Solvothermal Reduction Research Articles

Plasmonic silver loaded anatase titanium dioxide nanospheres photoanode for dye-sensitized solar cell

Silver (Ag) loaded TiO2 nanospheres (Ag-TiO2 NS) are synthesized by a combination of solvothermal and chemical reduction routes and characterized by FESEM, HRTEM, EDAX, UV–Vis DRS, XRD and PL techniques. The Ag-TiO2 NS have exhibited strong light absorption and better dye adsorption. The dye-sensitized solar cell (DSSC) performance of pristine TiO2 NS and Ag-TiO2 NS photoanodes is examined under artificial light illumination. The DSSC with 2 wt% loaded Ag-TiO2 NS photoanode has delivered PCE of 6.04 % with short-circuit photocurrent density of 13.56 mA cm−2 and open circuit voltage of 0.75 V that is ∼43 % greater over the PCE of DSSC containing pristine TiO2 NS photoanode (4.16 %). This boosted performance can be accredited to visible light harvesting and fast photogenerated electrons transfer facilitated by the plasmonic Ag.

Magnetic response of photonic crystals based on nucleating agents of binuclear complexes

In the synthesis of Fe3O4 MRPCs via the solvothermal reduction route, The formation of a binuclear iron complex involving both Fe2+ and Fe3+ is key to imparting the product with monodispersity, superparamagnetism and magnetochromatic properties.

Engineering High-Performance SiOx Anode Materials with a Titanium Oxynitride Coating for Lithium-Ion Batteries.

Micron-sized silicon oxide (SiOx) has been regarded as a promising anode material for new-generation lithium-ion batteries due to its high capacity and low cost. However, the distinct volume expansion during the repeated (de)lithiation process and poor conductivity can lead to structural collapse of the electrode and capacity fading. In this study, SiOx anode materials coated with TiO0.6N0.4 layers are fabricated by a facile solvothermal and thermal reduction technique. The TiO0.6N0.4 layers are homogeneously dispersed on SiOx particles and form an intimate contact. The TiO0.6N0.4 layers can enhance the conductivity and suppress volume expansion of the SiOx anode, which facilitate ion/electron transport and maintain the integrity of the overall electrode structure. The as-prepared SiOx-TiON-200 composites demonstrate a high reversible capacity of 854 mAh g-1 at 0.5 A g-1 with a mass loading of 2.0 mg cm-2 after 250 cycles. This surface modification technique could be extended to other anodes with low conductivity and large volume expansion for lithium-ion batteries.

Carbon Quantum Dot Modified Reduced Graphene Oxide Framework for Improved Alkali Metal Ion Storage Performance

Organic materials with redox-active oxygen functional groups have attracted great attention as electrode materials for alkali-ion storage due to their earth-abundant constituents, structural tunability, and enhanced energy storage properties. Therefore, the development of advanced carbon nanostructures is highly desirable for improving the electrochemical performance of organic electrodes. While nanoscale carbon materials like carbon quantum dots (CQDs) have been identified as promising candidates for a variety of applications such as sensing, catalysis, drug delivery...etc., their utilization in electrochemical energy storage remains challenging with limited investigations. Herein, a hybrid carbon framework consisting of reduced graphene oxide (rGO) and carbon quantum dots is developed via a simple one-pot solvothermal reduction method, and a systematic study is conducted to investigate its redox mechanism and electrochemical properties with Li-, Na-, and K-ions. With the incorporation of carbon quantum dots, the hybrid rGO-CQD cathode exhibited much improved charge storage performance. In particular, the Li-ion cell delivered impressive reversible capacity (257 mAh g-1 at 50 mA g-1), rate capability (111 mAh g-1 at 1 A g-1) and cycling stability (79% capacity retention after 10,000 cycles). The charge storage behavior of various alkali-ions was also confirmed by density functional theory calculations. Furthermore, our calculations uncovered the CQD structure-electrochemical reactivity relationships, which could pave the way for the tailoring of CQD species to achieve optimal alkali-ion storage.

