H2PtCl6 Research Articles

Bi-Functional Oxygen Electrodes for a Rechargeable Zinc/Air Battery with Choline Acetate Electrolyte

The primary alkaline zinc/air battery is known for its high energy density and is commonly used as energy supply for hearing aids devices with practical energy density values in the range of 700-850 mWh gzinc -1. However, recharging process is very challenging because of its low energy efficiency (<60%) due to high overpotential and poor cycling ability of the air electrode as well as dendrite and carbonate formation in alkaline solution. To overcome some drawbacks, alternative electrolytes such as ionic liquids (IL´s) are promising candidates.1 Room Temperature Ionic liquids (RTILs) are low temperature (<100°C) molten salts composed of organic cations and anions characterized by extremely low vapor pressure, high decomposition temperature, but also by high viscosity and poor/moderate conductivity. For electrochemical applications, and more especially for metal/air battery in which oxygen reactions occur, presence of proton species in ionic liquid is preferred since aprotic ones allow “only” 1e- oxygen reduction reaction (ORR) step.2 High surface tension is also a prerequisite for triple-phase boundary formation in the gas diffusion electrode (GDE). In this work, feasibility of choline acetate (ChAcO) with zinc salt as electrolyte mixture and AB2O4structured materials as bifunctional cathode catalyst was investigated. In this work, precious metal and spinel oxide bifunctional catalyst were prepared. 20 wt% Pt was deposited on commercial carbon (C65) by chemical reduction of hexachloro-platinic acid in formaldehyde at 80°C for 1 h. MnCo2O4 (MCO) and NiCo2O4 (NCO) Spinel were synthesized by hydrothermal (HT) and hard template (SS) methods. The structural characterization of the as-prepared catalysts was performed by means of XRD, SEM/EDX and TEM. Average size of as-prepared oxide particles was estimated to approximately 28, 100, 300 and 500 nm for HT-MCO, HT-NCO, SS-MCO and SS-NCO catalysts, respectively. Gas diffusion electrodes (GDE) with catalyst loading of 1 mgcat cm-2 were fabricated by airbrush spraying. Contact angle of electrode/electrolyte interface was measured for 100 h at room temperature and 30% RH. The electrochemical activity of commercial Pt/C and spinel-based GDE for ORR and OER were studied by cyclic voltammetry (CV) under half cell condition. The EL-Cell (ECC-Air) and coin cell (CR2032) were manufactured by assembling a Zn foil as active electrode, a glass fibre separator and a GDE. The cell performance was evaluated by U-I polarization at 1-100 µA cm-2 for 1-3 h charge/discharge cycle. A preliminary screening of catalysts in terms of activity and stability was conducted in EL-Cell with dry air at RT. At 50 µA cm-2, comparison of charge/discharge kinetics of the different catalysts over 5 h/cycle is shown in fig.1a. An effect of addition of water in the IL was studied at 100 µA cm-2 in ambient air (30% RH at 22°C), 24 h/cycle for one month (fig.1b). The best system was HT-MCO that was further investigated under coin cell (CR2032) condition (Zn || ChAcO + 30 wt% H2O + 0.01 M Zn AcO || MnCo2O4/C65). At 100 µA cm-2, an energy and columbic efficiency of 50 and 100% was calculated for the 3 h cycle, respectively. The same cell was successfully tested in ambient air (RT, 30% RH) for 700 h (140 cycles) at 50 µA cm-2. Average cell voltage was 0.75 V (discharge) and 1.9 V (charge). A discharge specific capacity of 725 mAh gZn -1 was achieved at 100 µA cm-2.

