Ru Oxidation Research Articles

Ru(NH3)63+/Ru(NH3)62+-Mediated Redox Cycling: Toward Enhanced Triple Signal Amplification for Photoelectrochemical Immunoassay.

Herein we report an effective Ru(NH3)63+/Ru(NH3)62+-mediated photoelectrochemical-chemical-chemical (PECCC) redox cycling amplification (RCA) strategy toward enhanced triple signal amplification for advanced split-type PEC immunoassay application. Specifically, alkaline phosphatase (ALP) label was confined via a sandwich immunorecognition to convert 4-aminophenyl phosphate to the signal reporter 4-aminophenol (AP), which was then directed to interact with Ru(NH3)62+ as a redox mediator and tris (2-carboxyethyl) phosphine (TCEP) as reducing agent in the detection buffer. Upon illumination, the system was then operated upon the oxidation of Ru(NH3)62+ by the photogenerated holes on the Bi2S3/BiVO4 photoelectrode, starting the chain reaction in which the Ru(NH3)62+ was regenerated by Ru(NH3)63+-enabled oxidization of AP to p-quinoneimine, which was simultaneously recovered by TCEP. Exemplified by interleukin-6 (IL-6) as the analyte, the Ru(NH3)63+/Ru(NH3)62+-mediated, AP-involved PECCC RCA coupled with ALP enzymatic amplification could achieve triple signal amplification toward the ultrasensitive PEC IL-6 immunoassay. This protocol can be extended as a general basis for other numerous targets of interest. Besides, we believe this work could offer a new perspective for the further exploration of advanced RCA-based PEC bioanalysis.

Structures analyses of supported ruthenium catalysts under asymmetric hydrogenation reaction

Ruthenium oxide catalysts supported on various metal oxides, such as zirconia, ceria, and alumina, were prepared by an impregnation method using RuCl3·3H2O as a precursor. Local structures of the supported Ru oxide and oxidation states of Ru species were analyzed by in situ Ru K-edge X-ray absorption fine structure measurements. Small RuO2 particles were highly dispersed on zirconia and ceria. On the other hand, bulk RuO2 was deposited on alumina. Enantioselective hydrogenation of diethyl itaconate was achieved by combining the supported RuO2 catalysts with chiral ligands. The 1 wt% RuO2 supported on zirconia provided 95% ee and 99% yield. The Ru oxide was partially reduced during the reaction.

Synthesis, Characterization and CO Tolerance Evaluation in PEMFCs of Pt2RuMo Electrocatalysts

Pt2RuMo/C catalysts were synthesized by the modified polyol method in the presence and absence of Li(C2H5)3BH (LBH), annealed at 600 °C under H2 atmosphere to improve the reduction of Pt and Ru to provide stronger interactions between Mo and another metals. LBH affected the physico-chemical characteristics of Pt2RuMo, that is, in the presence of LBH an increment of Mo(IV) amount and a decrease in the PtRu alloying degree were observed. The catalytic activity for hydrogen oxidation in the presence and absence of CO (CO tolerance) of the Pt2RuMo/C catalysts as anodes in polymer electrolyte membrane fuel cells (PEMFCs) was compared to that of a commercial PtRu/C catalyst. The results indicated that the CO tolerance increased with an increase in Mo(IV) content, but the stability increased with an increment of the amount of Ru oxides in the catalysts.

Electrochemical Behavior of Pt–Ru Catalysts Supported on Graphitized Ordered Mesoporous Carbons toward CO and Methanol Oxidation

In this work, graphitized ordered mesoporous carbons (gCMK-3) were employed as support for Pt and Pt–Ru nanoparticles synthesized by different reduction methods. The catalysts displayed metal contents and Pt:Ru atomic ratios close to 20 wt % and 1:1, respectively. A comparison of the physical parameters of Pt and Pt–Ru catalysts demonstrated that Ru enters into the Pt crystal structure, with well-dispersed nanoparticles on the carbon support. The Pt catalysts exhibited similar surface oxide composition, whereas a variable content of surface Pt and Ru oxides was found for the Pt–Ru catalysts. As expected, the Pt–Ru catalysts showed low CO oxidation onset and peak potentials, which were attributed to the high relative abundances of both metallic Pt and Ru oxides. All the studied catalysts exhibited higher maximum current densities than those observed for the commercial Pt and Pt–Ru catalysts, although the current–time curves at 0.6 V vs. reversible hydrogen electrode (RHE) demonstrated a slightly higher stationary current density in the case of the Pt/C commercial catalyst compared with Pt nanoparticles supported on gCMK-3s. However, the stationary currents obtained from the Pt–Ru/gCMK-3 catalysts surpassed those of the commercial Pt–Ru material, suggesting the suitability of the prepared catalysts as anodes for these devices.