Carbon-modified TiO2 nanourchin with Ag nanoparticle decoration for environmental remediation

Multifunctional critical nano-composite material assembling Carbon-modified Ag@TiO2 nanourchin was synthesized to investigate visible light photocatalytic activity. The Carbon-modified Ag@TiO2 nanourchin was prepared by a facile two-step chemical synthesis through solvothermal and chemical reduction. Carbon nanospheres as the substrate play a key role for three dimensional nanourchin structure as well as carbon doping. The morphology, crystal structure, and chemical states were characterized carefully by different analytical procedures via transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDAX), X-ray diffraction (XRD), RAMAN spectroscopy, X-ray photoelectron spectroscopy (XPS) and UV–Vis spectroscopy. It shows that the uniform loaded silver (Ag) on TiO2 surface was metallic Ag0 state. The exist of interstitial carbon and Ag NPs on TiO2 nanostructure collectively enhance the visible light photocatalytic activity. The visible light photocatalytic degradation of methyl orange (MO) studies revealed that Ag@C0.1TiO2 exhibited enhanced photocatalytic efficiency compared with the pure TiO2 nanourchin and commercial TiO2 powder. The improved photocatalytic property can be attributed to lower recombination of the photogenerated e− and h+ pairs in catalyst due to the formation of a Schottky barrier between Ag NPs and TiO2 which improved the surface charge separation greatly and presence of carbon serve as a sensitizer to absorb visible light which inject e- into conduction band (CB) of TiO2.

Platinum-Nickel alloy supported on Nitrogen-Doped carbon modified titanium nitride nanotubes derived from metalorganic frameworks as an efficient catalyst for methanol electrooxidation

Synthesis of high-performance MOR electrocatalysts is of vital importance for the development of DMFCs as a viable technology for portable applications. Herein, we present a systematic study of a nanostructured Pt99Ni1/TiN NTs@NC catalyst for MOR, synthesized by a process concluding solvothermal, chelation, post-nitriding, and ethylene glycol reduction. The simultaneous production of TiN NTs@NC and Ni nanoclusters was obtained from the Ni/TiO2 NTs@PDA complexes derived from Ni-MOF and its pyrolysis under NH3 annealing process. The Ni/TiN NTs@NC substrate is in possession of a mesoporous nanotubes structure with unique sharp nanothorns on surface owing to the usage of Ni-MOF as precursor, resulting in the homogeneous distribution and intimate contact of Ni nanoclusters on the TiN NTs@NC substrate. The unique nanostructure, formation of open active diffusion channels and a large number of accessible active sites on supports provided an opportunity for nucleation and growth of PtNi alloys, leading to the improved metal-support interaction. The formation of PtNi alloys with small size and well-dispersion view not only improves the synergistic effect of electronics and strain but also weakens interaction between Pt and intermediate. Benefiting from above advantages, the Pt99Ni1/TiN NTs@NC exhibits superior MOR performance with enhanced catalytic activity, remarkable CO-resilient capacity, and excellent stability.

Preparation, Characterization, and Photocatalytic Performance of Ag/BiOBr0.85I0.15 Nanocomposites.

In the present paper, a series of Ag/BiOBr0.85I0.15 composite nanoparticles with different silver loading were prepared by a combined solvothermal and photocatalytic reduction method. The composite samples have been characterized by XRD, XPS, SEM, EDX, TEM, UV-Vis, and N2 adsorption/desorption techniques. The characterization results showed that BiOBr0.85I0.15 composite nanoparticles have a tetragonal phase structure. Silver nanoparticles are uniformly distributed on the BiOBr0.85I0.15, which results in surface plasmon resonance absorption, effectively increasing the visible light absorption ability of BiOBr0.85I0.15. The photocatalytic activity of the samples was evaluated by photocatalytic degradation of ammonia nitrogen in circulating aquaculture water under simulated sunlight irradiation. The effect of the Ag loading amount on the photocatalytic degradation of ammonia nitrogen was investigated. Silver loading of 1% (molar ratio) can effectively improve the degradation capacity of the catalyst for ammonia nitrogen in water. The recycling experiments show that 1%Ag/BiOBr0.85I0.15 has good photocatalytic stability. ESR characterization and oxidation species scavenging experimental results suggest that h+, 1O2, and ·O2− are the main oxidizing species in the photocatalytic system.