Manufacturing of Bi-functional Nano-sensor of Nobel Metal for Hydrocarbon Gas Detection in Petroleum Sector Using Pulse Laser Deposition Technique

In the present investigation bi-functional nano-gas-sensor was manufactured from two types of metals: ZnO metal oxide and Pt noble metal. The nano-gas-sensors were designed for monitoring and control the environmental pollution in petroleum sector. The preparation technique was carried out by design and construction of a pulse laser deposition unit (PLD) with Nd: YAG laser (λ=532nm, laser fluence 2 J/cm2, repetition rate 6 Hz and the pulse duration 7ns). The target was pure ZnO and Pt:ZnO that containing 4%wt Pt. The hexachloroplatinic acid (H2PtCl6) was used as Pt source. The PLD films were deposited at three different temperatures 200, 250, and 300oC. Many characterization tests are used to study the influence of temperature on surface morphology of prepared films: Scanning Electron Microscope (SEM), Atomic Force Microscope (AFM), x-ray Diffraction (XRD) and (UV) visible. The results pointed to a direct relationship between the deposition temperature and the grain sizes of the nanoparticles formed on the substrate. On the other hand, the results of RMS roughness of AFM showed an increased value with increasing of deposition temperature. The best value of RMS roughness was 10.3nm for thin films deposited at 250ºC. The x-ray results shows formation of nanostructure on the substrate at deposition temperature of 250ºC, in which represent high surface area of gas sensor and especially with Pt. In addition, the UV-VIS transmittance measurements have shown that the films are highly transparent in the Visb-NIR wavelength region, with an average transmittance of about 90%. These results pointed to that the manufactured bi-metals nano-gas-sensor (Pt:ZnO) at 250oC is more suitable for LPG hydrocarbons detection application in petroleum positions.

Peroxidase activity of biogenic platinum nanoparticles: A colorimetric probe towards selective detection of mercuric ions in water samples

A biogenic green method for the synthesis of platinum nanoparticles (Pt NP) was developed using non-toxic, renewable, biodegradable plant exudate gum, gum olibanum (Boswellia serrata). The effect of parameters such as concentrations of gum (0.1–0.5%) and chloroplatinic acid (0.125–1.0mM) on nanoparticle synthesis was studied. Techniques such as UV–vis spectroscopy (UV-vis), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), dynamic light scattering (DLS) and zeta potential measurements were used to characterize the generated nanoparticles. The Pt NP formation was evidenced from the broad continuous absorption in the UV–vis spectra and appearance of black colour. The XRD pattern established the face centered cubic crystal structure of the fabricated nanoparticles. The produced NP were quasi-spherical in shape with a particle size of 4.4±0.5nm. The resulting nanoparticles exhibited excellent peroxidase activity which catalyzes the oxidation of the chromogen 3, 3′, 5, 5′-tetramethylbenzidine (TMB) to a blue colour product, in the presence of hydrogen peroxide. The peroxidase activity of the nanoparticles was selectively inhibited by mercuric ions (Hg2+) due to the formation of amalgam by Hg-Pt specific interaction. Notably, the inhibition was not affected by other metal ions even at a concentration of 5μM. The decrease in oxidized TMB intensity at 652nm (blue colour), upon addition of mercuric ions was linear in the range of 50–500nM for MilliQ, tap and ground waters and the respective limit of quantification values for Hg2+ using the developed method were 16.9, 26 and 47.3nM. The proposed method was effectively applied for the determination of Hg2+ in various ground water samples and verified with CVAAS. We envisage that the biogenic Pt NP based colorimetric probe can have promising applications in the screening and field detection of mercuric ions in various water bodies and public drinking water distribution systems.

Synthesis of 5-(dimethylsilyl)pentylalkylferrocene-grafted HTPB (alkylFc-HTPB) via platinum-catalyzed hydrosilylation

