Catalytic Metal Nanoparticles Research Articles

Mesoporous Silica Encapsulated Metal-Organic Frameworks for Heterogeneous Catalysis

Encapsulation of metal-organic frameworks (MOFs) with a shell of mesoporous silica can boost overall performance of MOFs, offering versatility for synthetic architecture of integrated nanocatalysts with reactor-like features. Recently, Yu et al. report a green approach to make yolk-shell nanoreactors.

High Performance UV-LED Activated Sensor Development By Modulating the Morphology and Composition

Metal Oxide Semiconductor (MOS) gas sensors have been studied for monitoring indoor/outdoor air pollutants. A drawback of conventional chemical-resistive gas sensing is the high operating temperature (up to 500°C) that is required for surface reactions. The high temperature operation, however, causes drift problems and makes sensors unsafe for environments containing flammable gases.Ultraviolet light-emitting diode (UV-LED) is a new technological field that has recently seen rapid improvements and novel possible applications. These include the development of UV-LED based gas sensors. UV photons emitted from UV-LED could activate sensors to allow detection of chemicals at ambient temperature. UV irradiation can also improve the sensor performance in harsh environments, where SO2 or NOx gases are present, through desorbing surface contaminants. The state-of-the-art ultraviolet light emitting diode (UV-LED) that emit radiation at a power of a few milli-watts is a promising UV source for this application.UV-activated sensors have a variety of advantages, compared to the traditional chemi-resistive metal oxide semiconductor (MOS) sensors, such as higher stability, lower preparation time, and the ability to safely detect flammable gases. The advances in ultra-violet light emitting diode (UV-LED) technology and its utilization in the gas sensing industry may offer a breakthrough in UV-based sensors, providing several important progresses such as broader application, smaller size, and higher efficiency of the developed sensors.Among the various metal oxides that have been studied for gas sensing applications, ZnO nano-materials have shown promisebecause of high electron conductivity features. ZnO has strong luminescent properties, broad UV absorption, and high stability. Thephoto-activity of ZnO can be improved by synthesizing one-dimensional (1D) nanostructuresand by functionalizing with catalytic metal nanoparticles. This combination lowers the requiredactivationenergy and reduces the recombination rate of photo-generated charge carriers.We will present the fabrication of a sensitive 1D nanostructure ZnO gas sensor decorated with Pt nanoparticles to detect low concentrations of toxic gases at room temperature under UV-LED irradiation (Figure 1). ZnO nanoparticles and nanowires decorated with platinum nanoparticles in different loading concentrations were prepared to detect low concentrations of NO2 under UV-LED irradiation. Solution precipitation, self-assembly crystallization, and photo-deposition techniques were used to synthesize the sensing material. The synthesized sensors at different stages of development were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) analyses.To obtain a certain visual evidence of Pt nanoparticleson the surface of ZnO nanowires, High-resolution transmission electron microscopy (HRTEM) and STEM imaging were employed. The presence of Pt nanoparticles was further confirmed through high-angle annular dark-field (HAADF) STEM analysis.Although the sensing response of the pristine ZnO nanoparticles was relatively high (0.4) for NO2 detection, the sensing response improved significantly using ZnO nanowires in the identical photo-activation settings. The decoration ofthe surface of the ZnO nanowires with Pt nanoparticles further enhanced the sensing performance, whereas the 0.1wt% Pt-decorated ZnO nanowire sensor exhibited a response of more than one order of magnitude higher (1.5) than the response generated by the ZnO nanoparticles. This improved performance is attributed to the role of Pt active sites in promoting NO2 adsorption on the ZnO nanowires’ surface as well as enhancing the layer electron utilization.We will present the results and discuss how UV-LED has the potential to significantly impact sensor development and portable gas monitoring systems by enabling novel sensor design concepts. Figure 1

Mixed-Metal-Oxide Based Hybrid Electrocatalytic Materials for Efficient Reduction of Carbon Dioxide

