Fabrication of three-dimensional structured graphene for supercapacitors

以氧化石墨为原料,采用电化学还原和超声剥离法制备了三维网状石墨烯,电化学法是在交变场中用方波实现的,最终制得的石墨烯具有明确的三维连通多孔网络结构,孔的大小在亚微米至数微米之间,孔壁由非常薄的石墨烯片堆积而成.用该材料做超级电容器电极材料,用循环伏安法,恒流充放电,交流阻抗法测试电极的电容性能,当扫描速率为10 mV/s时,电容器比电容为140 F/g,等效电阻小于1 Ω,三维网状石墨烯具有性能稳定,充放电效率高,循环性能好,适合于大电流充放电等优良性能.     

Rational design of hierarchical core-shell structured CoMoO4@CoS composites on reduced graphene oxide for supercapacitors with enhanced electrochemical performance

Engineering multicomponent active materials as an advanced electrode with the rational designed core-shell structure is an effective way to enhance the electrochemical performances for supercapacitors. Herein, three-dimensional self-supported hierarchical CoMoO₄@CoS core-shell heterostructures supported on reduced graphene oxide/Ni foam have been rationally designed and prepared via a facile approach. The unique structure and the synergistic effects between two different materials, as well as excellent electronic conductivity of the reduced graphene oxide, contribute to the increased electrochemically active site and enhanced capacitance. The core-shell CoMoO₄@CoS composite displays the superior specific capacitance of 3380.3 F g⁻¹ (1 A g⁻¹) in the three-electrode system and 81.1% retention of the initial capacitance even after 6000 cycles. Moreover, an asymmetric device was successfully prepared using CoMoO₄@CoS and activated carbon as positive/negative electrodes. It is worth mentioning that the device delivered the high energy density of 59.2 W h kg⁻¹ at the power density of 799.8 W kg⁻¹ and the excellent cycle performance (about 91.5% capacitance retention over 6000 cycles). These results indicate that the core-shell CoMoO₄@CoS composites offers the novelty strategy for preparation of electrodes for energy conversion and storage devices.     

PdZn alloys decorated 3D hierarchical porous carbon networks for highly efficient and stable hydrogen production from aldehyde solution

PdZn alloys and Pd catalyst decorated 3D hierarchically porous carbon (HPC) network catalysts were prepared by a facile and simple impregnation/carbonization process from energetic MOFs of MET-6. Due to the high uniformly dispersion of metal nanoparticles and strong metal-support interactions, the as prepared HPC-PdZn catalysts exhibited highly efficient catalytic hydrogen production from formaldehyde solution at room temperature, which is much higher than that of pure Pd nano-particles. By further optimizing the reaction parameters such as reaction temperature, formaldehyde concentrations, and NaOH concentrations, the hydrogen generation rates could be further increased to unprecedented 572.6 mL·min⁻¹ g⁻¹, which was nearly 4 times as much as the solely Pd nanoparticles counterparts. Owing to its high efficiency and stability at room temperature, the as-prepared HPC-PdZn architectures catalyst based hydrogen generation reaction may serve as state-of-the-art candidate in both hydrogen supply and environmental cleaning.     

Walnut shell-derived hierarchical porous carbon with high performances for electrocatalytic hydrogen evolution and symmetry supercapacitors

Walnut Shell-derived hierarchical porous carbon has been successfully synthesized by the efficient KOH activation process. The hierarchical porous carbon material activated at 600 °C, has the specific micropore area of 1037.31 m² g⁻¹ and micropore volume of 0.51 cm³ g⁻¹, which leads to have electrochemical performances of the hydrogen evolution reaction (HER) and supercapacitors. Specifically, as the hydrogen evolution reaction electrocatalyst, the walnut shell-derived carbon material activated at 600 °C exhibits a lower onset potential of 6.00 mV, a smaller Tafel slope of 69.76 mV dec⁻¹ and outstanding stability above long-term cycling. As a supercapacitor electrode material, the sample possesses specific capacitance of 262.74 F g⁻¹ at 0.5 A g⁻¹, the remarkable rate capability of 224.60 F g⁻¹ at even 10 A g⁻¹ and good long-term stability. A symmetric supercapacitor shows the highly energy density of 7.97 Wh kg⁻¹ at a power density of 180.80 W kg⁻¹. This novel and low-cost biomass material is very promising for the electrocatalytic water splitting and supercapacitors.     