Role of Ammonium Ions in Colloidal Silica Slurries for Ru CMP

The chemical mechanical polishing (CMP) of ruthenium (Ru) based barrier layer has been a pivotal process in the manufacture of a novel copper (Cu) interconnect structure. This paper mainly investigated the role of NH4+ in colloidal silica slurries for Ru CMP. The polishing results show that the Ru removal rate increases with the increasing concentration of NH4+. The influence mechanism of NH4+ on removal rate of Ru was investigated by electrochemistry, scanning electron microscope (SEM) and zeta potential. It is revealed that the NH4+ can promote the surface corrosion rate of Ru by forming a water-soluble Ru-NH4 complex with Ru oxide, meanwhile can also result in the neutralization of the zeta potentials of both silica particles and the Ru surface, and thus can lead to the decrease of the electrostatic repulsive force and the increase of the mechanical abrasion intensity between silica particles and Ru surface. Further, the surface quality of the polished Ru wafer and slurry stability were evaluated, and the results show that the addition of an appropriate amount of NH4+ can achieve a low surface roughness of Ru and a high slurry stability.

Strategies for the analysis of the elemental metal fraction of Ir and Ru oxides via XRD, XANES, and EXAFS.

Iridium and ruthenium oxide are active electrocatalysts for oxygen evolution. The relation between preparation method, structure, and behavior of mixed oxides of iridium and ruthenium are of interest in order to obtain active and stable catalysts. In this work the structure of mixed Ru-Ir oxides synthesized by the polymeric precursor method, which involves the formation of a gel containing the metal precursors and subsequent heat-treatment in air, was studied for the IrxRu1-xO2 system. An in-depth analysis of X-ray diffraction (XRD) and X-ray absorption (XAS) data, including EXAFS and linear combination of XANES, shows that the polymeric precursor synthesis method is capable of providing an intimate mixing of Ir and Ru in the catalyst. In addition to the oxide phase, metal phases, i.e. with Ru or Ir or both in oxidation state zero (Ir(fcc) and Ru(hcp)), were also found in the product materials. Facing complex structures such as some of those synthesized here, we have shown that a representation of shells with more than one atom type are efficiently represented using mixed sites, i.e. including scattering contributions from several elements in a site corresponding to a partial occupancy of the site by these elements, this method forming a very efficient basis for analyzing EXAFS data.

Catalytic wet oxidation of N,N-dimethyl formamide over ruthenium supported on CeO2 and Ce0.7Zr0.3O2 catalysts

A series of Ru supported on CeO2 and Ce0.7Zr0.3O2(CeZrO) was prepared by incipient-wet impregnation method and investigated in the catalytic wet oxidation of N,N-dimethyl formamide (DMF) in batch reactor. The physicochemical property of the catalysts was characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), H2 temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS) and thermogravimetry (TG). Compared with 3%Ru/CeO2, 3%Ru/Ce0.7Zr0.3O2 catalyst exhibits much higher performance for DMF degradation due to the promotion of Ru dispersion and the transfer of active oxygen, and 99% DMF conversion and 97% COD elimination are obtained at 453 K, 2.5 MPa oxygen pressure after 5 h. The reaction mechanism of DMF degradation was suggested. The carbonaceous species deposition and oxidation of Ru can be responsible for catalyst deactivation. And the catalyst activity can be recovered by air calcination and H2 reduction.

Electrocatalytic Oxidation of Organic Pollutants on Boron-Doped Diamond and Ti–Ru Oxide Anodes in Sulfate Medium

Electrochemical oxidation for degradation of industrial dye Methyl Orange in aqueous sulfate solutions with various electrocatalytic materials: boron-doped diamond electrode and electrode based on titanium and ruthenium oxides. The influence exerted by the main working parameters of electrolysis (current density, concentration of Methyl Orange, pH) on the discoloration efficiency and on the chemical oxygen demand (COD) was examined. It was shown that an increase in the current density and a decrease in the pollutant concentration improve the process efficiency. However, this leads to an increase in the specific electric energy consumption per unit mass of COD. It was found that the boron-doped diamond electrode is a more efficient electrocatalytic material, compared with electrode based on titanium and ruthenium oxides. At low concentrations of Methyl Orange (<50 mg L–1), there exists the possibility in principle of using the electrode based on titanium and ruthenium oxides not only for discoloration, but also for making lower the COD level.

