Narrow Results

A facile and green synthetic method for the synthesis of a Ln${}^{3+}$(Eu, Tb)-doped SrMoO₄ (SMO) microcrystals were developed using an environment-friendly low temperature hydrothermal method assisting with phenol formaldehyde resin (PFr). The microcrystals show narrow distribution and uniform particle size, and strong red and green emissions from Eu${}^{3+}$ and Tb${}^{3+}$ ions, and it is selectively quenched upon addition Fe${}^{3+}$ ions, thus making the microcrystals as a potential Fe${}^{3+}$ ions sensing material, and the detection limit is nearly micromole level.

The hydrothermal method, using the template is a conspicuous way to change the morphology of the product, so it is used widely in many reports. The effect of temperature on morphology of NiCo₂S₄ by hydrothermal synthesis and its electrochemical properties is distinct as high-performance electrode materials for supercapacitors. With the help of the template (carbon sphere), different morphologies of NiCo₂S₄ under 90${}^{\circ }$C, 120${}^{\circ }$C and 180${}^{\circ }$C were obtained. They have different properties after electrochemical analysis. In order to build a hierarchical multi-level structure, two-step vulcanization was carried out at each temperature, resulting in the difference in the morphology and performance of the six sample of electrodes. The obtained NiCo₂S₄ electrodes exhibit 1000Fg${}^{-1}$ at the current density of 1Ag${}^{-1}$ in the second-step of the hydrothermal process under 120${}^{\circ }$C, which is superior to the microblocks NiCo₂S₄ electrode (90${}^{\circ }$C, 888Fg${}^{-1}$ at the current density of 1Ag${}^{-1}$) and microparticles NiCo₂S₄ electrode (180${}^{\circ }$C, 574Fg${}^{-1}$ at the same current density) in the second-step hydrothermal, which shows a high-rate capability (640Fg${}^{-1}$ at 20Ag${}^{-1}$). The obtained nanoparticles NiCo₂S₄ under 180${}^{\circ }$C in the first-step hydrothermal electrode had an excellent cycle retention rate (89.7%), although its specific capacitance was lower. At the same time, the specific capacitance of these sample electrodes obtained in the second-step hydrothermal process is superior to those from the first-step. It was mainly attributed to the fact that temperature can influence the morphology by controlling ion exchange. And our experiment aims to use the hydrothermal method and the template method to find a more suitable temperature range to provide more ideas.

Herein, $\alpha$-Fe₂O₃ hollow cage-like nanostructures were prepared via a simple in situ template-assisted hydrothermal route. The results showed that the shell and the size of the $\alpha$-Fe₂O₃ hollow nanostructures could be easily controlled by adjusting the amount of Fe source (FeCl${}_3)$. By increasing the amount of Fe source, the size increases, and the shells are built up from the dense single nanoparticle aggregations to crosslinked nanoparticle aggregations with large cavities gradually. It is found that the surface morphology has great impact on charge separation and transport of the $\alpha$-Fe₂O₃ cage-like nanostructures, too dense particle aggregations and too many large cavities are unfavorable for electron transport, only the product with an optimal primary particles and channels could exhibit good catalytic performance in photo-Fenton degradation of rhodamine B (RhB) with visible light.

The monoclinic phase of VO₂ has promising application as a smart window material because it possesses a reversible metal-to-semiconductor transformation with a critical temperature of $68^{\circ }$C. The high critical temperature must be lowered to achieve a possible application. Anion doping has been widely researched as possible doping of VO₂(M) with fluorine is the main option nowadays. However, other halogen elements such as chlorine have not been investigated albeit possessing possible advantages properties. In this work, we report the use of chlorine anion as doping for VO₂(M) to lower its critical temperature and to enhance its thermochromic performance. The synthesis was performed using a facile one-step hydrothermal reduction of vanadium pentoxide by hydrazine at 350–$490^{\circ }$C, using ammonium chloride as the source of the anion. The result showed that the optimum temperature to synthesize Cl-doped VO₂(M) was $490^{\circ }$C. The lowest critical temperature that can be achieved by chlorine-doped VO₂(M) was at $59.9^{\circ }$C. The thermochromic performance of Cl-doped VO₂(M) was improved compared to pristine VO₂(M) nanoparticle. This finding provides a novel use of chlorine-doped VO₂(M) with a facile one-step hydrothermal method to synthesize chlorine-doped VO₂(M) as well as the feasibility of chlorine-doped VO₂(M) as a smart window material.

Here, a series of Fe_x${\text{Co}}_{1-x}$S₂ ($x=0$–1) samples were synthesized by a hydrothermal approach. The bimetallic sulfides exhibited superior ORR and OER performances compared to the corresponding monometallic sulfides. Among all synthesized samples, the ${\text{Fe}}_{0.25}$${\text{Co}}_{0.75}$S₂ sample showed the best catalytic activities, indicating that the optimal properties were related to the combination amount. Similarly, thanks to the synergistic effect of bimetallic ions, the Li–O₂ batteries with ${\text{Fe}}_{0.25}$${\text{Co}}_{0.75}$S₂ cathode catalysts displayed the highest initial charge/discharge capacities and best cycle performance compared with CoS₂ and FeS₂. Moreover, the cell with ${\text{Fe}}_{0.25}$${\text{Co}}_{0.75}$S₂/Super P electrode cycled for 70 times, while the cells with CoS₂/Super P and FeS₂/Super P electrode only reached 49 and 45 cycles, respectively, at a limited capacity of 500mAh/g at 100mA/g. These results demonstrated that the combination of different element ions could be an efficient strategy to facilitate the reaction rate of ORR and OER.

