Solvothermal Strategy Research Articles

Facile construction of a hierarchical Bi@BiOBr–Bi2MoO6 ternary heterojunction with abundant oxygen vacancies for excellent photocatalytic nitrogen fixation

A facile two-step solvothermal strategy was applied to prepare Bi@BiOBr–Bi2MoO6 ternary heterojunction with plentiful oxygen vacancies that can be used to effectively fix nitrogen without any organic scavengers or noble-metal cocatalysts.

Improving the electrocatalytic activity and stability of spinel sulfide counter electrodes by trimetallic synergy effects for quantum dot sensitized solar cells

Spinel trimetallic sulfide M0.5Ni0.5Co2S4 (M = Cu and Mn) nanostructures are designed and synthesized for the first time via a facile one-pot solvothermal strategy and used as efficient counter electrodes (CEs) for quantum dot sensitized solar cells (QDSSCs).

Electrochemical oxidation of 5-hydroxymethylfurfural on ternary metal–organic framework nanoarrays: enhancement from electronic structure modulation

A facile one-step solvothermal strategy has been developed for the in situ growth of ternary MOF nanoarrays onto Ni foam, which exhibits superior electrocatalytic activity and stability for the electrochemical 5-hydroxymethylfurfural oxidation.

Controllable construction of core–shell CuCo2S4@polypyrrole nanocomposites as advanced anode materials for high-performance sodium ion half/full batteries

Core–shell CuCo2S4@polypyrrole (CS-CuCo2S4@PPy) nanocomposites, as advanced anode materials for sodium ion batteries with outstanding cycling stability and rate capability, were prepared by a facile solvothermal strategy and subsequent in-situ chemical oxidation polymerization.

Hollow Co9S8 spheres-derived polyhedrons uniformly anchored on N, S-doped graphene for efficient oxygen electrocatalysts

Exploring highly efficient and low-cost bifunctional electrocatalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is significant for the development of renewable energy. Here, Co9S8 nanospheres with hollow structure anchored on N and S dual-doped graphene oxide (Co9S8-NSGO) are synthesized by solvothermal strategy. After pyrolyzed, advanced bifunctional electrocatalysts with feature of sea-island architecture of Co9S8 polyhedrons evenly dispersed on N and S co-doped graphene sheets (Co9S8-NSG) are obtained, in which Co9S8 polyhedrons stem from the derivative of Co9S8 nanospheres. Ascribed to large surface area, sea-island structure of uniform dispersion of Co9S8 nanoparticles on graphene, synergistic effect between Co9S8 and graphene and more active sites based N and S doping, the as-prepared Co9S8-NSG catalyst exhibits excellent OER performance with a small overpotential (240 mV at 10 mA cm−2) and satisfactory ORR performance with half-wave potential (0.79 V). Notably, a zinc-air battery using Co9S8-NSG as air cathode shows high peak power density (120 mW cm−2) and outstanding cycling stability (120 h at 10 mA cm−2).

Nature of Alkali Ion Conduction and Reversible Na-Ion Storage in Hybrid Formate Framework Materials

The cost advantage of Na-ion batteries has spurred intensive research effort in the last 10 years to develop reversible Na+ storage materials. Although classic host materials—analogous to those in the Li-ion system—are potentially straightforward targets, sluggish Na+ diffusion in many inorganic structures limits options. In this regard, open framework inorganic–organic hybrids such as metal–organic framework materials are considered as viable alternatives. Herein, we introduce heterometallic formate frameworks as potential candidates for reversible Na+ storage. As a first, we present a microwave solvothermal strategy for rapid synthesis of phase-pure microcrystalline Na2Co(HCO2)4 and AB(HCO2)3 (A: Li/Na; B: Co/Mn). By combining in-depth impedance analysis with ab initio molecular dynamics simulation, we reveal that the Li+/Na+ conduction—which follows a “pinball” mechanism—in these materials is extrinsic defect-dominated. Calculation suggests that a librational motion of the formate anions facilitates the diffusion of Na+ compared to Li+, explaining the origin of anomalously higher ionic conductivity for the Na analogue compared to the Li one. Preliminary electrochemical investigation reveals reversible Na+ storage in Na2Co(HCO2)4 and NaMn(HCO2)3 at an average voltage of 2.5–3 V.

