Nano-sized Catalysts Research Articles

Nanoseed-assisted synthesis of nano-sized SAPO-34 zeolites using morpholine as the sole template with superior MTO performance.

Nano-sized SAPO-34 catalysts have been for the first time prepared using morpholine as the sole template by using a one-pot nanoseed-assisted method. The obtained nano-sized SAPO-34 catalysts exhibit about 4-fold prolonged lifetime and nearly 5% increased selectivity for ethylene and propylene compared to conventional micron-sized counterparts in methanol-to-olefin reactions.

A novel nano-sized calcium hydroxide catalyst prepared from clam shells for the photodegradation of methyl red dye

Semiconductor photocatalysis is a promising approach to combat both environmental pollution and the global energy shortage. Advanced photocatalysts with novel photoelectronic properties are benchmark materials that have been pursued for their high solar-energy conversion efficiency. Consequently, this paper discusses a new nano-sized calcium hydroxide (Ca(OH)2) photocatalyst synthesised by a precipitation method from the raw materials derived from sea shells. The as-prepared Ca(OH)2 samples were characterised by Scanning Electron Microscopy (SEM). The Ca(OH)2 samples were then immobilised in Alginate beads and they showed excellent photocatalytic degradation activities against methyl red (MR) aqueous solution under UV light radiation. Dependence of the activity on various experimental conditions was investigated, and the results showed promising utilization of the immobilised Ca(OH)2 photocatalysts. The influence of initial dye concentration and catalyst loading were studied and it was found that maximum% degradation was achieved with 20mg/L of initial dye concentration and 3g/L of catalyst loading. In addition, the photocatalytic degradation of MR was well fitted into pseudo first order kinetics and heterogeneous catalytic kinetic model. Studies over recyclability of immobilised catalysts were performed and the results showed that the alginate immobilised catalysts were efficient enough to reuse for several times.

Fischer–Tropsch synthesis and hydrogenolysis of long-chain alkanes over cobalt-containing nanosized catalysts in a slurry reactor

Fischer–Tropsch synthesis in the presence of nanosized cobalt-containing catalysts suspended in a mixture of long-chain alkanes has been studied. It has been found that the molecular-mass distribution of the products differs substantially from the typical Anderson–Schulz–Flory distribution. The most evident cause of this phenomenon is the intense hydrogenolysis of long-chain alkanes of the liquid medium which occurs during catalyst activation; this process may proceed to a sufficient extent during Fischer–Tropsch synthesis. The molecular-mass distribution of hydrogenolysis products shows a number of specific features that differ appreciably from those for both classical hydrogenolysis (cracking) in the presence of zeolites and terminal methanolysis, which is frequently observed in the presence of group VIII metals. Problems encountered during the construction of models for the observed distribution are discussed.

Synthesis and study of catalysts of electrochemical oxygen reduction reaction based on polymer complexes of nickel and cobalt with Schiff bases

The article presents the results of studies of new nanosize catalysts of electrochemical oxygen reduction reaction (ORR) obtained using the method of thermal decomposition of polymer complexes of nickel and cobalt with tetradentate (N2O2) Schiff bases. The catalysts are characterized using the methods of thermogravimetry, electrochemical quartz microgravimetry, scanning electron microscopy with X-ray microanalysis, XPS. The ORR process on electrodes modified by the above catalysts was studied using the voltammetry and rotating disk electrode techniques. The obtained catalysts manifested high specific activity per initial polymer mass (more than 600 mA/mg).

One-Pot Selective Catalytic Synthesis of Pyrrolidone Derivatives from Ethyl Levulinate and Nitro Compounds.

