Template-free Approach Research Articles

Template-Free Synthesis of Hollow Iron Phosphide–Phosphate Composite Nanotubes for Use as Active and Stable Oxygen Evolution Electrocatalysts

The oxygen evolution reaction (OER) is a half-cell reaction that is of importance to many electrochemical processes, especially for electrochemical and photoelectrochemical water splitting. Developing efficient, durable, and low-cost OER electrocatalysts comprising Earth-abundant elements has been in the focus of electrocatalysis research. Herein, we report a cost-effective, scalable, and template-free approach to the fabrication of hollow iron phosphide–phosphate (FeP–FePxOy) composite nanotubes (NTs), which is realized by hydrothermal growth of iron oxy-hydroxide nanorods (NRs) and a subsequent postphosphorization treatment. The hollow interior of NTs results from the Kirkendall effect occurring upon phosphorization. When used to catalyze the OER in basic medium, the as-synthesized FeP–FePxOy composite NTs exhibit excellent catalytic activity, delivering the benchmark current density of 10 mA cm–2 at a low overpotential of 280 mV and showing a small Tafel slope of 48 mV dec–1 and a high turnover frequen...

Solvothermal Synthesis of Sphere-Like ZnS Microparticles and Its Visible-Light Catalytic Properties.

The cauliflower-like ZnS microspheres consisting of the nanospheres were prepared via one step template-free approach employing a solvothermal process using Zn(NO3)2·6H2O and CH4N2S as precursors in the mixture solution. The morphology, structure characterization, and crystal structure of the as-prepared ZnS were performed by X-ray diffraction, scanning electron microscopy, UV-visible absorption, and X-ray photoelectron spectroscopy. The results showed that cauliflowerlike ZnS microspheres were prepared under this condition and the size of the particles were about 3~5 μm. In addition, the excellent photocatalytic activity and degradation mechanism of ZnS microspheres have been investigated and discussed in detail. The degradation of Rhodamine B (RhB) aqueous solution was carried out to investigate the visible-light catalytic activity under metal halide lamp. The results indicated that different size of ZnS had photocatalytic activity to RhB under visible light, and sphere-like ZnS displayed high photodegradation efficiency with degradation rate of 98% within 140 min.

Template-Free Synthesis of Aligned Polyaniline Nanorods/Tubes and Copper/Copper Hydroxide Nanowires for Application as Fillers in Polymer Nanocomposites

Aligned polyaniline nanorods were synthesized in the presence of salicylic acid. Nanorods and nanotubes were also formed in the presence of camphorsulfonic acid (CSA) and para-toluenesulfonic acid (pTSA). Electrical conductivity measurements showed that the aligned nanorods had better electrical conductivity than the non-aligned nanostructures. Nanospheres were also observed in some cases. The formation of elongated nanostructures or spheres depended on the aniline monomer to surfactant molar ratio. This method in which nanostructures are formed using soft templates is often referred to as the template-free approach. Our success motivated us to explore the feasibility of obtaining similar metallic nanostructures without the use of a template. We successfully synthesized copper and copper hydroxide nanowires. While the copper nanowires formed as a mesh, the copper hydroxide nanowires formed as winding bundles. Upon switching the order in which the reactants were added, copper hydroxide nanoribbons were formed instead of bundles. Characterization of these nanostructures was done using Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR) and the Four-point probe to measure electrical conductivity. Both metallic and organic nanowires that are fabricated by template-free methods are potential candidates for use as fillers in polymer nanocomposites. Polymer nanocomposites are found to be used in many advanced modern applications such as thermal interface materials in electronic devices which continue to be miniaturized, aerospace engineering where lightweight and robustness are important, sensors, medicine and catalytic activity.

Multiple heteroatom-doped few-layer carbons for the electrochemical oxygen reduction reaction

We demonstrate a template-free and scalable approach towards synthesis of a new family of multiple heteroatom-doped (N/O, N/S/O, N/P/O, and N/S/P/O) few-layer carbons as metal-free catalysts for the high performance oxygen reduction reaction under pH-universal conditions.

