Heterogeneous catalysis plays a significant role in the modern chemical industry. Towards the rational design of novel catalysts, understanding reactions over surfaces is the most essential aspect. ...Typical industrial catalytic processes such as syngas conversion and methane utilisation can generate a large reaction network comprising thousands of intermediates and reaction pairs. This complexity not only arises from the permutation of transformations between species but also from the extra reaction channels offered by distinct surface sites. Despite the success in investigating surface reactions at the atomic scale, the huge computational expense of
ab initio
methods hinders the exploration of such complicated reaction networks. With the proliferation of catalysis studies, machine learning as an emerging tool can take advantage of the accumulated reaction data to emulate the output of
ab initio
methods towards swift reaction prediction. Here, we briefly summarise the conventional workflow of reaction prediction, including reaction network generation,
ab initio
thermodynamics and microkinetic modelling. An overview of the frequently used regression models in machine learning is presented. As a promising alternative to full
ab initio
calculations, machine learning interatomic potentials are highlighted. Furthermore, we survey applications assisted by these methods for accelerating reaction prediction, exploring reaction networks, and computational catalyst design. Finally, we envisage future directions in computationally investigating reactions and implementing machine learning algorithms in heterogeneous catalysis.
Machine learning algorithms can facilitate the reaction prediction in heterogeneous catalysis.
Precise determination of the structure‐property relationship of zeolite‐based metal catalysts is critical for the development toward practical applications. However, the scarcity of real‐space ...imaging of zeolite‐based low‐atomic‐number (LAN) metal materials due to the electron‐beam sensitivity of zeolites has led to continuous debates regarding the exact LAN metal configurations. Here, a low‐damage high‐angle annular dark‐field scanning transmission electron microscopy (HAADF‐STEM) imaging technique is employed for direct visualization and determination of LAN metal (Cu) species in ZSM‐5 zeolite frameworks. The structures of the Cu species are revealed based on the microscopy evidence and also proved by the complementary spectroscopy results. The correlation between the characteristic Cu size in Cu/ZSM‐5 catalysts and their direct oxidation of methane to methanol reaction properties is unveiled. As a result, the mono‐Cu species stably anchored by Al pairs inside the zeolite channels are identified as the key structure for higher C1 oxygenates yield and methanol selectivity for direct oxidation of methane. Meanwhile, the local topological flexibility of the rigid zeolite frameworks induced by the Cu agglomeration in the channels is also revealed. This work exemplifies the combination of microscopy imaging and spectroscopy characterization serves as a complete arsenal for revealing structure‐property relationships of the supported metal‐zeolite catalysts.
A low‐damage HAADF‐STEM imaging technique is employed for direct visualization and determination of Cu species in ZSM‐5 zeolite frameworks. The structure of the Cu species are revealed based on the microscopy evidence and also proved by the complementary spectroscopy results. The mono‐Cu species stably anchored by Al pairs inside the zeolite channels are identified as the key structure for higher C1 oxygenates yield and methanol selectivity for direct oxidation of methane.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
To explore high-performance electrocatalysts, electronic regulation on active sites is essentially demanded. Herein, we propose controlled phosphorus doping to effectively modify the electronic ...configuration of nanostructured Mo2C, accomplishing a benchmark performance of noble-metal-free electrocatalysts in the hydrogen evolution reaction (HER). Employing MoOx–phytic acid–polyaniline hybrids with tunable composition as precursors, a series of hierarchical nanowires composed of phosphorus-doped Mo2C nanoparticles evenly integrated within conducting carbon (denoted as P-Mo2C@C) are successfully obtained via facile pyrolysis under inert flow. Remarkably, P-doping into Mo2C can increase the electron density around the Fermi level of Mo2C, leading to weakened Mo–H bonding toward promoted HER kinetics. Further density functional theory calculations show that the negative hydrogen-binding free energy (ΔGH*) on pristine Mo2C gradually increases with P-doping due to electron transfer and steric hindrance by P on the Mo2C surface, indicating the effectively weakened strength of Mo–H. With optimal doping, a ΔGH* approaching 0 eV suggests a good balance between the Volmer and Heyrovsky/Tafel steps in HER kinetics. As expected, the P-Mo2C@C nanowires with controlled P-doping (P: 2.9 wt%) deliver a low overpotential of 89 mV at a current density of −10 mA cm−2 and striking kinetic metrics (onset overpotential: 35 mV, Tafel slope: 42 mV dec−1) in acidic electrolytes, outperforming most of the current noble-metal-free electrocatalysts. Elucidating feasible electronic regulation and the remarkably enhanced catalysis associated with controlled P-doping, our work will pave the way for developing efficient noble-metal-free catalysts via rational surface engineering.
