Self‐supporting 3D (SSD) carbon nitrides (UCN‐X, X = 600–690; where X represents the pyrolytic temperature) consisting of curved layers, with plenty of wrinkles and enlarged size, are synthesized via ...a facile stepwise pyrolytic strategy. Such unique features of the SSD structure exhibiting dramatically improved charge mobility, extended π‐conjugated aromatic system, and partial distortion of heptazine‐based skeleton can not only keep the easier activation of the intrinsic π → π* electronic transition but also awaken the n → π* electronic transition in carbon nitride. The n → π* electronic transition of UCN‐X can be controllably tuned through changing the pyrolytic temperature, which can greatly extend the photoresponse range to 600 nm. More importantly, the change regularity of H2 evolution rates is highly positive, correlated with the change tendency of n → π* electronic transition in UCN‐X, suggesting the positive contribution of n → π* electronic transition to enhancing photocatalytic activity. The UCN‐670, with optimal structural and optical properties, presents enhanced H2 evolution rate up to 9230 µmol g−1 h−1 (Pt 1.1 wt%). This work realizes the synergistic optimization of optical absorption and exciton dissociation via fabricating an SSD structure. It offers a new strategy for the development of novel carbon nitride materials for efficient photocatalytic reactions.
Self‐supporting 3D (SSD) polymeric carbon nitride (PCN), with tunable n → π* electronic transition, is successfully synthesized via a facile stepwise pyrolytic strategy. The synergistic optimization of the SSD structure and n → π* electronic transition in PCN significantly advance the exciton dissociation and optical absorption, leading to enhanced visible‐light H2 evolution activity in the spectral region above 500 nm.
Spatially proximate amino acids in a protein tend to coevolve. A protein's three-dimensional (3D) structure hence leaves an echo of correlations in the evolutionary record. Reverse engineering 3D ...structures from such correlations is an open problem in structural biology, pursued with increasing vigor as more and more protein sequences continue to fill the data banks. Within this task lies a statistical inference problem, rooted in the following: correlation between two sites in a protein sequence can arise from firsthand interaction but can also be network-propagated via intermediate sites; observed correlation is not enough to guarantee proximity. To separate direct from indirect interactions is an instance of the general problem of inverse statistical mechanics, where the task is to learn model parameters (fields, couplings) from observables (magnetizations, correlations, samples) in large systems. In the context of protein sequences, the approach has been referred to as direct-coupling analysis. Here we show that the pseudolikelihood method, applied to 21-state Potts models describing the statistical properties of families of evolutionarily related proteins, significantly outperforms existing approaches to the direct-coupling analysis, the latter being based on standard mean-field techniques. This improved performance also relies on a modified score for the coupling strength. The results are verified using known crystal structures of specific sequence instances of various protein families. Code implementing the new method can be found at http://plmdca.csc.kth.se/.
•HATN with rich electroactive sites and MXene jointly build a unique 3D structure.•HATN/MXene hybrid was applied as capacitive deionization electrode.•HATN/MXene exhibits a good performance with high ...desalination capacity and rate.
In this work, we report a hybrid material of pyrazine based π-conjugated organic molecule, hexaazatrinaphthalene (HATN), and MXene. In this hybrid, MXene serves as a conductive substrate and HATN provides multiple electroactive sites, which are jointly combined to build a unique 3D structure with more ion transport channels for accelerating the charge transfer and ion diffusion rates. The as-obtained HATN/MXene composite displays a superior desalination capacity of 57.5 mg g−1 with an excellent desalination rate of 13.2 mg g−1 min−1 and good long-term stability. This work provides a meaningful guidance for designing and applying organic molecules in capacitive deionization field.
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•A hierarchical three-dimensional ternary carbon hybrid nanostructure has been fabricated.•A device with negative CNTs@Gr-CNF and positive NiCo2S4/Ni electrode is prepared.•The device ...shows a capacitance of 218 F g−1 at 1 A g−1 and 94.98% retention after 10,000 cycles.•The device shows an energy density of 62.13 Wh kg−1 at 789.66 W kg−1 power.
