Template-Free Synthesis of Boron-Doped Graphitic Carbon Nitride Porous Nanotubes for Enhanced Photocatalytic Hydrogen Evolution.

The photocatalytic activity of g-C3N4 can be enhanced by improving photoinduced carrier separation and exposing sufficient reactive sites. In this study, we synthesized B-doped porous tubular g-C3N4 (BCNT) using a H3BO3-assisted supramolecular self-template method, wherein H3BO3 helped in B-doping, building a porous structure, and maintaining one-dimensional nanotubes. The tubular structure had an ultrathin tube wall and large aspect ratio, which are conducive to the directional transmission and separation of photogenerated carriers; moreover, the abundant pore structure of the tube wall could fully expose the reactive sites. The introduction of B and the cyano group modulated the bandgap of g-C3N4 and elevated the position of the conduction band, thus enhancing the photoreduction ability and effectively improving the hydrogen evolution performance. Consequently, the hydrogen evolution of BCNT-2 (220.8, 53.2 µmol·h-1) was 1.82 and 1.54 times that of ultrathin g-C3N4 nanosheets (CNN, 121.3, 34.6 µmol·h-1) under simulated sunlight and LED lamp irradiation, respectively. Thus, this work provides in-depth insights into the rational design of one-dimensional g-C3N4 nanotubes with high hydrogen evolution activity under visible irradiation.

In-situ formatting donor-acceptor polymer with giant dipole moment and ultrafast exciton separation.

Donor-acceptor semiconducting polymers present countless opportunities for application in photocatalysis. Previous studies have showcased their advantages through direct bottom-up methods. Unfortunately, these approaches often involve harsh reaction conditions, overlooking the impact of uncontrolled polymerization degrees on photocatalysis. Besides, the mechanism behind the separation of electron-hole pairs (excitons) in donor-acceptor polymers remains elusive. This study presents a post-synthetic method involving the light-induced transformation of the building blocks of hyper-cross-linked polymers from donor-carbon-donor to donor-carbon-acceptor states, resulting in a polymer with a substantial intramolecular dipole moment. Thus, excitons are efficiently separated in the transformed polymer. The utility of this strategy is exemplified by the enhanced photocatalytic hydrogen peroxide synthesis. Encouragingly, our observations reveal the formation of intramolecular charge transfer states using time-resolved techniques, confirming transient exciton behavior involving separation and relaxation. This light-induced method not only guides the development of highly efficient donor-acceptor polymer photocatalysts but also applies to various fields, including organic solar cells, light-emitting diodes, and sensors.

Synergistic Effects of Co3Se4 and Ti2C3Tx for Performance Enhancement on Lithium-Sulfur Batteries.

As electronic equipment develops rapidly, higher requirements are placed on electrochemical energy-storage devices. These requirements can be met by a lithium-sulfur (Li-S) battery since it has an impressive energy density of 2600 Wh kg-1 and a high theoretical specific capacity of 1675 mAh g-1. Pitifully, the sluggish redox reaction kinetics and the shuttle effect of polysulfide seriously limit its applications. Separator modification has been proven to be an effective strategy for improving the performance of Li-S batteries. Herein, we have designed a competent three-dimensional separator. It is obtained by embedding Co3Se4 nanoparticles on nitrogen-doped porous carbon (Co3Se4@N-C) by high-temperature selenization of ZIF-67, which are compounded with Ti3C2Tx by electrostatic dispersion self-assembly, and the compound is used to adjust the surface properties of a polypropylene (PP) separator. Due to the synergistic effect of the superior catalytic performance of Co3Se4@N-C and the enhancement of adsorption and conductivity bestowed by Ti3C2Tx, lithium-sulfur batteries perform excellently with the modified PP separator. Specifically, the battery with a Co3Se4@N-C/Ti3C2Tx-modified PP separator exhibits an outstanding rate performance of 787 mAh g-1 at 4C, and stable performance is maintained after 300 cycles at 2C. The density functional theory (DFT) calculations are also performed to confirm the synergistic effect of Co3Se4@N-C and Ti3C2Tx. This design integrates the merits of catalysis and adsorption and provides a new method for constructing high-performance lithium-sulfur batteries.