Cobalt phosphide nanoparticles embedded in 3D N-doped porous carbon for efficient hydrogen and oxygen evolution reactions

An electrocatalyst based on a unique three-dimensional (3D) N-doped porous carbon sheet networks embedded with CoP₂ nanoparticles (CoP₂@3D-NPC) was synthesized by a facile pyrolysis process as well as an in-situ phosphatization method. The improved CoP₂@3D-NPC hybrid materials show excellent electrocatalytic activity toward HER and OER. This material provides a low overpotential of 126 mV at 10 mA cm⁻² in 0.5 M H₂SO₄ and 167 mV at 20 mA cm⁻² in 1.0 M KOH for HER with a small Tafel slope value of 59 mV dec⁻¹, respectively. Besides, it is also active for the OER under alkaline conditions. Such a prominent property of the CoP₂@3D-NPC electrocatalyst could be attributed to its excellent electrical conductivity of 3D carbon substrate, strong synergistic effect between CoP₂ nanoparticles and carbon nanosheet as well as extra active sites created by the N-doped structure.     

Enhanced hydrogen storage performance of three-dimensional hierarchical porous graphene with nickel nanoparticles

Three-dimensional hierarchical porous graphene with nickel nanoparticles (3DHPG-Ni) was synthesized through electrostatic assembly method with the assistance of poly (methyl methacrylate) (PMMA) template and subsequent removal of PMMA template by calcination. The morphology, microstructure and hydrogen adsorption properties of 3DHPG-Ni nanocomposites were examined in detail. The obtained 3DHPG-Ni nanocomposite exhibited hierarchical porous structure composed of macro-, meso- and micropores, high specific surface area (925 m² g^?1), large pore volume (0.58 cm³ g^?1) and excellent hydrogen storage capacity. Under the pressure of 5 bar, 3DHPG-Ni nanocomposite showed a maximum hydrogen capacity of 4.22 wt% and 1.95 wt% at 77 K and 298 K, respectively, demonstrating that the as-prepared 3DHPG-Ni nanocomposite was supposed to be a promising material with outstanding properties for practical applications in the field of hydrogen storage. The three-dimensional hierarchical porous structure, evenly distributed Ni nanoparticles and hydrogen spillover effect were responsible for the enhanced hydrogen storage capacities.     

Nickel silicate hydroxide on hierarchically porous carbon derived from rice husks as high-performance electrode material for supercapacitors

Nickel silicate hydroxide on hierarchically porous carbon derived from rice husks is prepared as electrode material for supercapacitors. AAEMs¹ in rice husks and CO₂ promote the development of pores, which act as pore-forming agent and catalyst respectively. The rice husks carbon is used as the substrate and the SiO₂ in rice husks is converted into Ni–Si compound by loading Ni. The C/NiSi-600-1 shows remarkable electrochemical performance with 237.07 F/g at 0.5 A/g. The performance declines with crystalline SiO₂ formed above 900 °C. A high-performance asymmetric water-system supercapacitor device is fabricated by C/NiSi-600-1 and activated carbon. This device shows capacitance of 142 mF/cm² at 4 mA/cm², the energy density of 25.24 Wh/kg at 551.4 W/kg and great cycle stability with 90% after 10,000 cycles. This work provides new insights into the green application of rice husks and promotes the development of electrode materials for supercapacitors.     

Controllable fabrication of 3D porous carbon nitride with ultra-thin nanosheets templated by ionic liquid for highly efficient water splitting

Modifying the texture of carbon nitride to adjust its physicochemical performance is a fascinating method for achieving high photocatalytic activity. Herein, we synthesized 3D porous carbon nitride with ultra-thin nanosheets by using cyanuric acid-melamine supramolecular and ionic liquid as precursor and template, respectively. The ionic liquid adjusts the morphology of materials and induces the carbon residue into the porous channels owing to its incomplete degradation. The 3D porous framework makes carbon nitride reflect the enhanced surface area, exposes adequate reaction sites, and offers a pathway for charge transport. And carbon residue and ultra-thin nanosheets further promote the photogenerated carriers transport and reduce the recombination rate of charge carriers. Consequently, 3D porous carbon nitride with ultra-thin nanosheets exhibit outstanding and stable hydrogen evolution under visible light irradiation. Significantly, as-fabricated sample CN-100 reflects an improved H₂ generation rate, up to 17,028 μmol h^?1 g^?1, which is 12 times higher than that of CN (1412 μmol h^?1 g^?1). The present work offers a unique synthesis strategy to develop the novel photocatalyst with efficient photocatalytic performance.     

