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Developing highly efficient and stable non-precious metal catalysts for water splitting is urgently required. In this work, we report a facile one-step molten salt method for the preparation of self-supporting Ni-doped Mo2C on carbon fiber paper (Ni-Mo2CCB/CFP) for hydrogen evolution reaction (HER). The effects of nickel nitrate concentration on the phase composition, morphology, and electrocatalytic HER performance of Ni-doped Mo2C@CFP electrocatalysts was investigated. With the continuous increase of Ni(NO3)2 concentration, the morphology of Mo2C gradually changes from granular to flower-like, providing larger specific surface area and more active sites. Doping nickel (Ni) into the crystal lattice of Mo2C largely reduces the impedance of the electrocatalysts and enhances their electrocatalytic activity. The as-developed Mo2C-3 M Ni(NO3)2/CFP electrocatalyst exhibits high catalytic activity with a small overpotential of 56 mV at a current density of 10 mA·cm−2. This catalyst has a fast HER kinetics, as demonstrated by a very small Tafel slope of 27.4 mV·dec−1, and persistent long-term stability. A further higher Ni concentration had an adverse effect on the electrocatalytic performance. Density functional theory (DFT) calculations further verified the experimental results. Ni doping could reduce the binding energy of Mo-H, facilitating the desorption of the adsorbed hydrogen (Hads) on the surface, thereby improving the intrinsic catalytic activity of Ni-doped Mo2C-based catalysts. Nevertheless, excessive Ni doping would inhibit the catalytic activity of the electrocatalysts. This work not only provides a simple strategy for the facile preparation of non-precious metal electrocatalysts with high catalytic activity, but also unveils the influence mechanism of the Ni doping concentration on the HER performance of the electrocatalysts from the theoretical perspective.

The kinetic process of a slow oxygen evolution reaction (OER) always constrains the efficiency of overall water electrolysis for H2 production. In particular, nonprecious metal electrodes for the OER have difficulty simultaneously possessing good electrocatalytic activity and long-term stability in pH-universal media. In this work, urea is first used as a pore-forming agent and active C/N source to fabricate a nanoporous NiFeCoCN medium-entropy alloy (MEA) by high-temperature sintering based on the nanoscale Kirkendall effect. The NiFeCoCN MEA achieves an overpotential of 432 mV at a current density of 10 mA cm-2 and a lower Tafel slope of 52.4 mV dec-1 compared to the IrO2/Ti electrode (58.6 mV dec-1) in a 0.5 M H2SO4 solution. In a 1 M KOH solution, the NiFeCoCN MEA obtains an overpotential of 177 mV for 10 mA cm-2 and a Tafel slope of 36.1 mV dec-1, which is better than IrO2/Ni foam. This work proves a novel strategy to design and prepare nanoporous MEA materials with desirable C/N species, which provides promising prospects for the industrial production of H2 energy.

ZrSiO4 demonstrates applicability as the SiC/SiC interphase. Via a non-hydrolyzed sol-gel method, the pyrolysis product, synthesis condition, and the formation effectiveness of the ZrSiO4 coating on SiC fibers were investigated. Mini-SiC/SiC composites with two layers of ZrSiO4 interface coatings were oxidized to preliminarily verify their oxidation resistance effect.

Semiconductor-based photocatalysis represents a promising technology for removing antibiotic given its cost effectiveness and environmental compatibility. However, finding suitable photocatalysts and semiconductors for practical applications can be challenging. This work aims to investigate the photocatalytic performance of as-synthesized photocatalysts under broad-spectrum from visible (Vis) to near-infrared (NIR) sunlight. In this work, a step-scheme (S-scheme) heterojunction photocatalyst, i.e., CuS/S–C3N4, was prepared, employing a single-step hydrothermal route. The synthesized photocatalyst showed excellent crystallinity and high purity content. The CuS loading provided a better NIR light response-ability and improved photocatalytic activity for CuS/S–C3N4. The 2 wt% CuS/S–C3N4 produced the highest tetracycline (TC) photodegradation rate, up to about 95% efficiency under Vis + NIR light irradiation. The result also showed that the 2 wt% CuS/S–C3N4 sample had a first-order kinetic constant (k) that was 6.2-fold higher than the pure S–C3N4 sample under Vis + NIR light irradiation. However, too much CuS content led to the presence of inactive sites on S–C3N4, which hampered the light absorption ability, thus leading to inadequate photocatalytic activity. In addition, the 2 wt% CuS/S–C3N4 sample also showed high photocatalytic stability and insignificant change of the composite structure before and after the experiments. In short, we can enhance the CuS/S–C3N4 photocatalytic activity by increasing the light response range and the separation efficiency of light-induced electrons and holes. Consequently, we have developed a novel strategy and experimental basis for S-scheme heterojunction to be fully utilized under broad-spectrum sunlight.

