Search

An anionic MOF separator is proposed to accelerate lithium-ion transport towards constructing high-performance dendrite-free LMBs.

In recent years, the crack fault is one of the most common faults in the rotor system and it is still a challenge for crack position diagnosis in the hollow shaft rotor system. In this paper, a method based on the Convolutional Neural Network and deep metric learning (CNN-C) is proposed to effectively identify the crack position for a hollow shaft rotor system. Center-loss function is used to enhance the performance of neural network. Main contributions include: Firstly, the dynamic response of the dual-disks hollow shaft rotor system is obtained. The analysis results show that the crack will cause super-harmonic resonance, and the peak value of it is closely related to the position and depth of the crack. In addition, the amplitude near the non-resonant region also has relationship with the crack parameters. Secondly, we proposed an effective crack position diagnosis method which has the highest 99.04% recognition accuracy compared with other algorithms. Then, the influence of penalty factor on CNN-C performance is analyzed, which shows that too high penalty factor will lead to the decline of the neural network performance. Finally, the feature vectors are visualized via t-distributed Stochastic Neighbor Embedding (t-SNE). Naive Bayes classifier (NB) and K-Nearest Neighbor algorithm (KNN) are used to verify the validity of the feature vectors extracted by CNN-C. The results show that NB and KNN have more regular decision boundaries and higher recognition accuracy on the feature vectors data set extracted by CNN-C, indicating that the feature vectors extracted by CNN-C have great intra-class compactness and inter-class separability.

The crack fault is one of the most common faults in the rotor system, and researchers have paid close attention to its fault diagnosis. However, most studies focus on discussing the dynamic response characteristics caused by the crack rather than estimating the crack depth and position based on the obtained vibration signals. In this paper, a novel crack fault diagnosis and location method for a dual-disk hollow shaft rotor system based on the Radial basis function (RBF) network and Pattern recognition neural network (PRNN) is presented. Firstly, a rotor system model with a breathing crack suitable for a short-thick hollow shaft rotor is established based on the finite element method, where the crack’s periodic opening and closing pattern and different degrees of crack depth are considered. Then, the dynamic response is obtained by the harmonic balance method. By adjusting the crack parameters, the dynamic characteristics related to the crack depth and position are analyzed through the amplitude-frequency responses and waterfall plots. The analysis results show that the first critical speed, first subcritical speed, first critical speed amplitude, and super-harmonic resonance peak at the first subcritical speed can be utilized for the crack fault diagnosis. Based on this, the RBF network and PRNN are adopted to determine the depth and approximate location of the crack respectively by taking the above dynamic characteristics as input. Test results show that the proposed method has high fault diagnosis accuracy. This research proposes a crack detection method adequate for the hollow shaft rotor system, where the crack depth and position are both unknown.

This review provides a route for constructing advanced IR-ECDs towards real-world applications in smart windows, IR sensors, thermal control and military camouflage.

Metal phosphide materials have drawn much attention due to their high supercapacitive activity.

Homogeneous ion transport during Li+ plating/stripping plays a significant role in the stability of Li metal anodes (LMAs) and the electrochemical performance of Li metal batteries (LMBs).

Lithium metal has been considered as a promising anode material for lithium secondary batteries due to its low intercalation potential and high specific capacity. Nevertheless, the application of Li metal...

The present work explored the effect of barley to wheat ratio in malt blends on protein composition and physicochemical characteristics of wort and beer. Results illustrated that the addition of wheat malt can significantly improve the soluble protein of wort and the final beer, and it can provide more 2.2 kDa protein in final beer, which is mainly derived from the raw wheat malt, but also including some protein produced in the fermentation process, such as some protein between 29 and 66.4 kDa. Though the content of 15 kDa protein was relatively lower than the protein whose molecular weight was 15 kDa, but it had important effects on total nitrogen, total water-soluble protein, free amino nitrogen, chromaticity, and viscosity of final beer. The addition of wheat malt significantly improved the concentration of 2.2-15 and 15 kDa protein, but higher percentage of addition ratio can decrease the foam stability of the beer. PRACTICAL APPLICATION: This findings can reasonably control the protein content and types of wheat beer, improve the quality of wheat beer, solve the key technological problems, and expand and popularize the application of wheat in beer industry.