One-step synthesis of 3D sulfur-doped porous carbon with multilevel pore structure for high-rate supercapacitors

In this work, three-dimensional (3D) interconnected S-doped porous carbon materials are fabricated using bio-waste sodium lignosulfonate as carbon and sulfur precursor by in situ carbonization and subsequent KOH activation process. The as-obtained S-PC-50 has high specific surface area of 1592 m² g^?1, high S weight percentage up to 5.2 wt% and interconnected porous framework consisting of micro-, meso- and macropores. As a result, the S-PC-50 exhibits a high specific capacitance of 320 F g^?1 at 0.2 A g^?1, excellent rate performance with 76.5% capacitance retention after a current density increasing from 2 A g^?1 (200 F g^?1) to 100 A g^?1 (153 F g^?1) and 99% capacitance retention after 10,000 cycles at 5 A g^?1. Besides, the symmetric supercapacitor can deliver a high energy density up to 8.2 Wh kg^?1 at 50 W kg^?1.     

Capacitance-dominated hierarchical porous three-dimensional carbon framework enhanced Prussian blue analogue as superior cathode for sodium-ion batteries

The 3D framework carbon is an ideal host of active materials for energy storage batteries. In this work, K_xNa_yMn[Fe(CN)₆] (KNMF) nanocubes were in-situ grown on hierarchical porous 3D framework carbon (3DFC) to construct a composite cathode (KNMF@3DFC) for sodium-ion batteries. Owing to the hierarchical porous structure and large specific surface area, the highly conductive 3DFC offers abundant active sites for sodium storage and contributes to extra capacity. The considerable content of surface capacitance-dominated sodium storage of KNMF@3DFC composite cathode reveals faster charge transfer and better reaction kinetics, conducing to its rate capability. Ex-situ XRD/Raman measurements further reveal well structural stability of KNMF@3DFC during the whole cycle. Consequently, the KNMF@3DFC composite electrode reveals excellent rate performance and superior long-term cycling stability. Combining active materials with 3D framework carbon to enable a capacitance-dominated sodium storage mechanism is a promising strategy to stimulate the development of advanced electrode materials.     

Phosphorus-doped Fe3O4 nanoflowers grown on 3D porous graphene for robust pH-Universal hydrogen evolution reaction

It is extremely necessary to develop highly efficient and low-cost non-noble metal electrocatalysts for hydrogen evolution reaction (HER) under a pH-universal condition in the realm of sustainable energy. Herein, we have successfully prepared phosphorus doped Fe₃O₄ nanoflowers on three-dimensional porous graphene (denoted as P–Fe₃O₄@3DG) via a simple hydrothermal and low-temperature phosphating reaction. The P–Fe₃O₄@3DG hybrid composite not only demonstrates superior performance for HER in 1.0 M KOH with low overpotential (123 mV at 10 mA/cm²), small Tafel slope (65 mV/dec), and outstanding durability exceeding 50 h, but also exhibits satisfying performances under neutral and acidic medium as well. The 3D graphene foam with large porosity, high conductivity, and robust skeleton conduces to more active sites, and faster electron and ion transportation. The phosphorus dopant provides low Gibbs free energy and ability of binging H⁺. The synergistic effect of 3DG substrate and P–Fe₃O₄ active material both accelerates the catalytic activity of Fe-based hybrid composite for HER.     

