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The electrochemical synthesis of hydrogen peroxide (H2O2) via a two-electron (2e-) oxygen reduction reaction (ORR) process provides a promising alternative to replace the energy- intensive anthraquinone process. Herein, we develop a facile template-protected strategy to synthesize a highly active quinone- rich porous carbon catalyst for H2O2 electrochemical production. The optimized PCC900 material exhibits remarkable activity and selectivity, of which the onset potential reaches 0.83 V vs. reversible hydrogen electrode in 0.1 M KOH and the H2O2 selectivity is over 95 % in a wide potential range. Comprehensive synchrotron-based near-edge X-ray absorption fine structure (NEXAFS) spectroscopy combined with electrocatalytic characterizations reveals the positive correlation between quinone content and 2e- ORR performance. The effectiveness of chair-form quinone groups as the most efficient active sites is highlighted by the molecule-mimic strategy and theoretical analysis

Electrochromic batteries (EBs) have been developed as a technical breakthrough to solve the energy issues of storage and saving. Multivalent-ions (Zn2+, Mg2+ and Al3+) have recently demonstrated attractive properties for EBs due to their multiple-electron redox nature. However, still now, reported multivalent-ion EBs are typically assembled with a small-area metallic anode and a large-area electrochromic cathode. Non-uniformity of coloration and unstable metal plating/stripping hinder the developments of these devices. Additionally, insufficient energy/power density of EBs is a huge technical challenge needed to be overcome. In this work, we demonstrated a new aqueous aluminum-ion electrochromic full battery (AIEFB) to overcome the challenges. Systematic studies of density functional theory calculation, molecular dynamics simulation, electrochemical analysis, and mechanical measurements were conducted to optimize electrode materials and electrolyte. A water-in-salt (WIS) Al(OTF)3 electrolyte and a new electrochromic material couple of anodic amorphous WO3 (a-WO3) and cathodic indium hexacyanoferrate (InHCF) were exploited for AIEFB. The AIEFB demonstrated advantages of a high average discharge potential (1.06 V), an attractive energy density of 62.8 mWh m−2 at a power density of 2433.8 mW m−2, a high transmittance modulation of 63% at 600 nm, and a distinct transparent-to-deep blue coloration during the Al-ion shuttling processes.

ispartof: ADVANCED FUNCTIONAL MATERIALS vol:33 issue:4 status: published

Carbon group element‐based materials are the most widely used anode materials for Li‐ion batteries (LIBs). However, their performance is limited by the low capacity (eg, graphite) or high‐volume changes (eg, Si and Sn). Therefore, exploring high‐performance anode materials is quite appealing and promising. By first‐principle calculations in this study, we found that distorted T‐carbon (DTC) as a desired LIB anode shows properties of the enhanced capacity, decreased volume change, and the increased ion migration. The origin of such improved properties is attributed to the interconnected tunnels and large cavities of the carbon skeleton. The theoretical specific capacity of DTC is found to be 558 mAh/g, which is 1.5 times higher than that of commercial graphite anodes. Interestingly, the volume change of the DTC anode is only 3% at the full‐lithiation state (one‐fifth of that of the commercial graphite anode), which can overcome the pulverization problem in most high‐capacity anode materials and attain a longer cycling lifetime. Both transition state calculations and molecular dynamics simulations demonstrate that the Li‐ion migration barrier is less than 0.1 eV and the Li‐ion vacancy is only 0.2 eV, enabling its promising rate performance. This study provides a new and effective strategy to improve the anode properties of LIBs.

The design and development of electrocatalysts composed of non-noble-metal catalysts with both large surface area and high electrical conductivities are crucial for the hydrogen evolution reaction (HER). Here, a xylose-based porous carbon is coupled with a MoS2−MoP heterojunction (MoS2−MoP/FPC) hybrid and used as a promising catalyst for HER. The hybrid is prepared by immobilizing petal-like MoS2 nanosheets on porous carbon (MoS2/FPC), followed by controlling the phosphidation in Ar/H2 to form MoS2−MoP/FPC. Red phosphorus provides the P species that can induce the construction of the heterojunction under the reducing atmosphere, along with the generation of a MoP phase and the splitting of the MoS2 phase. The as-prepared MoS2−MoP/FPC catalyst offers a low overpotential of 144 mV at a current density of 10 mA cm−2 and a small Tafel slope of 41 mV dec−1 for the HER in acidic media, as well as remarkable stability. Apart from the active nature of the hybrid, its outstanding activity is attributed to the MoS2−MoP heterojunction, and the good charge/mass-transfer ability of porous carbon. This strategy provides a new method to develop and design low-cost and high-performance catalysts for the HER.

