Search

The hydrophilic surface of defective titanium dioxide lowers its adsorption capacity towards CO2 molecules. To get rid of this drawback, we conducted surface-functionalization of defective titania by ammonium fluoride in order to acquire hydrophobicity and increase the adsorption capacity for CO2 molecules. Besides, the surface Ti-F bonds and excess substitution of bulk oxygen vacancies with F ions formed upon the fluorination treatment of defect TiO2 to jointly function promote the separation of photoinduced carriers, and the Ti3+-F species formed upon surface-functionalization by the surface fluoride and bulk Ti3+ can form self-built electric field to allow Ti3+ impurity level upward and improve the reduction ability of photogenerated electrons. Compared with unmodified defective TiO2, the generation rates of CH4 and CO of the optimized F-TiO2-SBO-3 increased more than 6 and 2 times, respectively. Moreover, corresponding DFT calculations give evidences to the improvement in the photocatalytic activity of fluorinated defect TiO2 photocatalysts; and relevant in-situ DRIFTS data provide insights into the increased selectivity of the fluorinated defective titania for CH4 production upon CO2 photoreduction. This approach could be helpful to better understanding the mechanism of CO2 photocatalytic reaction and to establishing feasible pathway to acquiring highly efficient photocatalyst for CO2 photoreduction.

Chiral metal halide perovskites with intrinsic asymmetric structures have drawn increased research interest for the application of second-order nonlinear optics (NLO). However, designing chiral perovskites with the features of a large NLO coefficient, high laser-induced damage thresholds (LDT), and environmental friendliness remains a major challenge. Herein, we have synthesized two chiral hybrid bismuth halides: (R/S-MBA)

One of the least understood aspects of prion diseases is the structure of infectious prion protein aggregates. Here we report a high-resolution cryo-EM structure of amyloid fibrils formed by human prion protein with Y145Stop mutation that is associated with a familial prion disease. This structural insight allows us not only to explain previous biochemical findings, but also provides direct support for the conformational adaptability model of prion transmissibility barriers.

The electrochemical oxygen reduction reaction (ORR) provides a green route for decentralized H2 O2 synthesis, where a structure-selectivity relationship is pivotal for the control of a highly selective and active two-electron pathway. Here, we report the fabrication of a boron and nitrogen co-doped turbostratic carbon catalyst with tunable B-N-C configurations (CNB-ZIL) by the assistance of a zwitterionic liquid (ZIL) for electrochemical hydrogen peroxide production. Combined spectroscopic analysis reveals a fine tailored B-N moiety in CNB-ZIL, where interfacial B-N species in a homogeneous distribution tend to segregate into hexagonal boron nitride domains at higher pyrolysis temperatures. Based on the experimental observations, a correlation between the interfacial B-N moieties and HO2 - selectivity is established. The CNB-ZIL electrocatalysts with optimal interfacial B-N moieties exhibit a high HO2 - selectivity with small overpotentials in alkaline media, giving a HO2 - yield of ≈1787 mmol gcatalyst -1 h-1 at -1.4 V in a flow-cell reactor. ispartof: ANGEWANDTE CHEMIE-INTERNATIONAL EDITION vol:61 issue:37 ispartof: location:Germany status: published

Awakening n→π* electronic transition in graphitized carbon nitride can extend the visible light absorption range of the original g-C3N4, which will contribute to improve the photocatalytic activity of carbon dioxide reduction. Here we report that the n→π* transition in g-C3N4 is activated by the cooperation of steam etching and alkali treatment. The CO and CH4 evolution yields of the NaOH/Vc‐CN sample are 4.3 and 16 times higher than those of original g-C3N4, respectively. The planar asymmetry structure of heptazine was fabricated due to the hydroxyl groups reacting with terminal N-H content produced by the construction of carbon vacancy and the Na+ ions insert into the interlayer. Therefore, n→π* electronic transition in g-C3N4 was awakened, extending the optical absorption range with light wavelengths longer than 470 nm. At the same time, the ability of CO2 chemisorption and activation was improved due to the NaOH modification. Therefore, the extended visible light absorption, the improved crystallinity and the increased active sites are beneficial to optimizing the utilization efficiency of photogenerated carriers and enhancing photocatalytic activity.

