Porous Metal Oxide Films Research Articles

Synergistic induction of mesoporosity in metal oxide film electrode through electrohydrodynamic splitting of precursor and simultaneous soft templating

Porous metal oxide films are formed over Ni foam using template-assisted electrospray deposition of precursor sol. Pluronic F127, a triblock organic copolymer surfactant as the template source is added to the respective metal acetate sols to prepare Ni and Co oxide films. The unique cubic phases of metal oxides with the meso-macroporous structure provide easier access for electrolyte ions for faradic charge storage. Hollow spherical and honeycomb-like morphologies, respectively in NiO, and Co3O4 film electrodes contributes to the specific capacities (108 mC cm−2 (270 mF cm−2) and 98 mC cm−2 (245 mF cm−2) respectively at 1 mA cm−2). These NiO and Co3O4 film electrodes, when placed with porous carbon films as counter electrode, derived from the electrospray coating of the polymer precursor shows specific energy at the levels of 11.7 Wh kg−1 and 18 Wh kg−1 respectively. The template-assisted electrospray approach reported here can be extended to the fabrication of other oxides, mixed metal oxides, or binary/ternary oxide systems.

Ferrocene-Containing Porous Poly(Ionic Liquid) Membranes: Synthesis and Application as Sacrificial Template for Porous Iron Oxide Films.

Herein, the fabrication of iron-containing porous polyelectrolyte membranes (PPMs) via ionic complexation between an imidazolium-based poly(ionic liquid) (PIL) and 1,1-ferrocenedicarboxylic acid is reported. The key parameters to control the microstructure of porous hybrid membranes are investigated in detail. Further aerobic pyrolysis of such porous hybrid membranes at 900°C can transfer the ferrocene-containing PPMs into freestanding porous iron oxide films. This process points out a sacrificial template function of porous poly(ionic liquid) membranes in the fabrication of porous metal oxide films.

Tuning Cooperative Assembly with Bottlebrush Block Co-polymers for Porous Metal Oxide Films Using Solvent Mixtures.

Block copolymer templating enables the generation of well-defined pore sizes and geometries in a wide variety of frameworks, typically through evaporation-induced self-assembly (EISA). Here, we systematically modulate the solvent quality with mixtures of tetrahydrofuran-ethanol (THF-EtOH) to manipulate the unimer/micelle ratio in the precursor solution to explore how the associated solution structure influences the final pore morphology. A bottlebrush block copolymer (BBCP) with poly(ethylene oxide) and poly(t-butyl acrylate) side chains was used as the template for pore formation. Irrespective of the solvent composition, a bimodal pore size distribution was obtained with mesopores templated by small aggregates of the BBCP unimers (potentially low aggregation number micelles) and macropores templated by large self-assembled BBCP micelles. The morphology and pore characteristics of the metal oxide films were dependent on the THF-EtOH composition. Interestingly, an intermediate solvent composition where the volume of micelles is approximately half the volume of unimers (in the precursor solution) leads to the best ordering of micelle-templated pores and also the maximum porosity in the films. The micelle/unimer ratios in the precursor solutions do not correspond directly to the bimodal pore distribution in the metal oxide films, which we attribute to kinetically trapped assembly of the BBCP at a low THF content. The increased critical micelle concentration at high THF composition leads to changes in the unimer/micelle ratio during solvent evaporation. These results appear to be universal for a number of metal oxides (cobalt, magnesium, and zinc) with the porosity maximized at a THF/EtOH ratio of 3:1. These results suggest the potential for enhancements in the porosity of block copolymer-templated films by EISA methods through judicious solvent selection.

Pi-pi* orbital transitions and photo-degeneracy of C.acuminata sensitized solar cells

Dye-sensitized solar cells (DSSCs) have acquired great prominence as favourable low-cost photovoltaics due to their ease of fabrication, all- year -availability, ease of obtaining raw materials and adjustable optical properties like transparency and colour. These advantages coupled with the ability to work under poor lighting makes them a suitable candidate for next generation of research. In this research, C.acuminata-sensitized photo anodes play an important role for achieving high performance since the porous metal oxide films provide a large specific surface area for dye loading and the possibility to extend the absorption threshold of past studies of sensitizers. The doctor blade method and high-temperature sintering were some of the methods used in the fabrication of the photo anode. A study of the performance of the C.acuminata-DSSCs with four different electrolyte sensitizers based on iodide redox mediator is determined. The result is DSSCs that exhibit a maximum power output of 39.37 W, fill factor of 0.7 and a power conversion efficiency of 0.6% under unfavourable sunlight intensity conditions and photo-degradation of about 37.5 % in absorbance after 425 suns.