Zinc-air batteries (ZABs) are regarded as attractive devices for electrochemical energy storage and conversion due to their outstanding electrochemical performance, low price, and high safety. However, it remains a challenge to design a stable and efficient bifunctional oxygen catalyst that can accelerate the reaction kinetics and improve the performance of ZABs. Herein, a phosphorus-doped transition metal selenide/carbon composite catalyst derived from metal-organic frameworks (P-CoSe

Metal–organic framework (MOF) is a promising electrochromic material due to its high specific surface area and tunable pore size, which can benefit the fast transportation of ion/charge. Here, a simple solvothermal deposition method for fabrication of Ni-MOF 74 electrochromic films on ITO is developed. It is found that the reaction temperature has played an important role in the morphology and electrochromic performance of as-prepared Ni-MOF 74 film. The film prepared at the optimized temperature exhibits the best electrochromic performance with a rapid switching speed (the coloration/bleaching time = 24.5/23.5 s). In addition, the optimized film displays a high optical contrast of 44.4% at 550 nm and can be stably switched for 650 cycles with

Two-dimensional transition metal dichalcogenides, which display considerable theoretical capacity and large layer spacing, have been regarded as promising candidates as anode materials for sodium-ion batteries (SIBs). However, their low conductivity and large volume change during charge-discharge cycles leads to performance degradation. Herein, polyvinylpyrrolidone (PVP) is used as a soft template to synthesize PVP-derived nitrogen-doped carbon-coated MoS

To compare the predictive value of Oxford acute severity of illness score (OASIS) and simplified acute physiology score II (SAPS II) for in-hospital mortality in intensive care unit (ICU) patients with sepsis.A retrospective cohort study was conducted using the data in the Medical Information Mart for Intensive Care-IV 0.4 (MIMIC-IV 0.4). Based on Sepsis-3 diagnostic criteria, the basic information of ICU adult sepsis patients with infection and sequential organ failure assessment (SOFA) score ≥ 2 within 24 hours of ICU admission admitted for the first time in the database was extracted, including gender, age, vasopressor drugs, sedative drugs, mechanical ventilation, renal replacement therapy, length of ICU stay, OASIS, SAPS II scores, etc. The primary outcome was in-hospital mortality. A receiver operator characteristic curve (ROC curve) was drawn, and the area under the ROC curve (AUC) was calculated to compare the prognostic value of OASIS score and SAPS II score.A total of 11 098 adult ICU sepsis patients were enrolled in the final analysis, of which 2 320 died and 8 778 survived in hospital, with a mortality of 20.90%. Compared with the survivors, the non-survivors were older [years old: 71 (60, 81) vs. 67 (56, 78)], had longer length of ICU stay [days: 6.95 (3.39, 13.07) vs. 4.23 (2.19, 9.73)] and higher proportions of using vasopressor drugs, sedative drugs, mechanical ventilation and renal replacement therapy [vasopressor drugs: 50.65% (1 175/2 320) vs. 33.05% (2 901/8 778), sedative drugs: 58.53% (1 358/2 320) vs. 48.41% (4 249/8 778), mechanical ventilation: 89.57% (2 078/2 320) vs. 81.66% (7 168/8 778), renal replacement therapy: 11.98% (278/2 320) vs. 6.57% (577/8 778), all P0.01]. Moreover, the non-survivors had higher OASIS score [43 (36, 49) vs. 35 (29, 41), P0.01] and SAPS II score [49 (40, 60) vs. 38 (31, 47), P0.01] as compared with the survivors. ROC curve analysis showed that the AUC of OASIS score and SAPS II score for predicting in-hospital death of ICU patients with sepsis was 0.713 [95% confidence interval (95%CI) was 0.701-0.725] and 0.716 (95%CI was 0.704-0.728), respectively, and the Delong test showed no significant difference in AUC between the two scoring systems (P0.05).OASIS score has a good predictive value for in-hospital mortality in sepsis patients, which is similar to SAPS II score. OASIS score is simpler and has a broader clinical application prospect than SAPS II score.