Dual plasmonic Au and TiN cocatalysts to boost photocatalytic hydrogen evolution.

Employing a suitable cocatalyst is very important to improve photocatalytic H2 evolution activity. Herein, two plasmonic cocatalysts, Au nanoparticles and TiN nanoparticles were in-situ coupled over the g-C3N4 nanotube to form a ternary 0D/0D/1D Au/TiN/g-C3N4 composite via a successive thermal polycondensation and chemical reduction method. The g-C3N4 nanotube acted as a support for the growth of Au and TiN nanoparticles, leading to intimate contact between g-C3N4 nanotube with Au nanoparticles and TiN nanoparticles. As a result, multiple interfaces and dual-junctions of Au/g-C3N4 Schottky-junction and TiN/g-C3N4 ohmic-junction were constructed, which helped to promote the charged carriers' separation and enhanced the photocatalytic performance. Furthermore, loading plasmonic cocatalysts of Au nanoparticles and TiN nanoparticles can enhance the light absorption capacity. Consequently, the Au/TiN/g-C3N4 composite exhibited significantly enhanced photocatalytic H2 evolution activity (596 µmol g-1 h-1) compared to g-C3N4 or binary composites of Au/g-C3N4 and TiN/g-C3N4. This work highlights the significant role of cocatalysts in photocatalysis.

Facile Hydrothermal Synthesis of ZnWO4 for Enhanced Photocatalytic Performance.

ZnWO4 with controllable morphology was successfully synthesized via a facile hydrothermal method. The relationships between the structure, morphology, and catalytic activity were systemically studied by varying both the hydrothermal time and pH value. The optimal synthesis conditions for ZnWO4 with superior catalytic activity were a hydrothermal time of 12 h and a pH value of 10. Impressively, the highest photocatalytic activity for the degradation of RhB was 91% for 60 min under ultraviolet light. The increased photodegradation performance was mainly ascribed to the high crystallinity and enlarged surface area of the optimal ZnWO4.

Review on nanoscale Bi-based photocatalysts.

Nanoscale Bi-based photocatalysts are promising candidates for visible-light-driven photocatalytic environmental remediation and energy conversion. However, the performance of bulk bismuthal semiconductors is unsatisfactory. Increasing efforts have been focused on enhancing the performance of this photocatalyst family. Many studies have reported on component adjustment, morphology control, heterojunction construction, and surface modification. Herein, recent topics in these fields, including doping, changing stoichiometry, solid solutions, ultrathin nanosheets, hierarchical and hollow architectures, conventional heterojunctions, direct Z-scheme junctions, and surface modification of conductive materials and semiconductors, are reviewed. The progress in the enhancement mechanism involving light absorption, band structure tailoring, and separation and utilization of excited carriers, is also introduced. The challenges and tendencies in the studies of nanoscale Bi-based photocatalysts are discussed and summarized.

Effects of the preparation method on the structure and the visible-light photocatalytic activity of Ag2CrO4.

Silver chromate (Ag2CrO4) photocatalysts are prepared by microemulsion, precipitation, and hydrothermal methods, in order to investigate the effect of preparation methods on the structure and the visible-light photocatalytic activity. It is found that the photocatalytic activity of the prepared Ag2CrO4was highly dependent on the preparation methods. The sample prepared by microemulsion method exhibits the highest photocatalytic efficiency on the degradation of methylene blue (MB) under visible-light irradiation. The enhanced photocatalytic activity could be ascribed to the smaller particle size, higher surface area, relatively stronger light absorption, and blue-shift absorption edge, which result in the adsorption of more MB molecules, a shorter diffusion process of more photogenerated excitons, and a stronger oxidation ability of the photogenerated holes. Considering the universalities of microemulsion, precipitation, and hydrothermal methods, this work may also provide a prototype for the comparative study of semiconductor based photocatalysis for water purification and environmental remediation.