Semiconductor-metal heterostructure, especially represented by various inorganic semiconductors-platinum (Pt) hybrids, is widely applied in converting solar power to chemical energy. Given the scarcity of Pt and the availability of coupling, the development of a non-Pt regimen and facile assembly strategy is critical. In this study, CdxZn1-xS/Ti3C2 ultrathin MXene composites were availably prepared with a facile electrostatic assembly strategy. The unique 0D/2D assembly demonstrated remarkably enhanced performance toward photocatalytic hydrogen production compared with bare CdxZn1-xS. Spectroscopic characterization analysis and band theory discussion substantiated the effects of electronic interaction and the Schottky barrier arising from intimate contact of CdxZn1-xS and Ti3C2 MXene on the swift separation of photoinduced electron-hole pairs. Successful application of electrostatic self-assembled CdxZn1-xS with ultrathin MXene opens a new area of utilizing electrical difference and band theory to prepare rational semiconductor/MXene Schottky structure towards various photocatalytic reactions.

N-containing Ce2Si2.5Al0.5O3.5N3.5 (CeSiAlON) melilite was synthesized at 1550 and 1600 °C for 5 h from CeO2, Si, Al, and Al2O3 in nitrogen by using Y2O3 and transition-metal nitrates (Co(NO3)2∙6H2O and Ni(NO3)2∙6H2O) as additives. The effects of Y2O3 and transition-metal nitrates on the phase, microstructures and photoluminescence properties of CeSiAlON melilite were studied. The incorporation of Y2O3 can promote the reaction of raw materials to a low degree, and results in a unit cell shrinkage of CeSiAlON due to the smaller radius of Y atom than that of Ce atom. The transition-metal nitrates can accelerate the reaction clearly and facilitate the formation of CeSiAlON fibers. The photoluminescence (PL) properties of CeSiAlON melilite presents a board violet emission band because of the 5d-4f transitions of Ce3+, and the additives can enhance the PL emission intensities of specimen significantly.

Iron carbide (Fe3C) has gained significant attention for use in energy storage applications. Furthermore, using a nano-scale metal as the catalyst can reduce the formation of a solid electrolyte interface (SEI), thus enhancing capacity. For these reasons, hierarchical Fe/Fe3C/C nanofibers are prepared by electrospinning with subsequent thermal treatment and used as the anodes for lithium ion batteries (LIBs). These anodes demonstrate a good rate and high capacities. At 0.1 A g−1, the Fe/Fe3C/C nanofiber electrode maintains 518 mA h g−1 after 100 cycles. When tested at 1 A g−1, the discharge capacity gradually increases and reaches 663 mA h g−1 after 1200 cycles. This work demonstrates the possibility to design and develop transition metal carbides (TMCs) for use in energy storage.

In this work, different carbon sources, such as nano-sized carbon black (CB), carbon nanotubes (CNT), carbon fibers (CF) and graphene (GR), were reacted with titanium micro-powders, to synthesise titanium carbide (TiC) in the mixed molten salts of LiCl–KCl–KF at 1100 °C for 6 h. There experiments were performed to investigate the accuracy of “carbon-template-growth” mechanism for the formation of TiC, that was proposed previously using micro-sized titanium and submicro-sized CB powders. The products synthesised from the different carbon sources were observed and characterised by scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The results showed that the visual morphologies of the TiC products mainly retained the shapes of the as-received carbon sources, that is, they presented an equiaxed-shape with a grain size of 10–20 nm from CB, a shell layer along the outer surface of the CNTs and CF, and a flake-shape with the GR. These morphologies reveal that the formation of TiC is indeed controlled by the “carbon-template-growth” mechanism.

The effective separation of photogenerated carriers plays a vital role in photocatalytic reactions. In addition to the intrinsic driving force of photocatalysis, an external field generating an enh...