One-step synthesis of N, P Co-doped orange carbon quantum dots with novel optical properties for bio-imaging

Chemical doping with heteroatoms can modulate physicochemical and photochemical properties of carbon dots (CDs). However, the development of multi heteroatoms co-doped CDs is still in early stage. In this work, a facile solvothermal synthesis strategy was applied to prepare multi heteroatoms (nitrogen and phosphorus) codoped carbon dots (N, P-CDs) using formamide and phosphoric acid as nitrogen source and phosphorus source, respectively. Compared with other CDs, the multi heteroatoms lead to dramatic improvement in the electronic characteristics and surface states. Thus, as the change of excitation wavelength, exciton recombination at different energy levels can be achieved, exhibiting the tunable luminescence from blue to orange regions. The prepared carbon dots have excitation dependence in the blue region, excitation independence in the orange region and high fluorescence stability. Its’ quantum yield (QY) is up to 47%. Plus, N, P-CDs is non-toxic to cells and can be used in cell imaging, which indicates carbon dots can be a potentially excellent bioimaging probe.

Morphology-controlled fabrication of NiCo2S4 nanostructures decorating carbon nanofibers as low-cost counter electrode for efficient dye-sensitized solar cells

The development of highly efficient, earth-abundant and low-cost counter electrode materials is of significant importance and challenge for practical application in dye-sensitized solar cells. In this work, morphology-controlled NiCo2S4 nanoparticles (NPs) and nanorods (NRs) decorating carbon nanofibers (CNFs) have been prepared via an electrospinning and hydrothermal or solvothermal strategy, which are further utilized as counter electrodes (CEs) in dye-sensitized solar cells (DSSCs). Benefitting from the rich nickel and cobalt ions redox chemistry and more exposed catalytically active sites from NiCo2S4 NRs grown vertically on the surface of CNFs as well as faster electron transporting capability providing by the highly conductive CNFs, the DSSC device based on NiCo2S4 NRs/CNFs CE yields an excellent power conversion efficiency of 9.47%, which is higher than that of the devices with NiCo2S4 NPs/CNFs (8.63%), Pt (8.18%) and CNFs (6.06%) as CEs under AM 1.5 G irradiation. Furthermore, the NiCo2S4 NRs/CNFs CE shows an excellent electrochemical stability in an iodine-based electrolyte. This study highlights a controllable and versatile route to rational design efficient counter electrode catalysts for high-performance CEs application.

Controllable design of nanoworm-like nickel sulfides for efficient electrochemical water splitting in alkaline media

Developing cost-effective electrocatalysts for electrochemical water splitting (EWS) is appealing and challenging for sustainable water electrolysis. Currently, nickel sulfides are considered as promising candidates for EWS due to their low cost and high catalytic activity. However, the facile design of nickel sulfides with high catalytic performance is still highly demanded. In this study, we have developed a one-step solvothermal strategy to construct nickel sulfides as efficient water splitting catalysts. By taking advantage of the small size, abundant active sites, large electrochemical surface area, and good conductivity, the nanoworm-like nickel sulfides (NiS-NW/Ni foam [NF]) exhibit better oxygen evolution reaction performance (a low overpotential of 279 mV to achieve 100 mA cm−2, Tafel slope of 38.44 mV dce−1) than the nanoplate-like analogs, as well as most of reported nickel sulfide–based electrocatalysts. In addition, the NiS-NW/NF directly used as bifunctional electrodes for overall water splitting requires a low voltage of 1.563 V to attain a current density of 10 mA cm−2 with good long-term durability. This work provides a facile strategy for the design of efficient nickel sulfide-based electrocatalysts for energy conversion applications.

Single Source, Surfactant‐Free, and One‐Step Solvothermal Route Synthesized TiO2 Microspheres for Highly Efficient Mesoscopic Perovskite Solar Cells

The instant extraction and transmission of photogenerated charge carriers is the key factor to obtain efficient perovskite solar cells (PSCs). The mesoporous electronic transport layer can provide heterogeneous nucleation sites for high‐quality perovskite films and expand the charge separation region to better balance charge transport. Therefore, compared with planar PSCs, most mesoporous PSCs usually exhibit superior photovoltaic performance. Herein, TiO2 microspheres with high crystallinity and purity are synthesized by a single source, surfactant‐free, and one‐step solvothermal reaction strategy. The morphology character of TiO2 mesoporous layers is conducive to good permeation and interfacial contact of perovskite. The gradient adjustment of energy level by the insertion of TiO2 mesoporous layer in the device is beneficial for the effective extraction of electrons. Finally, the optimized mesoporous PSCs can achieve an efficiency of 20.95% with slight hysteresis and satisfactory reproducibility.

