Metal-Oleate Complex-Derived Bimetallic Oxides Nanoparticles Encapsulated in 3D Graphene Networks as Anodes for Efficient Lithium Storage with Pseudocapacitance.

In this manuscript, we have demonstrated the delicate design and synthesis of bimetallic oxides nanoparticles derived from metal-oleate complex embedded in 3D graphene networks (MnO/CoMn2O4 ⊂ GN), as an anode material for lithium ion batteries. The novel synthesis of the MnO/CoMn2O4 ⊂ GN consists of thermal decomposition of metal-oleate complex containing cobalt and manganese metals and oleate ligand, forming bimetallic oxides nanoparticles, followed by a self-assembly route with reduced graphene oxides. The MnO/CoMn2O4 ⊂ GN composite, with a unique architecture of bimetallic oxides nanoparticles encapsulated in 3D graphene networks, rationally integrates several benefits including shortening the diffusion path of Li+ ions, improving electrical conductivity and mitigating volume variation during cycling. Studies show that the electrochemical reaction processes of MnO/CoMn2O4 ⊂ GN electrodes are dominated by the pseudocapacitive behavior, leading to fast Li+ charge/discharge reactions. As a result, the MnO/CoMn2O4 ⊂ GN manifests high initial specific capacity, stable cycling performance, and excellent rate capability.

Visible-light-driven removal of tetracycline antibiotics and reclamation of hydrogen energy from natural water matrices and wastewater by polymeric carbon nitride foam.

Water and energy are key sustainability issues that need to be addressed. Photocatalysis represents an attractive means to not only remediate polluted waters, but also harness solar energy. Unfortunately, the employment of photocatalysts remains a practical challenge in terms of high cost, low efficiency, secondary pollution and unexploited water matrices influence. This study investigated the feasibility of photocatalysis to both treat water and produce hydrogen with practical water systems. Polymeric carbon nitride foam (CNF) with large surface area and mesoporous structure was successfully prepared via the bubble-template effect of ammonium chloride decomposition during thermal condensation. The reaction kinetics, mechanisms, and effect of natural water matrices and wastewater on CNF-based photocatalytic removal of tetracycline hydrochloride (TC-HCl) were systematically investigated. Furthermore, the efficiency of clean hydrogen energy from natural water matrices and wastewater was also evaluated. It was found that the photocatalytic performance of CNF for TC-HCl removal was principally affected by calcination temperature in the presence of NH4Cl. The degradation rates of CNF-4 (calcined at 550 °C) were approximately 1.84, 2.49 and 7.47 times than that of the CNF-2 (calcined at 600 °C), CNF-1 (calcined at 500 °C) and GCN (without NH4Cl), respectively. Results indicate that the improved photocatalytic performance was predominantly ascribed to the large specific surface area, increased availability of exposed active sites, and enhanced transport and separation efficiency of the photogenerated carrier. Based on electron spin resonance, chemical trapping experiment and density functional theory calculation, photoinduced oxidizing species (·O2- and holes) initially attacked the C-N-C fragment of TC molecules, which were finally mineralized to CO2, water and inorganic matters. Under the synergistic influence of water constituents (including acidity and alkalinity, ion species and dissolved organic substances), various water matrices greatly affected the degradation rate of TC-HCl, with the highest removal efficiency of 78.9% in natural seawater, followed by reservoir water (75.0%), tap water (62.3%), deionized water (49.8%), reverse osmosis concentrate (32.7%) and pharmaceutical wastewater (18.9%). Interestingly, low amounts of the emerging microplastics slightly improved TC-HCl removal, whereas high amounts (1.428 × 107 P/cm3) restricted removal due to light absorption and the intrinsic adsorption interaction. Moreover, the photocatalysts were able over repeated usage. Notably, the hydrogen yields rates of polymeric carbon nitride foam were 352.2, 299.8, 184.9 and 94.3 µmol/g/h in natural seawater, pharmaceutical wastewater, water from reservoir and tap water, respectively. This study proves the potential of novel nonmetal porous photocatalyst to simultaneously treat wastewater while converting solar energy into clean hydrogen energy.

Three-dimensional nitrogen and sulfur co-doped holey-reduced graphene oxide frameworks anchored with MoO2 nanodots for advanced rechargeable lithium-ion batteries.