N-substituted 5-methyl-2-pyrrolidones were prepared in a one-pot process starting from ethyl levulinate and nitro compounds in the presence of a nanosized Pt-based catalyst. Pt supported on TiO2 nanotubes (Pt/TiO2 -NT) catalyzed the synthesis of N-substituted 5-methyl-2-pyrrolidones through a cascade process involving the reduction of nitro compounds, formation of the intermediary imine, hydrogenation, and subsequent cyclization. A bifunctional metal-acid system was a suitable catalyst for the process. Pt supported on TiO2 showed lower catalytic activity than Pt/TiO2 -NT owing to the strong adsorption of nitro compounds during the first reaction step that poisoned the acidic sites and strongly decreased the rate of amination and cyclization. However, Pt/TiO2 -NT with milder acid sites was less affected by the adsorption of nitro compounds and the full cascade process could proceed. The results indicate that the prepared Pt/TiO2 -NT is a chemoselective and reusable catalyst that can be applied to the synthesis of a variety of N-substituted 5-methyl-2-pyrrolidones starting from nitro compounds with excellent yields in absence of an additional organic solvent under mild reaction conditions.

Promoting hydrogen production and minimizing catalyst deactivation from the pyrolysis-catalytic steam reforming of biomass on nanosized NiZnAlOx catalysts

Hydrogen production from the thermochemical conversion of biomass was carried out with nano-sized NiZnAlOx catalysts using a two-stage fixed bed reactor system. The gases derived from the pyrolysis of wood sawdust in the first stage were catalytically steam reformed in the second stage. The NiZnAlOx catalysts were synthesized by a co-precipitation method with different Ni molar fractions (5, 10, 15, 25 and 35%) and a constant Zn:Al molar ratio of 1:4. The catalysts were characterized by a wide range of techniques, including N2 adsorption, SEM, XRD, TEM and temperature-programmed oxidation (TPO) and reduction (TPR). Fine metal particles of size around 10–11nm were obtained and the catalysts had high stability characteristics, which improved the dispersion of active centers during the reaction and promoted the performance of the catalysts. The yield of gas was increased from 49.3 to 74.8wt.%, and the volumetric concentration of hydrogen was increased from 34.7 to 48.1vol.%, when the amount of Ni loading was increased from 5 to 35%. Meanwhile, the CH4 fraction decreased from 10.2 to 0.2vol.% and the C2–C4 fraction was reduced from 2.4vol.% to 0.0vol.%. During the reaction, the crystal size of all catalysts was successfully maintained at around 10–11nm with lowered catalyst coke formation, (particularly for the 35NiZn4Al catalyst where negligible coke was found) and additionally no obvious catalyst sintering was detected. The efficient production of hydrogen from the thermochemical conversion of renewable biomass indicates that it is a promising sustainable route to generate hydrogen from biomass using the NiZnAl metal oxide catalyst prepared in this work via a two-stage reaction system.

ChemInform Abstract: Solvent‐Free Condensation Reactions to Synthesize Five‐Membered Heterocycles Containing the Sulfamide Fragment.

We report a study of the solvent-free condensation reaction of 1,2-dicarbonyl compounds with sulfamide catalyzed by a Keggin-type acid (H3PMo12O40·nH2O, MPA) to obtain 3,4-disubstituted 1,2,5-thiadiazole 1,1-dioxide derivatives. Some reactions were also performed in solution or using nano-sized silica-supported MPA catalyst in order to compare the results under different experimental conditions. Effects of the temperature used for the thermal pretreatment of the catalyst, the reaction temperature, the molar ratios sulfamide/1,2-dicarbonyl compound and MPA/1,2-dicarbonyl compound, and alternative experimental procedures on the yield of the reaction product were investigated. Under suitable experimental conditions eight compounds were obtained in good yields. The catalyst was recycled and reused, but with some loss of its catalytic activity. The presented synthetic method is a simple, clean, and environmentally friendly alternative for synthesizing different 1,2,5-thiadiazole 1,1-dioxide derivatives.