Carbon Quantum Dot Modified Reduced Graphene Oxide Framework for Improved Alkali Metal Ion Storage Performance.

Organic materials with redox-active oxygen functional groups are of great interest as electrode materials for alkali-ion storage due to their earth-abundant constituents, structural tunability, and enhanced energy storage properties. Herein, a hybrid carbon framework consisting of reduced graphene oxide and oxygen functionalized carbon quantum dots (CQDs) is developed via the one-pot solvothermal reduction method, and a systematic study is undertaken to investigate its redox mechanism and electrochemical properties with Li-, Na-, and K-ions. Due to the incorporation of CQDs, the hybrid cathode delivers consistent improvements in charge storage performance for the alkali-ions and impressive reversible capacity (257 mAh g-1 at 50mA g-1 ), rate capability (111 mAh g-1 at 1 A g-1 ), and cycling stability (79% retention after 10000 cycles) with Li-ion. Furthermore, density functional theory calculations uncover the CQD structure-electrochemical reactivity trends for different alkali-ion. The results provide important insights into adopting CQD species for optimal alkali-ion storage.

Study and Comparison of Different Routes to Synthesize Reduced Graphene Oxide

The feasibility of graphene oxide (GO) obtained by both Hummers and Tour method to prepare reduced graphene oxide (rGO) as well as chemically reduction under different experimental conditions were evaluated with the objective of establishing the key items that should be considered when performing the synthesis of GO and rGO. This key items can be supportive to select the most feasible methodology to synthesize GO and rGO depending on the future application. Reduced graphene oxide was prepared by combining chemical and solvothermal as well as combined reduction adding a final thermal annealing step. Obtained GO and rGO were characterized by XRD, Raman spectroscopy, XPS and BET analysis. A higher oxidation degree was achieved for samples from Tour method than those oxidized by Hummers method. On the contrary, lower oxidation degree from Hummers graphene oxide (GO-H) facilitates the subsequent reduction process, leading to a higher reduced rGO. Hence, rGO samples obtained from the Hummers method in the different reduction treatments presented higher C/O atomic ratios than the corresponding Tour method. In addition, the combination of a solvothermal treatment and chemical reduction, including a final annealing stage, increases significantly the value of the C/O ratio as well as it contributes to decrease the defect density and the restoration of π-conjugated structure. Besides, rGO samples obtained from Tour method presented higher SSA and pore volume than those samples obtained from Hummers method. Results from this study suggest the suitability of Tour graphene oxide (GO-T) for chemical functionalization which is very useful for several applications. In addition, GO and rGO coming from Tour method are more appropriate to applications in which high surface area is required. Taking into account the vast possible applications for chemically-exfoliated graphene the findings of this study could help to select the best method for oxidising graphite depending on the intended application.

Tuning reactivity of Bi2MoO6 nanosheets sensors toward NH3 via Ag doping and nanoparticle modification

Noble metal-doping and modification are proved effective in improving the gas-response performance of semiconductor sensors. In this study, we developed a promising Bi2MoO6 (BMO)-based gas sensor capable of sensing ppb-level NH3 at room temperature via introducing silver (Ag). The BMO samples with different Ag doping and modification ratios were successfully formed via one-step solvothermal and glucose reduction techniques, respectively, which could be confirmed by the results of X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM) techniques. Compared to bare BMO, the gas-sensing properties of both Ag-doped and Ag surface-modified BMO samples were improved to various extents, respectively. In particular, the 5% Ag-modified BMO sensor with the highest response (Gg/Ga = 37.6 to 200 ppb NH3), long-term stability, and low threshold concentration (50 ppb) at 20% RH. Based on the spillover effect and metal–semiconductor junctions of Ag nanoparticles, the enhanced sensing response towards NH3 can be thoroughly illustrated. Combined with the first-principles calculations, the adsorption energy, density of states, and charge transfer of Ag-modified BMO were further performed to demonstrate the high sensing response and ultra-low detection limit.

Nickel Nanoflowers with Controllable Cation Vacancy for Enhanced Electrochemical Nitrogen Reduction.

