Self-Reconstructed Two-Dimensional Cluster-Based Co-Organic Layer Heterojunctions for Enhanced Oxygen Evolution Reactions.

When it comes to an efficient catalytic oxygen evolution reaction (OER) in the production of renewable energy and chemicals, the construction of heterogeneous structures is crucial to break the linear scalar relationship of a single catalyst. This heterogeneous structure construction helps creatively achieve high activity and stability. However, the synthesis process of heterogeneous crystalline materials is often complex and challenging to capture and reproduce, which limits their application. Here, the dynamic process of structural changes in Co-MOFs in alkali was captured by in situ powder X-ray diffraction, FT-IR spectroscopy, and Raman spectroscopy, and several self-reconfigured MOF heterogeneous materials with different structures were stably isolated. The created ß-Co(OH)2/Co-MOF heterojunction structure facilitates rapid mass-charge transfer and exposure of active sites, which significantly enhanced OER activity. Experimental results show that this heterogeneous structure achieves a low overpotential of 333 mV at 10 mA cm-2. The findings provide new insights and directions for the search for highly reactive cobalt-based MOFs for sustainable energy technologies.

Rapid Synthesis of Si-Rich SSZ-13 Zeolite under Fluoride-Free Conditions.

Rapid synthesis of Si-rich (SiO2/Al2O3 > 100) SSZ-13 zeolite under fluoride-free conditions is highly desirable but still challenging. Herein, we for the first time report a rapid synthesis of all silica and aluminosilicate (SiO2/Al2O3 > 100) SSZ-13 zeolite without the addition of fluoride species. The crystallization could be fully completed at 160 °C for 4 h when the aging of the starting gel is 3 h at room temperature after the addition of a zeolite seed. The key to success is the formation of more basic building units (4- and 6-membered rings) in the initial gel with the aging time of 3 h after the addition of a zeolite seed, leading to the successful rapid synthesis of Si-rich SSZ-13 zeolite. The obtained Si-rich SSZ-13 zeolite displays high crystallinity, uniform cubic morphology with a nanoparticle feature, and a large surface area. More importantly, the obtained Si-rich SSZ-13 zeolite displays excellent performance in the adsorption of ethanol and methanol-to-olefin reaction.

Highly Stable Two-Dimensional Cluster-Based Ni/Co-Organic Layers for High-Performance Supercapacitors.

Basic requirements for advanced and practical supercapacitors need electrode materials with strong stability, high surface area, well-defined porosity, and enhanced capability of ion insertion and electron transfer. It is worth mentioning that the two-dimensional cluster-based Ni/Co-organic layer (Ni0.7Co0.3-CMOL) inherits high stability from the Kagóme lattice and shows excellent pseudocapacitance behavior. As an optimized atomic composition, this crystalline CMOL exhibits excellent performance and stability both in 1.0 M KOH and All-Solid-State Flexible Asymmetric Supercapacitor (ASCs). The specific capacitance values are 1211 and 394 F g-1 and the energy density is 54.67 Wh kg-1 at 1 A g-1. Good cycling stability is characterized by its capacitance retention, maintained at 92.4% after 5000 cycles in a three-electrode system and 90% after 2000 cycles at 20 A g-1 for assembled All-Solid-State Flexible ASCs. An in situ XRD technique was used in the three-electrode system, which showed that there was no signal of crystalline substance that affected the cyclic stability of the material while charging and discharging. These superior results prove that Ni0.7Co0.3-CMOL is a promising candidate for supercapacitor applications.

Deterministic growth of AgTCNQ and CuTCNQ nanowires on large-area reduced graphene oxide films for flexible optoelectronics.

We describe a synchronous reduction and assembly procedure to directly produce large-area reduced graphene oxide (rGO) films sandwiched by a high density of metal nanoparticles (silver and copper). Further, by using the sandwiched metal NPs as sources, networks consisting of AgTCNQ and CuTCNQ nanowires were deterministically grown from the rGO films, forming structurally and functionally integrated rGO/metal-TCNQ hybrid films with outstanding flexibility, bending endurance, and electrical stability. Interestingly, due to the p-type nature of the rGO film and the n-type nature of the metal-TCNQ NWs, the hybrid films are essentially thin-film p-n junctions which are useful in ubiquitous electronics and optoelectronics. Measurements of the optoelectronic properties demonstrate that the rGO/metal-TCNQ hybrid films exhibit substantial photoconductivity and highly reproducible photoswitching behaviours. The present approach may open the door to the versatile and deterministic integration of functional nanostructures into flexible conducting substrates and provide an important step towards producing low-cost and high-performance soft electronic and optoelectronic devices.

