One-step Solvothermal Process Research Articles

Solvothermal synthesis of Y-doped α-nickel hydroxide flower-like nanostructure for aqueous asymmetric supercapacitors

Y-doped α-nickel hydroxide flower-like nanostructure was successfully prepared via one-step solvothermal process. The BET surface areas of the Ni(OH)2 flower-like are improved by doping of Y. When the Y3+/Ni2+ mole ratio is 5%, the doped Ni hydroxide obtains a maximum specific capacity (735.36 C g−1 at a current density of 1 A g−1), which is higher than pure sample (489.4 C g−1). The enhanced electrochemical performances may be attributed to fact that the doped samples expose more active sites for fast redox reactions, and the incorporation of Y accelerates the reaction kinetics and charge transfer efficiency and reaction kinetics. Aqueous asymmetric supercapacitor using YNi5 as the positive electrode and AC material as negative electrode shows an energy density of 68.3 Wh kg−1 at a power density 1093.7 W kg−1, and good cycling performance (82.37% retention after 8000 cycles).

In-situ N-doped MnCO3 anode material via one-step solvothermal synthesis: Doping mechanisms and enhanced electrochemical performances

In-situ N-doped MnCO3 microcrystal was prepared by a mild one-step solvothermal process for the first time. The influences of N-doping on microstructures and electrochemical performances of MnCO3 microcrystal have been investigated systematically. A plausible mechanism for the in-situ N-doping in MnCO3 also has been proposed. It is found that nitrogen was successfully doped into the MnCO3 by the substitution of lattice oxygen, generating a specific defect structure with oxygen vacancies and narrowing the band gap of MnCO3 effectively from 5.021 to 3.885 eV. When used as anode material, the as-obtained N-doped MnCO3 exhibits outstanding electrochemical performances: it delivers a large capacity of 685 mAh g−1 after 600 cycles at 1 C; exhibits a superior high-rate performance and long-term stability with a high capacity of 437 mAh g−1 even after 1000 cycles at a very large current rate of 5 C. Compared with the pristine MnCO3, such the outstanding electrochemical performances of N-doped MnCO3 should be attributed to the specific defect structure provided by N-doping, which can not only create more active sites for lithium storage, but also improve the poor electronic conductivity of MnCO3. This work can offer an effective and facile strategy to realize in-situ N-doping by wet chemical synthesis route, as well as enhance the electrochemical performances of transition metal carbonates.

Crumpled Quaternary Nanoarchitecture of Sulfur-Doped Nickel Cobalt Selenide Directly Grown on Carbon Cloth for Making Stronger Ionic Soft Actuators.

A novel crumpled quaternary sulfur-doped nickel cobalt selenide nanoarchitecture grown on carbon cloth (S-(NiCo)Se/CC) has been successfully synthesized as an electrode material for high-performance ionic polymer-carbon cloth composite (IP-CCC) actuators. A facile one-step solvothermal process has been introduced here to synthesize S-(NiCo)Se/CC, resolving the time-consuming, complicated, and costly problems of existing methods. Taking advantage of the outstanding electron transport kinetics and three-dimensionally interconnected nature of the transition-metal chalcogenide structure, the hybrid carbon cloth electrode with quaternary sulfur-doped selenide nanoarchitectures exhibits low electrical resistivity (3 times lower than that of bare CC), high areal capacitance (409 mF/cm2), and excellent cycle stability (over 4000 cycles). Moreover, due to the synergistic effect between S-(NiCo)Se and a carbon cloth substrate, the S-(NiCo)Se/CC electrode-based actuator exhibits high blocking force (38.5 mN), 6 h durability, and large bending strain (0.47%). Compared with other actuators reported in the literature, the S-(NiCo)Se/CC electrode-based actuator shows much higher normalized blocking force, leading to opening of new potential applications in the field of next-generation soft electronics. Moreover, stacked multiple IP-CCC actuators in parallel exhibit an exceptional blocking force of 0.174 N under direct current 4 V.

