Hexachloroplatinic Acid Solution Research Articles

Ultrasound-Driven Defect Engineering in TiO2-x Nanotubes─Toward Highly Efficient Platinum Single Atom-Enhanced Photocatalytic Water Splitting.

Single-atom catalysts (SACs) have demonstrated superior catalytic activity and selectivity compared to nanoparticle catalysts due to their high reactivity and atom efficiency. However, stabilizing SACs within hosting substrates and their controllable loading preventing single atom clustering remain the key challenges in this field. Moreover, the direct comparison of (co-) catalytic effect of single atoms vs nanoparticles is still highly challenging. Here, we present a novel ultrasound-driven strategy for stabilizing Pt single-atomic sites over highly ordered TiO2 nanotubes. This controllable low-temperature defect engineering enables entrapment of platinum single atoms and controlling their content through the reaction time of consequent chemical impregnation. The novel methodology enables achieving nearly 50 times higher normalized hydrogen evolution compared to pristine titania nanotubes. Moreover, the developed procedure allows the decoration of titania also with ultrasmall nanoparticles through a longer impregnation time of the substrate in a very dilute hexachloroplatinic acid solution. The comparison shows a 10 times higher normalized hydrogen production of platinum single atoms compared to nanoparticles. The mechanistic study shows that the novel approach creates homogeneously distributed defects, such as oxygen vacancies and Ti3+ species, which effectively trap and stabilize Pt2+ and Pt4+ single atoms. The optimized platinum single-atom photocatalyst shows excellent performance of photocatalytic water splitting and hydrogen evolution under one sun solar-simulated light, with TOF values being one order of magnitude higher compared to those of traditional thermal reduction-based methods. The single-atom engineering based on the creation of ultrasound-triggered chemical traps provides a pathway for controllable assembling stable and highly active single-atomic site catalysts on metal oxide support layers.

Transmission spectra of transparent electrodes based on oriented platinum nanowires at various concentrations of the metal used

The paper investigates the optical transparency dependence of a coating based on an oriented network of platinum nanowires on the amount of metal used. Oriented platinum nanowires on a glass surface are produced by chemical deposition from an aqueous hexachloroplatinic acid solution. The topography of the deposited metal layer on glass is visualized using atomic force microscopy. Optical transparency was investigated with a spectrophotometer. In almost the entire region of optical radiation, the transparency is approximately 98%. The absorption spectrum shows that the absorption coefficient increases sharply in the near UV region.

Relation of the electrochemical interplay between H2PtCl6 and H2O/H3O+/H2+ and the hydrogen‐evolution reaction

AbstractThe electrodeposition of platinum from hexachloroplatinic acid solutions, on glassy carbon, was studied by developing multiple cyclic voltammetry transients. The development of an isopotential point, only observed under hydrogen‐evolution conditions, is postulated to be associated with the reduction of [PtCl4]2− to Pt0 and the oxidation of the adsorbed molecular hydrogen ion (H2+)ads species to (H3O+)ads. The adsorption of H2+ inhibits the continued reduction of [PtCl4]2− and the ‘cleansing’ of the platinum surface, that is, the removal of H2+ through hydrogen evolution, results in the opening up of active sites to allow for the continued reduction of [PtCl4]2− on the return sweep, which results in an isopotential point (IPP). This IPP is not observed in the absence of hydrogen evolution, due to saturation of the surface by (H2+)ads, and correlates with a model that explains the interplay between platinum chloride species, hydrogen containing species (H2O/H3O+/H2+), and the hydrogen‐evolution reaction.

Optical transparency and conductivity of oriented platinum nanonetworks on a glass surface

The work is aimed at creating an optically transparent conductive coating based on platinum nanowires which can become an alternative to the existing indium tin oxide. This coating can be used as transparent electrodes in solar panels, organic LEDs and many areas of modern electronics and optoelectronics. In work, the dependence of the sheet resistance of oriented platinum nanowires network on the amount of metal used is investigated. Oriented platinum nanowires are obtained by chemical deposition from an aqueous solution of hexachloroplatinic acid on a glass surface. The topography of the deposited metal layer on the glass is visualized by atomic force microscopy. It has been established that the platinum layer has good optical transparency. The synthesized coating would be of interest in terms of applicability as an optically transparent electrode.