Highly-dispersed nickel species on nitrogen-doped porous carbon: Significant local pH-buffering capacity and favorable CO desorption for efficient and robust electro-reduction of CO2.

Electrocatalytic reduction of CO2 (CO2RR) to value-added fuels and chemicals can potentially serve as a promising strategy to curb CO2 accumulation and carbon neutral cycle, but is still plagued by sluggish kinetics, poor selectivity and weak durability. Herein, we developed highly-dispersed nickel species on the nitrogen-doped carbon materials (Ni/NC) via the double solvent method (DSM), followed by the pyrolysis. The as-prepared Ni/NC possesses high CO2-to-CO selectivity of 93.2%∼98.6% at broad potential range (0.57 âˆ¼ 0.97 VRHE), decent jCO of 57.9 mAcm-2 at -1.07 VRHE, and significant robustness (retaining 96.3% of the initial faradaic efficiency for CO formation after 50 h electrolysis). As manifested by the rotating ring-disk electrode (RRDE) tests, the DSM-based Ni/NC possesses more significant pH-buffering capacity than Ni nanoparticles, thus promotes the CO2-to-CO. DFT calculations unveil that Ni/NC exhibits relatively lower d-band center, hence resulting in favorable desorption of CO from the catalyst surface that intrinsically boost the CO2-to-CO compared with the nanoparticle catalyst. These results suggest that the DSM-derived Ni/NC catalysts is a promising candidate towards large-scale application of CO2-to-CO.

Graphene oxide enabled self-assembly of silver trimolybdate nanowires into robust membranes for nanosolid capture and molecular separation.

A graphene oxide (GO) assisted self-assembly strategy for growing a silver trimolybdate nanowire membrane with capabilities of nanosolid capture and small molecule separation is reported. Thanks to the GO bridges and the accurate self-assembly process, the resulting membrane exhibits outstanding mechanical properties (can withstand 4300 times its weight) and impressively high porosity (97%). On the basis of the robustness and high porosity of the membrane, column-shaped filter apparatus has been fabricated, in which the membrane served as a self-standing permeation barrier to assess its permeability and practical application as a nanosolid filter and molecule filter. The permeability test of the membrane with pure water uncovers that the membrane exhibits fast permeability while driven by hydrostatic pressure only because of its significantly high porosity. The separation test of the membrane with P25 TiO2 solution, 13 nm Au solution, and yellow-emitting CdTe QDs reveals that all the tiny nanosolids are completely removed from the solution, which suggests that the membrane is an efficient nanosolid filter. Its efficiency is increased by the induction of surface collision from numerous nanowire barriers and the deposition of nanosolids on the nanowire surface. The separation test of the membrane with a mixed-dye solution reveals that sulfur containing methylene blue (MB) molecules are highly efficiently extracted under various chemical conditions, evidencing that the membrane is an ideal molecule filter too. Its high selectivity and high efficiency originated from the Ag-S bonding between the interlayered silver ions of the silver trimolybdate nanowire and the sulfur atom of MB molecules. Based on the above results, the silver trimolybdate nanowire membrane has been applied to purify drugs, which successfully removed sulbactam sodium impurity F from sulbactam sodium, demonstrating a purity increment from 98.92% to 99.93%. The present work should provide a significant step forward to bringing macroscopic 1D nanomaterial architectures much closer to real-world applications involving isolation and enrichment of catalyst reclamation, high-value chemical recovery, drug purification, and environmental remediation.

Upcycling waste expanded polystyrene into UV-excited dual-mode multicolor luminescent electrospun fiber membranes for advanced anti-counterfeiting.

Expanded polystyrene (EPS) is causing severe environmental problems due to its high consumption and non-biodegradability. Upcycling waste EPS into high value-added functional materials is highly advisable in terms of sustainability and environmental concerns. Meanwhile, it is imperative to develop new anti-counterfeiting materials with high security against increasingly high-tech counterfeiting. Developing UV-excited dual-mode luminescent advanced anti-counterfeiting materials that can be excited by commonly used commercial UV light sources (such as 254 nm and 365 nm wavelengths) remains a challenge. Herein, UV-excited dual-mode multicolor luminescent electrospun fiber membranes were fabricated from waste EPS by co-doping with a Eu3+ complex and a Tb3+ complex via electrospinning. The SEM results prove that the lanthanide complexes are uniformly dispersed in the PS matrix. The luminescence analysis results suggest that all the as-prepared fiber membranes with the different mass ratios of the two complexes can exhibit the characteristic emission of Eu3+ ions and Tb3+ ions under UV light excitation. The corresponding fiber membrane samples can exhibit intense visible luminescence with different colors under UV lights. Moreover, each membrane sample can display different color luminescence irradiated with UV light at 254 nm and 365 nm, respectively, e.g. show excellent UV-excited dual-mode luminescent properties. This is owing to the different UV absorption properties of the two lanthanide complexes doped in the fiber membrane. Finally, the fiber membranes with different color luminescence from green light to red light were achieved by tuning the mass ratio of the two complexes in the PS matrix and changing UV irradiation wavelengths. The as-prepared fiber membranes with tunable multicolor luminescence are very promising for high-level anti-counterfeiting applications. This work is very meaningful not only to upcycle waste EPS to high value-added functional products but also to develop advanced anti-counterfeiting materials.

