Highly efficient self-floating jellyfish-like solar steam generators based on the partially carbonized Enteromorpha aerogel.

Solar steam generation (SSG) is a very promising desalination technology. However, new photothermal materials are still to be explored to further reduce the cost, and the device structure is still to be innovated to improve the structural integrality and evaporation performance. In this work, an all-in-one highly-efficient and self-floating jellyfish-like SSG (SFJ-SSG) is developed based on partially carbonized Enteromorpha (EA) aerogel (PCEAA). The carbonized top surface exhibits high solar absorption ability and excellent photothermal effect, while the uncarbonized EA retains the hydrophilicity and high-water transport capability due to the nature of tubular algal plant. Moreover, the heat produced by photothermal effect of the carbonized EA is confined at the top surface due to the thermal insulation of the uncarbonized layer, which is very beneficial for interfacial water evaporation. After optimizing the carbonization time and the height of the SFJ-SSG, a high evaporation rate of 1.87 kg m-2h-1 is obtained under 1.0 sun irradiation, which outcompetes most SSG based on carbonized biomass. The development of SFJ-SSG based on EA not only minimizes the cost of SSG, but also solves the EA pollution, ensuring the broad prospect in practical applications.

A self-floating and integrated bionic mushroom for highly efficient solar steam generation.

Solar desalination is considered as a promising approach to solve the shortage of fresh water resources. In this work, inspired by the transpiration of trees, a self-floating and integrated bionic mushroom solar steam generator (BMSSG) is proposed for highly efficient water evaporation. A wooden strip is used to mimic the stipe of the mushroom for water transportation, meanwhile polyvinyl alcohol (PVA) modified graphene aerogels (GA) is used to imitate the pileus of the mushroom for photothermal conversion. After optimizing compositions of the aerogel and sizes of the wooden strip, a high evaporation rate of 1.67 kg m-2h-1 is obtained, outcompeting most of other wood-based evaporators. Compared to traditional interfacial evaporation devices, BMSSG is an integrated structure without a thermal insulation layer and an absorbent wick, which not only increases the compactness that is good for stability and reliability, but also reduces the manufacturing cost. Moreover, the BMSSG can self-float on the water like a roly-poly. These advantages indicate that BMSSG will play a significant role in seawater desalination. The feasibility as well as stability and recyclability of the BMSSG for seawater desalination are demonstrated. This bioinspired design provides a low-cost and scalable SSG, which will have a profound impact in future practical applications.

Sintering Bonding of SiC Particulate Reinforced Aluminum Metal Matrix Composites by Using Cu Nanoparticles and Liquid Ga in Air.

SiC particulate reinforced aluminum metal matrix composites (SiCp/Al MMCs) are characterized by controllable thermal expansion, high thermal conductivity and lightness. These properties, in fact, define the new promotional material in areas and industries such as the aerospace, automotive and electrocommunication industries. However, the poor weldability of this material becomes its key problem for large-scale applications. Sintering bonding technology was developed to join SiCp/Al MMCs. Cu nanoparticles and liquid Ga were employed as self-fluxing filler metal in air under joining temperatures ranging from 400 °C to 500 °C, with soaking time of 2 h and pressure of 3 MPa. The mechanical properties, microstructure and gas tightness of the joint were investigated. The microstructure analysis demonstrated that the joint was achieved by metallurgical bonding at contact interface, and the sintered layer was composed of polycrystals. The distribution of Ga was quite homogenous in both of sintered layer and joint area. The maximum level of joint shear strength of 56.2 MPa has been obtained at bonding temperature of 450 °C. The specimens sintering bonded in temperature range of 440 °C to 460 °C had qualified gas tightness during the service, which can remain 10-10 Pa·m3/s.

Molten-salt-assisted synthesis of onion-like Co/CoO@FeNC materials with boosting reversible oxygen electrocatalysis for rechargeable Zn-air battery.

A melt-salt-assisted method is utilized to construct an onion-like hybrid with Co/CoO nanoparticles embedded in graphitic Fe-N-doped carbon shells (Co/CoO@FeNC) as a bifunctional electrocatalyst. The iron-polypyrrole (Fe-PPy) is firstly prepared with a reverse emulsion. Direct pyrolysis of Fe-PPy yields turbostratic Fe-N-doped carbon (FeNC) with excellent oxygen reduction reaction (ORR) electrocatalysis, while the melt salt (CoCl2) mediated pyrolysis of Fe-PPy obtains onion-like Co/CoO@FeNC with a reversible overvoltage value of 0.695 V, largely superior to Pt/C and IrO2 (0.771 V) and other Co-based catalysts reported so far. The ORR activity is mainly due to the graphitic FeNC and further enhanced by CoNx bonds, whereas the oxygen evolution reaction (OER) activity is principally due to the Co/CoO composite. Concurrently, Co/CoO@FeNC as cathode catalyst enables Zn-air battery with a high open circuit voltage of 1.42 V, a peak power density of 132.8 mW cm-2, a specific capacity of 813 mAh gZn-1, and long-term stability.

Nonsymmetrical Segregation of Solutes in Periodic Misfit Dislocations Separated Tilt Grain Boundaries.

Interfacial segregation is ubiquitous in mulit-component polycrystalline materials and plays a decisive role in material properties. So far, the discovered solute segregation patterns at special high-symmetry interfaces are usually located at the boundary lines or are distributed symmetrically at the boundaries. Here, in a model Mg-Nd-Mn alloy, we confirm that elastic strain minimization facilitated nonsymmetrical segregation of solutes in four types of linear tilt grain boundaries (TGBs) to generate ordered interfacial superstructures. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy observations indicate that the solutes selectively segregate at substitutional sites at the linear TGBs separated by periodic misfit dislocations to form such two-dimensional planar structures. These findings are totally different from the classical McLean-type segregation which has assumed the monolayer or submonolayer coverage of a grain boundary and refresh understanding on strain-driven interface segregation behaviors.