Diethylenediamine-assisted template-free synthesis of a hierarchical TiO2 sphere-in-sphere with enhanced photocatalytic performance.

With the assistance of diethylenediamine (DETA), a template-free solvothermal approach is employed to one-step synthesize a hierarchical TiO2 sphere-in-sphere, which has a unique structure: an interior nanosized sphere is contained in the cavity of another hollow microsphere, and numerous nanosheets of width ca. 20-26 nm vertically distribute on the surface. It is proved that DETA added in solution plays an important inducing role in the formation of both the hollow sphere-in-sphere structure and surface sheet-assembled network. Therefore, a DETA-assisted formation mechanism of the hierarchical TiO2 sphere-in-sphere has been described in detail. The unique hierarchical sphere-in-sphere structure endows the TiO2 product with increasing light-harvesting efficiency and specific surface area, resulting in its enhanced photocatalytic activity for the degradation of various organic pollutants under the illumination of UV light.

Mesoporous layered hexagonal platelets of Co3O4 nanoparticles with (111) facets for battery applications: high performance and ultra-high rate capability.

The thermally stable and crystalline 2D layered mesoporous hexagonal platelets of cobalt oxide (Co3O4) with (111) facets were prepared by using the template-free wet chemical synthesis approach. The high surface energy (111) facets known for a highly electroactive surface are expected to enhance the electrochemical properties, especially the rate capability. The highly crystalline Co3O4 with an average particle size of 25 nm formed a 2D mesoporous layered structure, with an average thickness of ∼40 nm, a pore size of 8-10 nm, and a specific surface area of 45.68 m2 g-1 promoting large surface confined electrochemical reaction. The 2D layered mesoporous Co3O4 exhibits a maximum specific capacity of 305 mA h g-1 at a scan rate of 5 mV s-1 and 137.6 mA h g-1 at a current density of 434.8 mA g-1. The maximum energy and power densities of 32.03 W h kg-1 and 9.36 kW kg-1, respectively, are achieved from the 2D hexagonal platelets of mesoporous Co3O4 nanoparticles with (111) facets. An excellent ultra-high rate capability of ∼62% capacity retention was observed after increasing the discharge current density from ∼434.8 mA g-1 to 43 480 mA g-1. Furthermore, a cycling stability of 81.25% was achieved even after 2020 charge-discharge cycles at a current density of 12 170 mA g-1. This high performance and ultra-high rate capability could be attributed to the (111) facets 'crystal plane' effect of Co3O4. Our results presented here confirm that the 2D mesoporous layered hexagonal platelets of Co3O4 exhibit "battery-mimic" behaviour in an aqueous electrolyte of KOH.

Single-phase cerium oxide nanospheres: An efficient photocatalyst for the abatement of rhodamine B dye.

Single-phase mesoporous CeO2 nanospheres were synthesized by template-free hydrothermal approach by the synthesis of CeCO3OH precursor combined with the calcination at 350°C for 3.0h. Precursor and calcined products were characterized by XRD, TGA, FESEM, EDX, TEM, N2 adsorption-desorption and pore size distribution analysis, UV-vis diffuse reflectance (UV-vis DRS), and photoluminescence (PL) analysis. The morphologies of CeO2 nanospheres were controlled via the optimization of urea concentration during the synthesis. Calcined CeO2 exhibited excellent photocatalytic activity of rhodamine B (RhB) dye degradation under UV-visible irradiation and mild acidic condition. Scavenger test analysis was used to confirm that the hydroxyl radicals, superoxide radicals, and photogenerated holes are the active photoinduced species of RhB degradation. A comparative study of PL intensity, dye adsorption, and zeta potential measurement revealed the efficient dye adsorption over different CeO2 photocatalysts. The RhB degradation rate constant has been found to raise linearly with increase of the surface properties. Repeatability test analysis proved the higher catalytic stability of CeO2 nanospheres without any noticeable loss of activity. Mass spectroscopy and ion chromatography analyses were used to detect the intermediate by-product formation. Finally, based on the results of intermediate detection, possible degradation pathways were also proposed including radical reactions, ring opening, and de-nitrification.