The key to the design of electrochemical nitrogen reduction (NRR) catalysts is that the reaction sites can not only activate the N≡N bond but also have high catalytic selectivity. Vacancy engineering is an effective way to modulate active sites, and cation vacancies are considered to have enormous potential in tuning catalytic selectivity. However, research on NRR activity is still at an early stage due to the difficulty in preparation and precise regulation. Here, we provided an adjusted method of cation vacancy through topotactic transformation, which combines solvothermal reduction with etching via lattice confinement effect to accomplish precursor reduction and vacancy construction while maintaining consistent material morphologies. Based on the topotactic transformation, NiAl-LDH precursor was reduced to Ni metal nanoflower, while Al is simultaneously etched by alkali, thus the precise tunability of the cation vacancy can be achieved by adjusting the Al content in the LDH. The Ni nanoflower achieved excellent stability and high ammonia yield by adjusting the vacancy concentration. In addition, the insight into the selectivity and intrinsic activity of cation vacancies on NRR process has been revealed. For the reaction selectivity, the cation vacancy is beneficial to activate N≡N but not conducive to the HER process. For the intrinsic NRR activity, the generation of cation vacancies can also significantly reduce the energy barrier of NRR process and accelerate the reaction kinetics.

Determination of 5-Hydroxymethylfurfural (5-HMF) in milk products by surface-enhanced Raman spectroscopy and its simulation analysis

5-Hydroxymethylfurfural (5-HMF) is a useful indicator of thermal damage degree and freshness of milk. It is of great importance to develop simple, rapid and accurate analytical methods for the sensitive detection of 5-HMF in milk and milk-based products. In this work, surface-enhance Raman spectroscopy (SERS) was used for rapid determination of 5-HMF in processed cheese by colloidal Au nanoparticles (AuNPs) substrate synthesized by the classical solvothermal reduction method. Density functional theory (DFT) calculations were carried out to determine the vibration assignments of 5-HMF and the surface enhancement effect of AuNPs substrate. The results found that a good linear response on the AuNPs substrate for 5-HMF in the concentration range of 0.1–75 mM was established with the detection limit of 75 μM (S/N = 3). Furthermore, the present method could be applied to the determination of 5-HMF in a cheese real sample which revealed its promising application in food safety and analysis.

Au doped In2O3 nanoparticles: Preparation, and their ethanol detection with high performance

Precious metals doping can greatly change the gas sensing performance of semiconductor metal oxide. Herein, the Au-doped In2O3 nanoparticles (NPs) were prepared via a combination solvothermal and liquid-phase reduction method, and the obtained nanoparticles were characterized by various techniques. The results indicated that Au nanocrystals with a diameter ca. 5 nm were uniformly distributed on the surface of the irregular In2O3 NPs. Importantly, compared with undoped In2O3, the specific surface area of all the Au-doped In2O3 NPs increased. And all the Au-doped In2O3 sensors greatly improved the gas sensing performance towards ethanol. The optimal operating temperature reduced from 240 °C for undoped In2O3 to 200 °C for Au-doped In2O3. Of them, the 4 wt% Au-doped In2O3 sensor displayed highly response (106 towards ethanol at 100 ppm) at the optimal operating temperature, good linear coefficient, high reproducibility, and long-term stability towards ethanol. Moreover, through the detection of seven gases including ethanol, such as methanol, acetone, benzene, formaldehyde, isopropanol, and nitrogen dioxide， we found that the fabricated sensor based on 4 wt% Au-doped In2O3 had good selectivity towards ethanol. Finally, the mechanism of the excellent performance of the 4 wt% Au-doped In2O3 sensor for ethanol was explained.