In this work, at first alkylferrocene derivatives were synthesized according to procedure described in the literature. (5-Chloropentanoyl)ferrocene derivatives were prepared by Friedel–Crafts acylation of ferrocene and alkylferrocene derivatives with 5-chloropentanoyl chloride in dichloromethane, and AlCl3 was used as catalyst. The corresponding 5-chloropentylferrocene derivatives were synthesized from reduction of these products by NaBH4 in diglyme at 0 °C. Finally (5-alkylferrocenylpentyl)dimethylsilane was synthesized from reaction of 5-chloropentylferrocene derivatives with magnesium in THF and reaction of corresponding Grignard reagents with chlorodimethylsilane in 82–87% yields. 1H and 13C NMR, FT-IR spectroscopy supported the predicted structure of the product. Nine samples of alkylferrocene-grafted hydroxyl-terminated polybutadiene (alkylFc-HTPB) derivatives, containing different percent of iron, were synthesized by hydrosilylation reaction of [5-(alkylferrocenyl)pentyl]dimethylsilane with hydroxy-terminated polybutadiene (HTPB), in the presence of catalytic amount of the hexachloroplatinic acid (Speier’s catalyst). FT-IR spectroscopy was utilized to follow the progress of the reaction, by monitoring the loss of the Si–H absorption at 2110 cm−1, and the reaction was completed in 24 h. Some properties of resulting prepolymer like viscosity, glass transition temperature and iron percentage as important parameters in production of composite propellants were investigated. For example, the viscosity increased with increasing iron content because of the greater extent of ferrocene grafting in the polymer.

Probing ethanol oxidation mechanism with in-situ FTIR spectroscopy via photodeposited Pt nanoparticles onto titania

Hybrid Pt/TiO2-C catalysts were synthesized via photodeposition in this study in order to increase the kinetics and the carbonate yield of the Ethanol Oxidation Reaction. Photodeposition was chosen because it was believed that the Pt nanoparticles would deposit predominately on top of the oxide sites, which would change the reactivity of the Pt nanoparticles. First, TiO2-C composites with varying TiO2 mass percentages were synthesized by sol gel using Vulcan Carbon XC-72R and titanium isopropoxide as precursors. The composites were dispersed in isopropanol and mixed with Chloroplatinic Acid such that the final Pt concentration was 20% by weight. This mixture was illuminated with UV light for 3h and the Pt/TiO2-C catalysts were recovered. Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) analysis showed that the Pt photodeposition was almost quantitative and XRD patterns showed that the average particle size ranged from 4 to 5nm. XPS Spectra showed that the Pt nanoparticles shifted to lower binding energies as TiO2 concentration increased, whereas Ti binding energies shifted to higher values with higher TiO2 concentrations. The synthesized catalysts showed increased current density in Linear Sweep Voltammetry when compared to a commercial Pt/C catalyst experiments which was attributed to increased nucleophilicity on the Pt which allowed for kinetically easier nucleophilic attacks. In-situ FTIR studies showed that the bands attributed to carbonate vibrations were more intense on the synthesized catalysts. All of these experiments allowed us to conclude that the increased electron density facilitates nucleophilic attacks and CC bond breaking.

In Situ PDF Study of the Nucleation and Growth of Intermetallic PtPb Nanocrystals

AbstractThe mechanism of Pt and PtPb nanocrystal formation under supercritical ethanol conditions has been investigated by means of in situ X‐ray total scattering and pair distribution function (PDF) analysis. The metal complex structures of two different platinum precursor solutions, chloroplatinic acid and Pt(acac)2 (acac=acetylacetonate) provide atomic‐scale detail about the nucleation mechanisms after initiation of the reaction with Pb(acac)2 by heating. The stronger Pt−O chemical bonding in the Pt(acac)2 precursor complex compared with the Pt−Cl bonding in the chloroplatinic acid precursor complex leads to a much slower reduction of the Pt center, and this allows more optimal co‐reduction conditions providing a pathway for formation of phase‐pure intermetallic PtPb product. The matching chemistry of the Pt(acac)2 and Pb(acac)2 precursors allow development of a facile continuous flow supercritical ethanol process for obtaining phase‐pure hexagonal PtPb nanocrystals. The study thus highlights the importance of in situ studies in revealing atomic‐scale information about nucleation mechanisms, which can be used in design of specific synthesis pathways, and the new continuous‐flow process to obtain PtPb nanocrystals holds potential for large‐scale production.

