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The traditional conversion of organic wastes into value-added products encounters bottlenecks such as the use of expensive, toxic solvents and cumbersome post-treatment of the separated products. To overcome these bottlenecks, the in situ air–water interface is employed to convert four waste surfactants into easily separable value-added products upon photoirradiation under ambient conditions. The results show that four representative amphiphiles with different functional groups can be directly transformed into automatically separated hydrocarbons and fluorescent nanoparticles (FNs) in the gas and solid phases respectively. Such an excellent separation performance is attributed to the fact that the Henry's law constant and dipole moment of the products are significantly reduced relative to those of their parents and the unique two-dimensional (2D) interface further accelerates their separation. In particular, the optimal selectivity of olefins is up to 99%, and the fluorescence quantum yield of FNs can reach as high as 44.35%. Combined with theoretical calculations, the referred mechanism and influences of functional groups on the resource transformation pathway and products are revealed in depth. This work provides important theoretical guidance for efficient, green and economical waste-to-resource conversion. [ABSTRACT FROM AUTHOR]

A major limitation of vanadium oxides in aqueous Zn/V2O5 ion battery applications is that they suffer from strong coulombic ion–lattice interactions with divalent Zn2+. Correspondingly, vanadium oxides show the poor utilization of their electrochemically active surface areas and unsatisfactory structural stability. The Gibbs free energy of Zn2+ adsorption in the vicinity of oxygen vacancies can be reduced to a thermoneutral value, which suggests that the Zn2+ adsorption/desorption process on the oxygen-deficient oxide lattice is more reversible as compared to a less defective vanadium oxide. In this work, it is demonstrated that these problems can be significantly ameliorated via creating oxygen vacancies in vanadium oxide host materials. Specifically, for the first time, vanadium oxides with abundant oxygen defects (labeled Vo-V2O5) are fabricated via a new water-steam activation strategy. Such water-steam activation forms abundant oxygen defects, and the as-prepared materials show a 3.5-fold increase in the carrier density, together with larger electrochemically active surface areas compared to a less defective vanadium oxide. When used as a cathode material for aqueous zinc ion batteries, Vo-V2O5 exhibits a high specific capacity (335 mA h g−1 at 0.2 A g−1) and excellent cell stability (∼87.2% capacity retention after 3500 continuous charge/discharge cycles at 5.0 A g−1). Thus, this water-steam activation approach for disordered metal oxides yields highly competitive cathode materials, which may also aid in the future development of advanced materials in related energy fields. [ABSTRACT FROM AUTHOR]

Recycling of spent lithium-ion batteries (LIBs) is of great importance for both critical metal supply and environmental protection. Although the physical chemistry is still focused on pyrometallurgy, hydrometallurgy and electrometallurgy, state-of-the-art recycling technologies are a trend that is turning towards being more material/energy efficient in line with the principles of green chemistry. For instance, selective recycling of specified metals and direct regeneration of battery materials are being trialled to develop short-cut processes that prevent secondary pollution generation and improve the atomic economy during the whole recycling process. In this review, a number of technologies for recycling spent LIBs are overviewed, especially at different recycling stages to stepwise recover battery materials. It is clearly understood that extraction of critical metals and subsequent regeneration of materials are only part of the recycling process, while pretreatment to obtain black mass powder from battery cells and pollution control, in view of the recycling process to minimise environmental impact, are also extremely important. Furthermore, green design of batteries, as well as process design in view of the whole life cycle of LIBs, are topping the list of the research which requires profound and elaborate efforts. It is expected that this review could provide a guideline for implementing green chemistry principles into spent LIB recycling and stimulate further discussions on improving the green degree of the process. [ABSTRACT FROM AUTHOR]