The rich electronic and band structures of monolayered crystals distinguished from their layered bulk counterparts offer versatile physical/chemical properties and applications.1-5 Their fabrications, particularly the top-down "exfoliations", are successful promised by the weak Van der Waals force between monolayers.6-9 Differentially, un-zipping ultra-thin crystals (e.g. with only one layer of crystal plane) from non-layered structures is highly challenging due to the strong chemical bond between planes and atoms. Alterative finely controlled growth of these ultra-thin materials is not really successful. This work demonstrates how a technique can be used to unzip and disintegrate ultra-thin crystal plane (e.g. monolayered nanocrystals and nanosheets) from bulk non-layered structures (ZnO, alpha/belta-MnO2, TiO2, alpha-TiB2), and present how the basic optical properties changed to distinguish from their bulk phases. The work here gives a strong tool kit to various novel 2D non-layered nanomaterials, providing significant contributions to the family of two-dimensional materials, potentially paving the way for various practical applications., Comment: 23 pages, 4 figures in the main manuscript, 13 figures in the supporting information part

SiO2-based anodes for lithium ion batteries (LIBs) suffer from low conductivity and volume change in charge/discharge processes. It is reported that reasonable amorphous and nanometric characteristics can effectively improve the activity of SiO2 for Li+ storage. So, highly active SiO2@C nanofibers were prepared by electrospinning. Using X-ray diffraction (XRD), its amorphous characteristics were revealed. The results from scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that it was a nanofiber structure. As an anode for LIBs, the SiO2@C nanofibrous electrode showed the discharge capacities of 675 and 188 mAh g−1 at 1 A g−1 (1000the cycle) and 10 A g−1 (5000th cycle), respectively. Even at 50 A g−1, it still maintained 88 mA h g−1 at 60,000 cycles, showing excellent stability and high rate.

The superhydrophobic surface was prepared on biomedical Ti–6Al–4V alloy by hydrothermal treatment coupled with subsequent hydrophobic treatment. The surface morphologies, surface roughness, phase and elemental compositions, water contact angle and hemocompatibility of the superhydrophobic samples were investigated. The results show that the hydrothermally treated sample is mainly composed of Na2Ti6O13 phase with some –OH groups. The surface morphologies of the hydrothermally treated samples change from feather-like structure to grass-like structure, and the surface roughness gradually increases with increasing the concentrations of NaOH solution. After hydrophobic treatment, the surface roughness of samples slightly decreases, and the water contact angles increase first, reaching the maximum value of 159.24° ± 1.89° at 3.75 mol/L, and then decrease with increasing the NaOH concentrations. The –C8H4F13 low surface energy fluorides are grafted onto the surface of hydrothermally treated sample by a self-assembly dehydration reaction, resulting in the formation of the superhydrophobic surface. The superhydrophobic surface effectively decreases the hemolysis ratio and platelets adhesion, and prolongs the dynamic coagulation time, indicating that it greatly improves the hemocompatibility of the biomedical Ti–6Al–4V alloy.

Sialon ceramics were prepared by the nitridation of Si, Al and Al2O3 powders with the transition metals (Fe, Co, Ni) catalysts. The phase composition, microstructure and mechanical properties of specimens were studied. Compared with the catalyst-free specimen, the addition of Fe, Co and Ni greatly promoted the nitridation process of Sialon ceramics and improved the weight gain rate and mechanical properties of specimens. With the increased content of catalysts, the apparent porosity of the products decreased first and then increased, contrary to flexural strength and compressive strength. The specimen with 2.5 wt% Fe had the highest flexural strength 145.8 MPa, and it exhibited the highest compressive strength of 594.6 MPa when Co content was 2.5 wt%, whereas they were 71.9 and 78.7 MPa, respectively, when without catalyst.

3C-SiC nanowires with nanosheets were synthesized via a direct reaction of Si vapor (from solid silicon) and SiO vapor (from silicon and silicon dioxide) with graphene nanosheets at 1500 °C without any additional metal catalyst. The resultant products were characterized by XRD, SEM, TEM and room-temperature photoluminescence (PL) spectroscopy. The results indicated that the product comprised SiC nanowires with nanosheets. The nanowires were mainly composed of curvy aggregated wires with diameters of 30–80 nm, some representative straight whiskers with a pellet at their tips, and some distinctive structures including connected particles, a dumbbell shape with dense stacking faults and periodic twins with screw dislocations. The nanosheets present in the products were thin SiC polycrystalline multilayers within a few nanowires. A combined VLS and VS mechanism was proposed for their formation. The PL spectra of the resultant SiC nanowires with nanosheets indicated a remarkable blue shift in comparison to the bulk SiC, implying their great potential applications in optoelectronic devices.

β-Sialon powder containing nanofibers was synthesized at 1300–1450 °C for 5 h in nitrogen by using transition metals (Fe, Co and Ni) as catalysts. Such synthesis conditions obviously reduced the nitriding temperature (~100 °C) of β-Sialon and increased the degree of nitridation. Observations from the weight gain rates of specimens relative to the content of catalysts suggest that the nitridation process was accelerated sharply via the addition of 0–2.5 wt% metallic catalysts. In addition, the amount of nanofibers of β-Sialon found in the specimens increased with the amount of transition metals, which was governed by the VLS formation mechanism with the help of transition metals. It could be concluded that transition metals not only greatly accelerated the nitridation of Si but also facilitated the formation of β-Sialon nanofibers in the specimens, as the formed metal-containing liquid greatly enhanced the amount of vapor generation.