Photocatalytic water splitting taking the advantage of using solar energy directly is one of the most effective strategies for hydrogen evolution. The development of facile methods for synthesizing highly efficient and stable photocatalysts for hydrogen production still remains a great challenge. Herein, a metal-organic framework (MOF)-templated strategy was designed for the synthesis of solid solutions of (Zn0.95Cu0.05)1-xCdxS that exhibit outstanding photocatalytic hydrogen production reaction activity. More importantly, efficient light capturing ability and photogenerated charges separation were accomplished via fine-tuning the composition of the photocatalysts by adjusting the concentrations of doping metals in the template MOFs. Under visible light (λ > 420 nm), an optimized nanocatalyst, (Zn0.95Cu0.05)0.6Cd0.4S, exhibited a higher durability and satisfied photocatalytic hydrogen evolution rate of 4150.1 μmol g-1 h-1 of water splitting.

Controlling interface gas adsorption properties of carbon materials is a prerequisite for exploiting efficient metal-free electrocatalysts but it is usually ignored. Herein, we fabricate a hierarchical porous carbon electrocatalyst with defect (DHPC) by carbon thermal reaction, which shows good CO2RR selectivity and stability. The experimental results indicated that the carbon defect might be the active center for efficient CO2RR performance because it can serve as a Lewis base center and provide an appropriate CO2-chemisorption energy. Moreover, X-ray absorption spectroscopy (XAS) results demonstrated that the carbon defect can induce a reversible carbon–carbon interface with CO2 gas molecule, which would be further strengthened under an applied bias. Besides, the 13CO2 isotope labelling experiment and density functional theory calculations further confirmed that the high CO2RR performance of DHPC comes from its intrinsic defect sites. This study not only provides a new avenue and concept to design CO2RR electrocatalysts but also, to some extent, indicates a possible catalytic mechanism for carbon defect-based electrocatalysts.

Data-driven fault diagnosis is critical for the rolling bearing to improve its healthy states and save invaluable cost. Nowadays, various intelligent fault diagnosis methods using machine learning (ML) or deep learning (DL) techniques have achieved much success. The convolutional neural network (CNN) based method, as a representative DL technique, can extract the features of raw data automatically for its excellent sparse connectivity and weight sharing properties. In this paper, a novel data-driven intelligent fault diagnosis method of rolling bearing under variable working loads has been proposed by using 1-D stacked dilated convolutional neural network (1D-SDCNN). First, 1-D vibration signals were used as input data without additional signal processing and diagnostic expertise. Second, the stacked dilated convolution, which can capture larger scale associated information and achieve large receptive fields with a few layers, was used to replace the traditional convolution and pooling structure. Third, the 1D-SDCNN architecture was flexible which is based on the relationship between receptive fields and the length of the input signal. And the number of network layers can be adjusted according to signal length. Further, it can adapt to the changing working loads of the mechanical environment. Finally, the effectiveness of the proposed method was confirmed through the experiment. And the results demonstrated that 1D-SDCNN was able to learn in-deep features under three variable working loads and the average accuracy was 96.8%.

Electrocatalytic organic compound oxidation reactions (OCORs) have been intensively studied for energy and environmentally benign applications. However, relatively little effort has been devoted to developing a fundamental understanding of OCORs, including the detailed competition with side reactions and activity limitations, thus inhibiting the rational design of high-performance electrocatalysts. Herein, by taking the NiWO4-catalysed urea oxidation reaction (UOR) in aqueous media as an example, the competition between the OCOR and the oxygen evolution reaction (OER) within a wide potential range is examined. It is shown that the root of the competition can be ascribed to insufficient surface concentration of dynamic Ni3+, an active site shared by both the UOR and OER. A similar phenomenon is observed in other OCOR electrocatalysts and systems. To address the issue, a “controllable reconstruction of pseudo-crystalline bimetal oxides” design strategy is proposed to maximise the dynamic Ni3+ population and manipulate the competition between the UOR and the OER. The optimised electrocatalyst delivers best-in-class performance and an ∼10-fold increase in current density at 1.6 V versus the reversible hydrogen electrode for alkaline urea electrolysis compared to those of the pristine materials.

A novel metallic carbon allotrope, Q-carbon, was discovered using first-principles calculations. The named Q-carbon possessed a three-dimensional (3D) cage structure formed by carbon atoms with three ligands. The energy distribution of electrons in different orbitals revealed that Q-carbon has a low degree of s-p orbital hybridization. The calculated Li

