•The EMD-based drift increment extraction method is proposed.•The drift increment is predicted based on the LSTM network.•A difference approximation method for the drift function derivative is ...proposed.•The drift-increment-based representation of RUL’s PDF is derived.•Advantages in the improvement of the prediction accuracy are justified.
In this paper, a novel remaining useful lifetime (RUL) prediction method that fuses stochastic degradation modeling and machine learning is proposed to improve the fitness of the model and quantify the uncertainty of the prediction results. First, a stochastic degradation model based on the Wiener process is built, and the drift increment is extracted using empirical mode decomposition (EMD). Second, a long short-term memory (LSTM) network is trained to learn the equipment degradation rule and predict the drift increment. The diffusion coefficient of the degradation model is then estimated according to the maximum likelihood principle. The final step is to derive the analytical expression for the probability distribution of remaining useful lifetime (RUL) based on the concept of first hitting time and the difference principle. The lithium battery degradation test confirmed the efficacy of the proposed method, achieving a life cycle average prediction accuracy of up to 97.45%.
To further reduce the complexity of the algorithm and improve the performance of remaining useful lifetime (RUL) prediction, an RUL prediction method based on the gated recurrent unit (GRU) and ...stochastic degradation modeling is proposed. First, a stochastic degradation model based on the Wiener process is established and a weighted kernel function is used to represent its drift increment. Then, a GRU is established to predict the degradation increment of the Wiener process and derive the probability density function (PDF) of the RUL. Finally, based on the lithium battery degradation data, the validity of the method is verified.
The Co/mCN-900 catalyst that was prepared by simple one-pot pyrolysis of the homogeneous mixture of melamine, polyacrylonitrile and Co(NO3)2·6H2O under N2 atmosphere can be used for catalytic ...hydrogenation of nitroarenes and direct reductive N-alkylation of nitroarenes with carbonyl compounds.
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Inexpensive and reusable transition metal heterogeneous catalysts exhibiting excellent catalytic performance represent an attractive alternative to noble metal and homogeneous catalysts. In this work, we fabricated a novel nanocatalyst comprised of Co nanoparticles (NPs) supported on a N-doped mesoporous carbon (Co/mCN-900) by simple one-pot pyrolysis of a homogeneous mixture of melamine, polyacrylonitrile, and Co(NO3)2·6H2O under a N2 atmosphere at 900°C. The as-obtained Co/mCN-900 catalyst displayed a fluffy mesoporous structure with highly dispersed and accessible Co NPs acting as catalytic active sites. The Co/mCN-900 catalyst was effective in hydrogenating nitroarenes at milder conditions (i.e., 1MPa H2 and 120°C) as compared to previously reported Co- and Ni-based catalysts. The Co/mCN-900 catalyst also catalyzed the reductive N-alkylation of nitroarenes with carbonyl compounds to form the corresponding aromatic secondary amines under very mild reaction conditions. In addition, the Co/mCN-900 catalyst showed good reusability since its morphology and activity were maintained after several reaction cycles. Therefore, this work provides a facile and promising method for fabricating non-precious transition metal-based catalysts with excellent performance and great potential for sustainable chemistry applications.
Nitrogen/carbon layer coordinated transition metal complexes are the most important alternatives to improve the catalytic performance of catalysts for energy storage and conversion systems, which ...require systematic investigation and improvement. The coordination mode of transition metal ions can directly affect the catalytic performance of catalysts. Herein, this paper reports that two kinds of Cu-based composites (CuSCN and CuSCN/C3N4) are prepared by in situ controllable crystallization of copper foam (CF) through electropolymerization and calcination. As a comparison, it is clarified that the different coordination modes of Cu1+ ions determine the different catalytic properties. The samples can be switched freely by tuning the electropolymerization period, which leads to different coordination modes of Cu1+ ions dramatically, thus affecting the electrocatalytic performance of composite materials for the hydrogen evolution reaction (HER) in turn. Thorough characterization using techniques, including X-ray photoelectron spectroscopy (XPS) and synchrotron-based near edge X-ray absorption fine structure (EXAFS) spectroscopy, reveals that strong interactions between CuSCN and C3N4 of CuSCN/C3N4 facilitate the formation of subtle coordinated N–Cu–S species, of which electronic structures are changed. Density Functional Theory (DFT) calculations indicate that the electrons can penetrate from CuSCN to N atoms present in C3N4. As a result, CuSCN/C3N4 demonstrates a better catalytic performance than the conventional transition-metal-based electrocatalysts. Besides, CuSCN/C3N4 reflects almost identical hydrogen evolution reaction (HER) activity and stability in an acid electrolyte with Pt/C.