Microwave Solvothermal Synthesis of Three-Dimensional Bi2MoO6 Microspheres with Enhanced Photocatalytic Activity.

In this study, three-dimensional (3D) Bi2MoO6 microspheres were successfully fabricated by a facile, rapid, and mild microwave solvothermal strategy for the first time. The resultant 3D Bi2MoO6 microspheres exhibited superior adsorption capacity and photocatalytic efficiency in the degradation of the representative antibiotic ciprofloxacin under visible light, for which the reaction kinetic rate constant is 7.5 times as high as that of the as-synthesized zero-dimensional Bi2MoO6 nanoparticles. The 3D hierarchical porous structure and the high Brunauer–Emmett–Teller surface area providing abundant reactive sites mainly contributed to the enhanced photocatalytic activity. The results highlight the feasibility of 3D Bi2MoO6 microspheres as an efficient visible-light-responsive photocatalyst for antibiotic removal in an aqueous system.

Deep eutectic solvent-assisted in-situ synthesis of nanosheet-packed Ni3S2 porous spheres on Ni foam for high-performance supercapacitors

Herein, self-supported Ni3S2 spherical clusters packed with well-defined nanosheets developed on Ni foam (NF) were rationally fabricated via a novel low-temperature solvothermal sulfurization approach in a choline chloride/ethylene glycol (Ethaline)-based deep eutectic solvent (DES). The DES-based sulfurization process drove an interesting time-dependent surface restructuring and phase transformation that occurred on the Ni substrate, leading to the in-situ formation of a Ni3S2 layer with controllable architecture. Pre-deposition of a Ni interlayer on the NF substrate provides more assessable electrochemical surface area and reaction sites, which favored fast crystal nucleation/growth and structural reconstruction. Benefiting from the integrated design and unique 3D interdigital architecture, the optimized Ni3S2_5/Ni/NF with a sulfurization time of 5 h exhibits a high specific capacitance (specific capacity) of 5,633 mF cm−2 (860.6 μAh cm−2) at a current density of 10 mA cm−2, and maintains 87.7% of initial specific capacitance after 1,000 charge–discharge process at a current density of 20 mA cm−2. This facile DES-driven solvothermal sulfurization strategy for the fabrication of integrated metal sulfides-based electrode materials could be promising for practical applications in high-performance electrochemical devices.

Approach of fermi level and electron-trap level in cadmium sulfide nanorods via molybdenum doping with enhanced carrier separation for boosted photocatalytic hydrogen production

Doping semiconductor with non-noble metal is a promising strategy to modulate the electronic structures and therefore develop efficient photocatalysts. In this study, we report a facile one-pot solvothermal strategy to synthesize Mo-doped CdS nanorods (NRs) using ammonium tetrathiomolybdate as the sources for both of S and Mo, cadmium acetate as the Cd source, and ethanediamine as the solvent heated at 180 °C for 24 h. The experimental characterizations and theoretical calculations reveal that Mo in the form of Mo4+ is incorporated into the CdS lattice to substitute Cd2+ ions and the Mo-S-Cd bonds are formed accordingly. The Mo doping not only introduces localized electron-trapping states at the bottom of conduction band minimum, but also elevates the Fermi level towards the defect level, which endows the doped system with enhanced n-type characteristic and the defect state with strong electron-trapping ability. Moreover, a nonuniform distribution of charge density is formed for the Mo-doped CdS NRs, facilitating the separation of photoexcited charge carriers. Therefore, the Mo-doped CdS NRs exhibit remarkably enhanced photocatalytic activity, with an average H2 production rate of 14.62 mmol·g−1·h−1 without using Pt as the co-catalyst, about 5.8 times higher than that of bare CdS. This work provides new insight into the facile synthesis of visible-light-driven photocatalysts as well as the effect of metal ion doping on the modulation of electronic structures.