ispartof: JOURNAL OF CATALYSIS vol:407 pages:1-9 status: published

Surface charge pattern analysis on HVDC insulators is a difficult task, which requires a comprehensive understanding of the physical mechanisms of surface charging. This paper provides a review on surface charge patterns and related models published within the past 30 years. In addition, based on the field-dependent charging theory, the research differences of various surface charge patterns obtained by previous researchers are explained. Difficulties and future prospects in modeling of surface charging phenomenon are also discussed. This paper may be used as a reference for the analysis of charge accumulation patterns and it would be helpful to researchers to compare and understand charge accumulation results published by earlier researchers.

Bismuth vanadate (BiVO₄) is an efficient photocatalyst or photoanode in water oxidation. However, the product selectivity in water oxidation over the most exposed clean and defective (001) and (101) facets is not clear. In this work, we investigated the water oxidation reaction on clean and oxygen deficient (001) and (101) facets and on Mo/W-doped facets using density functional theory. The pure (001) facet, we found, promotes OH radical formation. In the presence of oxygen vacancies, the O₂ evolution is preferred on the (101) facet with an overpotential of 0.52 V. On doping with Mo/W, the H₂O₂ evolution is preferred on the (101) facet with the overpotential of about 0.40 V; while on the (001) facet, the O₂ evolution is preferred with the overpotential of about 0.5 V. We also found that, on the (101) facet, there is a strong charge transfer from Bi atoms to the intermediates of water oxidation; but on the (001) facet, there is not. Our calculations could guide the design of the photocatalyst toward specific products of the water oxidation reaction, such as an OH radical, H₂O₂, or O₂. Moreover, the results show that the preferred sorption on the (101) facet may be a reason for the photoinduced charge separation between (101) and (001) facets of BiVO₄.

Photocatalytic method has been intensively explored for Cr(VI) reduction owing to its efficient and environmentally friendly natures. In order to obtain a high efficiency in practical application, efficient photocatalysts need to be developed. Here, ZnIn2S4/SnS2 with a three-dimensional (3D) heterostructure was prepared by a hydrothermal method and its photocatalytic performance in Cr(VI) reduction was investigated. When the mass ratio of SnS2 to ZnIn2S4 is 1:10, the ZnIn2S4/SnS2 composite exhibits the highest photocatalytic activity with 100% efficiency for Cr(VI) (50 mg/L) reduction within 70 min under visible-light irradiation, which is much higher than those of pure ZnIn2S4 and SnS2. The enhanced charge separation and the light absorption have been confirmed from the photoluminescence and UV-vis absorption spectra to be the two reasons for the increased activity towards photocatalytic Cr(VI) reduction. In addition, after three cycles of testing, no obvious degradation is observed with the 3D heterostructured ZnIn2S4/SnS2, which maintains a good photocatalytic stability.

TiO2-Based photocatalysts with hollow structure have attracted much attention owing to their low density, scattering effect and slow photon effect. However, the wide bandgap (Eg = 3.2 eV) and high recombination rate of photogenerated charges hinder their practical application. Herein, a novel hollow urchin-like black RuO2/TiO2/Pt photocatalyst with surface Ti3+ and bulk single-electron oxygen vacancies (Vo·) due to self-doping is reported for visible-light photocatalytic activity. Space-separated dual cocatalysts (RuO2 and Pt NPs) with redox capability can greatly improve the separation efficiency of photogenerated electrons and holes of TiO2. Furthermore, constructing surface Ti3+ and bulk Vo· in TiO2 is considered an efficient approach for narrowing bandgap and enhancing the visible-light absorption. In particular, the surface Ti3+ promotes a self-hydrogenated shell to reduce the activation barrier of H2, which enhances the hydrogen evolution. However, excessive bulk Vo· as carrier recombination centers are not conducive to the hydrogen production. Positron annihilation lifetime spectra (PALS) indicated that the concentration ratio of surface Ti3+ and bulk Vo· is a key factor for efficient photocatalytic hydrogen evolution. The synergy between the spatially separated dual cocatalysts and optimum surface Ti3+/bulk Vo· ratio greatly increases the activity of the catalyst under visible light.