There is a vital need to explore highly efficient and stable non‐precious‐metal catalysts for the oxygen evolution reaction (OER) to reduce the overpotential and further improve the energy‐conversion ...efficiency. Herein, we report a unique and cost‐effective lyophilization and thermal treatment two‐step procedure to synthesize a high‐performance hybrid consisting of CoFe alloy nanoparticles embedded in N‐doped carbon nanosheets interspersed with carbon nanotubes (CoFe‐N‐CN/CNTs) hybrid. The lyophilization step during the catalyst preparation leads to a uniform dispersion of carbon‐like precursors and avoids the agglomeration of metal particles. In addition, the inserted CNTs and doped N in this hybrid provide a good electrical conductivity, an abundance of chemically active sites, good mass transport capability, and effective gas adsorption/release channels. All these lead to a high specific surface area of 240.67 m2 g−1, favorable stability, and remarkable OER activities with an overpotential of only 285 mV at a current density of 10 mA cm−2 and a Tafel slope of 51.09 mV dec−1 in 1.0 m KOH electrolyte, which is even superior to commercial IrO2 catalysts. The CoFe‐N‐CN/CNTs hybrid thus exhibits great potential as a highly efficient and earth‐abundant anode OER electrocatalyst.
Alloys on my mind: A novel lyophilization and thermal treatment‐based two‐step procedure is adopted to synthesize a high‐performance hybrid consisting of CoFe nanoparticles embedded in N‐doped carbon nanosheets interspersed with carbon nanotubes (CoFe‐N‐CN/CNTs) that displays a remarkably long durability and excellent oxygen evolution reaction activities with a low overpotential.
The sustainable and green transformation of benzyl alcohols to high value-added esters and carboxylic acids using a low-cost heterogeneous Co catalyst and air as the sole oxidant.
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...•The highly dispersed and low-cost Co-Co3O4@NC-T catalysts were prepared.•High value-added carbonyls are synthesized from inexpensive alcohols.•The transformation is green (air as the sole oxidant and water as the solvent).•The possible mechanisms were proposed via experiments and EPR analysis.
The sustainable catalytic transformation of alcohols to high value-added fine chemicals is a significant and challenging research topic. Herein, a set of nitrogen-doped carbon encapsulated Co-based catalysts (Co-Co3O4@NC-T) were prepared by using low-cost dicyandiamide, glyoxal and cobalt nitrate as precursors. The obtained catalysts were utilized for the selective oxidation of alcohols to high value-added esters and carboxylic acids with air as the oxygen source and displayed wide applicability for the oxidation of both aromatic and aliphatic alcohols. Based on the controlled experiments, the protective effect of N-doped carbon structure and the synergistic effect between Co core and Co3O4 species guaranteed the high reaction conversion and selectivity. Benefitting from heterogeneity and magnetism of the catalyst, it can be easily recycled and reused for long-term stability. Reasonable mechanisms of selective oxidation reaction were proposed through EPR analysis and controlled experiments. The present work provides a facile strategy for potential large-scale preparation of heterogeneous catalyst for sustainable and green catalytic transformations.
Nowadays, disorder engineering of catalytic materials has attracted significant attention because it can increase catalytic active sites and thus enhance their catalytic activity for electrocatalytic ...reactions. However, it is extremely important to uncover the relationship between disorder engineering and catalytic activity. Particularly, deep exploration of the relationship is very important for fabricating excellent highly active catalysts for oxygen evolution reaction (OER), which is one of the promising technologies in energy transition. In this study, we prepared Fe-doped Ni3S2 materials and simultaneously controlled the disorder degree by regulating the ion concentration to improve the activity for OER. By investigating the as-prepared catalysts with various disorder degrees for OER, we also explored the relationship between the disordered structure and OER catalytic performance. In particular, the optimized electrocatalyst with an appropriate disorder degree showed excellent activity and stability. We hope that this study provides a feasible direction to fabricate and optimize transition metal chalcogenide (TMC) electrocatalysts as efficient and stable electrocatalysts for OER.