The construction of 3D hierarchical CdS/NiAl-LDH photocatalyst for efficient hydrogen evolution

The development of excellent photocatalysts for hydrogen evolution is of great significance to solving the global energy crisis. In this work, a novel 3D hierarchical CdS/NiAl-LDH photocatalyst was fabricated by a facile electrostatic assembly strategy, which was composed of 1D CdS nanorods and 3D flower-like NiAl-LDH microspheres. Under the visible irradiation, the CNA-20 hierarchical photocatalyst presents the optimum hydrogen evolution rate achieved to 3.24 mmol g^?1 h^?1, which is improved 6.23-fold in comparison with the pure CdS. Through the analysis of energy band structures and first-principles calculation, the type-Ⅱ charge transfer mechanism was proposed. Driven by the built-in electric field, as well as the effect of intimate interface contact of CdS and NiAl-LDH, the photogenerated charge could be achieved rapidly separate and migrate, which effectively promotes the H₂ evolution. This well-designed synergistic 1D/3D interface interaction and provides an economic approach to rationally developing metal-free photocatalysts for hydrogen production.     

Composite of manganese dioxide impregnated in porous hollow carbon spheres for flexible asymmetric solid‐state supercapacitors

Compared with symmetric supercapacitors, asymmetric supercapacitors are been widely applied in energy storage devices because of delivering an impressible energy density. Herein, a simple temple strategy was used to fabricate the porous hollow carbon spheres (PHCS) with high specific surface area of 793 m² g^?1, large pore volume of 1.0 cm³ g^?1 and pore size distribution from micropores to mesopores, serving as the capacitive electrodes of asymmetric supercapacitors. Subsequently, manganese dioxide (MnO₂) was impregnated into the PHCS to form a faradic electrode with a promising performance, owing to a synergistic effect between high capacity MnO₂ and conductive PHCS. Furthermore, the flexible asymmetric solid‐state devices were constructed with PHCS anode, PHCS@MnO₂ cathode, and PVA/LiCl electrolyte, extending a voltage window up to 1.8 V. The extensive voltage window would lead to an increased energy density. In our case, the flexible asymmetric sandwich exhibit excellent electrochemical performance in terms of a high energy density capacity of 26.5 W·h kg^?1 (900 W kg^?1) and superior cycling performance (10 000 cycles). Therefore, the developed strategy provides a strategy to achieve the PHCS‐based composites for the application in the asymmetric solid‐state supercapacitors, which will enable a widely field of flexible energy storage devices.     

3D SnO2/sulfonated graphene composites with interpenetrating porous structure as anode material for lithium-ion batteries

Combine SnO₂ nanoparticles with some conductive carbonaceous materials has been regarded as one of the most effective strategies to solve the problems of poor conductivity and volume change. In this work, a SnO₂/sulfonated graphene composite with 3D interpenetrating porous structure (3D SnO₂/SG) was synthesized. The elaborate designed 3D SG structure not only generates an excellent electronic conductivity, but also buffers the volume expansion of the SnO₂ particles. As a result, the desirable 3D possesses enhanced performance when used as anode material in lithium battery. For example, the electrochemical results showed that the 3D SnO₂/SG presents a high reversible specific capacity (928.5 mA h g^?1 at the current density of 200 mA g^?1). Even after 120 cycles, the specific capacity of 679.7 mA h g^?1 (at the current density of 400 mA g^?1) are still maintained.     

Electrocatalysis by design: Enhanced electro-oxidation of glycerol at NiOx nanoparticle modified 3D porous carbon felts

This paper addresses the preparation of three-dimensional functionalized carbon felts (CFs), which were coated with nickel (Ni) nanostructures and used as an electrocatalyst for glycerol electrooxidation in alkaline medium. The commercial CFs (3D-carbon fibers) were first functionalized with O- and S- like functionalities via electrochemical pretreatment in NaOH and H₂SO₄, then the impacts of this pretreatment on the electrodeposited Ni nanoparticles (NiNPs) morphology, distribution, structure and performance for glycerol electrooxidation was investigated. X-ray diffraction (XRD) together with cyclic voltammetry (CV) techniques were used to detect the changes of the electrodeposited Ni oxide phases. Contact angle was used to determine impact of pretreatment on the wettability of CF. X-ray photoelectron spectroscopy (XPS) was used to get information about the added functional groups while scanning electron microscope (SEM) was used to observe the changes of NiNPs morphology, distribution, and particle size. As-synthesized NiNPs modified functionalized CFs exhibited an excellent activity concurrent with good stability for glycerol electrooxidation. The pretreatment of CF in either NaOH or H₂SO₄ resulted in a significant increase in the Ni surface active sites and improved their electrocatalytic activity for glycerol electrooxidation.     

