Effect of TiO2 surface treatment on electron transfer in dye-sensitized solar cells

Defect states in the TiO2 nanoparticles can cause severe charge recombination and poor electron-transport efficiency when used as a photoanode in dye-sensitized solar cells (DSSCs). Herein, we report a simple and practical way to passivate the surface defects of TiO2 through hydrothermal treating with acetic acid and H2SO4, introducing a high percentage of 101 facets and sulfonic acid functional groups on the TiO2 surface. A high efficiency of 8.12% has been achieved, which is 14% higher than that of untreated TiO2 under the same condition. EIS results prove that the multiacid-treated TiO2 can promote electron transport and reduce charge recombination at the interface of the TiO2 and electrolyte. This work provides an efficient approach to engineer the electron-transport pathway in DSSCs.

First-principles investigations of the half-metallic ferromagnetic LaCoTiIn equiatomic quaternary Heusler alloy for spintronics

We have evaluated the structural and mechanical stability, electronic structure, total spin magnetic moment, and Curie temperature of LaCoTiIn Equiatomic Quaternary Heusler Alloy (EQHA) using first-principles studies. The Generalized Gradient Approximation (GGA) and GGA+U schemes have been used as exchange-correlation functional for the above calculations. From the ground state calculation, LaCoTiIn EQHA with a Type-III structure in the ferromagnetic (FM) state is found to be stable. The electronic structure of LaCoTiIn EQHA depicts half-metallic behavior which has metallic overlap in the spin up ([Formula: see text] channel and a semiconductor band gap in the other channel. The spin–orbit coupling of LaCoTiIn has a great influence on the band gap of the material. The computed band gap values for the spin down ([Formula: see text] channel are 0.480 eV and 0.606 eV by using the GGA and GGA+U schemes. The total spin magnetic moment is 1 [Formula: see text], according to the Slater–Pauling rule, [Formula: see text] = ([Formula: see text] - 18) [Formula: see text]. These results obtained can be used as a valuable reference for future research, or they will be used to further motivate the experimental synthesis of the corresponding alloy.

Gel polymer electrolyte combined lignocellulose with sodium alginate in lithium-ion battery

The adoption of gel polymer electrolyte (GPE) is a solution to efficiently solve the serious security risk of lithium-ion batteries (LIBs). GPE based on lignocellulose (LC) and sodium alginate (SA) was prepared. When the proportion of SA reaches up to 20 wt.%, the obtained composite membrane has a liquid electrolyte uptake of 337 wt.% and a porosity of 58%, and its mechanical strength is over four times than that of pure LC-based membrane. In addition, the corresponding GPE with 20 wt.% SA (GLCSA-20) presents high lithium-ion transference number of 0.76, distinguished ion conductivity of 2.70 × 10[Formula: see text] S cm[Formula: see text], excellent discharge specific capacity (124 mAh cm[Formula: see text] at 1 C when 200th cycle of Li∥GLCSA-20∥LiFePO[Formula: see text] and outstanding cyclic stability. These virtues support that the GLCSA-20 has great potential for applications in safe LIBs.

One-step route for Z-scheme Al2(WO4)3/Bi2WO6 heterojunction toward superior photoelectric and photocatalytic performance

Herein, Al2(WO[Formula: see text]/Bi2WO6 heterojunctions with [Formula: see text]-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[Formula: see text]/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[Formula: see text]/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[Formula: see text]/Bi2WO6 heterojunction possessed superior photoelectric conversion capacity and outstanding photocatalytic performance. Moreover, based on the obtained experimental results, a [Formula: see text]-scheme mechanism of catalytic degradation of RhB and TC under simulated solar light was proposed and discussed.