Sodium-ion (Na-ion) hybrid capacitors as a novel electrochemical energy storage device have triggered considerable attention in recent years. However, the sluggish kinetics at anode and low specific capacity at cathode greatly hinder the overall performance output of Na-ion hybrid capacitors. Herein, we design a high-performance quasi-solid-state Na-ion hybrid capacitor assembled with the Mo2N quantum dots coupled carbon nanotubes as anode, decoupled hierarchical carbon nanotubes as cathode, and a porous poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) membrane based gel electrolyte. For the anode, the uniformly dispersed Mo2N quantum dots offer abundant ion-accessible active sites and shortened ion diffusion path, which effectively accelerate Na ion storage kinetics. After decoupling and activation, the hierarchical carbon nanotubes with high specific surface area and numerous in-plane nanopores contribute to fast reversible anion adsorption and desorption, greatly boosting the specific capacity. Additionally, the low-tortuosity nanotubular electrode microstructure with open framework is conducive to unimpeded electrolyte ion permeation and thereby can maximize the utilization of active materials. Benefiting from the elaborate electrode architecture engineering and rational device configuration, the assembled quasi-solid-state Na-ion hybrid capacitor can achieve a high energy density of 100.6 Wh kg−1 at a power density of 117.5 W kg−1, which is among the best compared with other Na-ion hybrid capacitors. The demonstration of proof-of-concept of the quasi-solid-state Na-ion hybrid capacitors offers new insights into rational design of high-energy-density hybrid energy storage systems.

To solve the agglomeration of Fe and low electronic conductivity of FeP anode, a simple route through metal organic framework (MOF)-derived phosphorization has been successfully explored for in-situ encapsulation of FeP nanoparticles in porous carbon framework (FeP@C). The MOF-derived FeP@C anode can substantially inhibit the coarsening of small Fe, improve the electroconductivity and moderate the volume expansion of electrode, leading to superior rate capability and excellent cycling performance for Li-, Na- and K-ions storage. For example, the FeP@C anode delivers a high reversible capacity of 700 mAh g−1 at 0.1 A g−1 over 180 cycles for Li-ion batteries, displays a high reversible capacity of 387 mAh g−1 at 0.1 A g−1 over 100 cycles for Na-ion batteries and achieve a high reversible capacity of 163 mAh g−1 at 0.2 A g−1 over 100 cycles for K-ion batteries. The kinetic analysis, calculated diffusion coefficient and partial density of states (PDOS) results also confirmed this in-situ carbon encapsulated strategy improves the conductivity of FeP particles facilitating the alkali-ion/electron's transportation.

Strong metal oxide-support interaction is crucial to activate high energy storage modes of carbon-supported hybrid electrodes in ionic liquid-based supercapacitors. Although it is known that conductive supports can influence the electrochemical properties of metal oxides, insights into how metal oxide-support interactions can be exploited to optimize joint energy storage properties are lacking. We report the junction between alpha-Fe2O3 nanosplotches and phosphorus-doped ordered mesoporous carbon (CMK-3-P) with strong covalent anchoring of the metal oxide. The oxide-carbon interaction in CMK-3-P-Fe2O3 is strengthening the junction and charge transfer between Fe2O3 and CMK-3-P. It enhances energy storage by intensifying the interaction between ionic liquid ions and the surface of the electrode. Density functional theory simulations reveal that the strong metal oxide-support interaction increases the adsorption energy of ionic liquid to -4.77 eV as compared to -3.85 eV for a CMK-3Fe(2)O(3) hybrid with weaker binding. In spite of the lower specific surface area and apparently similar energy storage mode, the CMK-3-P-Fe2O3 exhibits superior electrical double-layer capacitor performance with a specific capacitance of 179 F g(-1) at 2 mV s(-1) (0-3.5 V) in comparison to Fe2O3-free CMK-3 and CMK-3-P reference materials. This principle for design of hybrid electrodes can be applicable for future rational design of stable metal oxide-support electrodes for advanced energy storage.

Transition metal sulfides are deemed as attractive anode materials for potassium-ion batteries (KIBs) due to their high theoretical capacities based on conversion and alloying reaction. However, the main challenges are the low electronic conductivity, huge volume expansion, and consequent formation of unstable solid electrolyte interphase (SEI) upon potassiation/depotassiation. Herein, zinc sulfide dendrites deeply nested in the tertiary hierarchical structure through a solvothermal-pyrolysis process are designed as an anode material for KIBs. The tertiary hierarchical structure is composed of the primary ultrafine ZnS nanorods, the secondary carbon nanosphere, and the tertiary carbon-encapsulated ZnS subunits nanosphere structure. The architectural design of this material provides a stable diffusion path and enhances effective conductivity from the interior to exterior for both K

To improve the solar energy utilization and photodegradation efficiency of ZnO and α-MnO2, ZnO/MnO2 composite materials were prepared by a facile method. The materials are characterized by XRD, Raman spectra, X-ray photoelectron spectroscopy, scanning electronic microscopy, transmission electron microscopy, and UV–vis diffuse reflection spectroscopy. The photocatalytic activity and microwave-assisted photocatalytic activity of the composite are much higher than that of ZnO or α-MnO2. The main active species in the reaction progress were confirmed by electron paramagnetic resonance spectra and trapping experiments. According to the DFT calculation result and photothermal images, the enhanced catalytic activity is attributed to the photothermal and microwave-assisted effect. The addition of α-MnO2 improves the absorption of light and microwave by the composite, which can further heat up the catalysts. As a result, the separation of photogenerated charge carriers is accelerated. Finally, a mechanism for the enhanced catalytic performance of the composite materials was proposed.