CNT/Co3O4 Based Air Electrode Selectively Wrapped By Polyaniline for High Performance Air Electrode

Li-Air battery is one of the most promising new energy storage systems because they provide much higher energy densities than lithium-ion batteries. Nevertheless, Li-air batteries have several issues to be solved before the commercialization. One of them is side reaction attributed to the reaction between carbon, a general component of the air electrode, and electrolyte/Li2O2. Actually, carbon with high surface area provides a large reaction sites to form and store the reaction products. And it compensates for the low electronic conductivity of oxide catalysts such as MnO2 and Co3O4. However, some studies have suggested that the carbon promotes side reaction such as electrolyte decomposition and formation of Li2CO3. The unwanted reaction products formed from side reaction is hardly decomposed on charging process. This results in the accumulation of reaction products on the surface of electrode during cycling, which leads to limited cycle life and high over-potential. As a new approach to address these issues, nano-sized cobalt oxide (Co3O4) particles were composited with carbon nanotube (CNT) to enhance the catalytic activity, and the surface of carbon nanotube was selectively wrapped with polyaniline, a conducting polymer, to suppress the side reaction between carbon (CNT) and electrolyte/Li2O2. CNT/Co3O4 based air electrode selectively wrapped by polyaniline is expected enhanced cyclic performance and low over-potential due to synergic effect of nano-sized Co3O4 catalyst composited with CNT and polyaniline coating layer on the surface of carbon.

Development of Nanoparticle Catalysts for Electrochemical Ammonia Production

Ammonia is one the most common industrial chemicals produced in the United States. It has a strong foothold in the agricultural, plastic, and textile industries. A process termed Haber-Bosch, named for its inventors, is the current method used for ammonia based fertilizer production in the agricultural industry. The process requires high temperatures of 400-500°C and high pressures of 150 – 200 atm to convert nitrogen into ammonia [1]. These extreme conditions only result in a 15% conversion at equilibrium [1]. Another problem associated with the Haber-Bosch process is the reforming of hydrocarbons, like coal and natural gas, resulting in the consumption of 3 to 5% of the world’s natural gas production and the release of large amounts of CO2 [2]. The total energy consumption for an ammonia plant is about 7.9 MW h tNH3 -1, and 13.5 MW h tNH3 -1 for natural gas and coal, respectively [1], and the energy use for the entire ammonia industry is approximately 2% of the world’s energy consumption [2]. The extreme conditions, low efficiency, environmental pollution, and energy consumption of the Haber-Bosch process have helped to push research efforts towards a more economically and environmentally viable electrochemical catalyst approach. The focus of this project is to develop a suitable nanoparticle catalyst for a solid state electrolyte electrochemical process. Electrochemical reduction of nitrogen to ammonia has been performed over non-precious monometallic and multi-metallic combinations, such as iron (Fe) and nickel (Ni). These metals are chosen because they have theoretical nitrogen binding energies that are close to the theoretically-predicted optimum [3]. However, thus far, most electrocatalysts have resulted in low Faradaic efficiencies due to the affinity of the catalyst surface for preferential hydrogen binding [4]. A catalyst made up of a combination of the metals at the nano-scale could balance the need for low applied potential while keeping hydrogen binding to a minimum. In particular, recent work by Licht and co-authors demonstrated that an iron oxide nanoparticle catalyst can be used at elevated temperature (200 oC) to achieve Faradaic efficiencies of greater than 30% [2]. In our initial work, nano-sized catalysts of Fe, Ni, and Fe-Ni were screened for efficiencies over a three hour span. Monometallic Fe nanoparticles showed a drastic decrease in efficiencies over time, whereas the efficiency of the monometallic Ni nanoparticles increased with time. The bimetallic Fe-Ni nanoparticles resulted in a combination of both Fe and Ni properties, depending on the composition and morphology of the nanoparticles. A low surface area, larger diameter Fe-Ni nanoparticle material had decreasing efficiencies over time, whereas a high surface area, nanoparticle cluster Fe-Ni sample had increasing efficiencies over time. In this presentation, we will show recent results on our continued work to develop Fe-Ni bimetallic nanoparticles as an electrocatalyst for nitrogen reduction. In particular, we will discuss progress on controlling nanoparticle size, morphology, and composition to optimize efficiency benefits of Fe while being able to gain stability due to Ni. Experimentally, we will discuss our efforts to investigate the role of certain synthesis parameters on nanoparticle morphology and catalytic performance by changing the timing of synthesis steps to control changes in Fe oxidation state, nickel deposition, and core morphology. Also the effects of changing the molar ratio of Ni to Fe in synthesis and molar ratio of ligand to metal to influence particle size will be explored. References K. Kugler, B. Ohs, M. Scholz, and M. Wessling, Phys.Chem.Chem.Phys., 16, 6129 (2014)S. Licht, B. Cui, B. Wang, F. Li, J. Lau, and S. Liu, Science, 345, 637 (2014)E. Skulason, T. Bligaard, S. Gudmundsdottir, F. Studt, J. Rossmeisl, F. Abild-Pedersen, T. Vegge, H. Jonsson, and J. K. Norskov, Phys. Chem. Chem. Phys., 14, 1235-1245 (2012)Xu, G.C., R.Q. Liu, and J. Wan, Science in China Series B: Chemistry, 52, 8 (2009)