Killing Two Birds with One Stone: Upgrading Organic Compounds via Electrooxidation in Electricity-Input Mode and Electricity-Output Mode.

The electrochemically oxidative upgrading reaction (OUR) of organic compounds has gained enormous interest over the past few years, owing to the advantages of fast reaction kinetics, high conversion efficiency and selectivity, etc., and it exhibits great potential in becoming a key element in coupling with electricity, synthesis, energy storage and transformation. On the one hand, the kinetically more favored OUR for value-added chemical generation can potentially substitute an oxygen evolution reaction (OER) and integrate with an efficient hydrogen evolution reaction (HER) or CO2 electroreduction reaction (CO2RR) in an electricity-input mode. On the other hand, an OUR-based cell or battery (e.g., fuel cell or Zinc-air battery) enables the cogeneration of value-added chemicals and electricity in the electricity-output mode. For both situations, multiple benefits are to be obtained. Although the OUR of organic compounds is an old and rich discipline currently enjoying a revival, unfortunately, this fascinating strategy and its integration with the HER or CO2RR, and/or with electricity generation, are still in the laboratory stage. In this minireview, we summarize and highlight the latest progress and milestones of the OUR for the high-value-added chemical production and cogeneration of hydrogen, CO2 conversion in an electrolyzer and/or electricity in a primary cell. We also emphasize catalyst design, mechanism identification and system configuration. Moreover, perspectives on OUR coupling with the HER or CO2RR in an electrolyzer in the electricity-input mode, and/or the cogeneration of electricity in a primary cell in the electricity-output mode, are offered for the future development of this fascinating technology.

Electrophoretic build-up of alternately multilayered films and micropatterns based on graphene sheets and nanoparticles and their applications in flexible supercapacitors.

Graphene nanosheets and metal nanoparticles (NPs) have been used as nano-building-blocks for assembly into macroscale hybrid structures with promising performance in electrical devices. However, in most graphene and metal NP hybrid structures, the graphene sheets and metal NPs (e.g., AuNPs) do not enable control of the reaction process, orientation of building blocks, and organization at the nanoscale. Here, an electrophoretic layer-by-layer assembly for constructing multilayered reduced graphene oxide (RGO)/AuNP films and lateral micropatterns is presented. This assembly method allows easy control of the nano-architecture of building blocks along the normal direction of the film, including the number and thickness of RGO and AuNP layers, in addition to control of the lateral orientation of the resultant multilayered structures. Conductivity of multilayered RGO/AuNP hybrid nano-architecture shows great improvement caused by a bridging effect of the AuNPs along the out-of-plane direction between the upper and lower RGO layers. The results clearly show the potential of electrophoretic build-up in the fabrication of graphene-based alternately multilayered films and patterns. Finally, flexible supercapacitors based on multilayered RGO/AuNP hybrid films are fabricated, and excellent performance, such as high energy and power densities, are achieved.

A green route for synthesizing pure silica zeolites with six-membered rings.

Green routes for synthesizing pure silica zeolites are attractive but still challenging. Herein, we for the first time report a green route for synthesizing pure silica zeolites with six-membered rings (6MRs) by a combined strategy of ethanol filling and zeolite seeding. As a result, pure silica zeolites with 6MRs, such as SOD, MTN, and NON, could be successfully synthesized.

Fluoride-free synthesis of beta zeolite with enrichment of polymorph B from a solvent-free route.

Beta zeolite with enrichment of polymorph B is successfully synthesized in the absence of fluorine species under solvent-free conditions. The phase composition of polymorph B in the sample is about 70%.

Facile synthesis of mesoporous polymeric carbon nitride nanosheets anchored by Pt with ultralow loading for high-efficiency photocatalytic H2 evolution.