Conductivity Enhancement of PEDOT:PSS via Addition of Chloroplatinic Acid and Its Mechanism

Readily obtained highly conductive, transparent, and flexible poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films is urgently needed in printing of flexible transparent electrodes. A simple and facile method to enhance the electrical conductivity of PEDOT:PSS films is reported. The conductivity is increased by four orders of magnitude after adding solid chloroplatinic acid (H2PtCl6) into the pristine PEDOT:PSS solution. The H2PtCl6‐doped PEDOT:PSS film exhibits a sheet resistance of 44 ± 5 Ω □‐1 and a transmittance of 84 ± 1% at 550 nm, corresponding to a figure of merit of 47 ± 4. Comparative study shows addition of solid acid like H2PtCl6 is more effective in conductivity enhancement than addition of polar organic solvents, such as dimethyl sulfoxide or ethylene glycol. The mechanism for the conductivity enhancement is attributed to both in situ doping and phase separation of PEDOT:PSS. PEDOT is oxidized and doped by Pt4+ of H2PtCl6, which is reduced simultaneously to Pt2+. Proton transfer from H2PtCl6 to PSS− of PEDOT:PSS causes formation of neutral PSSH, leading to phase separation between insulating PSS and conducting PEDOT. Such a phase separation results in conformational changes of PEDOT chains and reduction in energy barrier for charge hopping.

Composition and structure of platinum-containing thin composite films prepared from silica sols

Chemical processes that can occur during aging of sols based on water–alcohol solutions of tetraethoxysilane (TEOS) and hexachloroplatinic acid and during formation of films from these sols are analyzed by the results of visible and UV spectroscopy and X-ray powder diffraction. The sizes and compositions of the platinum particles that are formed in xerogels and in thin films on the nanometer and submicron levels are estimated based on X-ray crystallography, energy dispersive spectral analysis, high-resolution scanning and transmission electron microscopy, and grazing incidence small-angle X-ray scattering studies.

Hydrogen peroxide sensor based on in situ grown Pt nanoparticles from waste screen-printed electrodes

Screen printing technology is widely used for the fabrication of low-cost disposable electrodes. However, this generates solid wastes that contain precious metals like platinum, which is highly polluting and quite valuable for different industries. Therefore, it is necessary to process spent platinum-containing materials to meet future demand and to protect resources. This work presents, for the first time, a procedure to recycle platinum from waste screen-printed electrodes using aqua regia as the leaching solution. Platinum from this solution was electrodeposited as nanoparticles onto the surface of screen-printed carbon electrodes (PtNPs@SPCEs) directly. PtNPs were characterized by SEM and X-ray diffraction analyses. PtNPs@SPCEs were applied as a hydrogen peroxide sensor, with similar results to those obtained with PtNPs from standard hexachloroplatinic acid solutions. With very small quantities of deposited platinum (μg), the reached sensitivity of the PtNPs@SPCEs was 687.3nAcm−2μM−1 and the limit of detection was 1.9μM (based on a S/N ratio=3). The sensitivity towards H2O2 was improved ∼360 times compared to commercial SPCEs, and ∼7 times compared to commercial screen-printed platinum electrodes.

Effect of platinum on sintering morphology of porous YSZ ceramics.

Platinum/yttria-stabilized zirconia (Pt/YSZ) porous ceramics were prepared by sintering of the Pt/PMMA/YSZ stripe-like membrane with a porogen of spherical polymethyl methacrylate (PMMA) and a precursor of platinum (Pt) of chloroplatinic acid. The microstructure of raw and processed material and Pt/ZrO2 calcination process at different sintering temperatures were investigated. The results showed that the spherically porous structure of Pt/YSZ was observed at a sintering temperature below 400 °C due to the thermal decomposition of PMMA. However, the pores were shrunk about 35% in diameter when YSZ compacts were sintered at the temperature of 1,450 °C. In addition, the spherical pores can be retained in the compacts when the content of Pt <5% and then gradually merged into changing when the content of Pt increased to 50%. The relative density was increased from 42% to 90% and the open porosity was decreased from 60% to 10% when Pt was added with content from 5% to 80%. The change of microstructure for Pt/YSZ is due to the migration of Pt and YSZ in the composites. The preferential migration and coalescence proceeded for Pt in Pt/YSZ is about 500 °C and YSZ clusters can keep stable until up to 900 °C. However, the growth of YSZ particle in the sintering process was hindered by the scattering of Pt phase.