Synthesis of carnation-like Ho3+/Co3O4 nanoflowers as a modifier for electrochemical determination of chloramphenicol in eye drop

A simple solvo-thermal strategy and different analytical techniques were applied for synthesizing carnation-like Ho3+/Co3O4 nanoflowers (CL-Ho3+/Co3O4-NFs). This research explained using a glassy carbon electrode (GCE) modified by Ho3+/Co3O4 nanoflowers to detect chloramphenicol. Such nanoflowers presented acceptable catalytic activities to determine chloramphenicol by cyclic voltammetry (CV) and different pulse voltammetry (DPV) techniques. Functions of the modified electrode has been dealt with through electrochemical impedance spectroscopy (EIS). Under optimal pH = 7.0, chloramphenicol reduction was observed at a potential approximately 267 mV less positive compared to the unmodified electrode. Considering DPV, chloramphenicol reduction showed a dynamic range of 0.01–800.0 µM and a limit of detection (3 s) of 7.1 nM. The research found an acceptable function of the modified electrode to detect chloramphenicol in real samples via the standard addition method.

5,10,15,20-tetrakis (4-carboxylphenyl) porphyrin functionalized NiCo2S4 yolk-shell nanospheres: Excellent peroxidase-like activity, catalytic mechanism and fast cascade colorimetric biosensor for cholesterol

5,10,15,20-tetrakis (4-carboxylphenyl) porphyrin functionalized NiCo2S4 yolk-shell nanospheres (Por-NiCo2S4) were fabricated by a facile and efficient solvothermal strategy and demonstrated to possess excellent peroxidase-like activity. Compared with pure NiCo2S4 nanospheres, Por-NiCo2S4 exhibits the superior peroxidase activity, which was evaluated by the fast oxidation of 3,3′,5,5′-tetramethylbenzidine (a chromogenic substrate, TMB) by H2O2 to form the blue product (oxTMB) only in 10 s. The systematic studies including radical scavenger, fluorescence probe, and electrochemical experiments confirm that superoxide free radicals (O2−) play a key role in catalytic reactions, in addition to the synergistic effect of holes (h+). Based on the developed peroxidase activity of Por-NiCo2S4, and combined with cholesterol oxidase (Chox), a fast cascade reaction sensing platform has been constructed to quantitatively determination cholesterol in a wide linear range of 0.1−9.0 mM with the detection limit of 19.36 μM. The Por-NiCo2S4 based colorimetric biosensing platform has been used for determining the levels of total cholesterol in serum samples, indicating Por-NiCo2S4 is expected to be used as the promising materials for fast visual colorimetry in clinical medical detection.

VS2 nanosheets vertically grown on graphene as high-performance cathodes for aqueous zinc-ion batteries

Aqueous rechargeable zinc-ion batteries (ZIBs) have been considered as potential grid-scale energy storage devices owing to their low cost, high safety, and environmental friendliness. However, the cathode materials of ZIBs usually show poor cycling stability and inferior rate performance. Here, a new 2D hierarchical composite comprised of ultrathin VS2 nanosheets perpendicularly grown on graphene sheets (rGO-VS2) is prepared through a one-step solvothermal strategy. Benefiting from the unique hierarchical structure and synergistic merits between the VS2 and graphene nanosheets, the rGO-VS2 composite exhibits excellent performance as new cathode materials for ZIBs. Specifically, it not only can deliver a high capacity of 238 mAh g−1 at 0.1 A g−1, but also maintains a capacity of 190 mAh g−1 at a quite high rate of 5 A g−1 with a capacity retention over 93% after 1000 cycles. This work highlights the great promise of rational designing high-performance rechargeable aqueous ZIBs.

Synthesis of tin-glycerate and it conversion into SnO2 spheres for highly sensitive low-ppm-level acetone detection

Tin-glycerate (Sn-Gly) spheres were synthesized through a simple solvothermal strategy, which was further thermally converted into SnO2. It is found that the loose SnO2 spheres have been built up from nanoparticles with about 10 nm in size. The use of such SnO2 nanostructures was further performed for low-ppm-level acetone detection. The results showed that the SnO2 presented response of 123 to 100 ppm acetone vapor at 260 °C. The sensor also exhibited rapid response/recovery time (24.5 s/6.5 s), low detection limit (1.5 at 1 ppm), excellent selectivity, and good reproducibility. Especially, a good linearity ranging from 1 to 100 ppm acetone was fitted, making it a promising candidate for acetone detection.