Gas–water interface mediated photoconversion of renewable biomass into fuels is a promising strategy to mitigate the impending environmental pollution and energy crisis. Herein, a gas–water interface is engineered to photoconvert fatty acids (FAs, C6–C9) into gaseous Cn-2 linear alpha-olefins (LAOs) with a high selectivity (87–91%) under mild conditions; especially, experiments with different interfaces demonstrate that the gas–water interface plays a crucial role in the enhanced selective production. The thinner molecular layer and ordered packing significantly promote the production of LAOs by maximizing the hydrogen bonding between FAs and interfacial water molecules. Furthermore, density functional theory (DFT) calculations, at the molecular level, elaborate that interfacial water could activate the reactions through hydrogen bonding lowering the reaction barrier of initial photoreaction of FAs. Additionally, different atmospheres are found to impact the pathways and products of photoconversion, thus enabling the controllable synthesis of LAOs. Unlike the metal/enzyme-involved harsh catalytic system, the gas–water interface serves as a green, low-cost and efficient 'venue' which can be infinitely reused for hydrocarbon production, pioneering a new way for mitigating the energy crisis and developing a truly green and sustainable society. [ABSTRACT FROM AUTHOR]

Recycling of spent lithium-ion batteries (LIBs) has attracted intensive attention owing to their potential environmental risk and the importance of the supply of critical metals. Sulfation roasting as a traditional technology is not considered environmentally friendly due to serious SOx emission. The usage of over-stoichiometric amounts of sodium salt results in high sodium content in the leaching solutions bringing about difficulties for the preparation of qualified lithium products. It is usually not easy to achieve high recovery selectivity of metals. Herein, we find it is possible to eliminate secondary emission and no sodium is included in the process of spent LIB (LiCoO2 as a case study) recycling if the transfer pathway of sulfur among different phases is well controlled. At the same time, high lithium recovery selectivity is achieved. The principles of green chemistry for substitution of chemicals with a low environmental impact and improving the atomic efficiency of sulfur are introduced during traditional sulfation roasting. A pretreatment step of aging with sulfuric acid at 393 K is introduced to form cobalt sulfate which in the following heat treatment step will further preferentially react with the remaining LiCoO2 until it is completely consumed. By controlling the amount of sulfuric acid, sulfur can be recirculated and recycled thoroughly in the form of SO42−, instead of SOx emission and the atomic efficiency of sulfur can be highly improved. After leaching with water, the concentration of Li+ in the leachate reaches 19.82 g L−1; 99.3% lithium and 98.7% cobalt were recuperated as Li2CO3 and Co3O4 with a purity of 99.89% and 99.95%, respectively. Our findings propose an environmentally benign and easily implemented strategy for selective recycling of spent LIBs. The fundamentals provide inspiration for separation and extraction fields such as mining and recycling of complex systems composed of multiple metals. [ABSTRACT FROM AUTHOR]

Fluorescent nanoarchitectures, such as hydrophobic micelles and hydrophilic vesicles decorated with fluorescent carbon nanoparticles, were fabricated from one fatty acid by means of photo-triggering. The biomimetic nanostructures, like cell membrane structures, have applications in fluorescence imaging in both the cell cytoplasm and nucleus. Besides, hydrophobic micelles can be used as very stable fluorescent inks. [ABSTRACT FROM AUTHOR]

In recent years, the recovery of metals from spent lithium ion batteries (LIBs) has become increasingly important due to their great environmental impact and the wastage of valuable metallic resources. Among different types of spent LIBs, processing and recycling the spent LiFePO4 batteries are challenging because of their relatively low extraction efficiency and recycling selectivity of valuable metal(s) and great potential for secondary waste generation. In this research, an effective and sustainable approach for selective leaching of lithium from spent LiFePO4 batteries was demonstrated. By properly adjusting or controlling the oxidative state and proton activity of the leaching solution, lithium was found to be selectively leached with a high recovery efficiency. The aluminium remained in the metallic form and iron as FePO4 in the solid residue which can be easily separated by sieving. The effects of a range of parameters (i.e. acid concentration, initial volume fraction of the oxidant, liquid-to-solid ratio, reaction temperature and time) during lithium leaching were comprehensively investigated. The selective reaction mechanisms were clarified and the controlling step for the leaching kinetics was identified. Based on the laboratory scale results, a pilot batch process was developed and simulated. The process is found to be techno-economically feasible and environmentally friendly for recycling of spent LiFePO4 batteries using selective leaching. High purity Li2CO3 (99.95 wt%) could be obtained with a high recovery rate. This research demonstrates the possibility of improving the metal recycling effectiveness from spent LiFePO4 batteries by incorporating the principles of green chemistry and probably contributes to the sustainability of the lithium ion battery industry. [ABSTRACT FROM AUTHOR]