The facile fabrication of low-cost photocatalysts with enhanced activity and high atomic utilization is becoming increasingly necessary for solar energy usage and/or conversion. In this work, a series of mesoporous carbon nitride nanosheets with an enlarged specific surface area was synthesized via an inorganic acid-assisted exfoliation method without any soft or hard templates. An ultralow loading of downsized noble metal Pt was anchored on these porous nanosheets, exhibiting enhanced photocatalytic activity. The formation of mesoporous nanosheets in carbon nitride was expected to boost the mass transfer and shorten the charge carrier transfer route during the photocatalytic reaction. The characterization of samples revealed that the enhanced conductivity and photocurrent of the carbon nitride nanosheets also contributed to the enhanced H2 evolution activity. The maximum H2 production rates of 172.92 µmol h-1 and 321 µmol h-1 were achieved over the nanosheets derived from melamine and urea under visible light irradiation, which are 10.92- and 2.22-fold that of the corresponding bulk carbon nitride, respectively. This exfoliation method was demonstrated to be an efficient and universal method for the preparation of carbon nitride nanosheets with a mesoporous structure and high atom utilization of the co-catalyst for H2 evolution from water.

A strategy for synthesis of magnetic nanoparticles with "well-defined" polymers via reversible addition fragmentation chain transfer polymerization under ultrasonic irradiation.

The controlled graft modification of Fe3O4 magnetic nanoparticles has been achieved by reversible addition fragmentation chain transfer (RAFT) polymerization under ultrasonic irradiation. The nanoparticles of Fe3O4 were first prepared by a chemical co-precipitation method, and reacted with 3-aminopropyltriethoxylsilane (KH550), and subsequently with S-1-dodecyl-S'-(alpha,alpha'-dimethyl-alpha'-acetic acid) trithiocarbonate (DDACT) to serve as RAFT agent. The graft polymerization of methyl acrylate was carried out under ultrasonic irradiation (28 KHz, 60 W). The first-order kinetics and the polymers with narrow molecular weight distributions suggested the polymerization proceeded via RAFT process. The resultant products were characterized by Fourier transform infrared spectrometer (FT-IR), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), high performance particle sizer (HPPS) and Gouy magnetic balance. The resultant products with good paramagnetism could be well modified with the "well-defined" polymers via RAFT polymerization under ultrasonic irradiation, thereby providing a new method to well modify magnetic nanoparticles.

Efficient treatment of brine wastewater through a flow-through technology integrating desalination and photocatalysis.

Many current treatments for brine wastewaters are energy-intensive, chemical-intensive, and involve independent process in the removal of salts and contaminants. We demonstrate that through the integration of capacitive deionization and photocatalysis reactions within carbon nanotubes (CNTs) based membrane system, we are able to realize the purification and desalination of wastewaters via single-step, energy-efficient, and environmentally friendly route. We firstly designed the membrane system consisting of graphitic carbon nitride (g-C3N4), CNTs membrane, and poly(vinyl alcohol)-formaldehyde (PVF) foam. Then, two identical membrane systems were used as permeable electrodes and photocatalytic microreactors to construct the flow-through setup. The tests of the setup with a variety of dye solution, antibiotics solution, and actual wastewaters prove that wastewaters passing through the setup promptly turn to clean water with significantly decreased salinity. This is because the setup can use C3N4 modified CNTs membrane to adsorb organic contaminants and inorganic ions and decompose contaminants via photocatalysis reactions. In addition, by discharging the setup, its adsorption capacity towards salts is easily recovered. Consequently, the flow-through setup is observed to exhibit stable performance for concurrent removal of organic contaminants and inorganic salts in multiple cycles.

In-Situ Fabrication of g-C3N4/ZnO Nanocomposites for Photocatalytic Degradation of Methylene Blue: Synthesis Procedure Does Matter.

The nanocomposite preparation procedure plays an important role in achieving a well-established heterostructured junction, and hence, an optimized photocatalytic activity. In this study, a series of g-C3N4/ZnO nanocomposites were prepared through two distinct procedures of a low-cost, environmentally-friendly, in-situ fabrication process, with urea and zinc acetate being the only precursor materials. The physicochemical properties of synthesized g-C3N4/ZnO composites were mainly characterized by XRD, UV⁻VIS diffuse reflectance spectroscopy (DRS), N2 adsorption-desorption, FTIR, TEM, and SEM. These nanocomposites' photocatalytic properties were evaluated in methylene blue (MB) dye photodecomposition under UV and sunlight irradiation. Interestingly, compared with ZnO nanorods, g-C3N4/ZnO nanocomposites (x:1, obtained from urea and ZnO nanorods) exhibited weak photocatalytic activity likely due to a "shading effect", while nanocomposites (x:1 CN, made from g-C3N4 and zinc acetate) showed enhanced photocatalytic activity that can be ascribed to the effective establishment of heterojunctions. A kinetics study showed that a maximum reaction rate constant of 0.1862 min-1 can be achieved under solar light illumination, which is three times higher than that of bare ZnO nanorods. The photocatalytic mechanism was revealed by determining reactive species through adding a series of scavengers. It suggested that reactive ∙O2- and h⁺ radicals played a major role in promoting dye photodegradation.