Synthesis and characterization of LaSmTiZrO7-SnSe composite for visible-light induced photocatalytic mineralization of Monoazo dyes

Owing to the boom in textile industry in the recent past, there is a stringent requirement to deal with the environmental hazards associated with the azo dyes, a run-off from textile industry, i.e. toxicity to aquatic life and health hazards to humans. The use of nano-sized catalysts for the degradation of these dyes into minerals using sunlight as a primary source of energy is proved as most promising approach to handle the problem. The development of visible light sensitive catalysts is of great concern for the practical realization of dyes degradation. In the present work, we have synthesized LaSmTiZrO7 via microemulsion technique, while SnSe and their composite by using the hydrothermal approach. The XRD analysis confirmed the formation of LaSmTiZrO7, SnSe and their composite. The morphology, specific surface area, oxidation states of elements, surface chemical composition and optical properties of photocatalyst studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) nitrogen adsorption–desorption, X-ray photoelectron spectroscopy (XPS), energy dispersive spectra (EDS) and UV–vis spectroscopy, respectively. The synthesized catalytic materials have then been used for the photocatalytic degradation of mono azo foron blue dye under the visible-light irradiation. The alignment of energy levels shows that the electrons/holes recombination can be minimized with the formation of LaSmTiZrO7-SnSe composite. The photodegradation results confirm that the composite has better efficiency under visible light irradiation as compared to that of individual catalysts. The XRD analysis after photodegradation process confirms the structural stability of the composite.

Nanoscale Pd-based catalysts for selective oxidation of glycerol with molecular oxygen: Structure–activity correlations

This work investigates selective oxidation of glycerol with molecular oxygen, one of the viable routes to obtain value-added products from bio-glycerol, using nanosized Pd-based catalysts. For this, three types of 1wt.% Pd catalysts supported on activated carbon (Ac), hydrotalcite (HTc), and activated carbon–hydrotalcite composite (Ac–HTc) were prepared. The physicochemical properties of the catalysts are characterized using various techniques, such as XRD, BET, XRF, H2-TPR, CO2-TPD, and TEM. The TEM images reveal the formation of Pd nanoparticles with an average diameter of 9.01, 9.10, and 11.16nm on the surface of HTc, Ac, and Ac–HTc supports, respectively. The CO2-TPD results show that the Pd@HTc catalyst exhibits higher concentration of basic sites compared with that of Pd@HTc-Ac and Pd@Ac catalysts. The H2-TPR profiles show that the reducibility of Pd species is highly dependent on the nature of the supports. Catalytic activity results reveal that the conversion of glycerol over Pd catalysts increased in the following order: Pd/Ac<Pd@HTc-Ac<Pd@HTc, while selectivity of the glyceric acid increased in the following order: Pd@HTc-Ac<Pd@Ac<Pd@HTc. The presence of more number of basic sites and high dispersion of Pd nanoparticles are found to be key factors for excellent catalytic performance of Pd@HTc catalyst in the oxidation of glycerol with molecular oxygen.