High Efficiency Gene Correction in Hematopoietic Cells by Donor-Template-Free CRISPR/Cas9 Genome Editing.

The CRISPR/Cas9 prokaryotic adaptive immune system and its swift repurposing for genome editing enables modification of any prespecified genomic sequence with unprecedented accuracy and efficiency, including targeted gene repair. We used the CRISPR/Cas9 system for targeted repair of patient-specific point mutations in the Cytochrome b-245 heavy chain gene (CYBB), whose inactivation causes chronic granulomatous disease (XCGD)—a life-threatening immunodeficiency disorder characterized by the inability of neutrophils and macrophages to produce microbicidal reactive oxygen species (ROS). We show that frameshift mutations can be effectively repaired in hematopoietic cells by non-integrating lentiviral vectors carrying RNA-guided Cas9 endonucleases (RGNs). Because about 25% of most inherited blood disorders are caused by frameshift mutations, our results suggest that up to a quarter of all patients suffering from monogenic blood disorders could benefit from gene therapy employing personalized, donor template-free RGNs.

Activated Carbon Monolith Derived from Amygdalus Pedunculata Shell and Polyacrylonitrile for Supercapacitors

Abstract Activated carbon monolith (ACM) was obtained from Amygdalus pedunculata shell (APS) and polyacrylonitrile (PAN) via a template-free approach. APS was uniformly distributed into the monolith matrix and an interconnected network was fully established. The present study greatly promotes the close contact between desert reclamation and green energy storage.

Template-free synthesis of hierarchical meso-macroporous γ-Al2O3 support: Superior hydrodemetallization performance

The design of hierarchically porous catalytic supports is considered as one of the most efficient strategies to achieve efficient mass transport and thus high catalytic performance in heterogeneous catalysis. As one of the most important catalytic supports, facile synthesis of γ-Al2O3 with hierarchical porosities is of great industrial importance. In this paper, nest-like hollow γ-AlOOH microspheres constructed from numerous hierarchically organized nanowires were synthesized via a template-free simple hydrothermal approach, from which hierarchically porous γ-Al2O3 microspheres with average macropores of 900nm, mesopores of 20nm and a pore volume of 0.93cm3/g were obtained readily. Due to their structural merits, such nest-like γ-Al2O3 microspheres could serve as excellent catalytic support. As a demonstration, a MoNi/γ-Al2O3 supported catalyst was prepared, which was applied for hydrodemetallization (HDM) catalysis. Compared with the catalyst prepared with the commercial γ-Al2O3, our catalyst exhibits superior catalytic performance and longer life due to enhanced diffusion of the reactants.

Urine to highly porous heteroatom-doped carbons for supercapacitor: A value added journey for human waste

Obtaining functionalized carbonaceous materials, with well-developed pores and doped heteroatoms, from waste precursors using environmentally friendly processes has always been of great interest. Herein, a simple template-free approach is devised to obtain porous and heteroatom-doped carbon, by using the most abundant human waste, “urine”. Removal of inherent mineral salts from the urine carbon (URC) makes it to possess large quantity of pores. Synergetic effect of the heteroatom doping and surface properties of the URC is exploited by carrying out energy storage application for the first time. Suitable heteroatom content and porous structure can enhance the pseudo-capacitance and electric double layer capacitance, eventually generating superior capacitance from the URC. The optimal carbon electrode obtained particularly at 900 °C (URC-900) possesses high BET surface area (1040.5 m2g−1), good conductivity, and efficient heteroatom doping of N, S, and P, illustrating high specific capacitance of 166 Fg−1 at 0.5 Ag−1 for three-electrode system in inorganic electrolyte. Moreover, the URC-900 delivers outstanding cycling stability with only 1.7% capacitance decay over 5,000 cycles at 5 Ag−1. Present work suggests an economical approach based on easily available raw waste material, which can be utilized for large-scale production of new age multi-functional carbon nanomaterials for various energy applications.