Quantifying Confidence in DFT Predicted Surface Pourbaix Diagrams and Associated Reaction Pathways for Chlorine Evolution

Density functional theory calculations can be used to identify dominant reaction mechanisms. However, the dominant reaction mechanism is sensitive to choice of the exchange correlation functional. Here, we demonstrate using the example case of chlorine evolution reaction on rutile oxides, which can occur through at least three reaction mechanisms each mediated by different surface intermediates and active sites. We utilize Bayesian error estimation capabilities within the BEEF-vdW exchange correlation (XC) functional to quantify the uncertainty associated with predictions of the operative reaction mechanism by systematically propagating the uncertainty originating from DFT-computed adsorption free energies. We construct surface Pourbaix diagrams based on the calculated adsorption free energies for rutile oxides of Ru, Ir, Ti, Pt, V, Sn and Rh. We utilize confidence-value (c-value) to determine the degree of confidence in the predicted surface phase diagrams. Using the scaling relations between the adsorption energies of intermediates we construct a generalized Pourbaix diagram showing the stable surface composition as a function of potential and the oxygen binding energy on the cus site. This is used to consistently determine activity volcano relationships. We incorporate the uncertainty in linear scaling relations to quantify the confidence in generalized Pourbaix diagram and the associated activity. This allows us to compute the expectation limiting potential as a function of $\Delta E_{O^c}$, which provides a more appropriate activity measure incorporating DFT uncertainty. We show that the confidence in the classification problem of identifying the active reaction mechanism is much better than the prediction problem of determining catalytic activity.

Fundamental Factors Impacting the Stability of Phosphonate-Derivatized Ruthenium Polypyridyl Sensitizers Adsorbed on Metal Oxide Surfaces.

A series of 18 ruthenium(II) polypyridyl complexes were synthesized and evaluated under electrochemically oxidative conditions, which generates the Ru(III) oxidation state and mimics the harsh conditions experienced during the kinetically limited regime that can occur in dye-sensitized solar cells (DSSCs) and dye-sensitized photo-electrosynthesis cells, to further develop fundamental insights into the factors governing molecular sensitizer surface stability in aqueous 0.1 M HClO4. Both desorption and oxidatively induced ligand substitution were observed on planar fluorine-doped tin oxide (FTO) electrodes, with a dependence on the E1/2 Ru(III/II) redox potential dictating the comparative ratios of the processes. Complexes such as RuP4OMe ( E1/2 = 0.91 vs Ag/AgCl) displayed virtually only desorption, while complexes such as RuPbpz ( E1/2 > 1.62 V vs Ag/AgCl) displayed only chemical decomposition. Comparing isomers of 4,4'- and 5,5'-disubstituted-2,2'-bipyridine ancillary ligands, a dramatic increase in the rate of desorption of the Ru(III) complexes was observed for the 5,5'-ligands. Nanoscopic indium-doped tin oxide thin films (nanoITO) were also sensitized and analyzed with cyclic voltammetry, UV-vis absorption spectroscopy, and X-ray photoelectron spectroscopy, allowing for further distinction of desorption versus ligand-substitution processes. Desorption loss to bulk solution associated with the planar surface of FTO is essentially non-existent on nanoITO, where both desorption and ligand substitution are shut down with RuP4OMe. These results revealed that minimizing time spent in the oxidized form, incorporating electron-donating groups, maximizing hydrophobicity, and minimizing molecular bulk near the adsorbed ligand are critical to optimizing the performance of ruthenium(II) polypyridyl complexes in dye-sensitized devices.

Electrocatalysts of Mn and Ru oxides loaded on MWCNTS with 3D structure and synergistic effect for rechargeable Li-O2 battery