Selective Loading of Platinum or Silver Cocatalyst on a Hydrogen-Evolution Photocatalyst in an Overall Water-Splitting System, Silver-Inserted Zinc Rhodium Oxide and Bismuth Vanadium Oxide

Since Fujishima and Honda reported photoelectrochemical water splitting using a TiO2 electrode in 1972 [1], solar hydrogen (H2) production from water using a photocatalyst has attracted attention as a clean energy resource. Most recent researches have been focusing on the visible-light sensitization of catalysts to effectively utilize solar energy. Recently, we have developed a novel solid-state photocatalyst by inserting silver (Ag) or gold (Au) as an electron mediator between zinc rhodium oxide (ZnRh2O4, Eg of 1.2 eV) and bismuth vanadate (Bi4V2O11, Eg of 1.7 eV) as H2- and oxygen (O2)-photocatalysts, respectively (ZnRh2O4/Ag/Bi4V2O11, ZnRh2O4/Au/Bi4V2O11) [2-4]. In this system, we achieved overall pure-water splitting, liberating H2 and O2 simultaneously from pure water at a stoichiometric ratio 2 to 1, photocatalyzed via the inserted Ag or Au which could transfer photo-excited electrons from the conduction band (CB) of Bi4V2O11 to the valence band (VB) of ZnRh2O4. The ZnRh2O4/Ag (Au)/Bi4V2O11 utilized visible light up to 740 nm. Notably, the ZnRh2O4/Ag/Bi4V2O11 system did not include a cocatalyst, which is inevitably required for the water-splitting reaction due to increasing the lifetime of electron-and-hole pairs and storing either electrons or holes. Thus, in the present study, we tried to load a cocatalyst, Ag or Pt, selectively onto the H2-evolution photocatalyst, ZnRh2O4, in ZnRh2O4/Ag/Bi4V2O11 to enhance the photosensitivity of this system.Powdered ZnRh2O4/Ag/Bi4V2O11 was prepared following the previously reported procedures [2]. The photo-deposition of Pt or Ag was performed under light irradiation at wavelength longer than 850 nm using hexachloroplatinic acid (H2PtCl6∙6H2O) or silver nitrate (AgNO3) solution as the source of Pt or Ag. Under these irradiated light conditions, only ZnRh2O4 was photo-excited because the energy of irradiated light was higher than the band-gap energy of ZnRh2O4 (1.2 eV) but smaller than that of Bi4V2O11 (1.7 eV). Due to the specific photoexcitation of ZnRh2O4, Pt or Ag was expected to be only photo-deposited onto this material, generating Pt/ZnRh2O4/Ag/Bi4V2O11 and Ag/ZnRh2O4/Ag/Bi4V2O11.To quantitatively determine the valencies of Pt and Ag, and analyze the amounts of Pt and Ag in the photocatalysts (bare ZnRh2O4/Ag/Bi4V2O11, Pt/ZnRh2O4/Ag/Bi4V2O11, and Ag/ZnRh2O4/Ag/Bi4V2O11), a peak deconvolution method was applied to the Bi 4f, Ag 3d, and Pt 4f spectra. Ag 3d peaks for the three photocatalysts were deconvoluted by one pair of Ag 3d peaks, Ag 3d5/2 and Ag 3d3/2, which were assigned to metallic Ag (Ag0). These results indicate that Ag was included as a metallic particle in the three photocatalysts. In contrast, the Pt 4f peaks for Pt/ZnRh2O4/Ag/Bi4V2O11 were deconvoluted by three pairs of Pt 4f peaks, attributable for metallic Pt (Pt0), Pt2+, and Pt3+ The atomic ratios of Pt0, Pt2+, and Pt3+ vs. total Pt were calculated to be 0.63, 0.25, and 0.12, respectively. Moreover, as we considered that the Bi4V2O11 surface remained unchanged even after the Pt or Ag deposition, we estimated the amount of Pt or Ag in the photocatalysts based on the amount of Bi. The weight percentage (wt%) of Ag in the three photocatalysts was calculated. As expected, the amount of Ag in ZnRh2O4/Ag/Bi4V2O11 and Pt/ZnRh2O4/Ag/Bi4V2O11 was identical at 2.1 wt%. The total amount of Ag in Ag/ZnRh2O4/Ag/Bi4V2O11 was calculated to be 3.2 wt%, thus the Ag cocatalyst deposited in Ag/ZnRh2O4/Ag/Bi4V2O11 was estimated to be 1.1 wt% based on the assumption that the amount of Ag inserted in Ag/ZnRh2O4/Ag/Bi4V2O11 was 2.1 wt%, identical to those in ZnRh2O4/Ag/Bi4V2O11 and Pt/ZnRh2O4/Ag/Bi4V2O11. Similarly, the amount of Pt cocatalyst in Pt/ZnRh2O4/Ag/Bi4V2O11 was calculated to be 1.2 wt%.The bare ZnRh2O4/Ag/Bi4V2O11, Pt/ZnRh2O4/Ag/Bi4V2O11, and Ag/ZnRh2O4/Ag/Bi4V2O11 photocatalysts evolved H2 and O2 from water at a molar ratio of ca. 2 to 1, indicating that the overall water splitting reaction proceeded. The deposition of Pt or Ag 3-fold enhanced the H2 and O2 evolution rates compared to those of bare ZnRh2O4/Ag/Bi4V2O11, demonstrating that Pt and Ag functioned as cocatalysts for the overall water-splitting reaction [5].This work was performed by Assoc. Prof. T. Takashima, Mr. M Yoda, and Mr. J. Osaki. I am deeply grateful to JSPS KAKENHI (Grant-in-Aid for Scientific Research) (B), Grant Number 17H03126 for its financial support.