A novel chondroitin sulfate decorated nano platinum for the treatment of osteoarthritis

The present work showed the biofabrication of platinum nanoparticles (PtNPs) using chondroitin sulfate via a facile, eco-friendly route by just heating leaf extract and H2PtCl6·6H2O (Chloroplatinic acid) solution which gave a brown-colored PtNPs dispersion. The assynthesized PtNPs were analyzed by using Transmission electron microscopy (TEM), Energy dispersive spectroscopy (EDX), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and Selected area electron diffraction (SAED). TEM analysis showed PtNPs of irregular shape with a size existed in the range from 3 to 5nm. From zeta potential studies it is found the surface charge of the synthesized PtNPs is negative (−25.6mV). FTIR analysis and zeta potential measurements of PtNPs confirm the capping of chondroitin sulfate onto the surface of nanoparticles. XRD and SAED pattern revealed the crystalline nature of synthesized nanoparticles. Further, the in-vitro cytotoxicity of PtNPs against the osteoarthritis chondrocytes showed their biocompatibility, hence the obtained nanoparticles may have future scope in the treatment of osteoarthritis. Also, the present approach is green alternative to the traditionally available chemical methods that are currently been used now a days using chemical reagents such that are hazardous to human and environment.

Highly Efficient and Magnetically Recyclable Pt Catalysts for Hydrosilylation Reactions

Fe3O4@SiO2-APTES-Pt was prepared from 3-aminopropyl triethoxysilane via immobilization on Fe3O4@SiO2, followed by reacted with chloroplatinic acid. The obtained catalyst was characterized by XRD, TEM, FT-IR, XPS and ICP-AES. This catalyst showed extraordinary catalytic performances for hydrosilylation of olefins with triethoxysilane. It was recovered from the reaction medium just by sequestering by a magnet and then reused several times without significant loss in catalytic activity and selectivity.

Construction of Au@Pt core—satellite nanoparticles based on in-situ reduction of polymeric ionic liquid protected gold nanoparticles

A method of in-situ reduction to prepare Au@Pt core-satellite nanoparticles (NPs) is described by using Au NPs coating poly[1-methyl 3-(2-methacryloyloxy propylimidazolium bromine)] (PMMPImB-@-Au NPs) as the template. After electrostatic complex chloroplatinic acid with PMMPImB shell, the composite NP was directly reduced with N2H4 to produce Au@Pt core-satellite NPs. The characterization of composite and core-satellite NPs under different amounts of chloroplatinic acid were studied by DLS, UV-vis absorption spectrum and TEM. The satellite Pt NPs with a small size (~2 nm) dotted around Au core, and the resulting Au@Pt core-satellite NPs showed a red-shift surface plasmon resonance (SPR) and a good dispersion due to effectively electrostatic repulsion providing by the polymeric ionic liquid (PIL) shell. Finally, Au@Pt core-satellite NPs exhibit an enhanced catalytic activity and cycled catalytic capability for the reduction of p-nitrophenol with NaBH4.

Alchornea laxiflora Bark Extract Assisted Green Synthesis of Platinum Nanoparticles for Oxidative Desulphurization of Model Oil