Highly efficient synthesis of cumene via benzene isopropylation over nano-sized beta zeolite in a submerged ceramic membrane reactor

Abstract A submerged ceramic membrane reactor was developed for the cumene production via liquid-phase isopropylation of benzene with isopropanol over beta zeolite catalyst, which realized the in-situ separation and reuse of nano-sized beta zeolite catalyst. Evaluation of the introduction of ceramic membranes with different pore sizes on the catalytic performance and filtration process was investigated. No considerable influence was observed in the catalytic performance as far as the benzene conversion and cumene selectivity are concerned, but the filtration rate was significantly affected by the membrane pore size. The reaction and filtration performance depended strongly on the operation conditions. Semi-continuous benzene isopropylation to cumene showed that the beta zeolite catalyst could maintain a benzene conversion at ∼2.8% and a cumene selectivity above 98.1%, and the ceramic membrane exhibited better filtration performance and excellent stability during the entire isopropylation process. The study provides new insights for the benzene isopropylation reaction.

금속 나노 촉매를 활용한 선택적 알코올 산화 반응

본 리뷰 논문은 지지화된 또는 고정화된 금속들 중 선택적 알코올 산화 반응에 적용된 나노 크기의 여러 금속 촉매들에 대해 집중적으로 서술한다. 금속 나노 촉매들은 넓은 표면적을 지닌 고체 지지체들의 표면 위에 금속 나노 입자들의 고른 분산을 통해 얻어진다. 이러한 나노 촉매들은 유기 합성, 연료 전지, 바이오 디젤 생산, 오일 크래킹, 에너지변환 및 저장, 의약, 수처리, 고체 로켓 추진체, 염료 제조 등 학문적 산업적 측면 모두 다양하게 사용될 수 있다. 더욱이, 응용성이 풍부한 중간체들을 생산하는 호기성 알코올 산화 반응에서 금속 나노 재료는 촉매로써 매우 중요하다. 금, 팔라듐, 류테늄, 바나디움 등과 같은 지지화된 금속 나노 촉매들의 알코올 산화 반응은 기존의 화학 당량적 반응과 달리 비용을 경감시키고 부반응물들을 줄임으로써 경제적이고 친환경적이다. 뿐만 아니라, 상온에서 진행된 나노 촉매 알코올 산화 반응에 대해서도 소개된다. This review article highlights different types of nano-sized catalysts for the selective alcohol oxidation to form aldehydes (or ketones) with supported or immobilized metal nanoparticles. Metal nanoparticle catalysts are obtained through dispersing metal nanoparticles over a solid support with a large surface area. The nanocatalysts have wide technological applications to industrial and academic fields such as organic synthesis, fuel cells, biodiesel production, oil cracking, energy conversion and storage, medicine, water treatment, solid rocket propellants, chemicals and dyes. One of main reactions for the nanocatalyst is an aerobic oxidation of alcohols to produce important intermediates for various applications. The oxidation of alcohols by supported nanocatalysts including gold, palladium, ruthenium, and vanadium is very economical, green and environmentally benign reaction leading to decrease byproducts and reduce the cost of reagents as opposed to stoichiometric reactions. In addition, the room temperature alcohol oxidation using nanocatalysts is introduced.

Design of Nano-Sized Polymer-Palladium Catalysts for Hydrogenation

&lt;p&gt;Nanoscale palladium/oxide catalysts stabilized with poly-2-methyl-5-vinylpyridine (P2M5VP) have been prepared and tested in the reaction of 3,7,11-trimethyldodecyne-1-ol hydrogenation in ethanol at 50 &lt;sup&gt;o&lt;/sup&gt;C and hydrogen atmospheric pressure. The catalysts showed high activity, stability and selectivity. Chemical interaction of PdCl&lt;sub&gt;2&lt;/sub&gt; with pyridyne groups of P2M5VP on oxides (ZnO and MgO) promotes formation of even distribution of uniformed metal particles. Polymer chains prevent agglomeration of active phase of Pd and deactivation of catalysts during hydrogenation reaction.&lt;/p&gt;

