Increasing visible light absorption of classic wide‐bandgap photocatalysts like TiO2 has long been pursued in order to promote solar energy conversion. Modulating the composition and/or stoichiometry ...of these photocatalysts is essential to narrow their bandgap for a strong visible‐light absorption band. However, the bands obtained so far normally suffer from a low absorbance and/or narrow range. Herein, in contrast to the common tail‐like absorption band in hydrogen‐free oxygen‐deficient TiO2, an unusual strong absorption band spanning the full spectrum of visible light is achieved in anatase TiO2 by intentionally introducing atomic hydrogen‐mediated oxygen vacancies. Combining experimental characterizations with theoretical calculations reveals the excitation of a new subvalence band associated with atomic hydrogen filled oxygen vacancies as the origin of such band, which subsequently leads to active photo‐electrochemical water oxidation under visible light. These findings could provide a powerful way of tailoring wide‐bandgap semiconductors to fully capture solar light.
In contrast to the common tail‐like absorption band in hydrogen‐free oxygen‐deficient TiO2, an unusual strong absorption band spanning the full spectrum of visible light is achieved in red anatase TiO2 by intentionally introducing atomic hydrogen‐mediated oxygen vacancies that subsequently lead to active photo‐electrochemical water oxidation under visible light.
Amorphous carbon nitride (ACN) with a bandgap of 1.90 eV shows an order of magnitude higher photocatalytic activity in hydrogen evolution under visible light than partially crystalline graphitic ...carbon nitride with a bandgap of 2.82 eV. ACN is photocatalytically active under visible light at a wavelength beyond 600 nm.
Single‐atom catalysts (SACs) are attracting significant attention due to their exceptional catalytic performance and stability. However, the controllable, scalable, and efficient synthesis of SACs ...remains a significant challenge. Herein, a new and versatile seeding approach is reported to synthesize SACs supported on different 2D materials such as graphene, boron nitride (BN), and molybdenum disulfide (MoS2). This method is demonstrated on the synthesis of Ni, Co, Fe, Cu, Ag, Pd single atoms as well as binary atoms of Ni and Cu codoped on 2D support materials with the mass loading of single atoms in the range of 2.8–7.9 wt%. In particular, the applicability of the new seeding strategy in electrocatalysis is demonstrate on nickel SACs supported on graphene oxide (SANi‐GO), exhibiting excellent catalytic performance for electrochemical CO2 reduction reaction with a turnover frequency of 325.9 h−1 at a low overpotential of 0.63 V and high selectivity of 96.5% for CO production. The facile, controllable, and scalable nature of this approach in the synthesis of SACs is expected to open new research avenues for the practical applications of SACs.
A facile, controllable, and scalable method is developed for the fabrication of single‐atom catalysts (SACs) on various 2D material supports with high loading and activities via a new seeding approach, significantly accelerating the practical application of SACs for the areas of electrocatalysis and catalysis.
A unique sandwich structure is designed with pure sulfur between two graphene membranes, which are continuously produced over a large area, as a very simple but effective approach for the fabrication ...of Li–S batteries with ultrafast charge/discharge rates and long lifetimes.
The flexibility in structural design of organic semiconductors endows organic solar cells (OSCs) not only great function-tunabilities, but also high potential toward practical application. In this ...work, simple non-fused-ring electron acceptors are developed through two-step synthesis from single aromatic units for constructing efficient OSCs. With the assistance of non-covalent interactions, these rotatable non-fused acceptors (in solution) allow transiting into planar and stackable conformation in condensed solid, promoting acceptors not only feasible solution-processability, but also excellent film characteristics. As results, decent power conversion efficiencies of 10.27% and 13.97% can be achieved in single and tandem OSCs consisting of simple solution-cast blends, in which the fully unfused acceptors exhibit exceptionally low synthetic complexity index. In addition, the unfused acceptor and its based OSCs exhibit promising stabilities under continuous illumination. Overall, this work reveals valuable insights on the structural design of simple and effective electron acceptors with great practical perspectives.
To understand the origin of the cycling performance improvement observed in lithium-sulfur (Li–S) batteries based on N-doped carbon materials, the interactions between lithium polysulfides (LiPSs) ...and N-doped graphene (N-G) with different doping configurations have been investigated by density functional theory calculations. It has been found that only N-G with clustered pyridinic N-dopants can strongly attract LiPSs with large enough binding energies to effectively anchor the soluble LiPSs, due to (i) an enhanced attraction between Li ions in LiPSs and pyridinic N-dopants and/or (ii) an additional attraction between S anions in LiPSs and Li ions captured by pyridinic N-dopants. This study has, for the first time, provided a fundamental understanding on the origin of the effective anchoring of LiPSs by N-doped carbon materials, which suppresses the shuttling of LiPSs and produces significant improvement in the cycling performance of Li–S batteries. These findings can also guide the design of more effective N-doped carbons or other N-rich materials for Li–S batteries, preventing the undesirable LiPS shuttling.