Template-Free Synthesis and Catalytic Applications of Microporous and Hierarchical ZSM-5 Zeolites from Natural Aluminosilicate Minerals

Organic templates play a crucial role in zeolite synthesis, but their use causes serious pollutant emissions and increases product costs. Herein, we report a template-free approach to synthesize both microporous and hierarchical ZSM-5 zeolites from natural aluminosilicate mineral, which is achieved by (1) utilizing the mother liquid to construct mesopores without using any mesoscale template and (2) reusing the Si-rich alkali liquor and ion-exchanging solution to improve the atom economy without any alkali/acid liquor discharges. The results show that the resultant zeolites own more open pore channels and less strong acid sites compared with a conventional ZSM-5 zeolite and demonstrate superior catalytic activity in n-octene hydroisomerization. Significantly, compared with the traditional synthesis process, our approach can greatly reduce the material and energy consumptions and pollutant discharges while significantly increase the raw material utilization efficiency, endowing itself as an economic, eco-s...

Enhanced Visible-Light-Driven Photocatalytic Disinfection Performance and Organic Pollutant Degradation Activity of Porous g-C3N4 Nanosheets.

Porous g-C3N4 nanosheet (PCNS) photocatalyst with a thickness of 2.0 nm, pore volume of 0.61 cm3 g-1, and surface area of 190.1 m2 g-1 was prepared by a simple two-step template-free approach without the addition of extra reagents. Compared with the bulk g-C3N4 (BCN), PCNS possesses a greater number of surface reactive sites, improved efficiency of charge transfer, and accelerated separation of photogenerated electron-hole pairs. Accordingly, the visible-light-driven photocatalytic disinfection performance and organic pollutant degradation activity of PCNS are significantly enhanced. Escherichia coli (E. coli) cells can be killed completely by PCNS within 4 h, whereas only 77.1% of E. coli cells can be killed by BCN. The photodegradation rates of PCNS on methylene blue, Acid Red 27, and bisphenol A are almost 6.4, 4.0, and 1.9 times as fast as that of BCN, respectively. The photocurrent intensity of PCNS is about 3.7 times in comparison with that of BCN. Considering the easy preparation and excellent performance, PCNS could be a promising and competitive visible-light-driven photocatalyst in the field of environment remediation.

CoMn2O4 Anchored on N-Doped High-Dimensional Hierarchical Porous Carbon Derived from Biomass for Bifunctional Oxygen Electrocatalysis

There is an emerging interest in developing bifunctional oxygen electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), being key electrochemical reactions that govern the overall performance of unitized regenerative fuel cells and rechargeable metal-air batteries. However, such undertaking has been a huge challenge due to the high cost of noble metals (e.g. Pt, Ir) and their stability when used as catalysts. Herein, we report CoMn2O4 embedded on three-dimensional (3D) hierarchical porous carbon (HPC) derived from waste corn cobs as a possible noble metal-free bifunctional electrocatalyst. The hybrid catalyst is fabricated by solvothermal reaction of as-prepared N-doped 3DHPC and CoMn2O4. The template-free approach in preparing N-3DHPC ensures ample nitrogen doping using melamine to improve electronic conductivity of carbon and formation of three-dimensional, interconnected pore network, which is favorable for CoMn2O4 crystal dispersion. The same hybrid material also presents good OER activity, rendering an active and inexpensive dual-function electrocatalyst.