Kolbach index (KI) is an important index to evaluate the qualities of malt, which will affect protein molecular composition, enzyme activity, and other macromolecules degradation during wheat malting. In this paper, the relationship between wheat (Triticum aestivum L.) malts KI and the (i) characterization of albumins, globulins, gliadins, and glutenins and their hydrolysis and (ii) the enzymatic breakdown of starch and arabinoxylans during malting were studied. As malt KI values increased, all fractions of glutenins and gliadins were extensively hydrolyzed. The higher Mw globulins (36.6 to 70.8 kDa) were also increasingly degraded at higher KI values, but the concentration of smaller globulin fractions (14.9 to 35.0 kDa) had increased significantly. As for albumins, although their overall concentration had increased as KI increased, changes in the concentration of individual albumin fractions was more complex. While there were significant increases in the concentration of some new albumin proteins (43.8 and 84.4 kDa), the concentration of some albumins decreased (21.1 to 64.3 kDa), and some fractions had completely disappeared (28.8 and 64.3 kDa). Following mashing, the hydrophobicity of the worts had decreased significantly at higher KI values. At malt KI values between 39.5% and 42.7%, the enzymatic activity was at its highest, the degradation of starch was adequate and stable, and the concentration of water-soluble arabinoxylans was optimal. A KI value of about 39.5% to 42.7% was therefore considered optimal for the production of wheat malts with superior quality attributes. PRACTICAL APPLICATION: The findings from this study will be valuable to beer companies; a more precise control of the malting and brewing parameters, fundamental for the production of high-quality wheat malts and wheat beer, can be achieved.

The selective transport of charge carriers has a great impact on the efficiency for electrochemical energy storage and conversion. However, pursuing membranes with high-performance ion selectivity is one of the most crucial issues for their further progress. In recent years, based on their intrinsic superior physical and chemical properties including abundant nano-sized channels, open metal sites and electrostatic interaction, metal-organic frameworks (MOFs) have shown enormous potential for the construction of membranes with ion selectivity. In this review, the design and mechanism for MOFs based membranes with ion selectivity is firstly discussed. Based on this, the applications of the membranes in typical electrochemical energy storage and conversion systems are summarized. Based on the recent advances, the existing challenges and the future perspectives are discussed. This review will offer new insights for understanding the ion transport in MOFs based membranes with ion selectivity towards high-performance electrochemical energy storage and conversion.

Electrochemical water splitting is the most direct and popular method to obtain hydrogen. However, the high activation barrier for water splitting greatly hinders large-scale hydrogen production, inspiring the necessity of using catalysts for the hydrogen evolution reaction and oxygen evolution reaction. Materials from precious metals to earth-abundant transition metals and their composites have been widely developed, in which transition metal selenides display a more outstanding bifunctional catalytic performance. This review aims to focus on the design strategies of transition metal selenide based catalysts from modification methods, including morphological control, anion substitution and cation substitution, as well as using composite materials modified by constructing heterostructures and the synergistic effect of different components. Finally, it provides guidance for the research status, and future development directions of multifunctional electrocatalytic selenide based materials are also suggested.

Zeolitic imidazolate frameworks (ZIF)-derived catalysts are being extensively investigated for the oxygen reduction reaction (ORR) due to its low cost, high tunability, and facile fabrication. However, an understanding of the critical role of temperature during pyrolysis remains lacking, which makes the design of catalysts by thermal activation rely on empirical engineering. In this work, we use ZIF-67 as a model material to study the impact of temperature on microstructural evolution by in situ transmission electron microscopy. Microstructural features of cobalt precipitation, nitrogen loss, and porous carbon support formation were investigated and semi-quantified. A tradeoff between the microstructural features is revealed and confirmed by the ORR performance. By understanding the temperature–microstructure–ORR performance relationship, we further design a simple low-temperature pyrolysis strategy and achieve outstanding ORR activity. Although demonstrated on ZIF-67, the critical role of temperature as disclosed by this work is beneficial for all ZIF-related materials to further boost ORR performance. Meanwhile, our one-step strategy is easy to implement and allows for scaling up for industrial application.