In this paper, disk-like α-Fe2O3 nanoparticles were synthesized by one-step via an n-octyl alcohol-mediated self-assembly process and were subsequently used as the catalyst for the updating of heavy crude oil. The characterization results show that the diameter of the as-prepared α-Fe2O3 disks is in the range of 150–200 nm and the nanoparticles have a hematite structure with [1 1 0] preferred orientation. The catalyst strongly acts on the asphaltene and causes its lower S content and N content, lower aromaticity and aromatic condensation, and higher branchiness index. Adding tetralin causes the increment of aromatics content, the decrease of resin, and more molecules containing aromatic moieties bearing 2 and 3 rings. The viscosity of the Shengli extra heavy oil reduced substantially from 161180 mPa∙s to 45882 mPa∙s (50 °C) through the combination of the α-Fe2O3 nanoparticles and tetralin (a hydrogen donor).

Three dimensional microporous zeolites have attracted much attention in catalysis because of their large BET surface area and abundant pores. Herein, Ti-MCM-41 zeolites with different molar ratio of Si/Ti were synthesized, and the surface acidity and active sites were adjusted by the modification of basic-earth metal oxides, and noble metal nanoparticles. The photocatalytic activity and selectivity were evaluated by the reduction of CO2 to CH4 and CO. The results indicated that the efficiency and selectivity of CO2 photoreduction to CH4 of Ti-MCM-41 zeolites were 93 ppm g−1 h−1 and 29% in the ratio Si/Ti = 10 under keeping the zeolite structure, and which is much higher than that of P25 with the value of 24 ppm g−1 h−1 and 23%. When the surface of Ti-MCM-41 zeolites was modified by different basic-earth metal oxides, the photo-reduction activity of CO2 to CH4 increased about 1.5 times with MgO modification, and the selectivity of CO2 to CH4 improved to 42%. Moreover, the photoactivity and selectivity enhanced to 8835 ppm g−1 h−1 and 93% when the surface was further decorated by Pt nanoparticles, while the selectivity of CO2 to CO reached 94% when Pd was loaded. Our work reveal reasonably that adjusting the acidity and active site of the microporous zeolites is a highly efficient way to improve the photocatalytic efficiency of CO2 reduction.

SrTiO3 (STO) is a widely used photocatalyst for water splitting, which has no photoactivity without a cocatalyst. The reason for this unclear. Here, we performed an oxygen evolution reaction (OER) ...

In this work, BCN-TiO2(A+R) heterojunctions were constructed via a simple one-step calcination method as efficient photocatalysts for H2 evolution. Simultaneously, an anatase/rutile phase-junction was also obtained due to the crystalline phase transformation that occurred during high-temperature calcination. The unique heterojunction and phase-junction lead to the formation of an intimate interface and large contact area between two semiconductors and extended the visible-light absorption range. Therefore, BCN-TiO2(A+R) heterojunctions with a mixed anatase and rutile phase exhibit enhanced photocarrier separation efficiency, realizing an eleven-fold increase in the electron lifetime compared to that of pure TiO2 and yielding a remarkable visible-light-driven H2 evolution rate nearly 7.5 and 12.2 times higher than that of TiO2(A+R) and pure BCN, respectively. This work provides a new strategy for designing efficient water-splitting photocatalysts with highly efficient charge separation and transfer.

Surface charging of spacers is one of the main factors restricting the industrialization of DC gas insulated lines (GILs). The effects of ion mobility, gas pressure and temperature on surface charge behavior are important issues to be clarified. In this paper, a selection method of ion mobility is reviewed and reconsidered. A multiphysics-coupled model considering ion mobility, species of ions, temperature, and gas pressure is investigated. A mathematical model of ion mobility under low and high electric fields is presented and the critical electric field strengths are calculated, based on the current density vs electric field strength. The results show that the two critical electric field strength have different characteristics with gas pressure and temperature. The ion mobility in SF 6 gas has a completely different calculation model in high electric field and low electric field, and these two ion mobilities are equal only at a specific temperature and gas pressure. This paper can provide a reference for the selection of ion mobility in DC GILs under conditions of temperature and pressure.

