Low Amount Of Pt Research Articles

High-Area Ti/Pt Electrodes for the Electrochemically Catalyzed Transesterification of Soybean Oil with Methanol

Biodiesel fuel is a renewable energy source normally produced in industry by using an alkaline homogeneous catalyst to promote the transesterification of oil and methanol to fatty acid methyl ester (FAME). Undesirable side reactions occur when poorly refined oils are used, leading to serious problems of product separation and low FAME yield. Therefore, about 85% of the cost of biodiesel is determined by the cost of the feedstock. Here, we describe the development of high-area Pt films deposited on Ti substrates for the electrolytic synthesis of biodiesel from soybean oil containing water, without the addition of catalyst. The higher both the calcination temperature and the number of layers deposited on the Ti surface, the higher the electrochemically active area of Pt exposed to surface. Conversion into esters in electrolysis is proportional to the increase in the superficial area of the Ti/Pt electrodes. Thus, it is possible to synthesize biodiesel using electrodes containing very low amounts of Pt (<0.441 mg cm−2), an important parameter in the industrial production of biodiesel.

Pd black decorated by Pt sub-monolayers as an electrocatalyst for the HCOOH oxidation

Pd black was modified by a very low amount of Pt corresponding to a sub-monolayer (ML). Spontaneous displacement method was employed. The catalysts with 0.02–0.12 ML were characterized by cyclic voltammetry and COads stripping and were tested for HCOOH oxidation under the potentiodynamic and potentiostatic conditions. All the Pt@Pd catalysts were more active for HCOOH oxidation than Pd black. The Pt@Pd with 0.08 ML of Pt exhibited the highest activity with the maximum current density under the potentiodynamic conditions of 8 mA cm−2 (vs. 2.7 mA cm−2 on Pd black). Contrasting HCOOH oxidation kinetics on Pt@Pd and Pt@Au catalysts revealed that the current densities are higher, and the poisoning rate is lower on Pt@Pd catalyst. This was ascribed to an optimal strength of the Pt–adsorbate bond when Pt is supported on Pd and to a possible influence of the Pt atoms on the Pd substrate.

Electrochemical properties of thermally treated platinized Ebonex® with low content of Pt

Effect of thermal treatment on the physicochemical and electrochemical properties of platinized Ebonex® electrodes, containing low amount of Pt has been investigated. New phases in systems Ti–O (310°C) and Pt–Ti–O (410°C) were found for treated Ebonex® that affects electrochemical behavior of electrodes. Ebonex®/Pt-electrodes were shown to be n-type highly doped semiconductors, as well as Ebonex®. Increase in treatment temperature leads to both oxidation of titanium suboxides and diffusion of Pt deep into substrate and results in shift of flatband potential to positive values and decrease in donor concentration as a rule. The peak of reduction of Pt phase oxides on the cathodic branch of voltammograms could be correlated with electrocatalytic activity of platinized Ebonex®-electrodes since it characterizes the amount of electrochemically active platinum on the electrode surface. Thermally treated platinized Ebonex® anodes could be applied in a trivalent chromium electroplating bath.

Trimetallic amorphous catalyst with low amount of platinum: Comparative study for ethanol, bioethanol and CO electrooxidation

The use of ethanol and bioethanol demonstrates the viability of alternative fuels to gasoline with optimum energy purposes. The development of suitable catalysts is fundamental to improve the electrical performance in Direct Alcohol Fuel Cells (DAFCs). For that reason, a series of amorphous Ni59Nb40Pt0.6Y0.2Z0.2 (PtYZ) alloys adding three different transition metals (Y, Z = Cu, Ru and Sn) were manufactured by Mechanical Alloying (MA) method. The low amount of Pt and bifunctional-electronic role of cocatalysts was analyzed using electrochemical techniques such as Cyclic Voltammetry (CV), chronoamperometry and CO stripping experiments. Concerning to reactivity towards alcohol electrooxidations, alloys with Cu showed the best catalytic performance. However, its use is limited by Cu dissolution in acid media. The PtYZ catalysts showed higher CO tolerance, achieving smaller rates of poisoning (δ) for PtRuSn alloy. CO stripping reveals that CO oxidation on alloys with Ru takes place at lower electrode potentials. The experimental results showed better electric performance, but higher poisoning of the catalytic surface for bioethanol electrooxidation. Acetaldehyde and formic acid were found in bioethanol by HPLC, influencing the electrochemical response.