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•The interactions between LiPSs and N-G are studied by DFT calculations.•Only N-G with clustered pyridinic N-dopants can effectively anchor LiPSs.•Clustered pyridinic N-dopants improve the cycling stability of Li-S batteries.
Graphene-sulfur (G-S) hybrid materials with sulfur nanocrystals anchored on interconnected fibrous graphene are obtained by a facile one-pot strategy using a sulfur/carbon disulfide/alcohol mixed ...solution. The reduction of graphene oxide and the formation/binding of sulfur nanocrystals were integrated. The G-S hybrids exhibit a highly porous network structure constructed by fibrous graphene, many electrically conducting pathways, and easily tunable sulfur content, which can be cut and pressed into pellets to be directly used as lithium-sulfur battery cathodes without using a metal current-collector, binder, and conductive additive. The porous network and sulfur nanocrystals enable rapid ion transport and short Li(+) diffusion distance, the interconnected fibrous graphene provides highly conductive electron transport pathways, and the oxygen-containing (mainly hydroxyl/epoxide) groups show strong binding with polysulfides, preventing their dissolution into the electrolyte based on first-principles calculations. As a result, the G-S hybrids show a high capacity, an excellent high-rate performance, and a long life over 100 cycles. These results demonstrate the great potential of this unique hybrid structure as cathodes for high-performance lithium-sulfur batteries.
A nitrogen‐doped porous carbon monolith was synthesized as a pseudo‐capacitive electrode for use in alkaline supercapacitors. Ammonia‐assisted carbonization was used to dope the surface with nitrogen ...heteroatoms in a way that replaced carbon atoms but kept the oxygen content constant. Ammonia treatment expanded the micropore size‐distributions and increased the specific surface area from 383 m2 g−1 to 679 m2 g−1. The nitrogen‐containing porous carbon material showed a higher capacitance (246 F g−1) in comparison with the nitrogen‐free one (186 F g−1). Ex situ electrochemical spectroscopy was used to investigate the evolution of the nitrogen‐containing functional groups on the surface of the N‐doped carbon electrodes in a three‐electrode cell. In addition, first‐principles calculations were explored regarding the electronic structures of different nitrogen groups to determine their relative redox potentials. We proposed possible redox reaction pathways based on the calculated redox affinity of different groups and surface analysis, which involved the reversible attachment/detachment of hydroxy groups between pyridone and pyridine. The oxidation of nitrogen atoms in pyridine was also suggested as a possible reaction pathway.
N donates more: A nitrogen‐doped carbon monolith was synthesized as a pseudo‐capacitive electrode for use in alkaline supercapacitors. Treatment with ammonia expanded the micropore size distributions and increased the specific surface area of the nitrogen‐doped carbon. Possible redox reaction paths were proposed based on the calculated redox affinity of different groups and surface analysis.
The stem cell-based therapies for intervertebral disc degeneration have been widely studied. However, the mechanisms of mesenchymal stem cells interacting with intervertebral disc cells, such as ...nucleus pulposus cells (NPCs), remain unknown. Exosomes as a vital paracrine mechanism in cell-cell communication have been highly focused on. The purpose of this study was to detect the role of exosomes derived from bone marrow mesenchymal stem cells (BM-MSCs) and NPCs in their interaction with corresponding cells.
The exosomes secreted by BM-MSCs and NPCs were purified by differential centrifugation and identified by transmission electron microscope and immunoblot analysis of exosomal marker proteins. Fluorescence confocal microscopy was used to examine the uptake of exosomes by recipient cells. The effects of NPC exosomes on the migration and differentiation of BM-MSCs were determined by transwell migration assays and quantitative RT-PCR analysis of NPC phenotypic genes. Western blot analysis was performed to examine proteins such as aggrecan, sox-9, collagen II and hif-1α in the induced BM-MSCs. Proliferation and the gene expression profile of NPCs induced by BM-MSC exosomes were measured by Cell Counting Kit-8 and qRT-PCR analysis, respectively.
Both the NPCs and BM-MSCs secreted exosomes, and these exosomes underwent uptake by the corresponding cells. NPC-derived exosomes promoted BM-MSC migration and induced BM-MSC differentiation to a nucleus pulposus-like phenotype. BM-MSC-derived exosomes promoted NPC proliferation and healthier extracellular matrix production in the degenerate NPCs.
Our study indicates that the exosomes act as an important vehicle in information exchange between BM-MSCs and NPCs. Given a variety of functions and multiple advantages, exosomes alone or loaded with specific genes and drugs would be an appropriate option in a cell-free therapy strategy for intervertebral disc degeneration.
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