NiO nanoparticles decorated hexagonal Nickel-based metal-organic framework: Self-template synthesis and its application in electrochemical energy storage

A one-pot solvothermal strategy and subsequent calcination were proposed for fabricating a composite of NiO nanoparticles on hexagonal Ni-based metal–organic framework (Ni-MOF) (Ni-MOF@NiO). The prepared NiO nanoparticles on the hexagonal Ni-MOF not only improves the electrical conductivity and increases redox active sites, but also prevents the agglomeration of NiO nanoparticles. In particular, highly dispersed and small-sized NiO nanoparticles on the hexagonal Ni-MOF facilitates the migration of electrolyte ions, and the pseudocapacitive performance is evaluated through electrochemical measurements. At 0.5 A g−1, the Ni-MOF@NiO composite shows a specific capacitance of up to 1192.7 F g−1 and a high capacity retention (93.23% over 5000 cycles) in 3 M KOH. Moreover, the Ni-MOF@NiO nanoparticles and activated carbon are assembled into aqueous devices with a maximum energy density of 62.2 Wh kg−1. These results indicate the potential of Ni-MOF@NiO composite as an electrode material for application in supercapacitors. Additionally, the method of synthesizing Ni-MOF@NiO in this study can be used to synthesize other MOF@metal oxide materials for electrochemical energy storage and other related applications.

Construction of spherical ZnTiO3/MWCNTs composites as anode material for high-performance Li-ion batteries

Spherical ZnTiO3 / multi-walled carbon nanotube (ZnTiO3 / MWCNTs) composite was synthesized via a simple one-step solvothermal strategy with subsequent sintering process. The obtained ZnTiO3 nanospheres in pure ZnTiO3 and ZnTiO3 / MWCNTs materials have a diameter of about 200–300 nm. The MWCNTs are well dispersed ZnTiO3 electrode materials and form a three-dimensional conductive network structure. The ZnTiO3 / MWCNTs composite shows higher reversibility of intercalation and deintercalation for Li ions, better electrochemical activity and smaller electrochemical polarization than those of ZnTiO3 negative electrode during cycling. The lithiation (delithiation) capacities for pure ZnTiO3 are only 270.9 (516.5), 256.3 (262.9), 201.8 (199.3), 162.3 (161.6), 131.4 (129.9) and 89.9 (90.4) mAh g−1 at the current densities of 50, 100, 300, 500, 800 and 1600 mA g−1, respectively. However, the ZnTiO3 / MWCNTs composite delivers lithiation (delithiation) capacities of 349.3 (633.0), 321.6 (329.1), 264.9 (262.5), 230.6 (229.2), 188.6 (188.5) and 136.4 (135.9) mA h g−1 at the same rates. The remarkable high rate capability of ZnTiO3 / MWCNTs electrode can be owed to the uniform distribution of ZnTiO3 nanopheres within the carbon matrix conductive network and the improvement of electronic conductivity. The results further indicate that MWCNTs modification is an effective mean to improve electrochemical properties of ZnTiO3 electrode material.

Nickel cobalt manganese ternary carbonate hydroxide nanoflakes branched on cobalt carbonate hydroxide nanowire arrays as novel electrode material for supercapacitors with outstanding performance

In this work, for the first time we are reporting the development of a kind of high rate and long cycle life electrode composed of nickel cobalt manganese ternary carbonate hydroxide (NiCoMn-CH) ultrathin nanoflakes coated on Co-CH nanowire arrays (NWAs), which are directly generated on a nickel foam (NF) support. The hierarchical heterostructures are synthesized via a scalable two step solvothermal strategy without any adscititious surfactant and binder. The smart combination of Co-CH and NiCoMn-CH nanostructures in the nanowire arrays shows significant synergistic effect on the enhancement of the electrochemical performance of the as-fabricated supercapacitors. The as-obtained electrode exhibits excellent conductivity and high specific surface area, resulting in an unprecedented high specific capacitance (up to 3224F g−1 at 1 A g−1 in a three-electrode system) and an ultralong cycling stability (92.4% retention after 6000 successive charge–discharge cycles 5 A g−1). Meanwhile, an asymmetric supercapacitor device assembled of the Co-CH@NiCoMn-CH hierarchical nanostructures as positive electrode and activated carbon (AC) as negative electrode delivers good energy density of 20.31 W h kg−1 at the power density of 748.46 W kg−1 in the operation window 0–1.5 V. This methodology could be generalized to the design of other novel structured nanomaterials for energy storage devices and other applications.