Transition-metal nitrides (TMNs), especially iron-based TMNs, have high electrical conductivity, superior chemical stability and unique oxygen-reaction ability, and have emerged as a new form of noble metal-free electrocatalysts. In this paper, we demonstrate that the ORR-active/OER-inert single function catalyst Fe-N can be made as the OER/ORR-active bifunctional catalyst Co-Fe-N by controlled substitution of Fe with Co. To obtain atomic insights of the Co-enhanced OER catalysis, we develop a new exfoliation method to prepare atomically thin (1.1 nm) nanosheets (NSs) of CoxFe1-xN0.5 (x = 0, 0.05, 0.1, 0.15 and 0.2). Our studies show that both electronic structure and local binding environment of Fe are modified by Co substitution and the Co-Fe-N NSs show a volcano−like OER catalysis with Co0.15Fe0.85N0.5 NSs being the most efficient OER catalyst, showing the lowest overpotential of 266 mV at 10 mA cm−2, a Tafel slope of ∼30 mV dec−1, and excellent stability in the 1.0 M KOH OER condition. Density functional theory (DFT) calculations suggest that the Co-Fe sites in the Co0.15Fe0.85N0.5 structure are optimized to promote OH* to O* conversion, O*-O* coupling and O2 formation. The Co0.15Fe0.85N0.5 NSs are a class of new noble-metal-free catalyst for OER.

Optimal path planning is required in autonomous navigation and intelligent control of the unmanned aerial vehicle (UAV). However, as a kind of common obstacles in complex three-dimensional (3-D) spaces, U-type obstacles may cause UAV to be confused and even lead to a collision or out of control. Although most of the Ant Colony Optimization (ACO) algorithm can generate proper path, solutions to U-type obstacles based on the specific behaviors of each ant are investigated rarely. Hence, different search strategies are studied and a novel ACO-based method called Self-Heuristic Ant (SHA) is proposed in this paper. The whole space is constructed by grid workspace model firstly, and then a new optimal function for UAV path planning is built. To avoid ACO deadlock state (i.e., ants are trapped in U-type obstacles when there is no optional successor node), two different search strategies are designed for choosing the next path node. In addition, the SHA is utilized to improve the ability of the basic ACO-based method. Specifically, besides pheromone update, a new information communion mechanism is fused to deal with the special areas which contain dense obstacles or many concave blocks. Finally, several experiments are investigated deeply. The results show that the deadlock state can be reduced effectively by the designed two different search strategies of ants. More importantly, compared with the conventional fallback strategy, the average number of retreats and the average running time of ACO can be reduced when SHA is applied.

The multi-metallene with an ultrahigh surface area has great potential in precise tuning of surface heterogeneous d-electronic correlation by surface strain effect for the distinctive surface electronic structure, which is a brand new class of promising 2D electrocatalyst for sustainable energy device application. However, achieving such an atomically thin multi-metallene still presents a great challenge. Herein, we present a new synthetic method for an atomic-level palladium-iridium (PdIr) bimetallene with an average thickness of only ∼1.0 nm for achieving superior catalysis in the hydrogen evolution reaction (HER) and the formic acid oxidation reaction (FAOR). The curved PdIr bimetallene presents a top-ranked high electrochemical active area of 127.5 ± 10.8 m2 gPd+Ir−1 in the reported noble alloy materials, and exhibits a very low overpotential, ultrahigh activity and improved stability for HER and FAOR. DFT calculation reveals that the PdIr bimetallene herein has a unique lattice tangential strain, which can induce surface distortion while concurrently creating a variety of concave-convex featured micro-active regions formed by variously coordinated Pd sites agglomeration. Such a strong strain effect correlates the abnormal on-site active 4d10-t2g-orbital Coulomb correlation potential and directly elevates orbital-electronegativity exposure within these active regions, resulting in a preeminent barrier-free energetic path for significant enhancement of FAOR and HER catalytic performance., This work reports the first-time synthesis of palladium-iridium bimetallene with lattice tangential strain, which achieves superior catalysis for hydrogen evolution reaction and formic acid oxidation reaction.

