Sublayer-Sulfur-Vacancy-Induced Charge Redistribution of FeCuS Nanoflower Awakening Alkaline Hydrogen Evolution.

Advancing the progress of sustainable and green energy technologies requires the improvement of valid electrocatalysts for the hydrogen evolution reaction (HER). Reconfiguring charge distribution through heteroatom doping-induced vacancy serves as an effective approach to implement high performance for HER catalysts. Here, we successfully fabricated Fe-doped CuS (FeCuS) with the sublayer sulfur vacancy to judge its HER performance and dissect the activity origins. Density functional theory calculation further elucidates that the primary factor contributing to the heightened HER activity is that the sublayer sulfur vacancies awaken the charge redistribution. In addition to effectively decreasing the energy barrier associated with the Volmer step, it modulates the adsorption/desorption capacity of H*. As a result, its intrinsic activity for the HER has significantly increased. Concretely, the obtained FeCuS displays an excellent catalytic performance, whose Tafel slope is only 59 mV dec-1 and the overpotential (at 10 mA cm-2) is as low as 71 mV in an alkaline environment, surpassing the majority of previously documented catalysts in scientific literature. This work shows that the construction of sublayer sulfur vacancies by Fe doping can achieve the charge redistribution and precise tuning of electronic structure; thereby, the inert CuS can be transformed into highly efficient electrocatalysts.

Fabrication and Process Optimization of Chinese Fir-Derived SiC Ceramic with High-Performance Friction Properties.

In this study, a novel friction material with biomass-ceramic (SiC) dual matrixes was fabricated using Chinese fir pyrocarbon via the liquid-phase silicon infiltration and in situ growth method. SiC can be grown in situ on the surface of a carbonized wood cell wall by mixing and calcination of wood and Si powder. The samples were characterized using XRD, SEM, and SEM-EDS analysis. Meanwhile, their friction coefficients and wear rates were tested to study their frictional properties. To explore the influence of crucial factors on friction performance, response surface analysis was also conducted to optimize the preparation process. The results showed that longitudinally crossed and disordered SiC nanowhiskers were grown on the carbonized wood cell wall, which could enhance the strength of SiC. The designed biomass-ceramic material had satisfying friction coefficients and low wear rates. The response surface analysis results indicate that the optimal process could be determined (carbon to silicon ratio of 3:7, reaction temperature of 1600 °C, and 5% adhesive dosage). Biomass-ceramic materials utilizing Chinese fir pyrocarbon could display great promise to potentially replace the current iron-copper-based alloy materials used in brake systems.

Assembly of Copolymer and Metal-Organic Framework HKUST-1 to Form Cu2-xS/CNFs Intertwining Network for Efficient Electrocatalytic Hydrogen Evolution.

The construction of complex intertwined networks that provide fast transport pathways for ions/electrons is very important for electrochemical systems such as water splitting, but a challenge. Herein, a three dimensional (3-D) intertwined network of Cu2-xS/CNFs (x = 0 or 0.04) has been synthesized through the morphology-preserved thermal transformation of the intertwined PEG-b-P4VP/ HKUST-1 hybrid networks. The strong interaction between PEG chains and Cu2+ is the key to the successful assembly of PEG-b-P4VP nanofibers and HKUST-1, which inhibits the HKUST-1 to form individual crystalline particles. The obtained Cu2-xS/CNFs composites possess several merits, such as highly exposed active sites, high-speed electronic transmission pathways, open pore structure, etc. Therefore, the 3-D intertwined hierarchical network of Cu2-xS/CNFs displays an excellent electrocatalytic activity for HER, with a low overpotential (η) of 276 mV to reach current densities of 10 mA cm-2, and a smaller Tafel slope of 59 mV dec-1 in alkaline solution.

A novel worm-like micelles@MOFs precursor for constructing hierarchically porous CoP/N-doped carbon networks towards efficient hydrogen evolution reaction.