Sulfur doped-copper oxide nanoclusters synthesized through a facile electroplating process assisted by thiourea for selective photoelectrocatalytic reduction of CO2

Development of effective methods for conversion of CO2 to useful chemicals is considered to be a prospective way in terms of energy economy and chemical industry. Due to the thermodynamic stability of CO2, the application of the low-cost eco-friendly catalyst or photocatalyts for CO2 reduction with high efficiency is a challenge. Herein, we report a simple template-free electrochemical approach for the preparation of sulfur doped copper oxide nanoclusters directly on the copper disc electrode using thiourea (TU) as sulfur precursor. The prepared Cu2O/CuO hybrid structures without TU exhibits photoelectrocatalytic fitness for CO2 reduction, while the catalytic activity and stability are significantly improved after sulfur substitution. Surface study by scanning electron microscopy (SEM) and atomic force microscopy (AFM) reveals an improved surface roughness alongside the formation and distribution of uniform nanoclusters of sulfur-substituted copper oxide. Also, optical analyses show a little increasing of band gap from 1.95eV to 2.05eV after sulfur substitution. Based on the experimental results, methanol and acetone are the main CO2 reduction products where, the overpotential of methanol and acetone evolution is in good agreement with the conduction band position of prepared nanoclusters. This work has a high competitive advantage of new sight to develop the novel doped materials via a simple way for high-performance photoelectrocatalysts for energy conversion.

CuO nanosheets/ZnO nanorods synthesized by a template-free hydrothermal approach and their optical and magnetic characteristics

Abstract Nanostructured CuO/ZnO heterojunctions were fabricated via a template-free hydrothermal reaction. The prepared CuO/ZnO nanocomposites are composed of one dimensional (1D) hexagonal ZnO nanorods and two-dimensional (2D) monoclinic CuO nanosheets. The single crystal nature of both ZnO and CuO was confirmed. Optical spectra show the widened absorption range from UV to visible light, which suggests the potential of the obtained CuO/ZnO composites for visible-light-driven photocatalyst. The point defects at the interface play the leading role in triggering ferromagnetism of CuO/ZnO composites. Fundamentally, the ferromagnetism can be understood by the charge-transfer mechanism according to Stoner theory. The findings can give a further insight into the ferromagnetic origin of nonmagnetic composites and the integration of ferromagnetic and photocatalytic properties into an identical sample.

Rational construction the composite of graphene and hierarchical structure assembled by Fe2O3 nanosheets for lithium storage

Taking the advantage of hierarchical nanostructures into consideration, herein a facile and template free approach to achieve hierarchical microspheres assembled from the α-Fe2O3 nanosheet was formulated. The followed freeze-drying treatment is employed to realize the construction of nanostructured Fe2O3/graphene composite. The unique hierarchical structure of α-Fe2O3 combined with the flexible graphene layer not only effectively buffer the volume expansion during the cycling process, but also promote the transport of lithium ion and electron through three-dimensional networks when being assessed for lithium ion battery. The as-obtained composite exhibits significantly enhanced cycling stability (1850mAhg−1 after 190 cycles at the current of 300mAg−1) and superior rate performance (around 520mAhg−1 for the current of 5000mAg−1). The obtained-results illustrate that the rational designing of the nanostructured composite can result in the fast lithium insertion/de-insertion in lithium ion batteries which mimic merits seen in high-power electrochemical capacitors.

CoMn2O4 Anchored on N-Doped High-Dimensional Hierarchical Porous Carbon Derived from Biomass As a Bifunctional Oxygen Electrocatalyst