Constructing 3D hierarchical Zn0.2Cd0.8S microspheres for the improved visible-light-driven photocatalytic performance

Nanorod assembled three-dimensional (3D) hierarchical Zn_0.2Cd_0.8S microspheres were successfully prepared by a facile one-pot microwave hydrothermal approach using ethylenediamine (EN) as a template agent. The optimal 3D hierarchical Zn_0.2Cd_0.8S microspheres (ZCS-30) is obtained when adding 30 mL into the synthetic system, which can function as a highly active photocatalyst for H₂ evolution under visible-light irradiation with the wavelength of 420 nm, delivering an activity approximately 2.5 and 7.5 times higher than that of Zn_0.2Cd_0.8S nanoparticles and CdS counterparts, respectively, and giving an apparent quantum efficiency (AQE) of 7.4%. Furthermore, the ZCS-30 photocatalyst shows the good stability after the catalytic H₂ evolution for 15 h (5 cycles). In addition, the ZCS-30 photocatalyst exhibits the excellent degradation of Rhodamine B (Rh B) almost up to 80% under the visible light irradiation over a period of 150 min. The results demonstrate that ZCS-30 can serve as a promising visible-light-driven bifunctional photocatalyst for water splitting and dye degradation.     

Three dimension (3D) hierarchical electrode (Au/rGO/CoPt3) for electrooxidation of ethanol in fuel cells

A highly efficient electrode for ethanol electrooxidation was successfully fabricated with the assistance of Nanoimprint Lithography (creation of 3D structure) and facile preparation method-electrodeposition. Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), X-ray Diffraction (XRD) and Raman spectroscopy were used to characterize the electrodes obtained, which were further evaluated by Cyclic Voltammetry Potentiostat. It concludes that the electrocatalytic activity of the electrodes towards ethanol oxidation is promoted in the sequence of Au < Au/rGO < Au/rGO/CoPt₃. The synergy effect of reduced GO and CoPt3 nanoparticle along with highly active gold thin layer forming 3D structure is responsible for the significant improvement of the catalysis.     

NiCo alloy nanoparticles encapsulated in N-doped 3D porous carbon as efficient electrocatalysts for oxygen reduction reaction

A series of N-doped three dimensional porous carbons loaded with NiCo alloy nanoparticles (NiCo@NpCs) have been successfully fabricated by a template-assisted in-situ pyrolysis strategy and the ORR activities of different-concentration alloy supported N-doped carbons are systematically investigated. The optimized sample exhibits a positive half-wave potential of 0.78 V (vs. RHE), a high diffusion-limited current density (5.120 mA cm⁻²), and a high durability over 92%, which is superior to the Pt/C. The excellent activity and stability are mainly due to synergistic effect between carbon matrix and NiCo alloy. The N-doped porous carbon support with high surface area and good conductivity not only provides more active sites but also promotes electron transport and mass transfer process. Furthermore, the unique core-shelled structure NiCo@NpCs can effectively avoid the dissolution and corrosion of alloy particles and the surface peeling of particles during the catalyze reaction, which is beneficial to improving the activity and stability.     

CoCO3 hierarchical structure embedded on g-C3N4 nanosheets to assemble 3D/2D Z-scheme heterojunction towards efficiently and stably photocatalytic hydrogen production

Structure and interface control of heterojunction is usually a challenging issue to improve the photocatalytic performance. Herein, a new 3D/2D CoCO₃/g-C₃N₄ heterojunction is assembled by embedding hexahedral CoCO₃ on g-C₃N₄ nanosheets. The unique step-like hierarchical structure of CoCO₃, the formed built-in electric field and Z-scheme charge transfer behavior at the interface jointly drive the high-efficient separation of photogenerated carriers to boost the photocatalytic H₂ production. It achieves the optimal H₂ production rate that is almost 2.6 times than g-C₃N₄, apparent quantum efficiency (AQE) of 10.1% at 400 nm and continuous running of 60 h over the 3D/2D CoCO₃/g-C₃N₄ heterojunction. This work endows a fresh structural control strategy for the fabrication of 3D/2D Z-scheme heterojunction to improve the photocatalytic H₂ production performance.