Ag-substituted Cu2ZnSnS4 (ACZTS) thin films were fabricated using a solution-processed method. The effects of Ag-substituted Cu sites on the crystallinity, band gap, band positions, and photoelectr...

Developing photocatalysts with a high-efficiency charge separation remains a challenge in the solar hydrogen production. Herein, we devised and prepared a unique 2D/2D heterojunction of CuInS2/ZnIn2S4 nanosheets for solar hydrogen evolution. Structural characterizations reveal that the CuInS2/ZnIn2S4 2D/2D heterojunction with lattice match consists of the thin thickness of nanosheets and has a large interface contact area, boosting charges transfer and separation. Benefiting from the favorable 2D/2D heterojunction structure, the CuInS2/ZnIn2S4 2D/2D heterojunction photocatalyst with 5 wt % CuInS2 yields the highest H2 evolution rate of 3430.2 μmol·g–1·h–1. In addition, the apparent quantum efficiency of 5%CuInS2/ZnIn2S4 2D/2D heterojunction reaches 12.4% at 420 nm, which is high among the ZnIn2S4-based 2D/2D heterojunctions. The enhanced photocatalytic H2 evolution comes from the boosting charge separation. This work demonstrates that a 2D/2D heterojunction provides a potential way for significantly impro...

Anatase titanium dioxide (TiO2) nanocrystals with different percentages (up to 95%) of exposed {101} facet and different concentration ratios of bulk single-electron-trapped oxygen vacancies (SETOVs) to surface oxygen vacancies (SOVs) were prepared by alcohol-thermal method with nanotube titanic acid as the precursor in combination with solid-state reduction by NaBH4. The as-prepared TiO2 nanocrystals were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, electron spin resonance spectroscopy, and ultraviolet–visible light spectrometry. The effects of the percentage of crystal facets and the concentration ratio of bulk SETOVs/SOVs on the photocatalytic hydrogen production rate of TiO2 nanocrystals were investigated with positron annihilation lifetime spectroscopy as well as photocurrent test. Findings indicate that the percentage of the exposed {101} facets of the as-prepared TiO2 nanocrystals and their concentration ratios of bulk SETOVs/SOVs can be well tuned by properly adjusting the amount of NaBH4 and the reduction reaction time as well. Increasing percentage of the {101} facet of anatase TiO2 nanocrystals contributes to improving their photocatalytic hydrogen production activity, because the {101} facets of the anatase TiO2 nanocrystals possess enriched electrons and can act as the reduction sites to enhance the reduction reaction of H+ affording H2 in the sacrifice system of splitting water. Both the bulk SETOVs and SOVs contribute to the improvement of the light absorption while SOVs can facilitate the separation of photogenerated charges, thereby adding to the photocatalytic activity. However, the bulk SETOVs and excessive SOVs are also the combination centers of photogenerated charges, which means it is essential to maintain a suitable concentration ratio of the bulk SETOVs/SOVs so as to enhance the light absorption and achieve the best separation efficiency of photogenerated charges and achieve the best photocatalytic activity for hydrogen production. Particularly, when anatase TiO2 nanocrystal with a high percentage (95%) of exposed {101} facet is reduced by NaBH4 at a mass ratio of 2: 1 for 20 min, the resultant reduced H-TiO2 nanocrystal (denoted as H-TiO2-R20(2:1)) provides the highest photocatalytic hydrogen productive rate. Furthermore, the combination of 0.5% Pt/H-TiO2-R20(2:1) with 0.5% Pt/WO3 can split water to simultaneously produce H2 and O2, showing promising potential for splitting water affording hydrogen and oxygen.

The reasons for the difference of visible light activity between the direct contact g-C3N4/TiO2 Z-scheme composites obtained by one-step or two-step calcination process were investigated in detail by XRD, TEM, XPS, Raman and ESR technologies. TEM results showed that only g-C3N4 obtained by two-step calcination (denoted as CN-TSC) presented the porous structure which was in favor of the light absorption. XPS analysis indicated that interstitial doped N species formed in one-step calcination composite (denoted as CT-OSC) while substitutional N would appear in two-step calcination composite (denoted as CT-TSC). Nevertheless, interstitial N located at the higher position in the band gap of TiO2 and usually acted as the strong capture center of holes which was unfavorable to charge transfer. ESR and Raman results indicated that CT-TSC with some concentration of surface Vo and lower concentration of bulk Vo had excellent charge separation efficiency, according to the surface-enhanced Raman scattering (SERS) results of photo-induced charge-transfer (PICT) enhancement mechanism. And as a result, the visible-light activity for propylene oxidation of CT-TSC was twice higher than that of CT-OSC.