White-light emitting organic materials attract broad attention which are ascribed to their potential for applications in lighting devices and display media. Most reported organic white-light emitters ...rely on the combination of several components that emit different colors of light (red/green/blue or orange/blue), which may cause problems to stability, reproducibility and device fabrication. By contrast, white-light emission from single-molecule systems offers opportunities to overcome these disadvantages, meanwhile engendering white-light with high quality. Nevertheless, limited cases of white-light emission at the molecular scale reported principally concentrate on organic solvents. Herein, we designed and synthesized new bi-functional organic molecules with a symmetric donor-acceptor-donor (D-A-D) type structure with the aim to construct a single-molecule white-light emitting system in aqueous solution. Further experiments and calculations demonstrate the possibility of stacking between the pyridinium-naphthalene (PN) core and coumarin groups in the designed molecules, ascribed to hydrophobic effects, π-π stacking and donor-acceptor interactions, which could dramatically enhance the intramolecular charge transfer (ICT) efficiency along with remarkable charge transfer (CT) emission. Based on this, multicolor photoluminescence including white-light can be finely tuned in various modes including excitation wavelength, solvent polarity, temperature, and host-guest interactions. A white-light emitting (WLE) hydrogel was also facilely prepared through the dispersion of one of the compounds in a commercial agarose gelator. This innovative study helps enrich the strategies to construct single-molecule organic white-light emitting materials in aqueous medium using the self-folding behavior.
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Anchoring‐based self‐assembly (ASA) has emerged as a material‐saving and highly scalable strategy to fabricate charge‐transporting monolayers for perovskite solar cells (PSCs). However, the ...interfacial hole‐extraction and electron‐blocking performances are highly dependent on the compactness of the ASA monolayers, which has been largely ignored though it is very crucial to the efficiency and stability of PSCs. Here, strategically designed hole‐transporting molecules with different anchoring groups are incorporated to investigate the effect of bonding strength on monolayer quality and correlate these with the performance of p‐i‐n structured PSCs. It is unraveled that the anchoring groups with a stronger bonding strength are advantageous for improving the assembly rate, density, and compactness of ASA monolayer, thus enhancing charge collection and suppressing interfacial recombination. The prototypical PSCs based on optimal ASA monolayer achieve a high power conversion efficiency (PCE) of 21.43% (0.09 cm2). More encouragingly, when enlarging the device area by tenfold, a comparable PCE of 20.09% (1.0 cm2) can be obtained, suggesting that the ASA strategy is practically useful for scaling‐up. The robust anchoring of the ASA monolayer also enhances devices stability, retaining 90% of initial PCE after three months. This study provides important insights into the ASA charge‐transporting monolayers for efficient and stable PSCs.
Molecular hole‐transporting materials with different anchoring groups are synthesized. The anchoring groups with a stronger bonding strength enable greatly enhanced compactness of self‐assembly monolayer, which benefits hole‐extraction and electron‐blocking in complete devices. When applied in inverted perovskite solar cells, 1 cm2 devices show a promising power conversion efficiency of over 20% with high stability.
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A complete catalytic cycle for methane combustion on the Co3O4(110) surface was investigated and compared with that on the Co3O4(100) surface on the basis of first-principles calculations. It is ...found that the 2-fold coordinated lattice oxygen (O2c) would be of vital importance for methane combustion over Co3O4 surfaces, especially for the first two C–H bond activations and the C–O bond coupling. It could explain the reason the Co3O4(110) surface significantly outperforms the Co3O4(100) surface without exposed O2c for methane combustion. More importantly, it is found that the cooperation of homogeneous multiple sites for multiple elementary steps would be indispensable. It not only facilitates the hydrogen transfer between different sites for the swift formation of H2O to effectively avoid the passivation of the active low-coordinated O2c site but also stabilizes surface intermediates during the methane oxidation, optimizing the reaction channel. An understanding of this cooperation of multiple active sites not only might be beneficial in developing improved catalysts for methane combustion but also might shed light on one advantage of heterogeneous catalysts with multiple sites in comparison to single-site catalysts for catalytic activity.
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To investigate the role of miR-337-3p targeting Rap1A in modulating proliferation, invasion, migration and apoptosis of cervical cancer cells.
The expression levels of miR-337-3p and Rap1A in ...cervical cancer tissues and normal tissues were evaluated through quantitative Real-time PCR (qRT-PCR) and Western blotting; and correlations of miR-337-3p with clinicopathological characteristics and prognosis of patients were also analyzed. Besides, human cervical cancer cell line HeLa cells were randomly divided into five groups (Mock, NC, miR-337-3p mimic, Rap1A, and miR-337-3p mimic + Rap1A groups). CCK-8 assay was utilized to measure cell proliferation, flow cytometry to evaluate cell apoptosis, and wound-healing and Transwell assays to detect cell migration and invasion.