Layered ternary lithium-ion batteries LiNixCoyMnzO2 (NCM) and LiNixCoyAlzO2 (NCA) have become mainstream power batteries due to their large specific capacity, low cost, and high energy density. However, these layered ternary lithium-ion batteries still have electrochemical cycling problems such as rapid capacity decline and poor thermal stability. These problems are mainly caused by (1) irreversible phase transition, (2) crack and pulverization of cathode electrode material particles, (3) dissolution of transition metal elements, (4) oxidative decomposition of electrolyte and (5) repeated growth and thickening of the SEI film on the anode electrode. In order to solve these problems, various strategies based on doping and coating of the cathode material, design of electrolyte, and anode coating have been studied to effectively stabilize the NCM/NCA cathode and achieve the purpose of improving its electrochemical cycling performance. This review briefly describes the working principle of lithium-ion batteries, the composition and structure of NCM/NCA cathode materials and the roles of transition metal elements. The capacity degradation mechanism of layered ternary lithium-ion batteries is reviewed from the perspectives of cathode, electrolyte and anode, and the research progress in the modification of cathode materials is emphatically discussed. Advances in the modification of anode materials and electrolyte design are also briefly introduced. Finally, some challenges and prospects are proposed for the future development of layered ternary lithium-ion batteries.

Blue energy harvesting based on the ion flow obtained from seas and rivers provides a clean, stable and continuous electric output that is highly dependent on ion-selective membranes (ISMs) that conduct single ions. In recent years, ISMs constructed based on two-dimensional (2D) nanofluidics have demonstrated promising application prospects in blue energy harvesting due to their facile fabrication, excellent ion selectivity and high ion flux. In this review, the principles of 2D nanofluidics in regulating ionic transport are firstly proposed and discussed, including ion selectivity and ultrafast ion transmission, which are considered as two critical factors for achieving highly efficient blue energy harvesting. The advantages of 2D nanofluidics towards blue energy harvesting are analyzed to reveal the necessity of this review. The construction of 2D nanofluidic membranes based on several typical materials and their recent research advances in salinity gradient- and pressure-driven blue energy harvesting are also summarized in detail. Finally, the existing challenges of 2D nanofluidic membranes regarding blue energy harvesting applications are discussed to provide new insights for the development of high-performance blue energy harvesting systems based on 2D nanofluidics.

Endo-β-1, 4-xylanase (EC 3.2.1.8) is a key enzyme in the degradation of Arabinoxylan (AX). AX and its degradation products are the key substances that affect the viscosity, turbidity, filtration speed, alcohol, foam performance, and health care function of wheat beer. A wheat malt-derived endo-β-1, 4-xylanase was isolated and purified by our group in the previous stage. The aim of this study was to investigate the effects of the wheat malt-derived endo-β-1, 4-xylanase addition on the quality and composition of AX in hopped wort and wheat beer. The results showed that the content and the average degree of polymerization (avDP) of water-soluble arabinoxylan (WEAX) in hopped wort and wheat beer decreased with the increase of the addition level of the wheat malt-derived endo-β-1,4-xylanase. When the addition of wheat malt-derived endo-β-1,4-xylanase was 2.5 times of the activity of endo-β-1,4-xylanase in raw malt, the degradation rate of WEAX in hopped wort was the maximum (33.71%), and the avDP of WEAX was the minimum (29.74) at the addition level of the endo-β-1,4-xylanase was 2 times. The viscosity and turbidity of hopped wort and wheat beer decreased continuously with the increase of the addition level of the endo-β-1,4-xylanase, while the foam stability of wheat beer increased continuously. Wheat malt-derived endo-β-1,4-xylanase could decrease the content of 1320-6200 Da polysaccharide in wheat beer, but increase the content of

Objective: Spent ginger is a byproduct of juice extraction from the rhizome of ginger (Zingiber officinale). Despite its nutritional value, it is difficult to preserve or further process and thus is often wasted. This study uses spent ginger as a substrate for fermentation and cultivates spent ginger yeast cultures (SGYCs) that are then added to the feed of laying hens. The effects of SGYCs on production performance, egg quality, serum composition, and intestinal microbiota of laying hens were investigated.Methods: Eighty 60-week-old Hy-Line Brown hens were separated into 5 experimental groups with 4 replicates per group (4 hens per cage, 4 cages per replicate). The control group was fed a basal diet while experimental groups were also given SGYCs at the levels of 5, 10, 20, and 40 g/kg for 6 weeks.Results: The addition of SGYCs significantly increased the laying rate and nutrient digestibility, decreased feed conversion ratio, and enhanced the color of egg yolks (p0.05), but the activities of superoxide dismutase, glutathione peroxidase, and peroxidase all significantly increased, and contents of malondialdehyde were significantly reduced (p