Of particular interest to the preparation of advanced catalytic materials is efficient utilization of catalytic sites (metal and metal oxide nanostructures, their stabilization and intentional activation, as well as organization into two-dimensional arrays, ultra-thin films or three-dimensional networks (e.g. through sequential deposition) on electrode surfaces. They can form nanosized materials with well-defined composition, structure and thickness that exhibit desirable electrocatalytic properties (e.g. toward reduction of CO2). We explore here the ability of polynuclear inorganic metal oxo systems to stabilize and functionalize metal (e.g. copper) nanostructures. Here certain nanostructured metal oxides of zirconium, titanium, zinc or tungsten have been demonstrated to influence supported metal centers in ways other than simple dispersion over electrode area. Evidence is presented that the support can modify activity (presumably electronic nature) of catalytic metal nanoparticles (e.g. Cu, Ag, Au, Pd, Ru) thus affecting their chemisorptive and catalytic properties. Metal oxide nanospecies can generate –OH groups at low potentials that induce proton mobility at the photo(electro)chemical interface.Our research interests concern development of systems for the electrocatalytic reduction of carbon dioxide not only in neutral but also in acid media. For example, nanosized Cu or Ru naoparticles immobilized within ultra-thin films of tungsten oxide or zirconia have been considered. Selectivity of the catalytic systems largely depends on the activing adsorptive (CO2) phenomena and the affinity of catalytic centers to the adsorbed carbon monoxide (CO) type intermediates leading to their protonation or hydrogenation. Reduction of carbon dioxide begins now at less negative potentials and is accompanied by significant enhancement of the CO2-reduction current densities relative to the competitive hydrogen evolution.

Improved catalytic effect and metal nanoparticle stability using graphene oxide surface coating and reduced graphene oxide for hydrogen generation from ammonia–borane dehydrogenation

GO and rGO supported metal NPs exhibited excellent catalytic performance for AB hydrolysis. It also provided a high turnover frequency (TOF) at 25 °C.

Artificial Reactor with Alterable Tandem Channeling for the Formation of Self‐Screened Catalytic Ability

AbstractInspired by the polymeric “soft” properties and divisional isolation of tandem processes in natural systems, an artificial reactor with self‐screened catalytic ability was fabricated with a polymeric tri‐layer architecture. The non‐responsive middle layer encapsulated catalytic metal nanoparticles, while the two outer layers consisted of a negatively and a positively thermosensitive imprinted polymer. The inverse responsiveness of the outer layers induced switchable shapes, which led to alterable tandem channeling to the reactive middle layer and, as a result, the divisional admission of different substrates. This way, the reactor led to the formation of self‐screened catalytic ability. The design for this artificial reactor offers promising prospects for struggling tandem catalysts, suggesting opportunities to develop schedulable tandem processes.

Catalytic CO2 hydrogenation using mesoporous bimetallic spinel oxides as active heterogeneous base catalysts with long lifetime

CO2 hydrogenation using H2 was investigated using mesoporous bimetallic aluminum spinel oxides (MAl2O4, where M was Mg, Co, Cu, or Zn) as heterogeneous base catalysts. They could catalyze CO2 hydrogenation without additional catalytic metal components. Most catalysts produced CO as the major product (>80%) and relatively small amounts of CH4 and CH3OH. However, when CoAl2O4 was used as catalyst, CH4 was the major product (>80%). A systematic relationship was discovered between the amount of strong basic sites and CO2 conversion. As the amount of strong basic sites increased, the CO2 conversion increased with a linear relationship over all the tested reaction temperatures (300–400 °C). However, no systematic relationship was observed between the CO2 conversion and total amount of basic sites, which suggested that only the sufficiently strong basic sites could activate CO2 efficiently. In addition, owing to the high surface area of the mesopores, the catalytic activity of the spinel oxides increased because of the facile diffusion of molecules through their mesoporous channels. Assuming that the strong basic sites were the actual catalytic sites, the apparent activation energies of all catalysts were derived. The results indicated that CuAl2O4 having the highest amount of strong basic sites presented the lowest activation energy of 13.0 kJ mol−1. This reemphasized the idea that the strong basic sites were useful for the effective activation of CO2 with small energy input. Accordingly, these spinel oxides could be further used for designing multifunctional catalysts supporting catalytic metal nanoparticles on their mesopore walls, which is under investigation.