In this manuscript, we synthesize a porous three-dimensional anode material consisting of molybdenum dioxide nanodots anchored on nitrogen (N)/sulfur (S) co-doped reduced graphene oxide (GO) (3D MoO2/NP-NSG) through hydrothermal, lyophilization and thermal treatment. First, the NP-NSG is formed via hydrothermal treatment using graphene oxide, hydrogen peroxide (H2O2), and thiourea as the co-dopant for N and S, followed by calcination of the N/S co-doped GO in the presence of ammonium molybdate tetrahydrate to obtain the 3D MoO2/NP-NSG product. This novel material exhibits a series of out-bound electrochemical performances, such as superior conductivity, high specific capacity, and excellent stability. As an anode for lithium-ion batteries (LIBs), the MoO2/NP-NSG electrode has a high initial specific capacity (1376 mAh g-1), good cycling performance (1250 mAh g-1 after 100 cycles at a current density of 0.2 A g-1), and outstanding Coulombic efficiency (99% after 450 cycles at a current density of 1 A g-1). Remarkably, the MoO2/NP-NSG battery exhibits exceedingly good rate capacities of 1021, 965, 891, 760, 649, 500 and 425 mAh g-1 at different current densities of 200, 500, 1000, 2000, 3000, 4000 and 5000 mA g-1, respectively. The superb electrochemical performance is owed to the high porosity of the 3D architecture, the synergistic effect contribution from N and S co-doped in the reduced graphene oxide (rGO), and the uniform distribution of MoO2 nanodots on the rGO surface.

Polycationic Polymer-Regulated Assembling of 2D MOF Nanosheets for High-Performance Nanofiltration.

Herein, a two-dimensional metal-organic framework (2D MOF) made of iron porphyrin complex (TCP(Fe)) interconnected with divalent metal ion (M = Zn, Co, and Cu) is used to construct a selective layer, which is explored as an ultrafast and energy-saving nanofiltration (NF) membrane for removing organic dyes from water. Among the layered 2D M-TCP(Fe) membranes, Zn-TCP(Fe) membranes display the highest water permeance, which is 3 times higher than graphene-based membranes with similar rejection. To further improve the separation performances, we utilize polycations to anchor the periphery carboxylic groups of nanosheets, regulating the assembly of 2D Zn-TCP(Fe) nanosheets to produce a new class of crack-free selective layer possessing ultrathin and highly ordered nanochannels for efficient NF. Benefiting from these structural features, our polycation-regulated 2D Zn-TCP(Fe) membranes could offer ultrahigh permeance of 4243 L m-2 h-1 bar-1 (2-fold higher than its pristine) and excellent rejection rates (over 90%) for organic dye with size larger than 0.8 × 1.1 nm. This permeance value is about 2 orders of magnitude higher than the commercial polymeric NF membrane. Additionally, the membranes demonstrate 20-40% salt rejection.

Highly Luminescent Heterostructured Copper-Doped Zinc Sulfide Nanocrystals for Application in Cancer Cell Labeling.

The structural characteristics of the seed-mediated synthesis of heterostructured CuS-ZnS nanocrystals (NCs) and Cu-doped ZnS (ZnS:Cu) NCs synthesized by two different protocols are compared and analyzed. At high Cu dopant concentrations, segregated subclusters of ZnS and CuS are observed. The photoluminescence quantum yield of ZnS:Cu NCs is about 50-80 %; a value much higher than that of ZnS NCs (6 %). Finally, these NCs are coated with a thin silica shell by using (3-mercaptopropyl)triethoxysilane in a reverse microemulsion to make them water soluble. Cytotoxicity experiments show that these silica-coated NCs have greatly reduced toxicity on both cancerous HeLa and noncancerous Chinese hamster ovary cells. The labeling of cancerous HeLa cells is also demonstrated.

3D Hierarchical Porous Mo2 C for Efficient Hydrogen Evolution.

Porous electrocatalyst for hydrogen production. 3D hierarchical porous molybdenum carbide provides a low operating potential (97 mV at 10 mA cm(-2) ). These beneficial textures of large specific surface area (302 m(2) g(-1) ) and hierarchical porous architecture containing dominant pore size distribution peak at 11 Å in width can provide large surface active sites and facilitate proton mass transport.

Metal coordination polymer derived mesoporous Co3O4 nanorods with uniform TiO2 coating as advanced anodes for lithium ion batteries.

In this work, a one-dimensional Co3O4@TiO2 core-shell electrode material with superior electrochemical performance is fabricated by a convenient and controllable route. The approach involves two main steps: the homogeneous deposition of polydopamine and TiO2 layers in sequence on the cobalt coordination polymer and the thermal decomposition of the polymer matrix. The as-prepared electrode material can achieve excellent electrochemical properties and stability as an anode material for lithium ion batteries, such as a high specific capacity of 1279 mA h g(-1), good cycling stability (around 803 mA h g(-1) at a current density of 200 mA g(-1) after 100 cycles), and stable rate performance (around 520 mA h g(-1) at a current density of 1000 mA g(-1)). This dramatic electrochemical performance is mainly attributed to the excellent structural characteristics, which could improve the electrical conductivity and lithium ion mobility, as well as electrolyte permeability and architectural stability during cycling.