Engineering Stable Surface Oxygen Vacancies on ZrO2 by Hydrogen-Etching Technology: An Efficient Support of Gold Catalysts for Water-Gas Shift Reaction.

The surface structure of supports is crucial to fabricate efficient supported catalysts for water-gas shift (WGS). Here, hardly reducible ZrO2 was etched with hydrogen (H), aiming to modify surface structures with sufficient stable oxygen vacancies. After deposition of gold species, the obtained khaki ZrO2-H notably improved WGS catalytic activities and stabilities in comparison to the traditional white ZrO2. The characterization results and quantitative analysis indicate that sufficient surface oxygen vacancies of ZrO2-H support give rise to more metallic Au0 species and higher microstrain, which all boost WGS catalytic activities. Furthermore, optoelectronic properties were successfully used to correlate with their WGS thermocatalytic activities, and then a modified electron flow process was proposed to understand the WGS pathway. For one thing, the introduction of surface oxygen vacancies narrowed the band gap of ZrO2 and decreased the Ohmic barrier, which facilitated the flow of "hot-electron". For another thing, the conduction band electrons can be easily trapped by oxygen vacancies of ZrO2 supports, and then these trapped electrons immediately take part in reduction of H2O to H2. Thus, the electron recombination was suppressed and the WGS catalytic activity was improved. It is worth extending H2-etching technology to improve other thermocatalytic reactions.

Chemical-free fabrication of N, P dual-doped honeycomb-like carbon as an efficient electrocatalyst for oxygen reduction.

Heteroatom-doped nanoporous carbons are now emerging as alternatives to platinum and its alloys as electrocatalysts to facilitate oxygen reduction reaction in metal-air batteries and fuel cells. However, the synthesis of nanoporous carbons usually involve in complicated procedures and intensive chemicals, which may dramatically raise their manufacture cost that even surpasses that of precious platinum. Herein, we demonstrate the single-step, chemical-free fabrication of N, P dualdoped honeycomb carbon that has hierarchically porous structure and oxygen electrocatalysis activity close to the benchmark Pt/C. This material was fabricated through the direct pyrolysis of popcorn in a static, semi-opened environment. With this strategy, nitrous and phosphoric groups from proteins and phosphates within the popcorn are condensed with graphitic matrix to form NC and PC bonds, and pyrolysis byproducts (such as H2O and CO2) can etch disordered carbon domains to form hierarchical pores and edge carbons. Practical test of this honeycomb carbon as air electrode of a primary Zn-air battery shows an open-circuit potential of 1.44V and peak power density of 36.6mWcm-2 that is even better than Pt/C. The impact of this work is that it will facilitate the targeted design and cost-saved fabrication of metal-free catalysts for electrocatalytic applications.

Interlocked multi-armed carbon for stable oxygen reduction.

Structurally interlocked multi-armed carbon with a highly extended surface may be conveniently prepared by the deterministic growth of ZIF-8 on ZnO multiarms and the subsequent pyrolysis, which exhibits excellent stability and methanol corrosion resistance for oxygen reduction application.

Development of one-dimensional nanostructures through the crystallization of amorphous colloids.

In this paper we have demonstrated that the crystallization method of amorphous colloids is convenient and feasible in the large-scale production of one-dimensional (1D) nanostructures. For the crystals with highly anisotropic structures, such as orthorhombic, trigonal, and hexagonal crystals, the crystallization generally tends to occur along the (001) axis. The preparation of orthorhombic bismuth sulfide (Bi2S3) nanorods and trigonal selenium ( t-Se) nanowires by the crystallization route was used as typical examples to illustrate the process and mechanism of crystallization. The as-prepared products were characterized with transmission electron microscopy, field-emission scanning electron microscopy, X-ray diffraction, and selected area electron diffraction. Additionally, the detailed crystal growth processes involved in the crystallization of amorphous Bi2S3 colloid were investigated by studying the morphology and structure of intermediates. It demonstrates that the growth of the nanorods is through two key steps: (1) the formation of multiple activated sites on the surface of spherical Bi2S3 colloid and (2) the subsequent preferential growth along these sites.