Carbon materials with hierarchical nanostructures are well accepted propitious materials for electrode application in supercapacitor devices. Herein, a hierarchical ternary carbon aerogel structure is designed by integrating graphene (Gr), carbon nanofibers (CNFs), and carbon nanotubes (CNTs). The as-synthesized CNTs@Gr-CNF materials are characterized by different analytical techniques for the electrode application in a supercapacitor. In the three-electrode system, CNTs@Gr-CNF electrode material exhibits an enhanced electrochemical performance in which a high specific capacitance of 521.5 F g−1 was obtained at 0.25 A g−1 along with the excellent capacitance retention of 98% after consecutive 10,000 charge-discharge cycles at 5 A g−1 in 6 M KOH. In addition, a hybrid supercapacitor device based on CNTs@Gr-CNF as the negative electrode and NiCo2S4 nanoneedle grown on nickel foam as the positive electrode was fabricated. The hybrid device shows 218 F g−1 of specific capacitance at 1 A g−1 and an energy density of 62.13 Wh Kg−1 at a power density of 789.66 W kg−1. Moreover, the device exhibits an excellent cyclic stability with the retention of 91.7% of its specific capacitance after 10,000 charge-discharge cycles. The obtained results signify that the CNTs@Gr-CNF material possesses highly desirable properties for negative electrode application in advanced hybrid supercapacitor.
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•P-doped three dimensional (3D) network of MoS2 was prepared.•P doping in MoS2 accelerates the cleavage of S-S or Li-S bonds in LiPSs.•Li-S battery with 3D P-MoS2-G interlayer ...delivered 884.4 mAh g−1 after 100 cycles.•Li-S battery exhibited excellent rate performance under 3.7 mg cm−2 sulfur loading.
To address the issues of “shuttle effect” of soluble polysulfides and sluggish redox kinetics in the cathodes of lithium-sulfur batteries, the acceleration of the polysulfides conversion via electrocatalysis is a promising solution. As a common electrocatalyst, the catalytic ability of two dimensional (2D) MoS2 is considerably diminished due to agglomeration of nanosheets and insufficient active sites. In this work, a phosphorus-doped three dimensional (3D) network of MoS2-based interlayer sandwiched between the S cathode and the separator is developed. The 3D network could prevent 2D nanosheets from stacking and provide fast diffusion channels for Li ions transfer. Phosphorus doped MoS2 forms stronger Mo-S and Li-P bonds to anchor polysulfides and to promote cleavage of S-S or Li-S bonds of lithium polysulfides to accelerate the polysulfides conversion. As a result, the cell exhibits a high specific capacity of 884.4 mAh g−1 after 100 cycles at 0.1C even under the high sulfur loading condition (3.7 mg cm−2). This work may encourage more efforts on heteroatom doping in electrocatalyst to realize a high performance in lithium–sulfur batteries.
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The research on the structure of advanced electrode materials is significant in the field of supercapacitors. Herein, for the first time, we propose a novel 3D/3D composite structure ...by a multi-step process, in which 3D hollow NiCo LDH nanocages are immobilized on 3D sea urchin-like CoO microspheres. Results show that the 3D CoO acts as an efficient and stable channel for ion diffusion, while the hollow NiCo LDH provides abundant redox-active sites. The calculated results based on density function theory (DFT) show that the CoO@NiCo LDH heterostructure has an enhanced density of states (DOS) near the Fermi level and strong adsorption capacity for OH−, indicating its excellent electrical conductivity and electrochemical reaction kinetics. As a result, the CoO@NiCo LDH electrode has an areal specific capacity of 4.71C cm−2 at a current density of 3 mA cm−2 (440.19C g−1 at 0.28 A g−1) and can still maintain 88.76 % of the initial capacitance after 5000 cycles. In addition, the assembled hybrid supercapacitor has an energy density of 5.59 mWh cm−3 at 39.54 mW cm−3.