Using elastin protein to develop highly efficient air cathodes for lithium-O2 batteries.

Transition metal-nitrogen/carbon (M-N/C, M = Fe, Co) catalysts are synthesized using environmentally friendly histidine-tag-rich elastin protein beads, metal sulfate and water soluble carbon nanotubes followed by post-annealing and acid leaching processes. The obtained catalysts are used as cathode materials in lithium-O2 batteries. It has been discovered that during discharge, Li2O2 nanoparticles first nucleate and grow around the bead-decorated CNT regions (M-N/C centres) and coat on the catalysts at a high degree of discharge. The Fe-N/C catalyst-based cathodes deliver a capacity of 12,441 mAh g(-1) at a current density of 100 mA g(-1). When they were cycled at a limited capacity of 800 mAh g(-1) at current densities of 200 or 400 mA g(-1), these cathodes showed stable charge voltages of ∼3.65 or 3.90 V, corresponding to energy efficiencies of ∼71.2 or 65.1%, respectively. These results are considerably superior to those of the cathodes based on bare annealed CNTs, which prove that the Fe-N/C catalysts developed here are promising for use in non-aqueous lithium-O2 battery cathodes.

Hydrophilic Nitrogen and Sulfur Co-doped Molybdenum Carbide Nanosheets for Electrochemical Hydrogen Evolution.

Nitrogen and sulfur dual-doped Mo2 C nanosheets provide low operating potential (-86 mV for driving 10 mA cm(-2) of current density). Co-doping of N and S heteroatoms can improve the wetting property of the Mo2C electrocatalyst in aqueous solution and induce synergistic effects via σ-donation and π-back donation with hydronium cation.

Platinum and palladium nanotubes based on genetically engineered elastin-mimetic fusion protein-fiber templates: synthesis and application in lithium-O2 batteries.

The coupling of proteins with self-assembly properties and proteins that are capable of recognizing and mineralizing specific inorganic species is a promising strategy for the synthesis of nanoscale materials with controllable morphology and functionality. Herein, GPG-AG3 protein fibers with both of these properties were constructed and served as templates for the synthesis of Pt and Pd nanotubes. The protein fibers of assembled GPG-AG3 were more than 10 µm long and had diameters of 20-50 nm. The as-synthesized Pt and Pd nanotubes were composed of dense layers of ~3-5 nm Pt and Pd nanoparticles. When tested as cathodes in lithium-O2 batteries, the porous Pt nanotubes showed low charge potentials of 3.8 V, with round-trip efficiencies of about 65% at a current density of 100 mA g(-1).

Fe-based metallopolymer nanowall-based composites for Li-O2 battery cathode.

Metallopolymer nanowalls were prepared through a simple wet-chemical process using reduced graphene oxides as heterogeneous nucleation aids, which also help to form conductive electron paths. The nanowalls grow vertically on graphene surface with 100-200 nm in widths and ∼20 nm in thickness. The Fe-based metallopolymer nanowall-based electrode shows best performance as O2 cathode exhibiting high round-trip efficiencies and stable cycling performance among other transition metal containing metallopolymer counterparts. The electrode delivers discharge-charge capacities of 1000 mAh/g for 40 cycles and maintains round-trip efficiencies >78% at 50 mA/g. The 1(st)-cycle round-trip efficiencies are 79%, 72%, and 65% at current densities of 50, 200, and 400 mA/g, respectively. The NMR analysis of the Fe-based metallopolymer based electrode after 40 cycles reveals slow formation of the side products, CH3CO2Li and HCO2Li.

Binder-free graphene foams for O2 electrodes of Li-O2 batteries.

We report a novel method to prepare bind-free graphene foams as O2 electrodes for Li-O2 batteries. The graphene foams are synthesized by electrochemical leavening of the graphite papers, followed by annealing in inert gas to control the amount of structural defects in the graphene foams. It was found that the structural defects were detrimental to the processes of the ORR and OER in Li-O2 batteries. The round-trip efficiencies and the cycling stabilities of the graphene foams were undermined by the structural defects. For example, the as-prepared graphene foam with a high defect level (ID/IG = 0.71) depicted a round-trip efficiency of only 0.51 and a 20(th)-cycle discharge capacity of only 340 mA h g(-1) at a current density of 100 mA g(-1). By contrast, the graphene foam electrode annealed at 800 °C with ID/IG = 0.07 delivered a round-trip efficiency of up to 80% with a stable discharge voltage at ~2.8 V and a stable charge voltage below 3.8 V for 20 cycles. According to the analysis on the electrodes after 20 cycles, the structural defects led to the quickened decay of the graphene foams and boosted the formation of side products.