Constructing electrocatalysts with plentiful active sites, great mass transfer ability, and high electrical conductivity is critical to realize efficient hydrogen evolution reaction (HER). Hierarchically porous cobalt phosphide/N-doped nanotubular carbon networks (CoP/NCNs) that have all the features were fabricated in this work. For the fabrication, the polymeric worm-like micelles (PWs) with a large aspect ratio were coated by a uniform nanolayer of Zn-Co zeolitic imidazolate frameworks (Zn-Co-ZIFs) on their surface, resulting in the hybrid nanofibers PWs@Zn-Co-ZIFs (HPWs). Inheriting the randomly curved and entanglement properity of PWs, the rigid HPWs formed hybrid networks with the packing voids sized tens to 200 nm. Then, the hybrid networks were treated by pyrolysis-oxidation-phosphidation and ZnO-removal processes, leading to the hierarchically porous CoP/NCNs. In the CoP/NCNs, there are plentiful CoP nanoparticles embedded on the surface of conductive carbon network and fully exposed. When used for HER electrocatalyst, the CoP/NCNs only need small overpotentials (98 and 118 mV in acid and alkaline electrolyte) at 10 mA cm-2. This novel strategy is instructive for tailoring hierarchically porous transition metal phosphide/carbon nanocomposites as promising electrocatalysts.

Strengthened Synergistic Effect of Metallic Mx Py (M = Co, Ni, and Cu) and Carbon Layer via Peapod-Like Architecture for Both Hydrogen and Oxygen Evolution Reactions.

The smooth electric transmission is crucial for the high-efficient electrocatalysis. Herein, a series of peapod-like metallic Mx Py /C (M = Co, Ni, and Cu) composites is developed as bifunctional catalysts toward hydrogen and oxygen evolution reactions. For the first time, the metallic property of Cu3 P is confirmed through the theoretical calculation. The in-depth composition, structural and catalytic mechanism analysis of Mx Py /C discloses that the comparable activity and considerable durability of these catalysts mainly result from the strengthened synergistic effect between metallic Mx Py and carbon layer based on the unique peapod-like architecture. Especially, the atomic contact between Mx Py and carbon not only provides an open channel for electronic transmission but also ensures the integrity of peapod-like structure. Furthermore, the high electric conductivity of the inner metallic Mx Py and the outer carbon layer endows the Mx Py /C catalyst with rapid charge migration during the electrocatalytic pathway. These findings shed light on the origin of high catalytic activity of Mx Py /C and open a path for purposefully rationally synthesizing superior electrocatalysts.

Unique Sandwiched Carbon Sheets@Ni-Mn Nanoparticles for Enhanced Oxygen Evolution Reaction.

A unique sandwich-like architecture, where Ni-Mn nanoparticles are enveloped in coupled carbon sheets (CS@Ni-Mn), has been successfully fabricated. In the synthesis process, a great quantity of uniform NiMnO3 nanosheets generated by a universal hydrothermal method acts as precursors and templates and the cheap, environmentally friendly and recyclable glucose functions as a green carbon source. Via subsequent hydrothermal reaction and thermal annealing, sandwiched nanocomposites with Ni-Mn nanoparticles embedded inside and carbon sheets encapsulating outside can be massively prepared. The novel sandwich-like CS@Ni-Mn possesses numerous advantages, such as an intrinsic porous feature, large specific surface area, and enhanced electronic conductivity. Moreover, as a promising NiMn-based oxygen evolution reaction (OER) catalyst, the special sandwiched nanostructure demonstrates improved electrochemical properties in 1 M KOH, including a low overpotential of about 250 mV, a modest Tafel slope of 40 mV dec(-1), excellent stability over 2000 cycles, and durability for 40 h.

Designed Functional Systems for High-Performance Lithium-Ion Batteries Anode: From Solid to Hollow, and to Core-Shell NiCo2O4 Nanoparticles Encapsulated in Ultrathin Carbon Nanosheets.