EFFECT OF POLYVINYLPYRROLIDONE ON THE SYNTHESIS AND CATALYTIC PROPERTIES OF PLATINUM-CONTAINING OXYGEN ELECTROREDUCTION CATALYSTS

Results of the work on the synthesis of highly effective nanocomposite platinum-containing oxygen reduction electrocatalysts for hydrogen-oxygen fuel cells are presented and ways of increasing their activity are considered. Fuel cells (FCs) represent the most promising renewable and environmentally friendly energy sources that can operate at low temperatures with high efficiency and with low or zero levels of hazardous waste. The main problem of fuel cells is that the oxygen reduction reaction is slowed down in relation to the hydrogen oxidation reaction, which leads to an increase in the overvoltage at the cathode and, as a result, to a decrease in the productivity of FCs. To solve this problem, the new methods are being developed for the synthesis of highly efficient platinum electrocatalysts, which currently have the best performance, since platinum has the highest specific catalytic activity among other materials used in low temperature FCs. The purpose of this work is to determine the optimal composition of reaction mixture and conditions for the preparation of a platinum based catalyst for oxygen electroreduction where Vulcan XC-72 nanodispersed carbon black is used as a carrier. We have worked out 6 methods for preparing Pt (40 %)/XC-72 catalysts. To evaluate the activity of the prepared catalysts and to determine the kinetic parameters of the oxygen reduction on them, cathodic stationary polarization curves were recorded in a 0.5 M H2SO4 solution on a floating gas diffusion electrode superficially modified by the catalysts. For preparation of all electrocatalysts we are used 3.6 ml of a hexachloroplatinic acid (H2PtCl6) solution, containing 18.8 mg Pt/ml, 100 ml of ethylene glycol or its mixture with deionized water (3 : 1) and 100 mg of Vulcan XC-72 carbon black, previously oxidized in HNO3 solution. 1 M NaOH or KOH solutions were used to create the necessary medium (pH = 11). Some Pt(40 %)/XC-72 electrocatalysts were prepared when additions of polyvinylpyrrolidone (PVP) (100 mg or 300 mg) and/or 60 ml of formaldehyde were introduced into reaction mixture. Temperature during syntheses was in the range 75 - 160 °C. It was shown that reducing the synthesis temperature from 160 to 75 °C and introduction of PVP together with formaldehyde into reaction mixture had a positive effect on the activity of obtained nanocomposite platinum-containing catalysts Pt(40 %)/XC-72 for oxygen electroreduction.The sizes of the obtained platinum clusters on the surface of carbon black nanoparticles were in the range of 1.7 - 5.7 nm, and under optimal synthesis conditions they were evenly and densely distributed on the surface of the carbon carrier. The obtained kinetic characteristics of oxygen electroreduction on the studied catalysts indicate that the mechanism of this process depended on both the current density and the method of catalyst synthesis.