Photocatalytic water splitting taking the advantage of using solar energy directly is one of the most effective strategies for hydrogen evolution. The development of facile methods for synthesizing highly efficient and stable photocatalysts for hydrogen production still remains a great challenge. Herein, a metal-organic framework (MOF)-templated strategy was designed for the synthesis of solid solutions of (Zn

The welding of thick W onto Cu, with good bonding, has been a big challenge due to the large differences in physical properties between W and Cu. Among various novel methods, explosive welding is the promising one to produce bimetals with large size and great thickness. However, the cracking of brittle W under high strain rate limits its application. In this work, hot-explosive welding technique was explored to overcome this problem. A 2 mm thick W plate was preheated to 500 ℃ and was successfully welded with pure Cu plate, without any cracks formed in W layer. The result suggests that preheating W to over its dynamic ductile-to-brittle transition temperature and decreasing the imported kinetic energy are two most important factors for the successful welding of thick W plate. The weldability window calculated using the parameters at 500 °C predicted the formation of a good wavy interface. The microstructures at W-Cu interface were characterized by optical microscope, SEM, EBSD and TEM. The mechanically mixed W-Cu phase and the 2∼6 nm thick amorphous layer along the interface created strong bonding between the immiscible W and Cu. The measured interfacial compressive shear strength reached 188 MPa, indicating a good bonding strength of the interface.

Neutral aqueous zinc–air batteries (ZABs) are an emerging type of energy devices with substantially elongated lifetime and improved recyclability compared to conventional alkaline ZABs. However, their development is impeded by the lack of robust bifunctional catalyst at the air-electrode for the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR). Here, we report the controlled synthesis of NiFe2O4/FeNi2S4 heterostructured nanosheets (HNSs) that are highly efficient in catalyzing OER and ORR, therefore enabling neutral rechargeable ZABs. Associated with the formation of abundant oxide/sulfide interfaces over NiFe2O4/FeNi2S4 HNSs’ surfaces, the catalyst’s oxygen binding energy can be effectively tuned to enhance the OER and ORR activities, as revealed by the density functional theory calculations. In 0.2 M phosphate buffer solution, the optimized NiFe2O4/FeNi2S4 HNSs present an excellent oxygen electrocatalytic activity and stability, with much lower OER and ORR overpotentials than sing...

3D-hydrogels have broad potential for wastewater treatment, for they are separation-free and have excellent adsorption capacity. However, the process of adsorption is only the enrichment of pollutants rather than elimination. Development of 3D-hydrogel/photocatalyst composite materials is a promising strategy for achieving the enrichment and mineralization of organic pollutants. This paper describes a facile and environmentally friendly synthesis of separation-free polyacrylamide/bentonite/graphitic carbon nitride 3D-hydrogel. When the mass of graphitic carbon nitride is 1/10 of acrylamide, the composite hydrogel displays excellent removal of tetracycline in both static and flowing state. The total removal efficiency is higher than that of adsorption or degradation. The enhanced removal of organic pollutants is attributed to the synergistic effect of adsorption and photocatalytic degradation, the enhanced light absorption and the accelerated separation of photogenerated charge carriers. More importantly, it has excellent stability and can be easily separated from water and reused. This 3D-hydrogel/photocatalyst composite materials has broad application potential to the elimination of organic pollutants in water.

Over the past several decades, extensive efforts have been undertaken to find methods to synthesize advanced electrocatalysts that possess rationally controllable sizes, shapes, crystallinities, compositions and structures for efficient energy conversion technologies. Of these methods, the one-pot seedless synthetic method in aqueous solution at ambient temperature has attracted extensive attention from researchers because it is a simple, inexpensive, energy-efficient, safe and less toxic method for the synthesis of electrocatalytic nanomaterials. In this review, recent developments in one-pot seedless synthetic strategies for the design of various structures of Au, Pt, Pd, Ag and multimetallic nanocrystals in aqueous solutions at ambient temperatures will be introduced, primarily focusing on the structure–electrocatalytic performance relationships of the as-prepared metal nanocrystals. Current challenges and outlooks for future research directions will also be provided in this promising research field.

The development of highly efficient and durable electrocatalysts for high-performance overall water-splitting devices is crucial for clean energy conversion. However, the existing electrocatalysts still suffer from low catalytic efficiency, and need a large overpotential to drive the overall water-splitting reactions. Herein, we report an iridium–tungsten alloy with nanodendritic structure (IrW ND) as a new class of high-performance and pH-universal bifunctional electrocatalysts for hydrogen and oxygen evolution catalysis. The IrW ND catalyst presents a hydrogen generation rate ∼2 times higher than that of the commercial Pt/C catalyst in both acid and alkaline media, which is among the most active hydrogen evolution reaction (HER) catalysts yet reported. The density functional theory (DFT) calculations reveal that the high HER intrinsic catalytic activity results from the suitable hydrogen and hydroxyl binding energies, which can accelerate the rate-determining step of the HER in acid and alkaline media. Moreover, the IrW NDs show superb oxygen evolution reaction (OER) activity and much improved stability over Ir. The theoretical calculation demonstrates that alloying Ir metal with W can stabilize the formed active iridium oxide during the OER process and lower the binding energy of reaction intermediates, thus improving the Ir corrosion resistance and OER kinetics. Furthermore, the overall water-splitting devices driven by IrW NDs can work in a wide pH range and achieve a current density of 10 mA cm–2 in acid electrolyte at a low potential of 1.48 V., We report a nanodendritic IrW alloy as a new class of high-performance overall water-splitting catalyst at all pH values, with optimized intermediate binding energy and enhanced corrosion resistance.