It is accepted that cerium doping is a great way to stabilize the structure of metallic oxides and improve the electrochemical performance of lithium (Li)-ion batteries (LIBs). Using a simple hydrothermal method, we doped Ce into tin-based oxides and synthesized Ce-doped SnO₂@Ti₃C₂ nanocomposites with Ti₃C₂-MXene as a framework. The as-prepared Ce-doped SnO₂@Ti₃C₂ nanocomposites show higher surface area and lower Li+ diffusion barrier, and the galvanostatic charge/discharge cycle stability is better than that of SnO₂@Ti₃C₂. Additionally, the nanocomposites exhibit excellent initial discharge capacity (1482.6 mAh g${}^{-1}$) at 100 mA g${}^{-1}$ and a remarkable cycle rate performance. After 150 cycles, the achieved discharge capacity remained at 310.8 mAh g${}^{-1}$. This study provides a new method of using two-dimensional (2D) layered materials and rare earth elements as lithium-ion storage materials.

Herein, Al₂(WO${}_4{)}_3$/Bi₂WO₆ heterojunctions with $Z$-type structure were successfully prepared by a one-step hydrothermal method. Moreover, the effects of different composite ratios on the properties of materials were explored. The electrochemical tests and photocatalytic degradation experiments showed that the corresponding Al₂(WO${}_4{)}_3$/Bi₂WO₆ heterojunctions all exhibited improved electrochemical performance and photocatalytic performance than that of the bare Bi₂WO₆ material. Especially, when the molar ratio of Al to Bi was 2:1, the obtained Al₂(WO${}_4{)}_3$/Bi₂WO₆ heterojunction displayed the optimal photoelectric and photocatalytic performance. In detail, it depicted the highest photocurrent density, the smallest resistance and the fastest charge transfer rate. What’s more, the RhB solution (10 ppm) could be completely degraded in 30 min under visible-light irradiation, and the removal rate was almost 1.6 times than that of pure Bi₂WO₆ nanosheets. In the same condition, it also exhibited excellent photocatalytic performance for the degradation of tetracycline (TC) solution (10 ppm) and the K₂Cr₂O₇ solution (40 ppm). These results fully manifested that the constructed Al₂(WO${}_4{)}_3$/Bi₂WO₆ heterojunction possessed superior photoelectric conversion capacity and outstanding photocatalytic performance. Moreover, based on the obtained experimental results, a $Z$-scheme mechanism of catalytic degradation of RhB and TC under simulated solar light was proposed and discussed.

Herein, a nitrogen, carbon co-doped anatase and rutile double-phase waxberry-shaped ${\mathrm{\text{TiO}}}_2$ composite photocatalyst is prepared with the one-step simple hydrothermal synthesis process, in which P25 was used as the precursor, and urea as the source of nitrogen and carbon. A suitable valence band position (2.52 eV) is provided by ${\mathrm{\text{N–C–TiO}}}_2$, with more active species (e.g. ${\text{h}}^{+}$, ${\text{e}}^{-}$, •$\mathrm{\text{OH}}$ and •${\mathrm{\text{O}}}_2$) being formed on the active catalysis surface, which is helpful to the redox reaction. Further comparison of experimental results ($E_g$ = 3.01 eV) proved that the novel ${\mathrm{\text{N–TiO}}}_2$ has preferable photocatalytic activity. In this study, an ingenious nitrogen- carbon co-doping structure was designed for the improvement of ${\mathrm{\text{TiO}}}_2$ photocatalytic performance, which is much for reference of this method to other photocatalyst designs.

Novel Bi₂S₃/BiOBr nanocomposites (NCs) were prepared via L-Cysteine-assisted hydrothermal avenue as efficient photocatalysts to degrade rhodamine B (RhB). As a result, the obtained Bi₂S₃/BiOBr NCs exhibited the slice-like microstructure with the average diameters of ca. 100 nm. The elemental analysis of X-ray photoelectron spectroscopy indicates that the nanocomposites were combined by Bi₂S₃ and BiOBr. Then, the photo-induced degradation of RhB was performed with a Xenon lamp to simulate the sunlight ($\lambda$> 400 nm) and the photo-decomposition rate was calculated. The following results showed that the Bi₂S₃/BiOBr NCs possessed excellent photocatalytice performance, which was better than that of other samples as control. Thus, this avenue provides a new reference for the facile synthesis of photocatalysts with low cost and high efficiency.

Constructing coupled semiconductor photocatalysts is an important approach to improve the photocatalytic activity of ${\text{TiO}}_2$. Herein, ${\text{SnO}}_2$/${\text{TiO}}_2$ composite photocatalysts were successfully synthesized through a hydrothermal method using yeast as a biological template. The as-obtained products were characterized by X-ray diffraction, Fourier-transformed infrared spectroscopy, scanning electron microscopy (SEM), ultraviolet-visible spectra and nitrogen adsorption/desorption testing methods. Results showed that the nano-sized ${\text{SnO}}_2$ particles could be solvothermally synthesized at 150–180${}^{°}$C, and the C=O and C–O groups in the yeast were the main capping ligands of the ${\text{SnO}}_2$ particles, playing a key role in the synthesis of ${\text{SnO}}_2$. SEM demonstrated that the ${\text{SnO}}_2$/${\text{TiO}}_2$ composites possessed very loose structures and good uniformity. Finally, the application experiment showed that the as-obtained ${\text{SnO}}_2$/${\text{TiO}}_2$ composites exhibited exceptional effectiveness in degrading Rhodamine B.