Optimum conditions for electrochemical deposition of 3-D mesoporous platinum framework

Here, we report a systematic investigation of the effect of experimental parameters on the structure, morphology and electrochemically active surface area of 3-D mesoporous platinum (Pt) framework. Template-assisted deposition of the mesoporous Pt framework is achieved using phytantriol-based inverse bicontinuous cubic phase of double diamond morphology (QIID) with Pn3m symmetry. Platinum is deposited electrochemically using hexachloroplatinic acid solution present within the aqueous domains of the cubic phase template. Deposition conditions, particularly the deposition potentials, are shown to significantly affect the surface morphology, porosity and electrochemically active surface area of the deposited Pt framework. Furthermore, the effect of underlying substrate on the structure and morphology of the mesoporous Pt framework is also investigated.

On the Controlled Loading of Single Platinum Atoms as a Co-Catalyst on TiO2 Anatase for Optimized Photocatalytic H2 Generation.

Single-atom (SA) catalysis is a novel frontline in the catalysis field due to the often drastically enhanced specific activity and selectivity of many catalytic reactions. Here, an atomic-scale defect engineering approach to form and control traps for platinum SA sites as co-catalyst for photocatalytic H2 generation is described. Thin sputtered TiO2 layers are used as a model photocatalyst, and compared to the more frequently used (001) anatase sheets. To form stable SA platinum, the TiO2 layers are reduced in Ar/H2 under different conditions (leading to different but defined Ti3+ -Ov surface defects), followed by immersion in a dilute hexachloroplatinic acid solution. HAADF-STEM results show that only on the thin-film substrate can the density of SA sites be successfully controlled by the degree of reduction by annealing. An optimized SA-Pt decoration can enhance the normalized photocatalytic activity of a TiO2 sputtered sample by 150 times in comparison to a conventional platinum-nanoparticle-decorated TiO2 surface. HAADF-STEM, XPS, and EPR investigation jointly confirm the atomic nature of the decorated Pt on TiO2 . Importantly, the density of the relevant surface exposed defect centers-thus the density of Pt-SA sites, which play the key role in photocatalytic activity-can be precisely optimized.

Electrodeposition of platinum on 3D-printed titanium mesh to produce tailored, high area anodes

ABSTRACTThe versatility and convenience of 3D printing can be used to produce tailored metal mesh electrodes, which offer a high volumetric area and good gas release properties for applications in electrochemical technology. In this work, a titanium mesh with 20 ppi triangular pores was designed and then manufactured by 3D printing. A thin coating of platinum with strong adhesion was then applied by electrodeposition in a solution of hexachloroplatinic acid in HCl at 90°C. For this, a current of 0.1 A, corresponding to a current density of 0.92 mA cm−2 was applied for 60 min to the work piece, which was previously etched in 10% (w/v) oxalic acid at 80°C. Compact, adherent and silver-grey platinum deposits, 0.16 µm average thickness and 0.33 mg cm−2 Pt loading were obtained. The product can be used as an inert anode in nickel plating baths and as a porous electrode in organic electrosynthesis or cerium-based flow batteries.