Surface engineering of Ti3C2Tx MXene by oxygen plasma irradiation as room temperature ethanol sensor

In this work, a surface modification strategy by oxygen plasma irradiation was introduced for the first time to significantly improve the room temperature sensing performance of Ti3C2T[Formula: see text] MXene. Oxygen plasma irradiation induced TiO2 formation on the Ti3C2T[Formula: see text] surface, produced lattice distortion, increased the specific surface area, and provided mesoporous structures. The gas sensitivity performance characterization results show the gas response value of Ti3C2T[Formula: see text] irradiated for 0.5 h (Ti3C2T[Formula: see text]0.5P) was hundreds of times better than the pristine Ti3C2T[Formula: see text]alongside with its sufficient response time (280 s) and rapid recovery time (11 s). The excellent sensing performance is attributed to the formation of more reactive sites on the edge and basal planes of Ti3C2T[Formula: see text] and mesoporous structures which greatly improved the adsorption of ethanol. Additionally, the relatively low work function of TiO2 facilitates the formation of a Schottky junction for easy migration of charge carrier, the thereby shortening the sensing response time. This strategy offers a facile and controllable surface modification of other 2D materials, without damaging their structures.

Hot pressing process ameliorates internal defects of PBZ/PVDF composite film for a high electrocaloric effect near room temperature

The poor interface compatibility between inorganic fillers and organic polymer matrix in nanocomposite has presented considerable challenges, which limit the applicable electric field ranges and reduce the interface polarization interaction. In this paper, Pb[Formula: see text]Ba[Formula: see text]ZrO3 (PBZ) nanofibers were introduced into the polyvinylidene fluoride (PVDF) matrix to prepare composite film, and the effect of hot pressing on interface compatibility was investigated at volume composite ratios of 3% and 4%. For the untreated film, [Formula: see text] and [Formula: see text] of the 3 vol.% composite film are 9.68 [Formula: see text]C/cm2 and 401 MV/m, respectively, and those for the 4 vol.% composite film are 9.15 [Formula: see text]C/cm2 and 408 MV/m, respectively. These differences are mainly due to the impact of internal defects. After hot pressing, [Formula: see text] and [Formula: see text] for the 3 vol.% composite film became 10.22 [Formula: see text]C/cm2 and 490 MV/m, respectively. Those for the 4 vol.% composite film are 9.85 [Formula: see text]C/cm2 and 485 MV/m. Experiment and simulation results showed the beneficial effect of hot pressing, which ameliorated poor interfacial compatibility, reduced internal defects, and improved the crystallinity of the composite film. A high electrocaloric effect (ECE) was obtained by using the direct measure method. At −30[Formula: see text]C, the [Formula: see text] values of hot-pressed PBZ/PVDF film at 3[Formula: see text] and 4[Formula: see text] vol.% were 23.81 and 19.73 K, respectively. When temperature increased to 70[Formula: see text]C, the [Formula: see text] values were 9.44 and 7.01 K, respectively, which were 1.58 times of the values of a non-hot-pressed film. These results indicated that hot pressing alleviated the interface problem and resulted in high EC performance under a high-strength electric field.

γ-phase evolution in aged Co–Ni–Ga shape memory alloy

A synchrotron X-ray diffraction study of high-temperature (HT) shape memory alloy 49Co–21Ni–30Ga (in at. pct.) was performed. The volume fraction, cell parameter and temperature evolution of the different secondary phases were analyzed. This study reports reliable experimental data on these parameters to be used as a future reference to adjust the composition of the material.

Low-temperature synthesis of oxygen-rich fish-scale-like porous boron nitride for effective water cleaning

Effective removal of the organic pollutants from aqueous solution is significative and challenging for environmental sustainability. The high-performance adsorbent materials need to be developed. In this study, oxygen-rich fish-scale-like porous boron nitride (O-PBN) was facilely synthesized only at 900[Formula: see text]C (about 400[Formula: see text]C lower than that of the conventional process) through the molten salt method. The adsorption capacity of the as-prepared O-PBN for Methylene Blue (MB) from water was 422.6 mg/g, resulting from oxidizing groups and B–O bonds induced by oxygen doping as well as fish-scale-like structure composed of the BN nanoflakes. Moreover, the initial removal capacity of O-PBN only lost 7.6% even after 10 adsorption–regeneration cycles due to their strong resistance to oxidation. The unique B–O polar covalent bond, fish-scale-like two-dimensional nanostructure exposing the active adsorption sites to the surface ((002) crystal plane) and high specific surface area of O-PBN are confirmed to be the key factors in significantly enhancing water purification and regeneration performance. Overall, the synthetic method should help to a low-temperature and facile fabrication of O-PBN for effective water cleaning.