Electrocatalysts with a high efficiency and durability for the hydrogen evolution reaction (HER) hold tremendous promise for next-generation energy conversion. Among the state-of-art catalysts for HER, organic-inorganic hybrid nanosheets exhibit a great potential with the merits of high activity, good durability, and low cost. Nevertheless, there is no general method for the synthesis of binary metal phosphide hybrid nanosheet HER catalysts with a tunable morphology and composition. Herein, we report a facile approach for the synthesis of nanosheets consisting of a binary cobalt nickel phosphide hybrid with a hierarchically porous nanostructures using an oxidation- phosphorization process. The as-optimized hybrid nanosheets annealed at 350 °C yield the highest pH-universal activity with overpotentials of 148, 111, and 173 mV in acidic, alkaline, and neutral media, respectively. Besides the promoted mass diffusion in the hierarchically porous structure, the extraordinary performance can be also attributed to the weakened adsorption of hydrogen as a result of the tunable composition of Co and Ni, which was revealed by first-principles calculations.

Photocatalytic water splitting for hydrogen production using sustainable sunlight is a promising alternative to industrial hydrogen production. However, the scarcity of highly active, recyclable, inexpensive photocatalysts impedes the development of photocatalytic hydrogen evolution reaction (HER) schemes. Herein, a metal-organic framework (MOF)-template strategy was developed to prepare non-noble metal co-catalyst/solid solution heterojunction NiS/Znx Cd1-x S with superior photocatalytic HER activity. By adjusting the doping metal concentration in MOFs, the chemical compositions and band gaps of the heterojunctions can be fine-tuned, and the light absorption capacity and photocatalytic activity were further optimized. NiS/Zn0.5 Cd0.5 S exhibits an optimal HER rate of 16.78 mmol g-1 h-1 and high stability and recyclability under visible-light irradiation (λ>420 nm). Detailed characterizations and in-depth DFT calculations reveal the relationship between the heterojunction and photocatalytic activity and confirm the importance of NiS in accelerating the water dissociation kinetics, which is a crucial factor for photocatalytic HER.

A Zr53Cu35Al12 bulk metallic glass (BMG) was welded to a crystalline Cu using explosive welding technique. The morphology and the composition of the composite were characterized using optical microscopy, scanning electron microscopy, energy-dispersive x-ray spectroscopy and transmission electron microscopy. The investigation indicated that the BMG and Cu were tightly joined together without visible defects, and a thin diffusion layer appeared at the interface. The captured jet at the end of the welding region mostly comes from the Cu side. Amorphous and partially crystallized structures have been observed within the diffusion layer, but the BMG in close proximity to the interface still retains its amorphous state. Nanoindentation tests reveal that the interface exhibits an increment in hardness compared with the matrix on both sides.

Silicon (Si) is a promising anode candidate for lithium-ion batteries (LIBs) owing to its unprecedented theoretical capacity of 4200 mA h g−1 and earth-abundant supply (26.2 wt%). Nevertheless, the huge volume expansion and unstable solid-electrolyte interface (SEI) of Si in multiple cycles make it very hard to simultaneously achieve high-energy and long-term cycle life for applications in large-scale renewable energy storage. Herein, we demonstrate a new class of Si/SiOx@void@nitrogen-doped carbon double-shelled hollow superstructure (Si/SiOx-DSHS) electrodes that are capable of accommodating huge volume changes without pulverization during cycling. Benefiting from the unique double-shelled hollow superstructure, Si/SiOx-DSHSs can facilitate the formation of a highly stable SEI layer and provide superior kinetics toward Li+-ion storage. The diffusion-controlled process and the capacitance-type reaction can work together to endow Si/SiOx-DSHSs with remarkable electrochemical characteristics, especially at high current density. These important characteristics make Si/SiOx-DSHSs deliver a large reversible capacity (1290 mA h g−1 at 0.1C), high first-cycle coulombic efficiency (71.7%), superior rate capability (360 mA h g−1 at 10C), and excellent cycling behavior up to 1000 cycles with a small capacity decay of 10.2%. The Si/SiOx-DSHSs are among the best Si-based anode materials for LIBs reported to date.