Coupling conversion of methanol and 1-butylene to propylene on HZSM-5 molecular sieve catalysts prepared by different methods

A series of HZSM-5 catalysts were synthesized by different methods. The physicochemical properties of the HZSM-5 catalysts were characterized by XRD, SEM, N2 isothermal adsorption-desorption, NH3-TPD, Py-IR and TGA, respectively. The results indicated that different preparation conditions lead to different morphologies, textures and the distribution of acid sites. The nanosized HZSM-5 catalysts exhibited better catalytic reactivity and coke capacity than the micro-sized HZSM-5 because nanosized HZSM-5 had larger specific surface area, higher pore volume, more exposed channels and more accessible acid sites. The large particles of NZ-3 in a reasonable range and the smooth surface were conducive to product diffusion; therefore, NZ-3 exhibited higher specific propylene yield and stability than the other nanosized catalysts. The moderate density and distribution of acid sites on NZ-3 also favored the formation of propylene.

Synthesis and characterization of nano-sized γ-Al2O3 for investigation the effect of temperature on catalytic dehydration of methanol to dimethyl ether

ABSTRACTThe new high surface area and high active nano-sized porous γ-Al2O3 catalyst was produced by a co-precipitation method. The synthesized catalyst was characterized by X-ray diffraction, Fourier transform infrared, NH3-temperature programmed desorption, and Brunauer-Emmett-Teller techniques. The results of characterization tests showed excellent textural and acidic properties of the synthesized catalyst for the methanol dehydration reaction. Catalytic dehydration of methanol to dimethyl ether was performed in an adiabatic fixed bed reactor using the new nano-sized catalyst at different operating temperatures. The results showed that the highest methanol conversion occurs in the temperature range of 300–350°C. Finally, a new correlation was developed to predict methanol conversion from operating temperature.

Study on Solid Oxide Fuel Cell with Porous Scaffold Electrode Manufactured By Tape Casting Process

Solid oxide fuel cell (SOFC) is energy conversion device which can converts chemical energy of hydrogen and oxygen to electrical energy. Conventional SOFC is fabricated by preparing anode support and coating electrolyte and cathode by spin coating or screen printing. One alternative way to fabricating SOFC is making porous scaffold on electrolyte support by same material with electrolyte and infiltrating electrode catalyst in porous scaffold. By this procedure, nano-sized catalyst network can be distributed in electrode and microstructure of electrode become easy to control and gas diffusion in electrode can be enhanced. However, conventional scaffold type SOFC has high ohmic resistance because of thick electrolyte support. To enhancing the performance of scaffold type SOFC, electrolyte thickness should be reduced. Moreover, there is problem that connectivity of electrolyte support and porous backbones is increased but porosity of scaffold is decreased as sintering temperature is increased. For solving these problems, tape casting process was applied to fabricate SOFC. By laminating tapes of each layers and co-sintering process, both connectivity and porosity can be obtained in high temperature sintering process. In this study, performance of scaffold electrode was compared with thick film electrode and SOFC single cell with porous scaffold electrode was fabricated by tape casting process. First, performance of scaffold electrode was compared with thick film electrode by electrochemical impedance spectroscopy analysis. La0.4Sr0.6Ti0.4Mn0.6O3-δ was infiltrated to porous scaffold as electrode catalyst and symmetric cells of scaffold electrode and thick film electrode were prepared. Area specific resistance (ASR) of scaffold electrode was 0.6 Ω·cm2 and ASR of thick film electrode was 3.4 Ω·cm2 at 800℃. SOFC single cell with porous scaffold electrode was fabricated by tape casting process. 8 mol % Yttria-stabilized Zirnocia (8YSZ) was used as electrolyte material. Electrolyte slurry and porous scaffold slurry with pore former were prepared and sequentially casted to make thin electrolyte and anode support. Cathode backbone tape was laminated on the sample by hot pressing. By sintering at 1400℃, thin electrolyte and porous scaffold were fabricated. La0.4Sr0.6Ti0.4Mn0.6O3-δ and La0.8Sr0.2MnO3 were infiltrated as anode catalyst and cathode catalyst, respectively. Open circuit voltage of the sample was 1.09V at 800℃, indicating that thin and dense electrolyte was formed. And the effects of porous scaffold were also investigated with respect to different porosity and different catalyst loading amount. Figure 1