The 2D/3D heterojunction structure emerges as a viable approach for enhancing the efficiency and stability of perovskite photovoltaics. However, the formation of an accumulative low-dimensional 2D ...perovskite (n=1) cladding layer often impedes carrier transport due to the insulating nature and high quantum confinement, and there is a paucity of detailed understanding regarding its surface phase control. This study introduces a Dion-Jacobson (DJ) phase 2D perovskite, employing decane-1,10-diammonium diiodide (DDADI) to interface with 3D perovskite, leveraging long-chain diammonium cations for structural stability and defect passivation on the 3D FAPbI3 perovskite surface. In addition, a novel PbI2-assisted phase control (PAPC) technique is proposed to mitigate the quantum confinement effects of the 2D layer, especially reducing the formation of the highly confined insulating n=1 phase. X-ray scattering analysis confirms the method's efficacy in promoting the formation of an n=2 phase, facilitating cascading HOMO levels and improving hole carrier transport. The optimized 2D/3D perovskite solar cell (PSC) achieve an exemplary efficiency of 25.16 %, with a notable open-circuit voltage of 1.192 V, and retain 92.9 % of its initial efficiency after 1000 hours in a nitrogen atmosphere, signifying a strategic advancement in 2D/3D PSC construction.
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•The study introduces a 2D/3D heterojunction using a Dion-Jacobson phase 2D perovskite.•Utilizes a novel PbI2-assisted phase control method to mitigate the quantum confinement effect.•Promotes the formation of an n=2 phase 2D perovskite, enhancing carrier transport.•Achieves exceptional efficiency of 25.16% and sustained 92.9% of initial performance after 1000 hours storage.
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Three-dimensional (3D) carbon-based materials have attracted growing attention in the field of electromagnetic wave absorption applications. However, their high conductivity results ...in high dielectric constant, leading to impedance mismatching, and this characteristic finally weakens their electromagnetic wave absorption performance. In this work, 3D carbon foam (3DCF) was successfully prepared by calcining the melamine foam as the carbon framework precursor under N2 atmosphere. Subsequently, 1T-2H MoS2 nanosheets were uniformly assembled on the surface of the 3DCF skeleton through a solvothermal process. The diameter of the 3DCF skeleton was about 1 μm and the thickness of the 1T-2H MoS2 on the surface was about 150 nm. The 3D network brings in many advantages for microwave attenuation, including numerous conductive pathways, excellent impedance matching and multi-polarization processes. The composites exhibited a maximum reflection loss (RLmax) of −45.88 dB at 10.2 GHz with the thickness of 2.2 mm, and the effective absorbing bandwidth (EAB) was as wide as 5.68 GHz, implying their superb microwave absorption behavior. This work is believed to offer a strategy for the design of efficient 3D electromagnetic wave absorbers with low density in the future.
Workflow of 3dRNA in prediction of RNA 3D structure.
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•The 3D structures of RNAs are very limited at present.•3dRNA was proposed to predict 3D structure of RNAs.•A score function ...3dRNAscore was built to evaluate predicted 3D structures.•Information of coevolution in the RNA sequences was incorporated into 3dRNA.•3dRNA is now extended to predict the 3D structures of circular RNAs.
3D structures of RNAs are the basis for understanding their biological functions. However, experimentally solved RNA 3D structures are very limited. Therefore, many computational methods have been proposed to solve this problem, including our 3dRNA. 3dRNA is an automated template-based method of building RNA 3D structures from sequences and secondary structures by using the smallest secondary elements (SSEs) (http://biophy.hust.edu.cn/new/3dRNA). The first version of 3dRNA simply predicts an assembled structure for a target RNA. Later, it is improved to generate a set of assembled models and a method to further optimize them using experimental or theoretical restraints. In particular, pseudoknot base pairings are treated as restraints to solve the problem of no 3D templates for pseudoknots. Here 3dRNA is further extended to predict the 3D structures of circular RNAs since thousands of circular RNAs have been found recently but no 3D structures of them have been determined up to now. We show that circular RNAs can be divided into four types and two types show similar 3D structures with their linear counterparts while two types very different. We also show that the predicted structures of circular RNAs can bind to their ligands more stable than those of their linear counterparts, consistent with experimental results.
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