Binary metal oxides have been considered as ideal and promising anode materials, which can ameliorate and enhance the electrochemical performances of the single metal oxides, such as electronic conductivity, reversible capacity, and structural stability. In this research, we report a rational method to synthesize some novel sandwich-like NiCo2O4@C nanosheets arrays for the first time. The nanostructures exhibit the unique features of solid, hollow, and even core-shell NiCo2O4 nanoparticles encapsulated inside and a graphitized carbon layers coating outside. Compared to the previous reports, these composites demonstrate more excellent electrochemical performances, including superior rate capability and excellent cycling capacity. Therefore, the final conclusion would be given that these multifarious sandwich-like NiCo2O4@C composites could be highly qualified candidates for lithium-ion battery anodes in some special field, in which good capability and high capacity are urgently required.

Tunable and Specific Formation of C@NiCoP Peapods with Enhanced HER Activity and Lithium Storage Performance.

The superior properties of nanomaterials with a special structure can provide prospects for highly efficient water splitting and lithium storage. Herein, we fabricated a series of peapodlike C@Ni2-x Cox P (x≤1) nanocomposites by an anion-exchange pathway. The experimental results indicated that the HER activity of C@Ni2-x Cox P catalyst is strongly related to the Co/Ni ratio, and the C@NiCoP got the highest HER activity with low onset potential of ∼45 mV, small Tafel slope of ∼43 mV dec(-1) , large exchange current density of 0.21 mA cm(-2) , and high long-term durability (60 h) in 0.5 m H2 SO4 solutions. Equally importantly, as an anode electrode for lithium batteries, this peapodlike C@NiCoP nanocomposite gives excellent charge-discharge properties (e.g., specific capacity of 670 mAh g(-1) at 0.2 A g(-1) after 350 cycles, and a reversible capacity of 405 mAh g(-1) at a high current rate of 10 A g(-1) ). The outstanding performance of C@NiCoP in HER and LIBs could be attributed to the synergistic effect of the rational design of peapodlike nanostructures and the introduction of Co element.

A Designed TiO2 /Carbon Nanocomposite as a High-Efficiency Lithium-Ion Battery Anode and Photocatalyst.

Herein, a peapod-like TiO2 /carbon nanocomposite has successfully been synthesized by a rational method for the first time. The novel nanostructure exhibits a distinct feature of TiO2 nanoparticles encapsulated inside and the carbon fiber coating outside. In the synthetic process, H2 Ti3 O7 nanotubes serve as precursors and templates, and glucose molecules act as the green carbon source. With the alliciency of hydrogen bonding between H2 Ti3 O7 and glucose, a thin polymer layer is hydrothermally assembled and subsequently converted into carbon fibers through calcinations under an inert atmosphere. Meanwhile, the precursors of H2 Ti3 O7 nanotubes are transformed into the TiO2 nanoparticles encapsulated in carbon fibers. The achieved unique nanocomposites can be used as excellent anode materials in lithium-ion batteries (LIBs) and photocatalytic reagents in the degradation of rhodamine B. Due to the synergistic effect derived from TiO2 nanoparticles and carbon fibers, the obtained peapod-like TiO2 /carbon cannot only deliver a high specific capacity of 160 mAh g(-1) over 500 cycles in LIBs, but also perform a much faster photodegradation rate than bare TiO2 and P25. Furthermore, owing to the low cost, environmental friendliness as well as abundant source, this novel TiO2 /carbon nanocomposite will have a great potential to be extended to other application fields, such as specific catalysis, gas sensing, and photovoltaics.

A self-supported peapod-like mesoporous TiO2-C array with excellent anode performance in lithium-ion batteries.

Herein, we introduce a novel peapod-like architectural array with TiO2 nanoparticles encapsulated in graphitized carbon fibers for the first time. The unique peapod-like TiO2 arrays with high conductivity architectures are designed and fabricated for application in Li-ion batteries. Since the as-synthesized TiO2 peapod array is characterized with the large surface area derived from the mesoporous carbon fiber, as well as the high conductivity further enhanced by a thin carbon coating layer, it has shown superior rate capability, high specific capacitances, and excellent cycling stability, e.g. the specific capacity can reach up to 162 mA h g(-1) over 200 cycles. A rational and universal approach to fabricate a high-performance TiO2 peapod array for constructing next-generation Li-ion batteries is demonstrated in this paper. Furthermore, due to the specificity of the structure and the versatility of TiO2, the nanocomposite can also be applied in photochemical catalysis, electronics, biomedicine, gas sensing and so on.