The Ni-deposited carbon felt as substrate for preparation of Pt-modified electrocatalysts: Application for alkaline water electrolysis

A Ni-modified carbon felt (C) electrode (C/Ni) was used as a substrate for preparation of Pt-modified electrode in view of its possible application as electrocatalytic material for the hydrogen evolution activity. The prepared electrode was characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and cyclic voltammetry (CV) techniques. The hydrogen evolution activity of the electrode was assessed by cathodic current–potential curves and electrochemical impedance spectroscopy (EIS) techniques. It was found that the modification of Ni-deposited C by loading low amount of Pt could enhance the hydrogen evolution activity of the electrode.

Enhancement of hydrogen evolution at cobalt–zinc deposited graphite electrode in alkaline solution

Thin Co layers were electrochemically deposited on a graphite electrode at different deposition current densities and thicknesses. After determining the best deposition conditions for hydrogen evolution (deposition current density and thickness), co-deposits of Co with Zn were prepared on the graphite electrode. The binary coatings prepared on the graphite electrode (CoZn) were etched in a concentrated alkaline solution (30% NaOH) to produce a porous and electrocatalytic surface suitable for use in the hydrogen evolution reaction (HER). After the leaching process, a low amount of Pt was deposited onto the etched CoZn deposit in order to further improve the catalytic activity of the electrode for the HER. The HER activity is assessed by recording cathodic current–potential curves, electrochemical impedance spectroscopy (EIS) and electrolysis techniques. Chemical composition of layers after alkaline leaching was determined by energy dispersive X-ray (EDX) analysis. The surface morphologies of coatings were investigated by scanning electron microscopy (SEM). It was found that, the HER activity of coatings depends on the metal ratio of Co and Zn, deposition current density and the thickness of coatings. The alkaline leached CoZn coating has a compact and porous structure as well as good electrocatalytic activity for the HER in alkaline media. Moreover, deposition of a low amount of Pt over the CoZn can further enhance its hydrogen evolution activity.

Structured catalysts for photo-Fenton oxidation of acetic acid

In this work photo-Fenton oxidation of acetic acid, was carried out on perovskites based structured catalysts, in the presence or in the absence of low amounts of Pt. Homogeneous photo-Fenton reaction by ferrioxalate complex has been also performed. The comparison of homogeneous and heterogeneous photo-Fenton oxidation indicates that the use of a heterogeneous structured catalyst greatly improves the total organic carbon (TOC) removal and leads to a more effective use of H 2O 2. The rate of TOC removal during the runtime decreased because of the occurring side H 2O 2 decomposition to O 2 that subtracts the oxidant to the photo-Fenton reaction. Moreover it allows enlarging the pH range of operation without the formation of sludge or significant metal leaching. LaFeO 3 and Pt/LaMnO 3 resulted the best catalysts for this process in terms of reaction rate.

Controlled synthesis of Pt-decorated Au nanostructure and its promoted activity toward formic acid electro-oxidation

Highly active Pt-decorated Au nanoparticles on carbon support with Pt:Au mole ratio ranging from 1:10 to 1:2 was successfully synthesized based on successive reduction strategy. The successful formation of this structure was suggested by transmission electron microscopy, UV–vis and voltammetry analyses. The electrocatalytic activity of this decorated structure toward formic acid oxidation surprisingly increases despite the low amount of Pt being used. At 0.1 V, the specific activity of PtAu/C with Pt/Au mole ratio 1:8 was more than one order of magnitude higher than the conventional Pt/C. The enhancement was attributed to the less Pt ensemble sites that the decorated structure possesses (ensemble effect) and the increase in the Pt atom reactivity on Au nanocrystal. The formic acid oxidation mechanism on this decorated structure was also elucidated using electrochemical impedance spectroscopy technique. It is proposed that besides the dehydrogenation reaction pathway happening on clean Pt sites, the reactive intermediate i.e. formate species could also be oxidized by the adsorbed water species on Pt at higher potential.

Electrocatalysis of oxygen reduction on carbon-supported Pt–Co nanoparticles with low Pt content

The oxygen reduction reaction (ORR) was investigated on carbon-supported Pt–Co nanoparticle electrocatalysts with low Pt content in alkaline electrolyte. High resolution transmission electron microscopy, In situ X-ray absorption spectroscopy, and X-ray diffraction analysis evidenced large structural differences of the Pt–Co particles depending on the route of the catalyst synthesis. It was demonstrated that although the Pt–Co materials contain low amounts of Pt, they show very good activities when the particles are formed by a Pt-rich shell and a Pt–Co core, which was obtained after submitting the electrocatalyst to a potential cycling in acid electrolyte. The high activity of this material was due to a major contribution from its higher surface area, as a result of the leaching of the Co atoms from the particle surface. Furthermore, its high activity was ascribed to a minor contribution from the electronic interaction of the Pt atoms, at the particle surface, and the Co atoms located in the beneath layer, lowering the Pt d-band center. As these electrocatalysts presented high activity for the ORR with low Pt content, the cost of the fuel cell cathodes could be lowered considerably.