Graphene fabricated by different approaches for supercapacitors with ultrahigh volumetric capacitance

Nanoporous structure and high surface area of graphene affords low volumetric capacitance when used as a supercapacitor. In this study, four different facile and economical fabrication techniques are reported for producing graphene nanosheets with high packing density. Successful fabrication was verified via X-ray diffraction, Fourier transform infrared analysis, and Raman spectroscopy. The as-prepared samples possess a compact layered structure with a packing density of 1.74–1.95 g cm−3, which is 79%–88.6% that of graphite density. Ultrahigh volumetric capacitances of 696 and 540 F cm−3 were obtained for graphene samples prepared via electrochemical exfoliation and solvothermal reduction methods, respectively (with excellent stability behavior of 103% after 9000 charge–discharge cycles). These volumetric capacitance care the highest values reported thus far for carbon materials in an aqueous electrolyte. These values were attained without any material addition and/or functionalization. A symmetric supercapacitor device assembled for the sample produced via electrochemical exfoliation achieved a volumetric capacitance of 204.5 F cm−3 with a high energy density of 16.3 Wh kg−1 at 0.3 A g−1 in 6 M KOH. The supercapacitor device exhibited high stability, retaining ~89% of the original specific capacitance after 3000 charge–discharge cycles. These findings indicate that selecting a siutable graphene fabrication technique corresponding to the required application is crucial. For the present study, graphene materials produced through solvothermal reduction and electrochemical exfoliation are promising for fabricating compact, high-energy, and high-power supercapacitors.

Selective cleavage of C–O bond in lignin and lignin model compounds over iron/nitrogen co-doped carbon supported Ni catalyst

The utilization of lignin to produce high value-added chemicals is conducive to alleviating the fossil energy crisis. Herein, Ni nanoparticles supported on iron/nitrogen co-doped carbon was prepared by co-pyrolysis and solvothermal reduction method for catalytic hydrogenolysis (CH) of dealkaline lignin and its model compounds. The catalysts were prepared under different calcination temperature, N/C ratio and Ni loading, and the optimal catalyst was Ni10%@Fe/NC0.33–800 (calcination temperature: 800 °C, N/C ratio: 0.33, Ni loading: 10%) based the on the CH of benzyl phenyl ether (BPE). Ni10%@Fe/NC0.33–800 showed good catalytic performance on the selective cleavage of C-O bond of lignin and its model compounds. The BPE conversion reached up to 97.7% over Ni10%@Fe/NC0.33–800 under mild conditions (230 °C, 1 MPa H2, and 0.5 h) with toluene and cyclohexanol as major products. Catalyst characterizations suggest that N content affects the formation of NiFe alloy and the synergistic effect between Ni and Fe plays an important role in CH of BPE. Moreover, Ni10%@Fe/NC0.33–800 could promote the cleavage of C-O bonds in dealkaline lignin through CH and hence enhance producing aromatics such as phenols, aromatic ethers, and aromatic esters, among which phenols are the main aromatics with guaiacols predominant.

The Oxygen Vacancy Defect of ZnO/NiO Nanomaterials Improves Photocatalytic Performance and Ammonia Sensing Performance.

In this paper, ZnO/NiO composites rich in oxygen vacancies are prepared by the solvothermal method and reduction method. In the test, through the use of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscope (TEM), diffuse reflectance spectroscopy (DRS), photoluminescence spectroscopy (PL), and electron paramagnetic resonance (EPR), we effectively prove the existence of phase, morphology and oxygen vacancies in the material. Through the photocatalysis test and gas sensitivity test, it is found that 10% Ni doped OZN-10 has the best photocatalytic activity and gas sensitivity characteristics. The degradation rate of methylene blue (MB) was 98%. The gas sensitivity test shows that OZN-10 has good selectivity, good response performance (3000 ppm, 27,887%) and excellent response recovery time (response time: 50 s, recovery time: 5–7 s) for saturated NH3 gas at standard atmospheric pressure (101.325 KPa) and room temperature (25 °C). The synergistic effect of oxygen vacancy as the center of a trap and p–n heterojunction forming an electric potential field at the interface is explained, and the mechanism of improving photocatalysis and gas sensitivity is analyzed. This work will provide an innovative vision for dual-performance oxygen vacancy modification of heterojunctions through photocatalysis.

Tuning Phase Structure of Nickel-Ruthenium Alloys via MOFs In Situ Hydrolysis toward Enhanced Hydrogen Evolution Performance in Alkaline.