Functional separators have played important roles in improving the electrochemical performance of lithium–sulfur (Li–S) batteries by addressing the key issues of both the sulfur cathode and lithium anode. Compared with other materials that are used for separator functionalization, two-dimensional (2D) materials with atomic layer thickness and infinite lateral dimensions feature several advantages of ultra-thin laminate structure, remarkable physical properties and tunable surface chemistry, which show potential applications in separator functionalization towards addressing the issues of both the shuttle effect and formation of Li dendrites in Li–S batteries. In this review, the unique advantages of 2D materials for separator functionalization in Li–S batteries and their common construction methods are introduced. Then, recent progress and advances in the construction of 2D materials functional separators are summarized in detail towards inhibiting the shuttle effect of polysulfides and suppressing Li dendrite growth in Li–S batteries. Finally, some opportunities and challenges of 2D materials for constructing high-performance functional separators are proposed. We anticipate that this review will provide new insights into separator functionalization for developing advanced Li–S batteries.

Electrochromic devices (ECDs) exhibiting tunable optical and thermal modulation in the infrared (IR) region have attracted extensive attention in recent years due to their attractive application prospects in both military and civilian settings. However, considering the continuous energy supply needed for driving the device operation, it is desired to develop advanced IR-ECDs with low energy consumption. Herein, a flexible self-driven IR-ECD is constructed for achieving variable optical and thermal management in a low-energy mode. In this device, a built-in potential difference of 1.36 V exists between the EC polyaniline cathode and the aluminum foil anode. Consequently, there is a rapid and obvious increase in the IR reflectance of the device after connecting the two electrodes. Such a self-driven reflectance contrast is over 20% at the wavelength of 1500 nm, and the coloration efficiency of the device reaches up to 93.6 cm2 C-1. Meanwhile, the maximum apparent temperature modulation on the surface of the device reaches up to 5.6 °C. Then, the self-driven IR-ECD could recover to its original state driven by a solar cell, indicating good reversibility and stability. We anticipate that this work may provide a new insight into developing advanced self-driven IR-ECDs for applications in dynamic military camouflage and commercial thermal control.

In this paper, a method based on the convolutional neural network (CNN) is proposed to effectively identify the crack location in the rotor system. Firstly, a dual-disks hollow shaft rotor system model with a breathing crack is established based on the finite element method. Then the dynamic response of the cracked rotor system is obtained by the 4th harmonic balance method (HBM) and the analysis results show that the super-harmonic resonance of the rotor system is closely related to the depth and location of the crack. Finally, the CNN is adopted to identify the crack position in the rotor system and it can achieve high accuracy. To understand the CNN, we visualize the features space and try to explain the reasons of the great performance of the CNN.

Lithium metal battery (LMB) is considered to be one of the most promising electrochemical energy storage devices due to the high theoretical specific capacity and the lowest redox potential of metallic lithium; however, some key issues caused by lithium dendrites on the lithium metal anode seriously hinder its real-world applications. As an indispensable part of LMBs, the separator could serve as a physical barrier to prevent direct contact of the two electrodes and control ionic transport in batteries; it is an ideal platform for the suppression of lithium dendrites. In this review, the mechanism of lithium dendrite nucleation and growth are firstly discussed and then some advanced techniques are introduced for the precise characterization of lithium dendrites. On the basis of dendritic nucleation and growth principle, several feasible strategies are summarized for suppressing lithium dendrites by utilizing functional separators, including providing a mechanical barrier, promoting homogeneous lithium deposition, and regulating ionic transport. Finally, some challenges and prospects are proposed to clear the future development of functional separators. We anticipate that this paper will provide a new insight into the design and construction of functional separators for addressing the issues of lithium dendrites in high-energy batteries.