Synthesis and Oxygen Evolution Performances of Iridium Oxide Electrocatalysts Supported on Tin Oxides for Polymer Electrolyte Membrane Water Electrolysis

Polymer electrolyte membrane water electrolysis (PEMWE) has received much attention as an attracting method to produce high-purity hydrogen with high energy conversion efficiency. However, conventional PEMWE cells are very expensive due to usage of a large amount of noble metal catalysts (a few mg cm–2). The aim of our research is the reduction of the amount of noble metal catalysts to 1/10 maintaining high-efficiency ≥ 90%. Although the amount of noble metal catalysts could be largely reduced by using nano-sized catalysts highly dispersed on support materials in place of conventional noble metal black (typically, ≥ 50 nm), carbon supports cannot be used at the anode due to the corrosion at high potentials of O2 evolution. Recently, our group succeeded in synthesizing Pt catalysts supported on corrosion-resistant M-SnO2 (M=Nb, Ta and Sb) with fused aggregated structures for polymer electrolyte fuel cells.1,2 In the present study, we newly synthesized IrOx nanoparticles dispersed on the M-SnO2(M=Nb, Ta and Sb) supports, and evaluated their oxygen evolution reaction (OER) activities for the PEMWE. The M-SnO2 (M=Nb, Ta and Sb) supports were prepared by flame pyrolysis of organometallic salt solution.3 IrOx nanoparticles were dispersed on them by a colloidal method.4 The catalysts thus prepared were characterized by XRD, TEM, XPS, ICP-AES, and apparent electrical conductivity measurement. For electrochemical measurements, a channel flow electrode cell was used.5 A catalyst ink was pipetted on a planar Au substrate electrode embedded in the Teflon® cell, followed by Nafion®-coating and drying. The OER activities were examined by linear sweep voltammetry (LSV) at 10 mV s–1 in 0.1 M HClO4 at 80oC under ambient air atmosphere. We observed XRD peaks assigned to rutile-type SnO2, but could not detect any other peaks attributed to Ir, IrO2 or impurities. As shown in Fig. 1, it was observed by TEM that nanoparticles with uniform size of ca. 2 nm were highly dispersed on the supports in all catalysts prepared. Because XPS of the catalysts indicated the presence of both Ir0 and Ir4+, we denote them as IrOx. By ICP-AES, the amount of Ir loaded in IrOx/M-SnO2 (M=Nb, Ta and Sb) catalysts were determined to be 11.3, 10.4 and 8.8 wt%, respectively. Thus, we successfully synthesized IrOx nanoparticle catalysts highly dispersed on the doped SnO2 supports with no large difference in the microstructure regardless of the kind of dopants. The apparent electrical conductivities σapp for the three supports and the corresponding catalysts measured under a pressure of 19 MPa are shown in Fig. 2. Sb-SnO2 support exhibited the σapp much higher than those of Nb-SnO2 and Ta-SnO2. The values of σapp were found to increase up to two orders of magnitude by loading IrOx, Especially, the σapp of the IrOx/Sb-SnO2 catalyst was the highest 0.80 S cm–1. Such a phenomenon accords with that observed for Pt catalysts supported on doped SnO2, which may be related to a decrease in the electronic depletion region of SnO2.6 Figure 3 shows LSVs of these catalysts compared with a conventional catalyst (mixture of commercial IrO2 and Pt black, 50:50 in weight ratio). The onset potential for the OER current for our catalysts was ca. 1.38 V vs. RHE. The IrOx/Ta-SnO2 and IrOx/Sb-SnO2 catalysts exhibited higher mass activities (MAs) for the OER at 1.50 V than that of IrOx/Nb-SnO2. The MA of 16 A mgIr –1 at IrOx/Ta-SnO2 was 30 times higher than that of the conventional catalyst. Such high MAs of IrOx/Ta-SnO2 or IrOx/Sb-SnO2 catalysts enable PEMWE operation efficiency of 90% at 1 A cm‒2 with the noble metal anode catalyst as low as 0.1 mgPt+Ir cm‒2. Acknowledgement This work was supported by the New Energy and Industrial Technology Development Organization (NEDO) of Japan. References 1) K. Kakinuma, Y. Chino, Y. Senoo, M. Uchida, T. Kamino, H. Uchida, S. Deki, and M. Watanabe, Electrochim. Acta, 110, 316 (2013). 2) Y. Senoo, K. Taniguchi, K. Kakinuma, M. Uchida, H. Uchida, S. Deki, and M. Watanabe, Electrochem. Commun., 51, 37 (2015). 3) K. Kakinuma, M. Uchida, T. Kamino, H. Uchida, and M. Watanabe, Electrochim. Acta, 56, 2881 (2011). 4) M. Watanabe, M. Uchida, and S. Motoo, J. Electroanal. Chem., 229, 395 (1987). 5) N. Wakabayashi, M. Takeichi, H. Uchida, and M. Watanabe, J. Phys. Chem. B, 109, 5836(2005). 6) Y. Senoo, K. Kakinuma, M. Uchida, H. Uchida, S. Deki, and M. Watanabe, RSC Adv., 4, 32180 (2014). Figure 1