Chemiresistors: Catalytic Metal Nanoparticles Embedded in Conductive Metal–Organic Frameworks for Chemiresistors: Highly Active and Conductive Porous Materials (Adv. Sci. 21/2019)

Chemiresistors: Catalytic Metal Nanoparticles Embedded in Conductive Metal–Organic Frameworks for Chemiresistors: Highly Active and Conductive Porous Materials (Adv. Sci. 21/2019)

Polymer Reactor with Alterable Substrate Channeling for the Formation of Cascade/Non-cascade-Switchable Catalytic Ability

This study is aimed at the present challenge in self-controlled catalysts, addressing how to furnish the catalysts with cascade/non-cascade-switchable catalytic ability. By borrowing the “soft” properties and autonomous ability from nature, this objective was met by reporting an artificial polymer reactor that was composite of tri-layer architectures made of two inversely-thermosensitive outward layers and a non-responsive middle layer. With the middle layer containing catalytic metal nanoparticles, the two thermosensitive outward layers consisted separately of a negatively-temperature responsive polymer and a positively-temperature responsive composite. The opposite responsiveness at the two thermosensitive outward layers induced convex/flat/concave-switchable shapes in this reactor, leading to cascade/non-cascade-alterable substrate channeling to the reactive middle layer. In this way, this polymer reactor led to the occurrence of cascade/non-cascade-switchable catalytic ability. This design shares a promising prospect with the struggling field of self-controlled catalysts, which allows opportunities to finely control catalytic processes.

Catalytic Metal Nanoparticles Embedded in Conductive Metal-Organic Frameworks for Chemiresistors: Highly Active and Conductive Porous Materials.

Conductive porous materials having a high surface reactivity offer great promise for a broad range of applications. However, a general and scalable synthesis of such materials remains challenging. In this work, the facile synthesis of catalytic metal nanoparticles (NPs) embedded in 2D metal–organic frameworks (MOFs) is reported as highly active and conductive porous materials. After the assembly of 2D conductive MOFs (C‐MOFs), i.e., Cu3(hexahydroxytriphenylene)2 [Cu3(HHTP)2], Pd or Pt NPs are functionalized within the cavities of C‐MOFs by infiltration of metal ions and subsequent reduction. The unique structure of Cu3(HHTP)2 with a cavity size of 2 nm confines the bulk growth of metal NPs, resulting in ultra‐small (≈2 nm) and well‐dispersed metal NPs loaded in 2D C‐MOFs. The Pd or Pt NPs‐loaded Cu3(HHTP)2 exhibits remarkably improved NO2 sensing performance at room temperature due to the high reactivity of catalytic metal NPs and the high porosity of C‐MOFs. The catalytic effect of Pd and Pt NPs on NO2 sensing of Cu3(HHTP)2, in terms of reaction rate kinetics and activation energy, is demonstrated.

Agarose biopolymer coating on polyurethane sponge as host for catalytic silver metal nanoparticles

In the present research work, we prepared a biopolymer-coated open pores polyurethane sponge (OPPUS) as an easily separating substrate for catalytic silver metal nanoparticles. The surface of OPPUS was coated with an agarose (AG) biopolymer. The prepared AG-OPPUS was immersed in AgNO 3 salt solution for the entrapment of the metal ions in the AG coating layer. This material was treated with strong reducing agent solution to reduce the metal ions to the metal nanoparticles (Ag 0 ). The successful synthesis of the material was confirmed through FESEM, XRD, EDX and XPS techniques. Ag/AG-OPPUS was utilized as catalyst in reducing different dyes and other nitroaromatic compounds by sodium borohydride. Kinetic studies for the said the catalytic reduction reactions were carried out. Ag/AG-OPPUS showed superior performance with a reaction rate constant of 0.752min −1 for the 4-nitrophenol reduction reaction. Another important aspect of the current developed catalyst is its separation and recovery without much compromising on the catalytic activity and efficiency. • Silver metal nanoparticles supported on agarose coated open pores polyurethane sponge (AG-OPPUS). • Ag-AG-OPPUS was demonstrated as catalyzing the reduction of toxic organic compounds. • The recovery of the catalyst was easy. • Ag-AG-OPPUS is a highly efficient catalyst.

