercapacitors

Phosphorus-doped mesoporous carbons (PMCs) were prepared using a self-doping and self-templating approach via direct pyrolysis of sodium phytate (C₆H₁₇NaO₂₄P₆). The one-pot method allows simultaneous carbonization and P doping, eliminating the need for pre-synthesis or post-activation treatment. The C₆H₁₇NaO₂₄P₆ is the source of both carbon and phosphorus, and the nano-Na₄P₂O₇ particles produced during pyrolysis act as hard templates for the honeycomb mesoporous structure with high specific surface area (884–827 m²/g), large mesopore volume ratio (67%–75%) and rich phosphorus content (0.53–2.34 at%). As electrodes of supercapacitors in 6 mol/L KOH, the PMCs showed outstanding performance with a high capacitance of 202 F/g and excellent rate performance of 148 F/g at 30 A/g. In addition, the PMCs-based symmetrical supercapacitors can operate in an expanded working voltage of 0–1.6 V in 3 mol/L H₂SO₄ aqueous electrolytes with high-density energy of 11.8 Wh/kg.