Synthesis of affordable electrocatalysts with high efficiency at low cost is crucial for large-scale water splitting. Molybdenum carbide (Mo2C) has been suggested to be a promising alternative to noble metal based electrocatalysts for water splitting. In this paper, we fabricated a nanotextured coating of wrinkled Ni-doped Mo2C on carbon fiber paper (CFP) from Ni, Mo and carbon black (CB) via a molten salt method. Such a novel electrocatalyst, denoted as Ni-Mo2CCB/CFP, shows an overpotential of 121.4, 209.3 and 426.4 mV to achieve a current density of 10, 20 and 50 mA cm−2 respectively in acidic medium. The hydrogen evolution reaction (HER) performance of other as-prepared CFP based electrodes (bare CFP, Mo2C/CFP, Mo2CCB/CFP, Ni-Mo2C/CFP and NiCx/CFP) also tested. We found that the addition of carbon black and the doping of Ni could significantly improve the electrocatalytic performance of Mo2C/CFP in terms of overpotential, Tafel slope and exchange current density. This work demonstrates a facile and scalable route using molten salt method for the synthesis of high-performance electrocatalysts from non-precious compounds on carbon materials.

Recently, g-C3N4 has exhibited excellent catalytic performances in photocatalytic water splitting for H2 and O2 generation, degradation of pollutants and CO2 reduction. However, the bulk g-C3N4 demonstrates some disadvantages such as low specific surface area, high defect density, fast recombination possibility of photogenerated electron-hole pairs, and non-recyclable characteristics, leading to low photocatalytic performance and efficiency. The three-dimensional (3D) network-like g-C3N4 composite materials constructed by nanotechnology can effectively improve the adsorption capacity, light response, structure stability and recyclability of photocatalysts, which results in a significant increase in the photocatalytic performance and utilization. It is a novel way to achieve high-efficient separation of photogenerated electron-hole pairs and improve photocatalytic activity. In this review, the recent research progresses especially the synthesis strategy of 3D g-C3N4 composite photocatalysts and their applications for photocatalytic water splitting, degradation of organic pollutants and CO2 reduction are firstly and systematically introduced and discussed. The review and prospect of 3D g-C3N4 composite materials can provide some new ideas and directions for the research and development of 3D g-C3N4 composite photocatalysts with high activity, strong adsorption, facile recyclability, and no secondary pollution.

In order to verify the “Al2O3-template-formation” mechanism of magnesium aluminate (MA) spinel proposed previously using Al2O3 and MgO micro-powders as raw materials, in this work, MA spinel was synthesized by nanograined, plate-like, and fibrous Al2O3 in LiCl molten salt at 1150 °C for 3 h, respectively. The products were characterized by XRD, SEM, TEM, and EDS techniques, and the grain size of the products and raw materials were analyzed. The results showed clearly that the MA spinel was initially nucleated and subsequently developed to octahedral crystal. When the reaction further took place, when using nanograined Al2O3, the newly formed MA spinel seeds initially moved and attached to the surface of the large octahedral MA spinel crystal, and they were subsequently engulfed by the large MA spinel crystal, which further grew via layer-by-layer to become micro-sized crystal. Using plate-like or fibrous Al2O3 raw material, MgO diffused continuously into the interior of Al2O3 to form MA spinel with a gradient growth from surface to depth. These revealed that whatever shape of Al2O3 was used, the synthesis of MA spinel was governed by “Al2O3-template formation mechanism”, i.e., by the reaction of MgO diffusion into the Al2O3 templet in the molten salt.

Due to various advantages, such as rich resources, sodium (Na) is considered an alternative to replace lithium (Li) for carbon nanomaterials. Na has a larger radius, which largely limits the application. With the analysis and discussion, it found that porous carbon with functional groups benefited for energy storage, so functional porous carbon was obtained by spray drying with subsequent annealing and nitric acid etching. Moreover, the surface was modified by functional groups, which can improve wettability and enhance cycling stability. So, as the anodes for sodium-ion batteries (SIBs), the porous C electrode can remain a discharge capacity of 150 mA h g−1 at 1 A g−1 after 1000 cycles. This study opens a pathway to the design of electrodes and hopes that it can apply in other relevant fields.