ChemInform Abstract: Recent Progress in Organic Sensitizers for Dye‐Sensitized Solar Cells

AbstractReview: [110 refs.

Electrodeposited porous metal oxide films with interconnected nanoparticles applied as anode of lithium ion battery

Controllable synthesis of porous metal oxide films is highly desirable for high-performance electrochemical devices. In this work, a highly porous NiO film composed of interconnected nanoparticles is prepared by a simple co-electrodeposition method. The nanoparticles in the NiO film have a size ranging from 30 to 100nm and construct large-quantity pores of 20–120nm. As an anode material for lithium ion batteries, the highly porous NiO film electrode delivers a high discharge capacity of 700mAhg−1 at 0.2C, as well as good high-rate performance. After 100 cycles at 0.2C, a specific capacitance of 517mAhg−1 is attained. The good electrochemical performance is attributed to the interconnected porous structure, which facilitates the diffusion of ion and electron, and provides large reaction surface area leading to improved performance.

Encapsulation of Supported Metal Nanoparticles with an Ultra-Thin Porous Shell for Size-Selective Reactions

Heterogeneous catalysts are widely used. However, heterogeneous catalysts cannot selectively convert specific molecules in the reactant mixture to catalyze only desired reactions. Size-selective catalysts with a metal core and porous oxide shell have a promising structure that can increase the reaction selectivity through reactant molecular discrimination. This paper describes a general method to create porous metal oxide films with well-defined porous structures and precisely controlled thickness down to several angstroms from dense organic/inorganic hybrid metal alkoxide films grown by molecular layer deposition (MLD). A novel nanostructured catalyst with an ultra-thin porous shell obtained from the thermal decomposition of an aluminum alkoxide film deposited by MLD for size-selective reactions was developed. The molecular sieving capability of the porous metal oxide films was verified by examining the liquid-phase hydrogenation of n-hexene versus cis-cyclooctene. The success of making these materials by MLD opens up a new method for preparing size-selective catalysts.

Application of Supercritical CO2 Emulsified Electrolyte in Cathodic Deposition of Metal Oxides

Metal oxides, such as TiO2 and ZnO, have been extensively investigated to foster their applications in various technologically important fields. There are many synthetic approaches proposed to fabricate metal oxide thin films. Among the different synthetic routes, electrochemical deposition affords an effective process for production of metal oxide thin films. Properties of the metal oxide films are highly dependent on desorption of gas generated on the surface of cathode, which can affect the pore structure of the porous metal oxide films deposited. Generation rate of hydroxyl ions on the surface of cathode and removal rate of the hydroxyl ions away from the surface of cathode can affect local pH on the surface cathode, which can affect grain size of the metal oxide formed.Supercritical CO2 (sc-CO2) emulsified electrolyte (SCE) is known to be effective in affecting desorption rate of gas formed on the surface of cathode, and influence transfer efficiency of reactive species to the surface of cathode. Therefore, properties of the TiO2 and ZnO thin films are expected to be influenced by the properties of the emulsion. In this work, a sc-CO2-assisted galvanostatic cathodic deposition process is developed for preparation of TiO2 and ZnO thin films with high structural uniformity. TiO2 and ZnO are deposited cathodically on a conductive substrate in a two-compartment cell under a fixed current density, in which platinum foil is employed as the counter electrode. Influences of sc-CO2 and reaction pressure on the crystal growth of TiO2 and ZnO thin films were investigated. The present synthetic approach could be further extended to obtain other metal oxide thin films such as SnO2, CuO, NiO and so on.

Highly sensitive porous metal oxide films for early detection of electrical fire: Surface modification and high throughput screening

In this study, an electrical fire simulator was fabricated and connected to a test platform which can take high throughput screening of materials through the method of combinatorial material science. WO3 and In2O3 were used as basis materials in the experiment and modified through the way of micro-injection in order to find the best one sensitive to electrical fire. It is found that CrCl3-modified and MgCl2-modified WO3, as well as LaOCl-modified and SmOCl-modified In2O3 show the best sensing performance. They can be used as sensitive materials for early detection of electrical fire because they have good sensitivity to the smell of PVC even if the working temperature of PVC insulated wires is lower than 200°C. Therefore, it confirms that the early detection of electrical fire in the invisible smoke stage is feasible by using the modified WO3 or In2O3.