(Invited) Mixed-Metal-Oxide Based Electrocatalysts for Efficient Reduction of Carbon Dioxide

Of particular interest to the preparation of advanced catalytic materials is efficient utilization of catalytic sites (metal and metal oxide nanostructures, their stabilization and intentional activation, as well as organization into two-dimensional arrays, ultra-thin films or three-dimensional networks (e.g. through sequential deposition) on electrode surfaces. They can form nanosized materials with well-defined composition, structure and thickness that exhibit desirable electrocatalytic properties (e.g. toward reduction of CO2). We explore here the ability of polynuclear inorganic metal oxo systems to stabilize and functionalize metal (e.g. copper) nanostructures. Here certain nanostructured metal oxides of zirconium, titanium, zinc or tungsten have been demonstrated to influence supported metal centers in ways other than simple dispersion over electrode area. Evidence is presented that the support can modify activity (presumably electronic nature) of catalytic metal nanoparticles (e.g. Cu, Ag, Au, Pd, Ru) thus affecting their chemisorptive and catalytic properties. Metal oxide nanospecies can generate –OH groups at low potentials that induce proton mobility at the electrochemical interface. Our research interests concern development of systems for the electrocatalytic reduction of carbon dioxide not only in neutral but also in acid media. For example, nanosized Cu or Ru naoparticles immobilized within ultra-thin films of tungsten oxide or zirconia have been considered. Selectivity of the catalytic systems largely depends on the activing adsorptive (CO2) phenomena and the affinity of catalytic centers to the adsorbed carbon monoxide (CO) type intermediates leading to their protonation or hydrogenation. Reduction of carbon dioxide begins now at less negative potentials and is accompanied by significant enhancement of the CO2-reduction current densities relative to the competitive hydrogen evolution.

Engineering of activated carbon surface to enhance the catalytic activity of supported cobalt oxide nanoparticles in peroxymonosulfate activation

Commercial activated carbon has been functionalized by chemical or thermal treatments to introduce surface oxygen functional groups able to anchor small cobalt nanoparticles with superior catalytic activity for peroxymonosulfate activation. The resulting activated carbon supports where characterized by combustion elemental analysis, Fourier-transformed infrared spectroscopy, Raman spectroscopy, isothermal N2 adsorption, temperature programmed desorption/mass spectrometry, X-ray diffraction and scanning electron microscopy. Activated carbon functionalization by nitric acid resulted the most appropriated method to provide a higher population of oxygenated functional groups able to anchor small cobalt nanoparticles. The catalytic activity of supported oxidized metal nanoparticles (4.7 ± 0.05 nm) was higher than analogous non-oxidized cobalt nanoparticles (2.9 ± 0.14 nm). The use of analogous supported oxidized iron or copper nanoparticles resulted in lower catalytic activity. Importantly, the supported oxidized cobalt nanoparticles at 0.2 wt% loading exhibit higher activity than benchmark catalysts such as unsupported Co3O4 solid or even homogeneous Co2+ ions. This is a reflection of the relatively low estimated activation energy for both processes, peroxymonosulfate decomposition and phenol degradation. The estimated activation energy values are about 30 and 32 kJ mol−1. The stability of the most active catalyst was assessed by performing eight consecutive uses without observing decrease of catalytic activity, neither metal leaching or metal nanoparticle aggregation. Turnover numbers/turnover frequencies values as high as 4·105/8·105 h−1 for peroxymonosulfate activation and 39·103/68·103 h−1 for phenol degradation at pH 7 and 20 °C have been estimated, respectively. Electron paramagnetic resonance measurements and selective quenching experiments revealed that the generated sulfate radicals from peroxymonosulfate rapidly are transformed in highly reactive hydroxyl radicals. In excellent agreement with previous reports, this work demonstrates the importance of an adequate activated carbon functionalization to obtain superior and stable catalysts for peroxymonosulfate activation.