The growing concern about the environmental consequences of anthropogenic CO
2
emissions significantly stimulated the research of low-cost, efficient, and recyclable solid adsorbents of CO
2
capture. ...Metal–organic frameworks (MOFs) are a promising porous material for CO
2
adsorption. Hybrid materials consisting in copper benzene-1,3,5-tricarboxylate (Cu-BTC) and Cu doped graphitic-carbon nitride (Cu-g-C
3
N
4
) were prepared through solvothermal method as CO
2
adsorbent. The size range of Cu-BTC@1.8%Cu-g-C
3
N
4
was 9.0 ~ 19.4 μm, which was lower than the size range of Cu-BTC (14.6 ~ 29.6 μm). The hybrid adsorbents had lower Brunauer–Emmett–Teller (BET) surface areas and pole volume due to the combination with Cu-g-C
3
N
4
. The CO
2
adsorption capacity of Cu-BTC@1.8%Cu-g-C
3
N
4
increased by 49.5% compared with that of pure Cu-BTC because of more adsorption sites including unsaturated metal centers and N atoms. Moreover, the Cu-BTC@1.8%Cu-g-C
3
N
4
had good stability in CO
2
adsorption capacity after multiple adsorption cycles.
Graphical abstract
The quest for developing electrochemical energy‐storage and ‐conversion technologies continues to be a great impetus to develop cost‐effective, highly active, and electrochemically stable ...electrocatalysts for overcoming the activation energy barriers of the oxygen evolution reaction (OER). Co3O4 nanocrystals have great potential as OER catalysts, and research efforts on improving the catalytic activity of Co3O4 are currently underway in many laboratories. Herein, CoFe layered double hydroxide (LDH) nanosheets were directly grown on the active Co3O4 substrate to form nanohybrid electrocatalysts for OER. The CoFe LDH/Co3O4(6:4) nanohybrid exhibited superior catalytic performance with a low overpotential and a small Tafel slope in alkaline solution. The outstanding performance of the CoFe LDH/Co3O4(6:4) nanohybrid was primarily owing to the synergistic effects induced by the strongly coupled interface between CoFe LDH and Co3O4; this feature enhanced the intrinsic OER catalytic activity of the nanohybrid and favored fast charge transfer. Compared with other Co3O4‐based catalysts, the nanohybrid shows advantages and offers a feasible avenue for improving the activity of Co3O4‐based catalysts.
Interesting interface: The coupled interface structure obtained through rational design endows a CoFe layered double hydroxide (LDH)/Co3O4(6:4) nanohybrid with significantly boosted activity and durability, as well as accelerated reaction kinetics for the oxygen evolution reaction (OER).
Nitrogen/carbon layer coordinated transition metal complexes are the most important alternatives to improve the catalytic performance of catalysts for energy storage and conversion systems, which ...require systematic investigation and improvement. The coordination mode of transition metal ions can directly affect the catalytic performance of catalysts. Herein, this paper reports that two kinds of Cu-based composites (CuSCN and CuSCN/C3N4) are prepared by in situ controllable crystallization of copper foam (CF) through electropolymerization and calcination. As a comparison, it is clarified that the different coordination modes of Cu1+ ions determine the different catalytic properties. The samples can be switched freely by tuning the electropolymerization period, which leads to different coordination modes of Cu1+ ions dramatically, thus affecting the electrocatalytic performance of composite materials for the hydrogen evolution reaction (HER) in turn. Thorough characterization using techniques, including X-ray photoelectron spectroscopy (XPS) and synchrotron-based near edge X-ray absorption fine structure (EXAFS) spectroscopy, reveals that strong interactions between CuSCN and C3N4 of CuSCN/C3N4 facilitate the formation of subtle coordinated N-Cu-S species, of which electronic structures are changed. Density Functional Theory (DFT) calculations indicate that the electrons can penetrate from CuSCN to N atoms present in C3N4. As a result, CuSCN/C3N4 demonstrates a better catalytic performance than the conventional transition-metal-based electrocatalysts. Besides, CuSCN/C3N4 reflects almost identical hydrogen evolution reaction (HER) activity and stability in an acid electrolyte with Pt/C.