Encapsulation of supported metal nanoparticles with an ultra-thin porous shell for size-selective reactions

A novel nanostructured catalyst with an ultra-thin porous shell obtained from the thermal decomposition of an aluminium alkoxide film deposited by molecular layer deposition for size-selective reactions was developed. The molecular sieving capability of the porous metal oxide films was verified by examining the liquid-phase hydrogenation of n-hexene versus cis-cyclooctene.

Template-Assisted Electrostatic Spray Deposition as a New Route to Mesoporous, Macroporous, and Hierarchically Porous Oxide Films

A novel film coating technique, template-assisted electrostatic spray deposition (TAESD), was developed for the synthesis of porous metal oxide films and tested on TiO(2). Organic templates are codeposited with the titania precursor by electrostatic spray deposition and then removed during calcination. Resultant films are highly porous with pores casted by uniformly sized templates, which introduced a new level of control over the pore morphology for the ESD method. Employing the amphiphilic block copolymer Pluronic P123, PMMA latex spheres, or a combination of the two, mesoporous, macroporous, and hierarchically porous TiO(2) films are obtained. Decoupled from other coating parameters, film thickness can be controlled by deposition time or depositing multiple layers while maintaining the coating's structure and integrity.

Sol–gel templating of membranes to form thick, porous titania, titania/zirconia and titania/silica films

Cellulose acetate, cellulose nitrate, polyamide, polyethersulfone and polypropylene membranes have been used as templates in which sol–gel chemistry was conducted to fabricate porous metal oxide films. Dilution of the metal alkoxide solution allowed for variation in the total amount of inorganic deposited per membrane. Multiple coatings with dilute precursor gave control of the final wall thickness. The correlation between the morphology of the metal oxide and the various structures of the membrane templates indicates the concise coating of the organic material during the templating process. Substantial variation in structure and characteristic properties of the membranes (i.e., ionic/nonionic, hydrophilic/hydrophobic, functional groups) did not hamper the coating mechanism. Multiple coatings could also be applied with variation in the type of metal oxide precursor; this ‘sequential coating’ approach yielded complex structured materials of layered metal oxides, such as TiO2 and ZrO2. Coatings followed by casting (filling of the void space) gave a unique TiO2 coated bimodal pored (macroporous/mesoporous) silica.

<emph type="2">Focus</emph>: Porous Metal Oxide Films Prepared by a Membrane-Coating Technique

Templating techniques are widespread methods used to produce materials with controlled morphologies and thereby tailored properties. 1.2] These techniques involve a template, which serves as a mold, around which the desired material is formed. This can result in either an inverse copy or an outlined representation of the original material, these being referred to as casting or coating respectively. A large number of different templates have been used. Recently, porous cellulose acetate (CA membranes were employed as templates to produce metal oxide films. Two simple methods that are based on the sol gel chemistry of the corresponding metal alkoxides were followed. In the first technique, the templates were soaked in the liquid alkoxide; afterwards hydrolysis was carried out, by transferring the membranes into a water/alcohol solution. Alternatively, the membrane was placed on a glass filter funnel and the two components were filtered through the template. Both methods involve drying of the composite material and heating it to 500°C to remove the organic template. The materials synthesized by this method are thought to be beneficial in many applications in which the metal oxides are already employed. The advantages of these materials include high porosity, allowing good accessibility of the whole surface, and the film form, which facilitates the removal of the material after the reaction.

An Electrochemical Route for Making Porous Nickel Oxide Electrochemical Capacitors

Porous nickel oxide films were prepared by electrochemically precipitating nickel hydroxide and heating the hydroxide in air at 300°C. The resulting nickel oxide films behave as an electrochemical capacitor with a specific capacitance of 59 F/g electrode material. These nickel oxide films maintain high utilization at high rates of discharge (i.e., high power density) and have excellent cycle life. Porous cobalt oxide films were also synthesized. Although the specific capacitances of these films are approximately one‐fifth that of the nickel oxide films, the results demonstrate the versatility of fabricating a wide range of porous metal oxide films using this electrochemical route for use in capacitor applications.