Effects of poly(vinylpyrrolidone) protected platinum nanoparticles on seed germination and growth performance of Pisum sativum

In this article, the effect of poly(vinylpyrrolidone) (PVP) stabilized platinum nanoparticles (Pt:PVP) on seed germination and growth performance of Pisum sativum (Pea) was investigated. Healthy mature Pea seeds were immersed for 1, 2 and 3 h into 1.0 mM concentrated Pt:PVP hydrosol and were sowed into soil. After immersing the seeds for 3 h into this solution, the germination rate decreased by 45% and the dormancy period increased from 2.5 days to 7 days. After 30 days of germination of saplings from seeds treated for 3 h, the root to shoot lengths were 20% less than the saplings from untreated seeds. 1 and 2 h of treatment did not have any significant impact on the germination rate, dormancy and plant growth. Arbuscular mycorrhizal fungi and rhizobial colonization in treated plants significantly decreased with soaking time prolongation. Arbuscular mycorrhizal fungi root colonization was significantly reduced in the plants from 3 h treated seeds group. The yield and biomass content of the produced plants were also calculated. For pea plants from seeds of the 3 h treatment group, the average number of seeds produced per plant increased by 163.5%, but the average seed weight decreased by 66.7%. Comparing with reported observations, it is inferred that either the modification of growth regulatory hormones or biochemicals associated with Pt:PVP during seed germination is responsible for such changes. 3.2 ± 0.8 nm Pt:PVP were prepared by high temperature ethanolic reduction of hexachloroplatinic acid solution containing PVP and were characterized by Transmission Electron Microscopy, X-ray Diffractometry and Ultraviolet–Visible Spectrophotometry.

Fabrication of Nano Flower‐shaped Platinum on Glassy Carbon Electrode as a Sensitive Sensor for Lead Electrochemical Analysis

AbstractPlatinum nanoflowers modified glassy carbon electrodes (PtNFs/GCE) was fabricated simply for lead determination in water samples. The modified electrodes were prepared by electrodeposition in hexachloroplatinic acid solution at constant potential. The influence of deposition time and potential on surface morphology, chemical composition, electrochemical properties of electrode were investigated. At −0.2 V of potential and 150 s of deposition duration, platinum developed as nanoflower shape and scattered densely all over the glassy carbon surface, producing the largest electrochemically active surface areas. The highest differential pulse stripping voltammetry (DPSV) signal of lead was obtained by using the prepared electrode. Under optimized experimental condition of electrolyte, accumulation potential and time, the peak current was found to be linear proportion to lead concentration in range of 1 to 100 μg L−1 (slope=0.371) with a limit of detection of 0.398 μg L−1. The method has good repeatability and reproducibility with relative standard deviations of 1.47 % and 4.83 %, respectively. The modified PtNFs/GCE also demonstrated an excellent long‐term stability with only 9 % decrease in Pb peak current over 30 days. Moreover, the performance of the modified PtNFs/GCE in determination of Pb(II) in two industrial wastewaters was good agreement with data obtained by a graphite furnace atomic absorption spectrometry (GFAAS) method.

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.

Cu-Pt bimetallic nanoparticles supported metal organic framework-derived nanoporous carbon as a catalyst for hydrogen evolution reaction

This work is allocated to preparation of Cu-Pt bimetallic nanoparticles supported nanoporous carbon composite (Cu-Pt/NPCC). This composite is synthesized by two steps procedure involving preparation of Cu/NPCC according to templating method through direct carbonization of metal organic framework-199 (MOF-199) as a template in N2 atmosphere at 900°C. This procedure is followed by partial galvanic replacement of Cu metals by PtIV ions, upon immersion in a hexachloroplatinic acid solution. The physical and electrochemical characterization of the materials are achieved by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), nitrogen adsorption/desorption and cyclic voltammetry (CV) methods. The EDS analysis has proven that the partial galvanic replacement is occurred. This composite is tested for the hydrogen evolution reaction (HER) in 0.5M H2SO4 solution. The linear sweep voltammetry (LSV) results have shown that the Cu-Pt/NPCC modified glassy carbon electrode (GCE) exhibit higher current density and less negative value of potential towards HER rather than the bare GCE. This is attributed to synergetic effect of the Cu-Pt bimetallic catalyst and uniform distribution of the Pt nanoparticles at the electrode surface.