Template-free synthesis of metallic WS2 hollow microspheres as an anode for the sodium-ion battery

In this work, an electrode has been proposed and designed on its interior structure and controlled morphology, Specifically, metallic WS2 hollow microspheres have been synthesized via a one-step solvothermal process, in the absence of additives, consisting of porous nanosheets with a large surface area. The individual nanosheet features an expanded interlayer distance of 1.02 nm and metallic characteristics, which can provide faster transport of electrons and reduce the diffusion pathway for sodium ions. Furthermore, the effects of anions in the ether-based electrolyte on the cycling performance were also investigated and optimized. As a result, such an anode can demonstrate superior capacitive behavior with excellent rate performance (388.2 mA h g−1 at 0.1 A g−1, 307.7 mA h g−1 at 1 A g−1) and long-term cycling stability (285 mA h g−1 at 2 A g−1 after 2000 cycles).

Three-dimensional Fe3S4@NiS hollow nanospheres as efficient electrocatalysts for oxygen evolution reaction

Due to outstanding performance in energy conversion and storage, transition metal sulfides as well as hollow microstructure have become possible alternatives to noble metal electrocatalyst and become a hot issue. Therefore, we successfully synthesized Fe3S4@NiS hollow nanospheres (HSs) by a one-step solvothermal process, applied in oxygen evolution reactions (OER) to provide sustainable energy. Owing to particular microstructure and proper elemental composition ratio, Fe3S4@NiS HSs (partially been oxidized) show an outstanding OER performance with the overpotential and Tafel slope of only 338 mV at 10 mA cm−2 and 73 mV dec−1 in 0.1 M KOH solution, respectively.

Highly active nanostructured CoS2/CoS heterojunction electrocatalysts for aqueous polysulfide/iodide redox flow batteries

Aqueous polysulfide/iodide redox flow batteries are attractive for scalable energy storage due to their high energy density and low cost. However, their energy efficiency and power density are usually limited by poor electrochemical kinetics of the redox reactions of polysulfide/iodide ions on graphite electrodes, which has become the main obstacle for their practical applications. Here, CoS2/CoS heterojunction nanoparticles with uneven charge distribution, which are synthesized in situ on graphite felt by a one-step solvothermal process, can significantly boost electrocatalytic activities of I−/I3− and S2−/Sx2− redox reactions by improving absorptivity of charged ions and promoting charge transfer. The polysulfide/iodide flow battery with the graphene felt-CoS2/CoS heterojunction can deliver a high energy efficiency of 84.5% at a current density of 10 mA cm−2, a power density of 86.2 mW cm−2 and a stable energy efficiency retention of 96% after approximately 1000 h of continuous operation.

Ni3S2-MoSx nanorods grown on Ni foam as high-efficient electrocatalysts for overall water splitting

In order to solve the problem of large overpotential in water electrolysis for hydrogen production, transition metal sulfides are promising bifunctional electrocatalysts for hydrogen evolution reaction/oxygen evolution reaction that can significantly reduce overpotential. In this work, Ni3S2 and amorphous MoSx nanorods directly grown on Ni foam (Ni3S2-MoSx/NF) were prepared via one-step solvothermal process, which were used as a high-efficient electrocatalyst for overall water splitting. The Ni3S2-MoSx/NF composite exhibits very low overpotentials of 65 and 312 mV to reach 10 mA cm−2 and 50 mA cm−2 in 1.0 M KOH for HER and OER, respectively. Besides, it exhibits a low Tafel slope (81 mV dec−1 for HER, 103 mV dec−1 for OER), high exchange current density (1.51 mA cm−2 for HER, 0.26 mA cm−2 for OER), and remarkable long-term cycle stability. This work provides new perspective for further the development of highly effective non-noble-metal materials in the energy field.

One-step template-free synthesis of Mn(II)-doped TiO2 hierarchical microspheres with unique radiating fibrous structure for efficient Fenton degradation

Herein, hierarchically spherical Mn(II)-doped TiO2 with a radiating fibrous structure was synthesized for the first time via a simple one-step template-free solvothermal process. Such a unique structure endowed the material with a considerably large surface area (413.3 m2 g−1), which was the highest value ever reported for Mn(II)-doped TiO2-type materials. Moreover, the large and straight inter-fiber pores (20–60 nm) were advantageous in facilitating fast molecular diffusion and promoting the accessibility of active sites. As a result, the hierarchical Mn(II)-doped TiO2 was demonstrated to be a high-performance Fenton catalyst for degradation of organic pollutants in the presence of H2O2, with significantly higher catalytic efficiency than many previously reported heterogeneous Fenton catalysts. Moreover, the catalyst could maintain its original activity even after being reused several times. The simple synthesis, high catalytic activity, and excellent reusability indicate this hierarchical Mn(II)-doped TiO2 is a promising candidate as a Fenton catalyst for wastewater treatment.