Single-atom catalysts provide an effective approach to reduce the amount of precious metals meanwhile maintain their catalytic activity. However, the sluggish activity of the catalysts for alkaline water dissociation has hampered advances in highly efficient hydrogen production. Herein, we develop a single-atom platinum immobilized NiO/Ni heterostructure (PtSA-NiO/Ni) as an alkaline hydrogen evolution catalyst. It is found that Pt single atom coupled with NiO/Ni heterostructure enables the tunable binding abilities of hydroxyl ions (OH*) and hydrogen (H*), which efficiently tailors the water dissociation energy and promotes the H* conversion for accelerating alkaline hydrogen evolution reaction. A further enhancement is achieved by constructing PtSA-NiO/Ni nanosheets on Ag nanowires to form a hierarchical three-dimensional morphology. Consequently, the fabricated PtSA-NiO/Ni catalyst displays high alkaline hydrogen evolution performances with a quite high mass activity of 20.6 A mg−1 for Pt at the overpotential of 100 mV, significantly outperforming the reported catalysts., While H2 evolution from water may represent a renewable energy source, there is a strong need to improve catalytic efficiencies while maximizing materials utilization. Here, authors examine single-atom Pt on nickel-based heterostructures as highly active electrocatalysts for alkaline H2 evolution.

Transition metal selenides (TMSs) have been considering as a kind of promising alternative anode materials for the application of sodium ion batteries due to their high electrical conductivity and high capacity. Here, hollow NiCoSe2 microspheres was prepared via an easy hydrothermal method, followed by the dopamine derived N-doped carbon coated which formed the hollow NiCoSe2@C composite. As-prepared hollow NiCoSe2@C composite has been first used as a new anode material for sodium ion batteries (SIBs). Our selenides displays a quite good electrochemical sodium storage performance. For example, the reversible capacity of as-prepared hollow NiCoSe2@C composite electrode can be maintained at 464.7 mAh g−1 at a current density of 100 mA g−1 after 200 cycles. Moreover, the rate performance of the hollow NiCoSe2@C composite is outstanding. The reversible capacities of 425.3, 420.8, 403.2, 394.7, 378.7, 367.8 and 337.5 mAh g−1 can be achieved at the current densities of 100, 200, 500, 1000, 2000, 3000 and 5000 mA g−1, respectively. Meanwhile, hollow NiCoSe2@C composite electrode exhibits a high discharge capacity of 338 mAh g−1 at a relatively high current density of 0.5 A g−1 after 250 cycles. In addition, the kinetic analysis of electrochemical Na + storage properties of the hollow NiCoSe2@C composite demonstrates that the extrinsic pseudo capacitive behaviour contributes significantly to excellent rate performance and good long-term cycling life. This method can be used to modify the morphologies and structures of the other TMSs for the development of new anode materials as anode materials in the application of sodium ion batteries.

Sodium ion batteries (SIBs) are deemed as the potential alternative for lithium ion batteries (LIBs) in the application of large-scale energy storage and conversion. The favorable anode materials play an important role for high-performance SIBs. Sn4P3 has been considered as one of the promising anode materials for sodium ion batteries due to the combination of high electrical conductivity from Sn and high specific capacity from P. In this work, Sn4P3/graphene aerogel (Sn4P3-GA) composite is prepared via a rapid low-temperature phosphidation reaction from SnO2-GA composite. The structural and morphological characterizations demonstrate that the Sn4P3 nanoparticles with an average size of 8 nm are uniformly and tightly embedded on the surface of 3D GA. The unique 3D network structure as well as the synergistic effect between graphene nanosheets and Sn4P3 nanoparticles would endow the as-prepared Sn4P3-GA composite with good electrochemical sodium storage performance. It delivers the high initial discharge capacity of 1180 mAh g−1 at 0.1 A g−1 and good cycle stability (657 mAh g−1 at 0.1 A g−1 after 100 cycles). Meanwhile, the Sn4P3-GA composite exhibits high-rate capacity of 462 and 403 mAh g−1 at a current density of 1 and 2 A g−1, respectively. Moreover, the contribution of the pseudocapacitance capacity can explicate the origin of good rate capability of the Sn4P3-GA composite. This work demonstrates the great potential of Sn4P3-GA composite as an alternative anode material for the low-cost and high-performance sodium ion batteries.

Rational synthetic design of Sn4P3-based materials with unique morphological structure and superior sodium storage capability for sodium ion batteries (SIBs) is crucially and urgently needed. In th...