Carbon-based 0D/1D/2D assembly with desired structures and defect states as non-metal bifunctional electrocatalyst for zinc-air battery.

For the design of electrocatalysts, the combination between components and the regulation of material structures tend to be neglected, giving rise to the constraint of catalytic performance and durability. Herein, we developed a graphene oxide quantum dots (GOQDs) with enhanced oxygen content by a one-step cutting method. Then, one-dimensional (1D) carbon nanotubes and two-dimensional (2D) reduced graphene oxide are crosslinked and self-assembled, thus attracting unsaturated-bond-riches GOODs (0D) to uniformly attach to the skeleton, simultaneously achieving nitrogen and sulfur co-doping. To the best of our knowledge, there is no report to prepare bifunctional electrocatalyst with GOQDs. Electrochemical tests show that even without metal-doping, the novel non-metal bifunctional electrocatalyst (N,S-GOQD-RGO/CNT) exhibits a higher half-wave potential (0.84 V) and enhanced limiting current density (5.88 mA cm-2) than commercial Pt/C catalyst. The density functional theory is implemented to reveal the coordination of nitrogen and sulfur co-doping on GOQDs, which results in the improvement of overall catalytic active sites. Furthermore, the rechargeable zinc-air battery based on N,S-GOQD-RGO/CNT exhibits a maximum power density of 134.3 mW cm-2, open circuit potential of 1.414 V, which is better than Pt/C+Ru/C mixed material. The obtained N,S-GOQD-RGO/CNT will provide a perspective application in fuel cells.

Flux-Free Diffusion Joining of SiCp/6063 Al Matrix Composites Using Liquid Gallium with Nano-Copper Particles in Atmosphere Environment.

A new method for flux-free diffusion joining of aluminum matrix composites reinforced with SiC particles (SiCp/Al MMCs) in atmosphere environment has been developed. Liquid gallium and nano-copper particles were employed as filler metal under joining temperatures ranging between 400 °C to 480 °C, with a holding time of 2 h and pressure of 3 MPa. The results showed that 65 vol.% SiCp/6063 Al MMCs were successfully joined together. X-ray diffraction (XRD) analysis confirmed the presence of Ga2O3 at the fracture. Meanwhile, neither copper oxide nor aluminum oxide was detected. The formation of Ga2O3 can protect nano-copper particles and SiCp/6063 Al MMCs from oxidation. The width of weld seam tended to be narrowed from 40 µm to 14 µm gradually with increasing temperature from 400 °C to 480 °C. The maximum shear strength level of 41.2 MPa was achieved with a bonding temperature of 450 °C. The change of the strength was due to the adequate elements' mutual diffusion and solution, as well as the change of the quantity and morphology of intermetallic compounds in the weld seam, such as Al2Cu and Cu3Ga. When the diffusion joining temperature reached 440 °C or above, the leak rate of the specimen remained under 10-10 Pa·m3/s.

Colloidal Cu2ZnSn(S1-x,Sex)4-Au nano-heterostructures for inorganic perovskite photovoltaic applications as photocathode alternative.

We concretely report feasible synthesis procedures of colloidal Cu2ZnSn(S1-x,Sex)4-Au (CZTSSe-Au) nano-heterostructured composites, and creatively employ them as the counter electrodes (CEs) of all-solid-state solar cells with inorganic CsSnI2.95F0.05 perovskite hole conductor. Acquired optical characterization indicates that integration of noble metal nanoparticles with cuprum-chalcogenide could heighten light absorption within visible-band due to localized surface plasmon resonance (LSPR) generated by Au, and the forbidden gap of nanocomposites gets adjustment accordingly. It is demonstrated that this novel photocathode alternative with favorable conductivity can not only match the energy level within the device band structure construction, but also restrain recombination so that accelerate charge transfer and extraction occurring on the photocathode. The photocurrent and photoelectric conversion efficiency (PCE) of cells conjugating CZTS-Au photocathodes turn to be respectively 43% and 25% higher than those using pure CZTS. Moreover, it has been demonstrated that CZTS-Au, coupling very well with inorganic perovskite, owns comparable electrocatalytic performance and even higher output photocurrent with respect to platinum CEs, which portends a potential substitution for conventional costly photocathodes. A comprehensive analysis on impedance spectroscopy data is subsequently carried out for the sake of deep understanding charge accumulation and transfer response at CsSnI2.95F0.05/CE interface, attempting to orient further optimization of device performance.

Theoretical study on the optical and electronic properties of graphene quantum dots doped with heteroatoms.

The effects of four heteroatoms (B, N, P, and S) with three doping patterns on graphene quantum dots (GQDs) are systematically investigated using time-dependent density functional theory (TD-DFT). The absorption spectra and HOMO-LUMO gaps are quantitatively analyzed to study the correlations between the optical properties and heteroatom doping of doped GQDs. Heteroatom doping can endow GQDs with various new optical and structural properties, depending on the dopants and doping configurations. Compared with the absorption spectra of pristine GQD, both N and S surface doping demonstrate a slight blue shift, whereas B and P doping lead to a blue shift for edge-doped GQDs with heteroatoms in a pentatomic ring. The absorption process is investigated along with excited state analysis, which includes the density of state, natural transition orbital, and charge difference density. The results indicate that large radius atoms assist charge transfer in the excited state and play an important role in recombining the electron density distribution in the doped GQDs.