First-principles calculations based on density functional theory were performed to investigate the electrochemical properties of K1−xVOPO4 in potassium-ion batteries (KIBs). The material showed multiple phase transitions during K ion extraction, which began with a two-phase transition (0 ≤ x ≤ 0.5), followed by a solid-solution transition (0.5 < x ≤ 0.625), another two-phase transition (0.625 < x ≤ 0.75), and finally a solid-solution transition (0.75 < x ≤ 1). These processes resulted in a small total unit cell volume variation of 6.6%, which was beneficial for the cycle stability of KIBs. Density of states and Bader charge analysis revealed that both V and O participated in the charge transfer process, where V acted as the redox center of KVOPO4 contributing to the K storage capacity, and O acted as a charge transfer medium between V and K. The stepwise increased repulsion between V cations caused three voltage plateaus for K1−xVOPO4. In addition, the one-dimensional diffusion pathway for K ions with low energy barriers of 0.214–0.491 eV ensured high K ion mobility resulting in superior high rate capability.

Hierarchical MoS 2 -reduced graphene oxide (RGO) nanocomposites were successfully synthesized via a hydrothermal synthesis approach, and their morphology, crystal structure of the composites as well as the photocatalytic activities in the degradation of methylene blue (MB) were investigated using scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and UV–vis absorption spectroscopy. The results demonstrated that the MoS 2 -RGO nanocomposites exhibited excellent photocatalytic performance with a maximum degradation rate up to 80% under visible light irradiation for 30 min. To understand the origin of the excellent photocatalytic properties, first-principles calculations were also carried out. It manifested that the excellent photocatalytic activity should be resulted from the existence of the potential electron transfer between conduction band maximum (CBM) of MoS 2 and CBM of RGO. Meanwhile, the enhanced visible light absorption, reduced electron–hole pair recombination, and enhanced surface area for absorption of dyes also could be the factors for the excellent photocatalytic performance.

The ever-increasing power and energy demands for modern consumer electronics and electric vehicles are driving the pursuit of energy-storage technologies beyond the current horizon. Pseudocapacitive charge storage is one of the most effective and promising approaches to fill this technology gap, owing to its potential to deliver both high power and energy densities. Typically, titanium niobium oxides (TiNbxO2+2.5x (x = 2, 5 and 24)) with intrinsic pseudocapacitance, high safety and theoretical capacities of 388–402 mA h g−1 are recognized as promising anode materials for lithium-ion batteries. However, their poor conductivity and low Li+-ion diffusion coefficient are known to be the major hurdles limiting the full utilization of their pseudocapacitive effects, leading to their lackluster rate capabilities. Herein, we employ a facile electrospinning method to prepare one-dimensional hierarchically porous ZrNb24O62 nanowires (P-ZrNb24O62) with an ultra-large Li+-ion diffusion coefficient as a new intercalating pseudocapacitive material for boosting Li+-ion storage. The P-ZrNb24O62 exhibits excellent electrochemical performances, including a high reversible capacity (320 mA h g−1 at 0.1C), safe working potential (∼1.67 V vs. Li/Li+), high initial coulombic efficiency (90.1%), outstanding rate capability (182 mA h g−1 at 30C) and durable long-term cyclability (90.2% capacity retention over 1500 cycles).

In this work, we for the first time synthesized nitrogen, boron co-doped curved graphene nanoribbons (NBCGNs) by a facile hydrothermal process using oxidized curved graphene nanoribbons (O-CGNs), urea and boric acid as the carbon precursor and heteroatom sources. The influence of N and B co-doping on the morphology, structure, composition and related electrochemical performance of the NBCGNs was systematically investigated, and the results show that urea and boric acid coexisting in the hydrothermal system not only act as the N and B doping sources but also act as the catalysts to boost the synergistical doping of N and B. It is the synergistical effect of N and B co-doping that endows the NBCGNs with enlarged specific surface area as well as pore volume, improved conductivity, promoted sulfur dispersibility and strengthened adsorbability for polysulfides caused by the notably increased doped N and B contents and higher percentage of the N–B structure when compared with the counterparts. As a result, the as-prepared NBCGN/S cathode presented synergistically enhanced cyclability and rate capability. Therefore, our results not only provide a superior carbon host for Li–S batteries but also offer a common approach to the preparation of heteroatom doped carbon nanomaterials with an optimized structure and composition.