SnO2 is considered as one of the most promising alternative anode materials for lithium ion batteries (LIBs) and sodium ion batteries (SIBs) due to high specific capacity, low discharge voltage plateau and environmental friendliness. In this work, 1D ultrafine SnO2 nanorods anchored on 3D graphene aerogel (SnO2 NRs/GA) composite is prepared through a simple reduction-induced self-assembly method in the solution of graphene oxide (GO), Vitamin C and SnO2 nanoparticles. Vitamin C plays an important role in the reduction of GO. The structural and morphological characterizations demonstrate that 1D ultrafine SnO2 nanorods are uniformly and tightly anchored on the surface of 3D graphene nanosheet aerogels. The unique 3D network structure as well as the synergistic effect between 3D graphene nanoshhet and 1D SnO2 nanorods endows the as-prepared SnO2 NRs/GA composite with the good electrochemical lithium/sodium storage performance. It delivers the high initial discharge capacity (1713 mA h g−1 at 0.1 A g−1 for LIBs and 539 mA h g−1 at 0.05 A g−1 for SIBs) and good cycle stability (869 mA h g−1 at 0.1 A g−1 after 50 cycles for LIBs and 232 mA h g−1 at 0.05 A g−1 after 100 cycles for SIBs). Moreover, the SnO2 NRs/GA composite exhibits excellent cycle stability for SIBs with a high reversible capacity of 96 mA h g−1 at as high as 1 A g−1 for 500 cycles. This work provides a simple method to fabricate the electro-active materials-graphene aerogel composites for high-performance LIBs and SIBs.

Flower-like Fe3O4/graphene aerogel (Fe3O4/GA) composite was prepared by water-bath vitamin C reduction self-assembly process followed by a heat treatment under N2 atmosphere. The morphological and structural results demonstrate that 3D flower-like Fe3O4 particles are homogenously embedded into the 3D conductive network of graphene nanosheet aerogels. Based on this unique structure, flower-like Fe3O4/GA composite exhibits a high reversible capacity of 797 mAh g−1 at 0.2 A g−1, and good rate capacity of 551 mAh g−1 at 3.2 A g−1 as well as excellent cycling performance with a stable capacity of ~1138 mAh g−1 after 100 cycles at 0.2 A g−1 compared with bare flower-like Fe3O4 electrode. Our work demonstrates this self-assembly approach can be used to prepare other electroactive metal oxides/graphene composite for the application of lithium ion batteries.

High-activity catalysts in alkaline media are compelling for durable hydrogen evolution reaction (HER). Single-atom catalysts (SACs) provide an effective approach to reduce the amount of precious metals meanwhile maintain their catalytic activity. However, the sluggish activity of SACs for water dissociation in alkaline media has extremely hampered advances in highly efficient hydrogen production. Herein, we developed a platinum SAC immobilized NiO/Ni heterostructure (PtSA-NiO/Ni) as an alkaline HER catalyst. It was found that Pt SACs coupled with NiO/Ni heterostructure enable the tunable binding abilities of hydroxyl ions (OH*) and hydrogen (H*), which efficiently tailors the water dissociation energy for accelerating alkaline HER. In particular, the dual active sites consisting of metallic Ni sites and O vacancies modified NiO sites near the interfaces of NiO/Ni in PtSA-NiO/Ni have preferred adsorption affinity for H* and OH* groups, respectively, which efficiently lowers the energy barrier of water dissociation of Volmer step. Moreover, anchoring Pt single atoms at the interfaces of NiO/Ni heterostructure induces more free electrons on Pt sites due to the elevated occupation of the Pt 5d orbital at the Fermi level and reaches a near-zero H binding energy (ΔGH*, 0.07 eV), which further promotes the H* conversion and H2 evolution. Further enhancement of alkaline HER performance was achieved by constructing PtSA-NiO/Ni nanosheets on the Ag nanowires to form a hierarchical three-dimensional (3D) morphology that provides abundant active sites and accessible channels for charge transfer and mass transport. Consequently, the fabricated PtSA-NiO/Ni catalyst displays extremely high alkaline HER performances with a quite high mass activity of 20.6 A mg-1 for Pt at the overpotential of 100 mV, which is 41 times greater than that of the commercial Pt/C catalyst, significantly outperforming the reported catalysts.