Pt-decorated Au Nanoparticles: Highly Active Catalyst for Formic Acid Oxidation

Highly active Pt-decorated Au nanoparticles on carbon support was successfully synthesized based on successive reduction strategy. The electrocatalytic activity of this decorated structure toward formic acid oxidation unexpectedly increases despite the low amount of Pt being used. The enhancement is attributed to the less Pt ensemble sites that the decorated structure possesses (ensemble effect) and the increase in the Pt atom reactivity on Au nanocrystal (electronic effect).

Ni–Pt/C as anode electrocatalyst for a direct borohydride fuel cell

In this study, a series of Ni–Pt/C and Ni/C catalysts, which were employed as anode catalysts for a direct borohydride fuel cell (DBFC), were prepared and investigated by XRD, TEM, cyclic voltammetry, chronopotentiometry and fuel cell test. The particle size of Ni 37–Pt 3/C (mass ratio, Ni:Pt = 37:3) catalyst was sharply reduced by the addition of ultra low amount of Pt. And the electrochemical measurements showed that the electro-catalytic activity and stability of the Ni 37–Pt 3/C catalysts were improved compared with Ni/C catalyst. The DBFC employing Ni 37–Pt 3/C catalyst on the anode (metal loading, 1 mg cm −2) showed a maximum power density of 221.0 mW cm −2 at 60 °C, while under identical condition the maximum power density was 150.6 mW cm −2 for Ni/C. Furthermore, the polarization curves and hydrogen evolution behaviors on all the catalysts were investigated on the working conditions of the DBFC.

Superior catalytic behaviour of Pt-doped Pd catalysts in the complete oxidation of methane at low temperature

The catalytic combustion of methane at low temperature under lean conditions was investigated over bimetallic palladium-platinum catalysts supported on alumina. Pd-Pt catalysts with constant 2 wt.% metal loading and varying compositions in Pt and Pd were prepared by successive impregnations of the metal salts. The catalysts were characterised by powder X-ray diffraction, transmission electron microscopy/electron dispersion X-ray spectroscopy (TEM/EDX), volumetry of H 2 chemisorption, FTIR study of CO adsorption and temperature-programmed oxidation (TPO). In the absence of water added to the feed, the methane conversion over Pd-rich bimetallic catalysts (Pt/Pt + Pd molar ratios less than 0.3) was found to be the same as that of the reference Pd/Al 2O 3 catalyst. Interestingly, under wet conditions, these bimetallic catalysts exhibited an improved performance with respect to Pd/Al 2O 3. This effect was found to be maintained upon mild steam ageing. An interaction between both metals was suggested to explain the enhanced activity of bimetallic catalysts. This was confirmed by TPO experiments indicating that formation and decomposition of PdO is affected upon Pt addition even for very low amounts of Pt. The adsorption of CO on reduced catalysts studied by FTIR revealed new types of adsorbed CO species, suggesting again an interaction between two metals.

Microstructure of oxide scales on aluminide diffusion coatings after short time oxidation at 1050 °C

Three commercial Pt-modified coatings (RT22, SS82A and MDC150L) and one aluminide diffusion coating without Pt (PWA73) applied on a Ni-based single crystal superalloy (CMSX4), were investigated after isothermal oxidation in laboratory air at 1050 °C for 1 h, using X-ray diffraction, scanning electron microscopy and transmission electron microscopy (TEM). TEM investigations reveal the presence of the metastable γ-Al 2O 3 phase on all the investigated coatings. The amount of the observed α-Al 2O 3 phase formed seems to depend on the Al and Pt contents in the coating. A high Al content in the coatings promotes formation of α-Al 2O 3. A continuous layer of α-Al 2O 3 grains was found at the coating/oxide interface of the coating containing 55 at.% Al. On the coating with a low Al content (≈40 at.%) and with low amount of Pt (4 at.%), no α-Al 2O 3 phase was observed while on the coating with a similar Al content but with much higher Pt level (16 at.%), grains of α-Al 2O 3 phase were detected.