Novel peapod-like Ni2P nanoparticles with improved electrochemical properties for hydrogen evolution and lithium storage.

A novel peapod-like Ni2P/C nanocomposite is designed and synthesized using NiNH4PO4H2O nanorods as templates. With enriched nanoporosity and large active surface areas, the peapod-like composites offer superb dual functionality as both electrocatalysts for the hydrogen evolution reaction (HER) and anodes for lithium ion batteries (LIBs). Electrochemical tests demonstrate that the Ni2P/C nanocomposite exhibits an overpotential as low as 60 mV and a notably low Tafel slope of 54 mV dec.(-1). When used as an anode material for lithium-ion batteries, the resulting peapod-like Ni2P/C nanocomposite delivers high specific capacitances of 632 mA h g(-1) at 0.1 A g(-1) and 439 mA h g(-1) at 3 A g(-1), and also exhibits a superior cycling performance, with nearly 100% capacity retention even after 200 charge-discharge cycles at a charge-discharge rate of 0.1 A g(-1). The work demonstrates that the peapod-like materials reported herein are promising materials for electrochemical energy-related applications such as HER and LIBs.

Designed synthesis of transition metal/oxide hierarchical peapods array with the superior lithium storage performance.

In this report, a novel hierarchical peapoded array with Co3O4 nanoparticles encapsulated in graphitized carbon fiber is introduced for the first time. The unique peapoded structure is suitable for the excellent anode in LIBs and demonstrates enhanced rate capability, cyclability and prolonged lifespan, e.g. the specific capacity can reach up to 1150 mAh/g. All the enhanced electrochemical performance is reasonably derived from the peapod-like and aligned conformation. Furthermore, due to the specialty of the structure and the versatility of Co3O4, the composite will find more applications in specific catalysis, biomedicine, electronics, optoelectronic engineering and gas sensing. The fabrication strategy developed here is also a rational and universal approach towards peapod-like architecture and has significantly widened the specific functional material domain we created before. In our design, more peapod-like aligned samples with various nanoparticles, e.g. oxides, phosphides, even nitrides, encapsulated in graphitized carbon fibers, have been lifted on the research agenda and the results will be presented soon.

A general strategy towards encapsulation of nanoparticles in sandwiched graphene sheets and the synergic effect on energy storage.

A novel and universal approach towards the unique encapsulation of nanoparticles in the sandwiched graphene sheets is presented here. In the method, a low-cost, sustainable and environmentally friendly carbon source, glucose, is firstly applied to yield the high-quality, uniform and coupled graphene sheets in a large scale, and the pre-fabricated hydrated nanosheets act as the sacrificial templates to generate the enveloped metallic nanoparticles. After controllable oxidation or removal of the encapsulated nanoparticles, sandwiched nanocomposite with oxidizes nanoparticles encapsulated in graphene sheets or pure phase of sandwich-like and coupled graphene sheets would be achieved. Moreover, the synergic effect on energy storage via Li-ion batteries is solidly verified in the Co(3)O(4)@graphene nanocomposite. More importantly, the unique structure of the nanoparticles-encapsulated sandwiched graphene sheets will definitely result in additional applications, such as biosensors, supercapacitors and specific catalyses. These results have enriched the family of graphene-based materials and recognized some new graphene derivatives, which will be considerably meaningful in chemistry and materials sciences.

Encapsulating magnetic nanoparticles in sandwich-like coupled graphene sheets and beyond.

The first syntheses of a series of novel graphene-based materials, nanoparticle-encapsulated sandwich-like coupled graphene sheets and pure sandwich-like coupled graphene sheets, are reported.