Black Silicon Photoanodes Entirely Prepared with Abundant Materials by Low-Cost Wet Methods

We report a new design for water-splitting photoanodes, based on a highly absorbing black silicon (BSi) substrate modified with catalytic metal nanoparticles (NPs). The overall fabrication strategy...

The Role of Metal Nanostructures in CO2 Photoreduction

Process of CO2 reduction requires substantial decrease of the energy barriers. Consequently, one of the promising way to approach this problem is using use of metal nanoparticles to accelerate electrons and make them more electronegative at the end of this process. Better understanding of the photo-induced phenomena enables to improve design & construction of semiconductor architectures governing the efficiency of CO2 reduction and its selectivity. The objective of this presentation will rely onto use of semiconductor photocathode with co-assembly of plasmonic and catalytic metal nanoparticles, such as silver or gold with other metal electrocatalysts which decrease the energy barriers of the CO2 reduction process through interaction of photo-excited surface plasmon states with adsorbed reaction intermediates. The significance to investigate reduction of CO2 with gold, silver and copper nanoparticles, enhanced by the extra activation of the process provided by the illuminated, incorporated plasmonic metallic nanostructures is supported by the occurrence of the photo-emission process associated with the decay of photo-excited surface plasmons. The occurrence, and contribution of this process to the overall efficiency of the CO2 reduction process as well as its impact on the distribution of the products will be investigated and discussed in detail. Moreover, the tradeoff between CO2 and water reduction will be continuously investigated and discussed in view of choice of the best metal-based catalyst designed for high efficiency and best selectivity CO2 reduction process.

Solvent-Free Synthesis of Zeolites: Mechanism and Utility.

Zeolites have been extensively studied for years in different areas of chemical industry, such as shape selective catalysis, ion-exchange, and gas adsorption and separation. Generally, zeolites are prepared from solvothermal synthesis in the presence of a large amounts of solvents such as water and alcohols in sealed autoclaves under autogenous pressure. Water has been regarded as essential to synthesize zeolites for fast mass transfer of reactants, but it occupies a large space in autoclaves, which greatly reduces the yield of zeolite products. Furthermore, polluted wastes and relatively high pressure due to the presence of water solvent in the synthesis also leads to environmental and safety issues. Recently, inspired by great benefits of solvent-free synthesis, including the environmental concerns, energy consumption, safety, and economic cost, researchers continually challenge the rationale of the solvent and reconsider the age-old question "Do we actually need solvents at all in zeolite synthesis?" In this Account, we briefly summarize our efforts to rationally synthesize zeolites via a solvent-free route. Our research demonstrates that a series of silica, aluminosilicate, and aluminophosphate-based zeolites can be successfully prepared by mixing, grinding, and heating starting solid materials under solvent-free conditions. Combining an organotemplate-free synthesis with a solvent-free approach maximizes the advantages resulting in a more sustainable synthetic route, which avoids using toxic and costly organic templates and the formation of harmful gases by calcination of organic templates at high temperature. Furthermore, new insights into the solvent-free crystallization process of zeolites have been provided by modern techniques such as NMR and UV-Raman spectroscopy, which should be helpful in designing new zeolite structures and developing novel routes for synthesis of zeolites. The role of water and the vital intermediates during the crystallization of zeolites have been proposed and verified. In addition to a significant reduction in liquid wastes and a remarkable increase in zeolite yields, the solvent-free synthesis of zeolites exhibits more unprecedented benefits, including (i) the formation of hierarchical micro-, meso-, and macrostructures, which benefit the mass transfer in the reactions, (ii) rapid synthesis at higher temperatures, which greatly improve the space-time yields of zeolites, and (iii) construction of a novel catalytic system for encapsulation of metal nanoparticles and metal oxide particles within zeolite crystals synergistically combining the advantages of catalytic metal nanoparticles and metal oxide particles (high activity) and zeolites (shape selectivity). We believe that the concept of "solvent-free synthesis of zeolites" would open a door for deep understanding of zeolite crystallization and the design of efficient zeolitic catalysts.