Indirect Z-Scheme Assembly of 2D ZnV2O6/RGO/g-C3N4 Nanosheets with RGO/pCN as Solid-State Electron Mediators toward Visible-Light-Enhanced CO2 Reduction

Indirect Z-scheme assembly of graphene-bridged 2D ZnV2O6/pCN nanosheets composite has been fabricated by one-step solvothermal process and tested for photoinduced CO2 conversion under visible-light irradiations. The highest CH3OH production of 3488 μmol g-cat–1 was obtained over ZnV2O6/RGO/g-C3N4 composite, 1.02 and 1.25 times higher comparing to ZnV2O6/RGO and ZnV2O6/g-C3N4 samples, respectively. This enhanced efficiency can be ascribed to well-designed ternary heterojunction with hierarchical structure and efficient charges separation by RGO. More importantly, CH3OH yield was further improved by introducing RGO/pCN as an electron sink, which led to a 1.07 times higher yield than using only RGO. This reveals that ternary 2D ZnV2O6/RGO/pCN nanostructure has higher visible-light absorption, improved charge separation, and enhanced photocatalytic efficiency due to RGO/pCN as multiple mediators. The stability of composite catalyst also prevailed for 32 h for continuous CH3OH production. Therefore, structured...

Transition Metal Oxides on Reduced Graphene Oxide Nanocomposites: Evaluation of Physicochemical Properties

Transition metal oxides on reduced graphene oxide (TMO@rGO) nanocomposites were successfully prepared via a very simple one-step solvothermal process, involving the simultaneous (thermal) reduction of graphene oxide to graphene and the deposition of TMO nanoparticles over its surface. Texture and morphology, microstructure, and chemical and surface compositions of the nanocomposites were investigated via scanning electron microscopy, X-ray diffraction, micro-Raman spectroscopy, and X-ray photoelectron spectroscopy, respectively. The results prove that Fe2O3@rGO, CoFe2O4@rGO, and CoO@rGO are obtained by using Fe and/or Co acetates as oxide precursors, with the TMO nanoparticles uniformly anchored onto the surface of graphene sheets. The electrochemical performance of the most promising nanocomposite was evaluated as anode material for sodium ion batteries. The preliminary results of galvanostatic cycling prove that Fe2O3@rGO nanocomposite exhibits better rate capability and stability than both bare Fe2O3and Fe2O3+rGO physical mixture.

A High-Efficiency Electrocatalyst for Oxidizing Glucose: Ultrathin Nanosheet Co-Based Organic Framework Assemblies

The glucose oxidation reaction (GOR) relies on noble metals (such as Au and Ag) and metal oxides (such as CuO, RuO2, and IrO2) as catalysts in a general way. However, these metal-based candidate materials often suffer from a variety of defects, including high cost, complexity of their synthesis method, and damage to the environment. Here, we synthesized ultrathin two-dimensional (2D) nanosheets (about 2.041 nm in thickness) that have a large surface area and good electrocatalytic properties for GOR. The destination product was prepared using a one-step solvothermal process involving Co(NO3)2·6H2O and p-phthalic acid synthesized in the presence of DMF/C2H5OH solution. The as-synthesized ultrathin 2D nanosheet Co-MOFs exhibited an electrocatalytic performance for the glucose that was better than that for the shell-like multilayer assemblies Co-MOFs in the alkaline electrolyte, including a higher stability, higher sensitivity, and better activity.

Purifying the Phase of NaTi2(PO4)3 for Enhanced Na+ Storage Properties.

Sodium-ion batteries (SIBs) are increasingly on demand owning to their prospect as an inexpensive alternative to Li-ion batteries. However, designing electrode materials with satisfactory rate capacity performance requires high electron transport and Na+ conductivity, which is extremely challenging. Herein, we report a hexadecylamine (HDA)-mediated synthesis of NaTi2(PO4)3 (NTP) electrodes via one-step solvothermal process. The addition of HDA material (1) enables the formation of a carbon coating that improves the electron conductivity and (2) importantly serves as a structure-directing agent reducing the NTP-impurity phases in which the transport of Na+ ions are sluggish. As a result, the synthesized NTP anode delivers superior rate of capacity retention of 77.8% under the 100-fold increase in current densities. Moreover, outstanding specific capacity of 117.9 mAh g-1 at 0.5 C and capacity retention of 88.6% after 1500 cycles at 1 C can be obtained. The findings of this work provide new opportunity to design SIBs electrodes with superior electrical and ionic conductivity.