Pt/graphite catalyst for hydrogen generation by HI decomposition reaction in S-I thermochemical cycle

Hydrogen is an attractive energy carrier for future because of various reasons. Therefore its large scale production is the need of the hour. One of the ways to achieve this is sulfur iodine thermochemical cycle and HI decomposition reaction is one of the three reactions constituting the cycle. Pt/graphite catalysts with different loading of platinum were prepared by impregnating colloidal graphite with hexachloroplatinic acid solution followed by reduction under N2 flow. The catalysts prepared have been characterized by X-ray diffraction, Raman, scanning electron microscopy, X-ray photoelectron spectroscopy and Brunauer–Emmett–Teller surface area. These catalysts have been employed for liquid phase HI decomposition under different conditions. To evaluate the stability of this catalyst against noble metal leaching under the reaction conditions, the eluent was analyzed by using ICP-OES. Platinum loaded catalysts (0.5%, 1% and 2%) show 8.4%, 17.5% and 23.4% conversion respectively. From the present study we conclude that Pt/graphite is a suitable and stable catalyst for liquid phase HI decomposition reaction. Copyright © 2015 John Wiley & Sons, Ltd.

On the mechanism of electrical conduction in thin films of some polysulfone-poly(alkylene oxide)-poly(dimethylsiloxane) block copolymers

Polysulfone poly(alkylene oxide)-poly(dimethylsiloxane) block copolymers have been prepared by the hydrosilylation reaction of allyl endcapped poly[(ethylene oxide) (propylene oxide)] oligomers with Si–H terminated polydimethylsiloxane in chlorobenzene using an isopropanol solution of hexachloroplatinic (IV) acid as catalyst for hydrosilylation.The temperature dependences of electrical conductivity and thermoelectric power (Seebeck coefficient) of copolymers were studied using thin-film samples deposited from dimethylformamide (spin coating technique) onto glass substrates. Organic films with reproducible electronic transport and optical properties can be obtained if, after deposition, they are submitted to a heat treatment consisting of several successive heating/cooling cycles within temperature range of (295–485) K. Investigated copolymers presents typical semiconducting characteristics. The values of some fundamental parameters (activation energy of electrical conduction, ratio of carrier mobilities, optical energy bandgap) have been determined. The mechanisms of electronic transport are identified in different temperature domains. Transmission and absorption spectra have been recorded and optical energy bandgaps are calculated from the absorption spectra. The thermistor effect of investigated copolymers is also discussed.

Platinum adsorption from chloride media using carbonized biomass and commercial sorbent

Pistachio nut shells, an agricultural waste biomass, and Lewatit TP 214, a commercial sorbent, were investigated as adsorbents for the adsorption of platinum from dilute hexachloroplatinic acid solutions. Before the pistachio nut shells were carbonized, adsorption percentage was 65%, whereas Lewatit TP 214 ensured almost 100% adsorption. However, after the pistachio nut shell was carbonized at 1,000° C under an argon atmosphere, the platinum adsorption (%) increased two-fold. The effects of such parameters as sorbent dosage, contact time, temperature and solution pH on adsorption were studied in detail in batch mode. The adsorption equilibrium data were best fitted with the Langmuir isotherm model. The maximum adsorption capacities, Qmax, at 25° C were found to be 38.31 and 33.22 mg/g for the carbonized pistachio nut shell and Lewatit TP 214, respectively. The adsorption of platinum on both sorbents was found to be described by the pseudo-second-order kinetic model. The results indicated that the activated carbon prepared from pistachio nut shells can be effectively used for the removal of platinum from acidic solutions.