This study reports the development of reliable and eco-friendly processes for the synthesis of platinum nanoparticles (PtNPs) via the reduction of chloroplatinic acid solution by the aqueous tree bark extract of Alchornea laxiflora at a reaction temperature of 100 °C. The mechanistic aspects of the reactions involved in the bioreduction process were proposed. The synthesized PtNPs were characterized by UV–visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), high resolution transmission electron microscopy (HRTEM), energy dispersive X-ray (EDX), and X-ray diffraction (XRD). The HRTEM image revealed that the PtNPs were in the size range of 3.68–8.77 nm with an average particle size of 5.93 ± 1.43 nm. The XRD pattern shows face centred cubic(fcc) phase structure while the FTIR analysis suggests that the obtained platinum nanoparticles were stabilized by the metabolites and protein through carbonyl and hydroxyl groups. Catalytic application of PtNPs for oxidative desulphurization of model oil (dibenzothiophene (DBT) dissolved in n-heptane) was investigated by comparing its catalytic potential with the conventional acetic acid catalyst. The results show that PtNPs has higher catalytic activity for oxidative desulphurization of model oil than acetic acid. Our results indicate that this eco-friendly, simple and cost-effective method will find useful applications in petroleum industry.

Synthesis and Characterization of Polysiloxane Grafted Polyamide‐Amine Surfactants

AbstractDendritic‐linear surfactants 1G PAMAM–Si and 2G PAMAM–Si were prepared by grafting the single epoxy terminated polydimethylsiloxane (SEPDMS) onto the 1G and 2G dendritic polyamide‐amine (PAMAM), respectively. SEPDMS was synthesized by hydrogen‐terminated polydimethylsiloxane and allyl glycidyl ether in chloroplatinic acid. The optimum grafting conditions were obtained by single‐factor experiments when the mole ratio of SEPDMS and PAMAM was 0.95:1, the reaction temperature was 60 °C, the reaction time was 5 h and the solvent percentage was 60%. The molecular structure of PAMAM–Si was characterized by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, gel permeation chromatograph and potentiometric acid‐base titration. Furthermore, the stability, surface activity and emulsifying ability of the prepared surfactants were studied. The results showed that PAMAM–Si has high stability against dilution, acids, alkalies and salts. PAMAM–Si surfactants can significantly reduce the surface tension of water. And 2G PAMAM–Si is superior to 1G PAMAM–Si at the ability of emulsifying oil.

无卤阻燃高温硫化硅橡胶的制备与性能研究

本文通过氢氧化铝和氯铂酸复配成功制备了无卤阻燃高温硫化硅橡胶。利用垂直燃烧实验研究了硅橡胶的阻燃性能；利用拉伸实验和硬度测试对所制备的阻燃硅橡胶进行了机械性能的研究。结果表明通过氢氧化铝和氯铂酸的协同作用，硅橡胶的阻燃性能明显提高，氯铂酸添加量10~50 ppm时硅橡胶的综合性能可满足用户使用需求。 The halogen-free flame retardant high temperature vulcanized silicone rubber was successfully prepared by aluminum hydroxide and chloroplatinic acid. The flame retardant properties of sili-cone rubber were studied by vertical combustion test. The mechanical properties of silicone rubber were studied by tensile test and hardness test. The results show that the flame retardant properties of silicone rubber were improved by the synergistic effect of aluminum hydroxide and chloroplatinic acid. When the chloroplatinic acid content is limited in 10 - 50 ppm, the compre-hensive properties of silicone rubber can meet the needs of users.

Fabrication of highly dispersed platinum-deposited porous g-C3N4 by a simple in situ photoreduction strategy and their excellent visible light photocatalytic activity toward aqueous 4-fluorophenol degradation

A series of highly dispersed platinum-deposited porous g-C3N4 (Pt/pg-C3N4) were successfully fabricated by a simple in situ photoreduction strategy using chloroplatinic acid and porous g-C3N4 as precursors. Porous g-C3N4 was fabricated by a pretreatment strategy using melamine as a raw material. The morphology, porosity, phase, chemical structure, and optical and electronic properties of as-prepared Pt/pg-C3N4 were characterized. The photocatalytic activity of as-prepared Pt/pg-C3N4 was preliminarily evaluated by the degradation of aqueous azo dyes methyl orange under visible light irradiation. The as-prepared Pt/pg-C3N4 were further applied to the degradation and mineralization of aqueous 4-fluorophenol. The recyclability of Pt/pg-C3N4 was evaluated under four consecutive photocatalytic runs.