Unraveling the effect of transition-metal doping on the energy storage properties of bimetallic sulfides remains a grand challenge. Herein, we construct bimetallic sulfide nanosheets and hence deliberately introduce transition-metal doping domains on their surface. The resulting materials show not only an enhanced density of states near the Fermi level but also partially delocalized charge as shown by density functional theory (DFT) calculations. Fe-doped NiCo2S4 nanosheets wrapped on N,S-doped ordered mesoporous carbon (Fe-NiCo2S4@N,S-CMK-3) are prepared, which show an enhanced specific capacitance of 197.8 F g(-1) in ionic liquid-based supercapacitors at a scan rate of 2 mV s(-1). This is significantly higher as compared to the capacitance of 155.2 and 135.9 F g(-1) of non-iron-doped NiCo2S4@N,S-CMK and Fe-NiCo2S4@CMK-3 electrodes, respectively. This result arises from the enhanced ionic liquid polarization effect and transportation ability from the Fe-NiCo2S4 surface and N,S-CMK-3 structure. Furthermore, the importance of matching multi-dimensional structures and ionic liquid ion sizes in the fabrication of asymmetric supercapacitors (ASCs) is demonstrated. As a result, the ASC device exhibits a high energy density of 107.5 W h kg(-1) at a power density of 100 W kg(-1) in a working-voltage window of 4 V when using Fe-NiCo2S4@N,S-CMK-3 and N,S-CMK-3 as positive and negative electrodes, respectively. This work puts forward a new direction to design supercapacitor composite electrodes for efficient ionic liquid coupling.

Potassium-ion batteries (KIBs) have come into the spotlight in large-scale energy storage systems because of cost-effective and abundant potassium resources. However, the poor rate performance and problematic cycle life of existing electrode materials are the main bottlenecks to future potential applications. Here, the first example of preparing 3D hierarchical nanoboxes multidimensionally assembled from interlayer-expanded nano-2D MoS2 @dot-like Co9 S8 embedded into a nitrogen and sulfur codoped porous carbon matrix (Co9 S8 /NSC@MoS2 @NSC) for greatly boosting the electrochemical properties of KIBs in terms of reversible capacity, rate capability, and cycling lifespan, is reported. Benefiting from the synergistic effects, Co9 S8 /NSC@MoS2 @NSC manifest a very high reversible capacity of 403 mAh g-1 at 100 mA g-1 after 100 cycles, an unprecedented rate capability of 141 mAh g-1 at 3000 mA g-1 over 800 cycles, and a negligible capacity decay of 0.02% cycle-1 , boosting promising applications in high-performance KIBs. Density functional theory calculations demonstrate that Co9 S8 /NSC@MoS2 @NSC nanoboxes have large adsorption energy and low diffusion barriers during K-ion storage reactions, implying fast K-ion diffusion capability. This work may enlighten the design and construction of advanced electrode materials combined with strong chemical bonding and integrated functional advantages for future large-scale stationary energy storage.

Due to the brittleness of molybdenum (Mo) and high difference in melting point, it is still a challenge to clad thick Mo onto copper (Cu) with high quality bonding. In this study, a 5 mm thick Mo plate was successfully welded with Cu plate by hot explosive welding, without any cracks being formed. The maximum shear strength of the interface exceeded 295 MPa. The calculated weldability window indicated that the welding was achieved with the parameters close to the lower boundary, and successfully predicted the wavy interfaces. The interfacial microstructures were investigated by scanning electron microscope, electron backscatter diffraction and transmission electron microscopy, the results showed that the dislocations in Cu were higher than the Mo side and the evolutions of interfacial structure due to severe deformation, such as misorientation angle, recrystallization and texture, were quite different for Mo and Cu.

In this work, seven novel phases of phosphorene were predicted to be existent by first-principles calculations, including six kinds of enantiomers corresponding to three kinds of structures with chirality. It is the first time to introduce chirality into two-dimensional (2D) phosphorus. The Poisson’s ratios have been investigated and show normal behavior, rather than the negative one of monolayer or bulk black phosphorus, due to the structures being non-puckered. Phase transformations of these enantiomers have been studied, revealing that there exists the possibility of transformations between them because of the energy barriers being low, which opens doors to possible applications in shape memory devices. This work may inspire new ideas of developing novel applications based on 2D phosphorus nanomaterials.

We investigated the existence possibility of homo-elemental bond BN porous nanosheet (homo-pBN) and homo-elemental bonding inorganic graphenylene (hIGP) by first principle simulation calculation and tuned down their band gap by the means of doping organic molecules. We studied the structure and charge population of BN porous nanosheet with homo-elemental N–N bond (pBNhN), BN porous nanosheet with homo-elemental B–B bond (pBNhB) and hIGP. Meanwhile, calculations show that they transferred charge to (from) organic molecules. The donor (TTF) and the acceptor (TCNQ) make BN structure transfer to n-type semiconductor and p-type semiconductor, respectively. Furthermore, band gap is significantly reduced when the donor and the acceptor are simultaneously adopted as a couple. This investigation may inspire the possibility of developing electronic material made by BN structure of 2-dimensional group.