(Invited) Ordered, Nanoporous Carbon Scaffolds (NCS) for Use in Energy Conversion and Related Applications

Nanoporous carbon materials are of significant interest for use in various electrochemical applications, including as catalyst supports in fuel cells, sensors, and as electrodes in supercapacitors, redox flow batteries, and lithium batteries. The nanoporous carbons under study in our group include both soft- and hard-templated ordered mesoporous carbons as well as colloid-imprinted carbons (CICs). While all of these carbons have well-controlled and narrow pore size distributions and high surface areas, they are all produced in the form of powders, which can cause problems when used in electrochemical devices. This is due to challenges in relation to reproducible powder packing and binders must normally be used to hold particles together. The binder may then block ions and electrons from passing through the pores and between particles, thus preventing full utilization of their surfaces. Furthermore, fine particulates may also cause health concerns (e.g., PM2.5). In order to overcome these challenges, our research group has focussed on the development of a series of novel nanoporous carbon scaffolds (NCS membranes), possessing a fully ordered and monodisperse porous structure. The NCS materials have pore diameters in the range of 5 to 100’s of nm and contain a fully inter-connected nano/macro-porous network (porosity ~80%). These NCS membranes, which can be made to be 0.5 - 100’s of microns in thickness, also have a very good conductivity of 2-10 S/cm and are fully electrochemically accessible in aqueous solutions, exhibiting a capacitance of 40-100 F/g. The fabrication method used to form these novel NCS membranes is also environmentally friendly and has been demonstrated to be applicable for manufacturing at large scale. Due to these exceptional properties, the NCS materials are of great interest for use in a wide range of clean energy and water remediation products. In this presentation, the preparation and properties of these materials will be discussed, including the successful loading of the NCS membranes with catalytic metal nanoparticles and internal surface functionalization. An overview of the application of the NCS material in PEM fuel cells, redox flow batteries, capacitors, and in nanofiltration applications will also be presented.

Role of membrane pore polymerization conditions for pH responsive behavior, catalytic metal nanoparticle synthesis, and PCB degradation

This article describes the effects of changing monomer and cross-linker concentrations on the mass gain, water permeability, Pd-Fe nanoparticle (NP) loading, and the rate of degradation of 3,3',4,4',5-pentachlorobiphenyl (PCB 126) of pore functionalized polyvinylidene fluoride (PVDF) membranes. In this study, monomer (acrylic acid (AA)) and cross-linker (N, N′- methylene-bis (acrylamide)) concentrations were varied from 10 to 20 wt% of polymer solution and 0.5–2 mol% of monomer concentration, respectively. Results showed that responsive behavior of membrane could be tuned in terms of water permeability over a range of 270–1 L m−2 h−1 bar−1, which is a function of water pH. The NP size on the membrane surface was found in the range of 16–23 nm. With increasing cross-linker density the percentage of smaller NPs (< 10 nm) increases due to smaller mesh size formation during in-situ polymerization of membrane. NP loading was found to vary from 0.21 to 0.94 mg per cm2 of membrane area depending on the variation of available carboxyl groups in membrane pore domain. The NPs functionalized membranes were then tested for use as a platform for the degradation of PCB 126. The observed batch reaction rate (Kobs) for PCB 126 degradation for per mg of catalyst loading was found 0.08–0.1 h−1. Degradation study in convective flow mode shows 98.6% PCB 126 is degraded at a residence time of 46.2 s. The corresponding surface area normalized reaction rate (Ksa) is found about two times higher than Ksa of batch degradation; suggesting elimination of the effect of diffusion resistance for degradation of PCB 126 in convective flow mode operation. These Pd-Fe-PAA-PVDF membranes and nanoparticles are characterized by TGA, contact angle measurement, surface zeta potential, XRD, SEM, XPS, FIB, TEM and other techniques reveal the details about the membrane surface, pores and nanoparticles size, shape and size-distribution. Statistical analysis based on experimental results allows us to depict responsive behavior of functionalized membrane. In our best knowledge this paper first time reports detail study on responsive behavior of pore functionalized membrane in terms of permeability, NPs size, metal loading and its effect on PCB 126 degradation in a quantified approach.