Urchin-like NiCo2S4 structures synthesized through a one-step solvothermal process for high-performance supercapacitors

Nickel cobalt sulfides (NiCo2S4) have attracted considerable attention as electrode materials for supercapacitors. Herein, a sea-urchin-like NiCo2S4 material was synthesized through a one-step solvothermal process. Polyethylene glycol (PEG) 200 and thiourea were used as a shape-control agent and sulfur source for in-situ sulfuration, respectively. The urchin-like NiCo2S4 was characterized by X-ray powder diffraction, scanning electron microscopy, Brunauer–Emmett–Teller surface area, and electrochemical measurements. The resulting NiCo2S4 with ion diffusion-favored structure demonstrated remarkable electrochemical characteristics for supercapacitor with a high specific capacitance (1334F/g at 0.5A/g) and superior rate capability (78.1% of the original capacity from 0.5 to 20A/g) in 6MKOH aqueous solution. Furthermore, an asymmetric supercapacitor was assembled using NiCo2S4 as a positive electrode and activated carbon (AC) as a negative electrode. A NiCo2S4//AC device exhibited a high energy density of 37.32Wh/kg at a power density of 317.8W/kg with capacity retention of 91.9% and up to 2000 charge/discharge cycles at 3A/g. The results demonstrate that the sea-urchin-like NiCo2S4 has potential applications in supercapacitors.

Ce-doped V2O5 microspheres with improved electrochemical performance for high-power rechargeable lithium ion batteries

The development of high performance cathode materials is of importance for the widespread application of lithium-ion batteries in advanced energy storage devices. V2O5 is an attractive cathode candidate for lithium ion batteries owing to its high capacity as well as abundant source and low cost. In this work, Ce-doped V2O5 microspheres were fabricated by a combine method of one-step solvothermal process and subsequently annealing treatment. The electrochemical performance of V2O5 microspheres was enhanced dramatically by Ce-doping. Ce0.1V2O5 microspheres exhibit a high initial reversible capacity of 280.7 mAhg−1 at 0.5C and an excellent rate capability of 163.1 mAhg−1 at 10C. The discharge capacity of Ce0.1V2O5 microspheres could maintain up to 193.7 mAhg−1 with a capacity retention of about 88.93% even after 200 cycles, displaying a good cycling stability. The improved electrochemical properties of the synthesized Ce-doped V2O5 microspheres can be attributed to the lattice expansion upon Ce ions doping that can enhance the Li+ diffusion coefficient of electrodes. Meanwhile, Ce-doped V2O5 microspheres is constructed with aggregated nanoparticles, which is benefit for superior Li+ transportation and structural stability. The Ce-doped V2O5 microspheres could be utilized as a promising cathode material for lithium-ion batteries.

Metal-organic framework derived 3D graphene decorated NaTi2(PO4)3 for fast Na-ion storage.

NASCION-type materials featuring super ionic conductivity are of considerable interest for energy storage in sodium ion batteries. However, the issue of inherent poor electronic conductivity of these materials represents a fundamental limitation in their utilization as battery electrodes. Here, for the first time, we develop a facile strategy for the synthesis of NASICON-type NaTi2(PO4)3/reduced graphene oxide (NTP-rGO) Na-ion anode materials from three-dimensional (3D) metal-organic frameworks (MOFs). The selected MOF serves as an in situ etching template for the titanium resource, and importantly, endows the materials with structure-directing properties for the self-assembly of graphene oxide (GO) through a one-step solvothermal process. Through the subsequent carbonization, an rGO decorated NTP architecture is obtained, which offers fast electron transfer and improved Na+ ion accessibility to active sites. Benefiting from its unique structural merits, the NTP-rGO exhibits improved sodium storage properties in terms of high capacity, excellent rate performance and good cycling life. We believe that the findings of this work provide new opportunities to design high performance NASICON-type materials for energy storage.