Highly-active Pd–Cu electrocatalysts for oxidation of ubiquitous oxygenated fuels

Nanostructured palladium-copper electrocatalysts with Pd:Cu ratios of 1:3, 1:1, and 3:1 were synthesized using a Sacrificial Support Method (SSM) in combination with the thermal reduction of metal precursors. The materials were comprehensively characterized by X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Scanning and Transmission Electron Microscopy (SEM and TEM), surface area measurements (Brunauer-Emmett-Teller, BET) and Differential Electrochemical Mass Spectroscopy (DEMS). The SSM method enables the preparation of nano-sized unsupported Pd-Cu catalysts with uniformly-distributed particles and high surface area, in the range of 40m2gcatalyst−1. Their catalytic activity for the electrooxidation of several alcohols (methanol, ethanol, ethylene glycol and glycerol) was investigated in alkaline media. In situ Infrared Reflection Adsorption Spectroscopy (IRRAS) and Density Functional Theory (DFT) calculations were used in order to understand the mechanism of the various alcohols electrooxidation reactions.

Solvent-Free Condensation Reactions To Synthesize Five-Membered Heterocycles Containing the Sulfamide Fragment

We report a study of the solvent-free condensation reaction of 1,2-dicarbonyl compounds with sulfamide catalyzed by a Keggin-type acid (H3PMo12O40·nH2O, MPA) to obtain 3,4-disubstituted 1,2,5-thiadiazole 1,1-dioxide derivatives. Some reactions were also performed in solution or using nano-sized silica-supported MPA catalyst in order to compare the results under different experimental conditions. Effects of the temperature used for the thermal pretreatment of the catalyst, the reaction temperature, the molar ratios sulfamide/1,2-dicarbonyl compound and MPA/1,2-dicarbonyl compound, and alternative experimental procedures on the yield of the reaction product were investigated. Under suitable experimental conditions eight compounds were obtained in good yields. The catalyst was recycled and reused, but with some loss of its catalytic activity. The presented synthetic method is a simple, clean, and environmentally friendly alternative for synthesizing different 1,2,5-thiadiazole 1,1-dioxide derivatives.