Carbon Precursor Structures and Graphene on Palladium Nanoparticles

Due to their stable catalytic properties graphene-encapsulated metal nanoparticles (NPs) have come into the focus of heterogeneous catalysis. Research on graphene’s atomic structure is a prerequisite for understanding and controlling catalytic processes; however, it is still at its very beginning considering metal NPs. This atomic-scale scanning tunnelling microscopy study documents preliminary growth stages and the structural properties of graphene on highly oriented pyrolytic graphite (HOPG) supported palladium NPs. It is shown that an annealing of the NPs at ∼650 °C in a few tens of Langmuir of ethylene (ethene) leads first to a carbon precursor structure covering the NP’s (111) facets. At higher ethylene exposures, the precursor structure turns into single-layer graphene encapsulating the NPs. Graphene-encapsulated palladium NPs with a size larger than ∼30 nm exhibit mostly one single and an almost defect-free graphene sheet on a facet. In most of the cases, such a perfect growth does not take place o...

3D-polythiophene foam on a TiO2 nanotube array as a substrate for photogenerated Pt nanoparticles as an advanced catalyst for the oxygen reduction reaction

The development of novel substrates that possess high durability, strong anchoring to catalytic metal nanoparticles and low charge transfer resistance as well as that can replace conventional carbon is of great importance. To improve the durability and reduce the cost of various energy devices, new methodologies are necessary. Therefore, we report the preparation of a macroporous hybrid material containing polythiophene electropolymerized onto TiO2 nanotubes (TNT). The prepared foam-like hybrid material exhibited a very low charge transfer resistance and was further modified with novel and green photogenerated Pt nanoparticles. The material exhibited very strong metal substrate interactions, resulting in high durability during the oxygen reduction reaction (ORR). This study proposes a novel macroporous organic/inorganic hybrid material for use as an alternative material to replace conventional carbon substrates in ORR catalysts. The present study details the preparation of a macroporous hybrid material containing polythiophene electropolymerized onto TiO2 nanotubes (TNT). The prepared foam-like hybrid material showed a very low charge transfer resistance. Upon decoration with Pt using our novel and green photogeneration method, the material exhibited very strong metal substrate interactions, resulting in high durability during the oxygen reduction reaction (ORR). This study proposes a novel macroporous organic/inorganic hybrid material for use as an alternative material to replace conventional carbon substrates in ORR catalysts.

(Invited) Specific Metal-Metal Oxide Interactions in Efficient Electroreduction of Carbon Dioxide

Of particular interest to the preparation of advanced catalytic materials is efficient utilization of carbon nanostructures and noble metal nanoparticles, their stabilization and intentional activation, as well as organization into two-dimensional arrays, ultra-thin films or three-dimensional networks (e.g. through sequential attraction) on electrode surfaces. They can form nanosized materials with well-defined composition, structure and thickness that exhibit desirable electrocatalytic properties (e.g. toward reduction of CO2). We explore here the ability of polynuclear inorganic systems to stabilize and derivatize metal and carbon nanostructures. Here certain nanostructured metal oxides of zirconium, titanium, zinc or tungsten have been demonstrated to influence supported metal centers in ways other than simple dispersion over electrode area. Evidence is presented that the support can modify activity (presumably electronic nature) of catalytic metal nanoparticles (e.g. Cu, Ag, Au, Pd, Pt or Ru) thus affecting their chemisorptive and catalytic properties. Metal oxide nanospecies can generate –OH groups at low potentials that induce proton mobility at the photo(electro)chemical interface. Our research interests concern development of systems for the reduction (conventional/electrocatalytic or photoelectrochemical) of carbon dioxide. For example, nanosized Cu or Au naoparticles immobilized within ultra-thin films of tungsten oxide or zirconia have been considered. Reduction of carbon dioxide begins now at less negative potentials and is accompanied by significant enhancement of the CO2-reduction current densities. When it comes to photoelectrochemical reduction, we are also going to demonstrate utility of zirconia or zinc oxide over-layers on copper(I) oxide photocathodes irradiated with visible light in aqueous solutions. The possibility of generation of localized surface plasmons with use of gold or silver nanoparticles, will also be considered. Special attention will be paid to stability and controlled reactivity of the proposed systems.