Spatially separated loading of reductive and oxidative cocatalysts is a useful strategy for expediting charge separation and surface reaction kinetics, which are two key factors for determining the photocatalytic efficiency. However, loading the spatial separation of dual cocatalysts on a 2D photocatalyst is still a great challenge. Herein, decorating the spatial separation of oxidative and reductive cocatalysts on ZnIn

Sodium ion batteries (SIBs) have been extensively investigated as a promising alternative for lithium ion batteries (LIBs) owing to the readily available character of sodium, lower costs of battery systems, as well as a similar working mechanism to LIBs. However, this view turns out to be oversimplified; countless reviews especially in the last years contradict each other, and it is still a challenging task to design highly performing electrode materials for SIBs. Due to the larger radius of Na+, its lower covalent character, and the resulting changes in intercalation chemistry, sodium is far from being only the bigger relative of lithium, and the difference leads to altered loading curves, and the occurrence of a multiplicity of binding sites. An in-depth holistic understanding of the sodium storage mechanisms is needed to resolve the controversial discussions in the research community, ideally starting with unquestionable thermodynamic points. Here, taking a tutorial perspective, first the recent discussions on the storage mechanism of sodium in carbons are reviewed from an unorthodox viewpoint, namely addressing sodium uptake as a multifaceted adsorption process with an added electrochemical binding potential. This model is based on literature data. Afterward, challenges and perspectives revealed by such a model are discussed.

Amyotrophic lateral sclerosis and several other neurodegenerative diseases are associated with brain deposits of amyloid-like aggregates formed by the C-terminal fragments of TDP-43 that contain the low complexity domain of the protein. Here, we report the cryo-EM structure of amyloid formed from the entire TDP-43 low complexity domain in vitro at pH 4. This structure reveals single protofilament fibrils containing a large (139-residue), tightly packed core. While the C-terminal part of this core region is largely planar and characterized by a small proportion of hydrophobic amino acids, the N-terminal region contains numerous hydrophobic residues and has a non-planar backbone conformation, resulting in rugged surfaces of fibril ends. The structural features found in these fibrils differ from those previously found for fibrils generated from short protein fragments. The present atomic model for TDP-43 LCD fibrils provides insight into potential structural perturbations caused by phosphorylation and disease-related mutations., Amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) patients have brain deposits with amyloid-like aggregates from large C-terminal fragments of the transactive response DNA-binding protein of 43 kDa (TDP-43). Here, the authors present the cryo-EM structure of amyloid fibrils generated from the complete C-terminal TDP-43 low complexity domain and they discuss the effects of disease-causing mutations and phosphorylation of specific Ser residues.

Efficient adsorption and utilization of carbon dioxide play an important role in mitigating the greenhouse effect and developing clean energy. Surface functionalization of photocatalyst is an efficient method to promote the adsorption of CO2 and convert it into hydrocarbon fuels. In this work, tetraethylenepentamine (TEPA) is used to functionalize Ti-MCM-41 molecular sieve photocatalyst to enhance the adsorption and activation of CO2. Ti-MCM-41 molecular sieve was modified without any precious metal additives. When the content of TEPA was 1%, the yield of CH4 was 232 ppm g−1 h−1. Furthermore, the results indicate that high impregnation amount of TEPA causes strong and higher adsorption of CO2 but inefficient for its conversion. This is probably due to the blockage of the channel when the impregnation amount of TEPA exceeds the threshold value, which hinders the further conversion of CO2 molecules. Functionalization Ti-MCM-41 zeolite photocatalyst with amino group is the prime reason for its excellent CO2 adsorption followed by activation capacity. In the future, this proposed composite might come up as a perspective photocatalyst in the field of photocatalysis for the purpose of environment remediation.