The stereo-microstructure of ZnO affects the lithium storage capacity of Li2ZnTi3O8 anode materials.

ZnO materials with multidimensional stereoscopic morphologies were synthesized via a one-step solvothermal process with water, ethanol and acetone as solvents. In this work, well-prepared ZnO was used as a Zn source for preparing pristine Li2ZnTi3O8 anode materials for the first time by a facile solid-state method. The resulting Li2ZnTi3O8 electrode material with rice-shaped ZnO as the zinc source (LZTO-E) possessed a smaller particle size and larger specific surface area, which were conducive to increase the electrochemical reaction area. Impressively, the LZTO-E electrode showed an excellent electrochemical performance with large discharge capacity (253.4 mA h g-1 at 100 mA g-1) and good cycling stability (175 mA h g-1, 133.4 mA h g-1, and 115.0 mA h g-1 at 1000 mA g-1, 2000 mA g-1, and 5000 mA g-1 after 500 cycles, respectively). This superior electrochemical performance of the as-synthesized Li2ZnTi3O8 was attributed to the specific microtopography of ZnO.

A Facile Green Approach for Synthesis of Selenium Nanowires with Visible Light Photocatalytic Properties.

In this work, high purity trigonal selenium (t-Se) nanowires were synthesized through a simple one-step solvothermal process at 50 °C. Sodium formaldehyde sulfoxylate (SFS) was used as a reducing agent. To our knowledge, this is the first time that SFS was used as the reducing agent for synthesis of Se nanostructures. In this method, Se nanowires were obtained at lower temperature, shorter period of reaction time and without using complex equipment. The experimental parameters, such as reaction duration, temperature and amount of surfactant, were investigated. The as-prepared Se nanowires have a diameter of about 100-200 nm and length of up to 10 μm. A "Solid-Solution-Solid" growth mechanism was proposed. In the presence of H₂O₂, the Se nanowires showed good catalytic performance, where over 99% of methylene blue (MB) was degraded in 3.0 h. Results from this study demonstrated that the Se nanowires exhibit a promising application for photodegradation.

TiO2 Nanoparticles Anchored onto the Metal–Organic Framework NH2-MIL-88B(Fe) as an Adsorptive Photocatalyst with Enhanced Fenton-like Degradation of Organic Pollutants under Visible Light Irradiation

A convenient one-step solvothermal process to construct TiO2 nanoparticles anchored onto NH2-MIL-88B(Fe) with enhanced adsorption capacity and photocatalysis performance was reported. The TiO2@NH2-...

Flexible Pt-Promoted Graphene Aerogel Monolith: Versatile Catalyst for Room-Temperature Removal of Carbon Monoxide, Formaldehyde, and Ethylene

Three-dimensional flexible Pt-promoted graphene aerogel monolith is developed through a one-step solvothermal process as a versatile catalyst for removal of CO, HCHO, and C2H4 at room temperature. In this synthesis, ethylene glycol was employed as both the reducing agent and the solvent which could accelerate the in situ reduction of GO and metal ions during the solvothermal process, leading to the assembly and cross-linking of GO to form a three-dimensional (3D) network. Therefore, the obtained Pt-promoted graphene aerogel monolith exhibits an interconnected, honeycomb-like 3D porous framework with highly dispersed Pt (0) species, making it ideal for catalytic oxidation. Such monolith shows a high performance for the catalytic oxidation of CO, HCHO, and C2H4, with 100% conversion at room temperature, with an excellent stability longer than 72 h. These results demonstrate that the flexible Pt-promoted graphene aerogel monolith gives significance on catalytic oxidation, which could be applied in eliminatin...

The preparation of urchin-like La2O3 film and the superlow voltage electrowetting-on-dielectric response

An effective one-step solvothermal process is developed to fabricate La2O3 film on Ti substrate at 130 °C. The surface morphology and roughness are controlled from urchin-like nanosphere to dense film by the reaction duration. The as-prepared La2O3 film has low surface free energy and a large initial contact angle (CA), about 120°. Due to the uniform distribution of the urchin-like nanosphere on the surface, the water droplet starts to be adsorbed into the interspace of film surface, and the wetting state gradually transforms from Cassie to Wenzel state as soon as the low voltage less than 1 V is applied. Obviously, the DC EWOD response with superlow voltage can be realized, and large CA modulation about 58° is also acquired.