PEM fuel cell electrode preparation using oxygen plasma treated graphene related material serving as catalyst support for platinum nanoparticles

This work deals with the preparation and investigation of polymer electrolyte membrane fuel cell (PEMFC) electrodes, which are obtained using gas diffusion layers coated with graphene related material (GRM) serving as a catalyst support for platinum nanoparticles. PEMFC electrocatalysts have been prepared by pulsed electrochemical deposition of platinum particles from hexachloroplatinic acid. Prior to GRM decoration with platinum, the graphene structures are functionalized by oxygen plasma treatment. This leads to oxygen containing functional groups on the GRM outer surface, providing an improved hydrophilic behavior, thus favoring the Pt deposition process. Membrane electrode assemblies (MEAs) with the so prepared electrodes are investigated in-situ in our fuel cell test system. Polarization plots (in-situ cell performance) using these MEAs have been tested under different operational conditions.

Electrocatalytic Investigation of Group X Metal Nanoparticles Loaded TiO2 Nanotubes Powder Prepared by Rapid Breakdown Anodization for Selective H2O2 Sensing

Amperometric based hydrogen peroxide (H2O2) sensor developed using a composite of Titania (TiO2) nanotubes (NTs) powder individually loaded with Ni, Pd or Pt metal nanoparticles is reported. The bundles of TiO2 NTs powder prepared via rapid breakdown anodization have a length of 5 to 6 μm and outer diameter of 20 to 25 nm. Sodium borohydride based reduction of chloroplatinic acid and palladium chloride with the TiO2 NTs powder resulted in Pt/TiO2 and Pd/TiO2 composite materials. Ni/TiO2 composite was prepared by mixing directly Ni nanoparticles (35 nm) and TiO2 NTs. The electrochemical performance of the Pt/TiO2, Pd/TiO2 and Ni/TiO2 electrodes exhibited better selectivity, sensitivity and wide linear range for the detection of the analyte H2O2, in comparison with pristine TiO2 NTs powder. Among the composites, the Ni/TiO2 electrode exhibited high electrocatalytic activity toward oxidation of H2O2 in 0.1 M NaOH solution. At an applied potential of +0.45 V vs. NCE, the Ni/TiO2 composite electrode exhibits a linear dependence (R2 = 0.997) in the H2O2 concentration up to 3365 μM with a sensitivity of 5.3 μA mM−1 and detection limit of 20 μM. In general, the Pt, Pd and Ni/ TiO2 nanocomposite electrodes exhibit better sensitivity to the detection of H2O2.

High performance noble-metal-free NiCo/AC bimetal for gasification in supercritical water

We report high performance Noble-metal-free NiCo/AC bimetal for gasification in supercritical water by the polyol reduction method with chloroplatinic acid as nucleation seed. At 475 °C and 20 min, the carbon efficiency (CE) for gasification of phenol with NiCo/AC has reached about 65%, which represents a more than 20-fold enhancement of carbon efficiency compared to the Co/AC and 6-fold compared to the Ni/AC. The CE of commercial noble Ru/C (5 wt%) catalyst is only about 15% higher than that of NiCo/AC catalyst. The catalyst was characterized by BET, XRD, XPS and TEM. The results indicate smaller and higher disperse of NiCo alloy has been achieved. By using NiCo/AC catalyst, the CE can reach about 90% at 525 °C and 60 min with a 5 wt% phenol, 0.098 kg/m3 density and catalyst loading of 0.5 g/g (the mass of NiCo/AC catalyst/the mass of phenol). The results of GC–MS indicate NiCo/AC can suppress tar successfully. A kinetic modeling was also proposed to describe gaseous product and tar formation, which gives the activation energy (Ea) 123.56 ± 31 kJ/mol and the frequency factor 16.93 ± 0.48 for gaseous products. While for tar formation, the Ea is 112.95 ± 24 kJ/mol and the frequency factor is 13.99 ± 0.37. The successful use of noble-metal-free NiCo/AC shows the potential to replace noble Ru-catalysts in SCWG process for gases fuels by bimetal.