Metal organic frameworks (MOFs) and corresponding derivatives have attracted wide attention. As electrocatalysts, these derivatives (metal, metal compound, and associated composites) have a wide range of application in water-splitting devices, fuel cells, and other hydrogen-related technologies. However, with the exception of pyrolysis, limited studies have documented generated metal nanoparticles from MOFs hydrolysis reactions. Herein, NiRu dual-phase alloy nanoparticles are synthesized via in situ MOFs hydrolysis mediating solvothermal reduction reaction. The hcp-phase NiRu alloys can be rationally tuned by modulating experimental parameters of feeding metal ratio and reaction time. The volcanic link between hydrogen evolution reaction activity and the descriptor of d band center is investigated using experimentally determined valence bands. Furthermore, compared with fcc-phase NiRu alloys, it is theoretically revealed that hcp-phase NiRu alloys optimize d band structure and have a lower energy barrier. This finding broadens the range of application for MOFs hydrolysis reactions and highlights advantages of metal alloys manufactured from MOFs hydrolysis reactions.

Mechanism of Photodegradation of Organic Pollutants in Seawater by TiO2-Based Photocatalysts and Improvement in Their Performance.

The mechanism of photodegradation of organic pollutants in seawater by TiO2-based catalysts irradiated by visible light was first explored by adding holes and free radical traps. The results showed that the photogenerated holes formed by the catalyst played a key role in the degradation of organic pollutants, regardless of whether the photodegradation occurred in seawater or pure water. Considering that the Yb-TiO2-rGO catalyst has a strong adsorption for organics, the salt ion almost did not interfere with the adsorption of pollutants by Yb-TiO2-rGO. Therefore, the degradation performance of Yb-TiO2-rGO did not remarkably change in the two water systems. For P25-ZN with a weak adsorption capacity for organics, several salt ions in the seawater hindered the contact of pollutants with the catalyst surface. Thus, the degradation rate of P25-ZN for phenol was significantly reduced. After the solvothermal reduction treatment for catalysts using ethylene glycol (EG) as the solvent, the increase in the Ti3+ content in the catalyst improved the visible-light response and activity of the catalyst. In addition, a small amount of EG grafted on the catalyst surface promoted the photocatalytic reaction process on the catalyst surface, thereby effectively resisting the interference of salt ions.

Investigation of the in-situ solvothermal reduction of multi-layered Graphene oxide in epoxy coating by acetonitrile on improving the hydrophobicity and corrosion resistance

In this study, a simple and effective green in situ solvothermal reduction method of multi-layered Graphene oxide (MLGO) was developed using acetonitrile (at 70 °C) for preparing a hydrophobic and corrosion-resistant epoxy coating on carbon steel. FT-IR, TGA, Raman spectroscopy and mapping EDX analysis showed a successful solvothermal reduction of MLGO by acetonitrile. The long-term salt spray and EIS study showed superior corrosion protection of reduced multi-layered Graphene oxide (RMLGO)/epoxy nano-coating compared to MLGO/epoxy. The water contact angle test on the pure epoxy, MLGO/epoxy, and RMLGO/epoxy coatings were 66.66°, 72.18°, and 91.66°, respectively that confirmed the hydrophobic property of the RMLGO/epoxy coating. Also, TEM images showed high-quality dispersion of the RMLGO prepared by in-situ solvothermal reduction compared to ex-situ solvothermal reduction.

CoNi bimetallic alloy cocatalyst-modified g-C3N4 nanosheets for efficient photocatalytic hydrogen production

Non-precious and Earth-abundant cocatalysts have emerged as promising alternatives to precious metal catalysts for hydrogen generation from photocatalytic water splitting. In this work, CoNi/g-C3N4 photocatalyst composed of g-C3N4 nanosheets and CoNi alloyed nanoparticles was prepared by a simple solvothermal and chemical reduction method. Bimetallic CoNi alloy was found to accelerate charge transfer and inhibit electron and hole recombination, thereby enhancing the photocatalytic activity of CoNi/g-C3N4. Under optimal conditions, the hydrogen production rate of CoNi/g-C3N4 reached up to 354.4 μmol h−1 g−1 with visible light (λ > 420 nm) in triethanolamine aqueous solution; this value greatly exceeded that of g-C3N4 by a factor of 188 times. A mechanism explaining the excellent photocatalytic performance was proposed accordingly. These results suggest that g–C3N4–based photocatalysts have good potential for hydrogen generation.