The commercialization of fuel cells and metal–air batteries can only be realized if expensive and scarce platinum-based catalysts are replaced by lower cost, efficient, and durable catalysts for the oxygen reduction reaction (ORR). Along with intensive research efforts in developing low-cost, metal-free catalysts to replace platinum-based catalysts, heteroatom doped graphitic carbon materials (especially graphene and carbon nanotubes) have been demonstrated to show superior ORR performance. However, graphdiyne, another member of the carbon family, has not been completely studied as an electrocatalyst for the ORR. We demonstrate here that nitrogen and fluorine co-doped, metal-free graphdiyne exhibits comparable electrocatalytic activity to commercial Pt/C both in half-cell and full-cell (primary Zn–air battery) tests, regarding its onset potential and limiting current density. Moreover, the new catalyst has better stability, as well as a higher tolerance to methanol crossover and CO poisoning effects, than the commercial Pt/C. [ABSTRACT FROM AUTHOR]

rGO–CdS–H2W12 nanocomposite film was successfully fabricated by a layer-by-layer self-assembly method. The composite film was characterized by techniques such as UV-Vis spectra, XPS, and AFM. The composite film showed high photoelectronic response under the illumination of sunlight. Both current–voltage curves and photocurrent transient measurements demonstrated that the photocurrent response of the rGO–CdS–H2W12 composite film was enhanced five-fold compared with CdS film. This can be attributed to the photoinduced electron transfer between CdS, H2W12 and rGO, which promotes the charge separation efficiency of CdS. The introduction of GO enhanced the charge separation and transportation. More importantly, various pollutants can be treated as electron donors, and can thus be degraded and produce hydrogen at the same time, at a low bias voltage under the irradiation of solar light. [ABSTRACT FROM AUTHOR]

We report a KOH self-templating synthesis of three-dimensional hierarchical porous carbon using resol as the precursor and KOH as both the template and activating agent. The resulting resol-derived porous carbon (RPC) exhibits a high surface area (up to 2700 m2 g-1) and well-interconnected macropores with micropores and mesopores decorated on the carbon walls. Consequently, the RPC shows low internal resistance, high specific capacitance, good rate capability and excellent cycling stability in 6 M KOH as a supercapacitor electrode. Because of its easy fabrication and low cost, it offers a good alternative method for synthesis of carbon electrodes for energy-storage devices such as Li-ion batteries, fuel cells and supercapacitors. [ABSTRACT FROM AUTHOR]

The photocatalytic hydrogen (H2) evolution with transition-metal substituted Keggin-type titanium tungstates Na5(6)[MTiW11O39]·xH2O (abbreviated as TiW11M (M = Fe, Co, Zn)) as photocatalyst was reported. They showed good photocatalytic activities toward H2 evolution in homogeneous systems under simulated solar light irradiation. The order of photocatalytic activity was TiW11Co ≈ TiW11Zn ＞ TiW11Fe > H3PW12O40 (PW12). The selected POMs showed good stability during the reactions. Karl Fischer analysis, ICPE (Inductive Coupled Plasma Emission) and FT-IR (Fourier Transform Infrared Spectroscopy) were used to confirm the composition and structure. UV-Vis absorption spectra, kinetics investigation and cyclic voltammetric characterizations were used to explain the photocatalytic results. Finally, an analogous “Z-scheme” mechanism was proposed for the homogeneous systems toward photocatalytic H2 evolution under simulated solar light irradiation. [ABSTRACT FROM AUTHOR]

The combination of two or more chemically distinct components in one single nanostructure will undoubtedly lead to useful applications of nanomaterials in various areas. Herein, we report our experimental observations on composite nanosystems consisting of metal sulfide and Au and/or Ag noble metals. A number of characterization techniques, including transmission electron microscopy (TEM), high-resolution TEM (HRTEM), high-angle annular dark-field scanning TEM (HAADF-STEM), X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX) are used to characterize the morphology of the formed nanocomposites, and to address the following critical issues: i) the deposition behavior of the noble metals on the semiconductor nanocrystals; ii) the relationship between the morphology of the nanocomposites and the structure of the semiconductors; and iii) the mechanism accounting for the morphology formation of the final composite nanoparticles. [ABSTRACT FROM AUTHOR]