Novel g-C3N4/h′ZnTiO3-a′TiO2 (CN/h′ZT-a′T) ternary composites were successfully prepared by combining in-situ precursor-synthesized h′ZnTiO3-a′TiO2 (h′ZT-a′T) nanoparticle with nanoporous g-C3N4 (CN) powders. X-ray diffraction (XRD), Transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) results revealed that the grains of hexagonal-phase ZnTiO3 (h′ZT) were in-situ generated together with anatase-phase TiO2 (a′T), forming a symbiotic structure of tightly bonded interface. Compared with CN and h′ZT-a′T, the absorption edge of CN/h′ZT-a′T exhibited a red-shift and the absorption intensity was obviously enhanced. With increasing CN content, the degradation efficiency of CN/h′ZT-a′T for methylene blue (MB) initially increased and then decreased, reaching the highest value of 99.8% with the CN content of 50 wt% (50CN/h′ZT-a′T). The 50CN/h′ZT-a′T composites exhibited the highest apparent reaction rate constant of 2.92 h−1, which was 37.4 and 3.0 times higher than that of h′ZT-a′T and CN, respectively. Photocurrent response of 50CN/h′ZT-a′T was indicative of the highest photocurrent value and the elongated lifetime of photogenerated charges. The greatly enhanced photocatalytic activity was attributed to the high mobility of photogenerated electrons. H′ZnTiO3 with high electron mobility in the direct Z-scheme heterojunction played a role of electronic transfer station and reduced the recombination probability of photogenerated carriers.

Developing an efficient, stable and low-cost noble-metal-free electrocatalyst for the hydrogen evolution reaction (HER) is an effective way to alleviate the energy crisis. Herein, we report a simple and facile approach to synthesize self-supported Ni-doped Mo2C via a molten salt method. By optimizing the content of Ni, the concentration of Ni(NO3)2, and the annealing time, self-supported nanoflower-like electrocatalysts composed of ultrathin nanosheets on carbon fiber paper (CFP) can be achieved. Such a fluffy and porous nanoflower-like structure has a large specific surface area, which can expose many active sites, and promote charge transfer; moreover, all of the above is beneficial for improving the HER performance. Density functional theory (DFT) calculations reveal that the doping of Ni leads to a down shift of the value of the d band center (ed), so that the adsorbed hydrogen (Hads) is easier to desorb from the catalyst surface, thus leading to an enhanced intrinsic catalytic activity of Ni doped Mo2C based catalysts. As a result, Mo2C-3 M Ni(NO3)2/CFP with a nanoflower-like structure prepared at 1000 °C for 6 h exhibits the best electrocatalytic performance for the HER in 0.5 M H2SO4, with a low overpotential of 56 mV (at j = 10 mA cm-2) and a Tafel slope (27.4 mV dec-1) comparable to that of commercial Pt/C (25.8 mV dec-1). The excellent performance surpasses most of the noble-metal-free electrocatalysts. In addition, the outstanding long-term durability of Mo2C-3 M Ni(NO3)2/CFP is demonstrated by showing no obvious fluctuations during 35 h of the HER testing. This work provides a simple and facile strategy for the preparation of nanoelectrocatalysts with high specific surface areas and high catalytic activities, both of which promote an efficient HER.

In this paper we report a "steel-concrete" inspired layered hybrid spine cage combining a titanium mesh and a bioceramic scaffold, which were welded together through a bioglass bonding layer using a novel multistep manufacturing methodology including three-dimensional slip deposition, gel casting, freeze-drying, and cosintering. The interfacial welding strength achieved 27 ± 0.7 MPa, indicating an excellent structural integrity of the hybrid cage construct. The biocramic scaffold layer consisting of wollastonite and hydroxyapatite had an interconnected, highly porous structure with a pore size of 100-500 μm and a porosity of85%, well fufilling the structural requirements of bone regeneration. Simulated body fluid immersion assay showed that the hybrid cage exhibited excellent biodegradability to facilitate rapid bone-like apatite formation. In vitro studies demonstrated that the bioceramic scaffold on the hybrid cage supported attachment, spreading, growth, and migration of bone/vessel-forming cells and triggered osteogenic differentiation of human mesenchymal stem cells. In vivo studies further suggested that the bioceramic scaffold on the hybrid cage could actively promote fast generation of new bone tissues within 12 weeks of implantation in a rabbit femoral condyle model. This study has provided a new design and fabrication methodology of hybrid cages by integrating strong mechanical properties with excellent biological activities including osteoinductivity and bone regeneration ability, for spine fusion and segmental bone reconstruction.