There is an emerging interest in developing bifunctional oxygen electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), as they are key electrochemical reactions that govern the overall performance of emerging rechargeable metal-air batteries. However, such undertaking has been a huge challenge due to the high cost of noble metals (Pt, Ir, and Ru) and their stability when used as catalysts for both the oxygen reactions. Herein, we report CoMn2O4 embedded on three-dimensional (3D) hierarchical porous carbon (HPC) derived from waste biomass (corn cobs) as an efficient noble metal-free bifunctional electrocatalyst for both ORR and OER. The hybrid catalyst (CoMn2O4/N-3DHPC) is fabricated by solvothermal reaction of as-prepared nitrogen-doped 3D HPC and CoMn2O4. The three-step template-free approach in preparing N-3DHPC ensures ample nitrogen doping using melamine as source to improve electronic conductivity of the carbon and formation of three-dimensional interconnected pore network which is favorable to a well-dispersion of CoMn2O4 crystals. Thus, the N-3DHPC possesses a high specific surface area and good electrical conductivity as a result of N doping. The same hybrid material also presents high catalytic activity towards OER, rendering them high-performing inexpensive dual-function electrocatalyst. Our result opens up new alternative cathode materials based on earth-abundant, scalable, noble metal-free catalysts for future electrochemical energy storage systems. Figure 1

Interface-defect-mediated photocatalysis of mesocrystalline ZnO assembly synthesized in-situ via a template-free hydrothermal approach

Both architecture construction and defects engineering of photocatalysts are highly vital in the photocatalytic activity. We report herein that the interface-defect-mediated photocatalytic activity of pompon-like ZnO (P-ZnO) mesocrystal photocatalyst synthesized via an aqueous approach, in the presence of sodium citrate without any other organic templates. The microstructure and defects of the diverse ZnO photocatalysts were examined with various techniques. The results indicated that the P-ZnO assemblies were composed of mesocrystal nanosheets exposed high energy (002) facet with high crystallinity. More importantly, the defects located at the interfaces among the nanocrystals in ZnO mesocrystals played an important role in the photocatalytic activity than that of interstitial zinc vacancies in bulk, which was confirmed by photocatalytic degradation of organic pollutants, such as methylene blue (MB) and 2,4,6-trichlorophenol (2,4,6-TCP). The results showed that the P-ZnO exhibited higher photocatalytic activity than that of the nanosized ZnO (N-ZnO), which could be attributed to not only the unique mesocrystal structure and high energy (002) facet exposed, but also the defects located at interfaces among nanocrystals in ZnO mesocrystals. In addition, the formation mechanism of the P-ZnO was investigated via a time-dependent method. It was found that the formation of P-ZnO hierarchical architecture assembled with ZnO mesocrystals involved a nonclassical crystallization growth and Ostwald Ripening process. This study provides a perspective on the improvement in photocatalytic activity via adjusting the bulk and interface defects and construction of hierarchical architectures of semiconductors.

Poly (pyrrole-co-aniline) hollow nanosphere supported Pd nanoflowers as high-performance catalyst for methanol electrooxidation in alkaline media

In this work, first poly (pyrrole-co-aniline) (PPCA) hollow nanosphere (HN) as a catalyst support material is fabricated through in-situ emulsion polymerization. Then we reported a one-step and template-free approach to fabricate Pd NFs on a PPCA HN coated glassy carbon electrode by a facile electrochemical approach. Several techniques such as FTIR (Fourier transform infrared spectroscopy), SEM (scanning electron microscopy) and EDS (energy dispersive spectroscopy) were utilized for the characterization of the synthesized materials. The catalytic performance of Pd NFs/PPCA HN catalyst is evaluated by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy toward methanol oxidation as a model reaction in alkaline media. The comparison of specific activities for Pd NFs/PPCA HN (1.79 mA cm−2), Pd NFs/PPy (1.28 mA cm−2), Pd NFs/PANI (0.93 mA cm−2) and Pd NFs (0.78 mA cm−2) shows that the PPCA supported Pd NFs with high surface area exhibits the excellent electrocatalytic activity than other electrodes for the electro-oxidation reaction in alkaline media. This might be due to the easier charge transfer at conductive copolymer interfaces, higher electrochemically accessible surface areas and electronic conductivity. This strategy provides a promising platform for direct methanol fuel cells.