A polyoxometalate (POM)-mediated green, facile and large-scale synthesis of 2D (2-dimensional) Ag NN/GNS nanohybrids (where NN stands for the nanonet and GNSs for graphene nanosheets) is reported. The synthesis is convenient, rapid and environmentally friendly. The POMs serve as reducing, encapsulating and bridging molecules, and avoid introducing any organic toxic molecules. The nanohybrids have been thoroughly characterized using SEM, EDX TEM, XRD, XPS and Raman spectroscopy. Most importantly, the nanohybrids were demonstrated to act as low cost catalysts for the oxygen reduction reaction in fuel cells with similar performance to Pt catalysts. We attribute it to the high catalytic activity of the Ag NN and the excellent electron transfer properties of GNSs and also their synergistic effect, being reinforced by the presence of molybdenum species on the Ag NN/GNS surface. [ABSTRACT FROM AUTHOR]

Mastery over the morphology/structure of nanoparticles enables control of their properties and enhancement of their usefulness for a given application. Herein, we report a systematic study on the synthesis of ruthenium nanoparticles in oleylamine, including the tuning of their morphology/shape by temperature or by seed-mediated growth. A phase-transfer based strategy for the fabrication of the Ru nanoparticles with hollow interiors has also been demonstrated in this work, which involves the phase transfer of the core–shell Ag–Ru nanoparticles prepared in oleylamine from organic solvent to aqueous phase and the subsequent removal of Ag cores from the core–shell nanoparticles by reacting with NaCl. This approach enables the synthesis of hollow structured Ru nanoparticles in a single aqueous phase, and avoids the use of expensive chemical reagents. Both of them are favorable for the large-scale synthesis of Ru nanoparticles with hollow interiors. [ABSTRACT FROM AUTHOR]

Novel ZnO@ZnS hollow dumbbells–graphene composites have been successfully fabricated through a polymer-assisted hydrothermal reaction and sulfurization treatment. Because of the formation of heterostructures and a new transfer pathway of electrons from ZnS to graphene, the composites show significantly superior photocatalytic activities than ZnO dumbbells and ZnO@ZnS hollow dumbbells. The improved electric conductivity and the improved adsorption and diffusion of gas molecules also endow them with excellent sensitivity and selectivity toward alcohol gas. This paper presents a promising method to fabricate semiconductor heterostructure–graphene composites for high-efficiency photocatalysts and gas sensors. [ABSTRACT FROM AUTHOR]

Mastery over the morphology/structure of nanoparticles enables control of their properties and enhancement of their usefulness for a given application. Herein, we report a systematic study on the synthesis of ruthenium nanoparticles in oleylamine, including the tuning of their morphology/shape by temperature or by seed-mediated growth. A phase-transfer based strategy for the fabrication of the Ru nanoparticles with hollow interiors has also been demonstrated in this work, which involves the phase transfer of the core-shell Ag-Ru nanoparticles prepared in oleylamine from organic solvent to aqueous phase and the subsequent removal of Ag cores from the core-shell nanoparticles by reacting with NaCl. This approach enables the synthesis of hollow structured Ru nanoparticles in a single aqueous phase, and avoids the use of expensive chemical reagents. Both of them are favorable for the large-scale synthesis of Ru nanoparticles with hollow interiors.

Heterogeneous Au-Pt nanostructures have been synthesized using a sacrificial template-based approach. Typically, monodispersed Au nanoparticles are prepared first, followed by Ag coating to form core-shell Au-Ag nanoparticles. Next, the galvanic replacement reaction between Ag shells and an aqueous H(2)PtCl(6) solution, whose chemical reaction can be described as 4Ag + PtCl(6)(2-)→ Pt + 4AgCl + 2Cl(-), is carried out at room temperature. Pure Ag shell is transformed into a shell made of Ag/Pt alloy by galvanic replacement. The AgCl formed simultaneously roughens the surface of alloy Ag-Pt shells, which can be manipulated to create a porous Pt surface for oxygen reduction reaction. Finally, Ag and AgCl are removed from core-shell Au-Ag/Pt nanoparticles using bis(p-sulfonatophenyl)phenylphosphane dihydrate dipotassium salt to produce heterogeneous Au-Pt nanostructures. The heterogeneous Au-Pt nanostructures have displayed superior catalytic activity towards oxygen reduction in direct methanol fuel cells because of the electronic coupling effect between the inner-placed Au core and the Pt shell.