Cervical cancer tissues presented a significant decrease in miR-337-3p and a remarkable increase in Rap1A protein. Besides, the expression levels of miR-337-3p and Rap1A were closely related to the major clinicopathological characteristics of cervical cancer; and patients with high-miR-337-3p-expression had the higher 5-year survival rate (all p< 0.05). When compared to Mock group, cells in miR-337-3p mimic group were suppressed in proliferation, migration, and invasion, but significantly promoted in apoptosis; meanwhile, cells in the Rap1A group showed changes in a completely opposite trend (all p< 0.05). Moreover, Rap1A can reverse the effect of miR-337-3p mimic on cell proliferation, invasion, migration and apoptosis (all p< 0.05).
MiR-337-3p was discovered to be decreased in cervical cancer, and miR-337-3p up-regulation may inhibit the proliferation, migration and invasion and promote the apoptosis of cervical cancer cells via down-regulating Rap1A.
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An efficient electrocatalyst for the reduction of polysulfide electrolytes is vital to the construction of quantum dot sensitized solar cells (QDSCs). Herein, Co,N-bidoped carbon nanomaterials, ...prepared simply via the pyrolysis of bimetallic (Zn and Co) zeolite-type-metal organic frameworks, were for the first time attempted as electrocatalysts to develop counter electrodes (CEs) for QDSCs. The CEs developed exhibit superior catalytic activity for polysulfide reduction in QDSCs, resulting in a low charge transfer resistance at the interface of the CE/electrolyte, an improved fill factor (FF) and a high short circuit current density ( J sc ). The outstanding performances of the CEs can be ascribed to the inherent characteristics of Co,N-bidoped carbons with homogeneously dispersed active dopants of Co and N atoms, large hydrophilic surface area, and good conductivity. Moreover, density functional theory (DFT) indicated that the Co–N x sites would be active sites for polysulfide reduction. When Co,N-bidoped carbons deposited on F-doped tin oxide glass were used as CEs, an impressive power conversion efficiency of 9.12% ( V oc = 0.635 V, J sc = 26.15 mA cm −2 , FF = 0.549) under one sun illumination with 100 mW cm −2 intensity was observed on QDSCs using Zn–Cu–In–Se QDs as sensitizers. Consequently, there is a good chance to fabricate QDSCs of high efficiency with the CEs derived from MOFs.
One of the big challenge of studying the core-shell iron nanostructures is to know the nature of oxide shell, i.e., whether it is γ-Fe
2
O
3
(Maghemite), Fe
3
O
4
(Magnetite),
α
-Fe
2
O
3
(Hematite), ...or FeO (Wustite). By knowing the nature of iron oxide shell with zero valent iron core, one can determine the chemical or physical behavior of core-shell nanostructures. Fe core-shell nanochains (NCs) were prepared through the reduction of Fe
3+
ions by sodium boro-hydride in aqueous solution at room atmosphere, and Fe NCs were further aged in water up to 240 min. XRD was used to study the structure of Fe NCs. Further analysis of core-shell nature of Fe NCs was done by TEM, results showed increase in thickness of oxide shell (from 2.5, 4, 6 to 10 nm) as water aging time increases (from 0 min, 120 min, 240 min to 360 min). The Raman spectroscopy was employed to study the oxide nature of Fe NCs. To further confirm the magnetite phase in Fe NCs, the Mössbauer spectroscopy was done on Fe NCs-0 and Fe NCs-6. Result shows the presence of magnetite in the sample before aging in water, and the sample after prolonged aging contains pure Hematite phase
.
It shows that prolonged water oxidation transforms the structure of shell of Fe NCs from mixture of Hematite and Magnetite in to pure hematite shell. The Magnetic properties of the Fe NCs were measured by VSM at 320 K. Because of high saturation magnetization (Ms) values, Fe NCs could be used as
r
2
contrasts agents for magnetic resonance imaging (MRI) in near future.
Rationally constructing atom-precise active sites is highly important to promote their catalytic performance but still challenging. Herein, this work designs and constructs ZSM-5 supported Cu and Ag ...dual single atoms as a proof-of-concept catalyst (Ag
-Cu
/ZSM-5 hetero-SAC (single-atom catalyst)) to boost direct oxidation of methane (DOM) by H
O
. The Ag
-Cu
/ZSM-5 hetero-SAC synthesized via a modified co-adsorption strategy yields a methanol productivity of 20,115 µmol g
with 81% selectivity at 70 °C within 30 min, which surpasses most of the state-of-the-art noble metal catalysts. The characterization results prove that the synergistic interaction between silver and copper facilitates the formation of highly reactive surface hydroxyl species to activate the C-H bond as well as the activity, selectivity, and stability of DOM compared with SACs, which is the key to the enhanced catalytic performance. This work believes the atomic-level design strategy on dual-single-atom active sites should pave the way to designing advanced catalysts for methane conversion.
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