Surface modification of commercial PtRu nanoparticles for methanol electro-oxidation

The surfaces of commercially available PtRu nanoparticles (PtRu/C) have been successfully modified via a displacement reaction between the Ru atoms on the PtRu/C and the Pt ions in an aqueous hexachloroplatinic acid solution. The concentration of the hexachloroplatinic acid solution was deliberately formulated to allow for the formation of sub-monolayered Pt (Pt(1/16)) and monolayered Pt (Pt(1/8)) on the surface of PtRu/C. Material characterization, including X-ray diffraction patterns and transmission electron microscopy images, showed that the PtRu phases of the samples were identical but that the particle sizes increased slightly after the surface modification. Data from inductively coupled plasma mass spectrometry confirmed the deposition of Pt with negligible loss of Ru. X-ray absorption spectroscopy showed Pt-enriched surfaces, and the surface Pt content decreased in the order Pt(1/8) > Pt(1/16) > PtRu/C. Cyclic voltammetry and chronoamperometry were conducted for methanol electro-oxidation, and our results indicated impressive catalytic ability and carbon monoxide tolerance for Pt(1/16), followed by Pt(1/8) and PtRu/C. The mass activities of Pt(1/16) and Pt(1/8) increased 223% and 135% over that of PtRu/C. We attributed the observed improvements to the reduced amount of Ru on the PtRu surface, which resulted in an optimized PtRu ratio with enhanced catalytic ability.

Novel Application of Platinum Ink for Counter Electrode Preparation in Dye Sensitized Solar Cells

Platinized counter electrode is common in most of the dye sensitized solar cell (DSSC) researches because of its high catalytic activity and corrosion stability against iodine in the electrolyte. Platinum (Pt) film coating on fluorine doped tin oxide (FTO) glass surface by using alcoholic solution of hexachloroplatinic acid (H2PtCl6), paste containing Pt precursors or sputtering are widely used techniques. This paper presents a novel application of Pt ink containing nanoparticles for making platinized counter electrode for DSSC. The characteristics of Pt films coated on FTO glass surface by different chemical methods were compared along with the performance parameters of the DSSCs made by using the films as counter electrodes. The samples coated with Pt inks were sintered at 300 o C for 30 minutes whereas Pt-film and Pt-paste were sintered at 400 o C for 30 minutes. The Pt ink diluted in n-hexane was found to a promising candidate for the preparation of platinized counter electrode. The ink may also be applicable for DSSC on flexible substrates after optimization its sintering temperature.

Production of Platinum Nanoparticles and Nanoaggregates Using Neurospora crassa

Fungal biomass and fungal extract of the nonpathogenic fungus Neurospora crassa were successfully used as reducing agents for the biosynthesis of platinum nanoparticles (PtNPs). The experiment was carried out by exposing the fungal biomass or the fungal extract to a 0.001 M precursor solution of hexachloroplatinic(IV) acid (H2PtCl6). A change of color of the biomass from pale yellow to dark brown was the first indication of possible formation of PtNPs by the fungus. Subsequent analyses confirmed the intracellular biosynthesis of single PtNPs (4-35 nm in diameter) and spherical nanoaggregates (20-110 nm in diameter). Using the fungal extract, similar results were obtained, producing rounded nanoaggregates of Pt single crystals in the range of 17-76 nm.

Degradation mechanisms of Pt counter electrodes for dye sensitized solar cells

This work investigates the stability of platinum (Pt) electrodes prepared by electrodeposition and thermal decomposition of hexachloroplatinic acid (H2PtCl6) solutions. To this aim, the electrodes were stored in an electrolyte solution (0.5M KI, 0.05M I2 in 90%/10% PC/EG) or in air, within a closed vessel, for up to 70 days. A drop of up to 40% in the current density for triiodide reduction was caused by storage in the electrolyte solution and of about 15%–20% when the electrodes were stored in air. Electrolyte storage was found to cause a 40% increase in the activation energy of both kinds of electrodes. XPS measurements have shown that the main degradation mechanism in the case of electrolyte storage is the dissolution of Pt from the substrate. Regeneration of the electrodes by heat or acid treatment was not possible. The observed electrode degradation is expected to appear in dye sensitized solar cells using this kind of counter electrodes and thus affect their long term stability.