The structure and electrochemical activity of electrocatalysts play a vital role in lithium-oxygen battery. Herein, three-dimensional Mn and Ru oxides loaded on multiwall carbon nanotubes (RuO2-MnO2/MWCNTs) was synthesized via a one-pot hydrothermal approach and served as cathode of rechargeable lithium-oxygen (Li-O2) batteries. SEM and TEM images both illustrated that RuO2 nanoparticles and MnO2 nanoflakes are well dispersed on the surface of MWCNTs and formed a three-dimensional structure, the cyclic voltammetry studies revealed that the RuO2-MnO2/MWCNTs nanocomposite can effectively integrate the oxygen reduction reaction (ORR) activity of MnO2 and oxygen evolution reaction (OER) activity of RuO2. Electrochemical results demonstrated that the RuO2-MnO2/MWCNTs as oxygen cathode of Li–O2 batteries could maintain a reversible capacity of 1000 mAh g−1 within 94 cycles at a rate of 200 mA g−1 and within 120 cycles at a rate as high as 1000 mA g−1. Moreover, the cell with the catalyst RuO2-MnO2/MWCNTs presented much lower voltage polarization (about 0.68 V at a rate of 50 mA g−1) than that measured with MnO2/MWCNTs during charge/discharge processes. Ex-situ SEM were conducted to investigate the morphology and decomposition of Li2O2, which were formed after discharge and decomposed almost after charge process. The excellent electrochemical performance could be contributed to the three-dimensional structure which benefited the diffusion of oxygen and the storage of Li2O2 as well as the synergy effect of MWCNTs as an ideal conductive support for RuO2-MnO2 as co-catalyst in Li-O2 battery.

Investigation of the structural and electrical properties of air-annealed ruthenium thin films on 6H–SiC at different temperatures

Ruthenium (Ru) Schottky contacts and thin films on n-type 6H–SiC were fabricated and characterised by physical and electrical methods. The characterisation was done after annealing the samples in air at various temperatures. Rutherford backscattering spectroscopy (RBS) analysis of the thin films indicated the oxidation of Ru after annealing at a temperature of 400 °C, and interdiffusion of Ru and Si at the Ru–6H–SiC interface at 500 °C. XRD analysis of the thin films indicated the formation of RuO2 and RuSi in Ru–6H–SiC after annealing at a temperature of 600 °C. The formation of the oxide was also corroborated by Raman spectroscopy. The ideality factor of the Schottky barrier diodes (SBD) was seen to generally decrease with annealing temperature. The series resistance increased astronomically after annealing at 700 °C, which was an indication that the SBD had broken down. The failure mechanism of the SBD is attributed to deep inter-diffusions of Ru and Si at the Ru–6H–SiC interface as evidenced by the RBS of the thin films.

The effect of metals and metal oxides on biodiesel oxidative stability from promotion to inhibition

Biodiesel, usually the methyl esters of plant oils or other triacylglycerol-containing materials, has become an established alternative to conventional, petroleum-derived diesel fuel. Several technical problems persist when using biodiesel, one of which is oxidation stability upon exposure to oxygen in air. Factors affecting oxidation stability are not only the composition of the fuel with polyunsaturated fatty acid methyl esters being more susceptible to oxidation but also temperature, presence of light, storage headspace, and presence of extraneous materials such as pro- and antioxidants, metals, and other substances. In case of metals, it has been stated/shown that some metals are especially effective in promoting oxidation of biodiesel, especially copper. In this work, studies on the effect of metals are expanded to include a total of 26 metals for their effect on biodiesel in form of soybean oil methyl esters. The metals included in this study are Ag, Al, Au, Co, Cr, Cu, Fe, In, Mg, Mn, Mo, Nb, Ni, Pd, Re, Rh, Ru, Sc, Si, Sn, Ta, Ti, V, W, Zn and Zr. Besides these neat metals, the oxides of 29 metals were studied. These oxides are those of Ag (I), Ag (II), Al (III), Au (III), Ba (II), Ca (II), Co, Cr (III), Cr (VI), Cu (II), Eu (III), Fe (II), Fe (III), In (III), La (III), Mg (II), Mn (III), Mn (IV), Mo (IV), Mo (VI), Nb (II), Nb (IV), Nb (V), Ni (II), Sc (III), Si (IV), Sn (IV), Sr (II), Pd (II), Re (VI), Re (VII), Ru (IV), Ta (V), Ti (II), Ti (III), V (V), W (IV), W (VI), Zn (II), Zr (IV). As experimental procedure the Rancimat method, which is included in biodiesel standards, was used. The results confirm that Cu indeed is the metal most strongly promoting oxidation, while most other metals gave results in which the induction time in the Rancimat test did not differ widely from that of the used biodiesel. Some metals, notably Mo and Re, showed an inhibitory effect on biodiesel oxidation. The metal oxides usually show similar effects on biodiesel oxidation from promotion to inhibition with oxides of Ag, Au, Cr, Cu, Re and Ru showing the greatest promoting effect and oxides of Mo the greatest inhibiting effect.

Enhancement of the catalytic performance of silica nanosprings (NS)-supported iron catalyst with copper, molybdenum, cobalt and ruthenium promoters for Fischer-Tropsch synthesis

Iron/nanospring (Fe/NS) catalysts with different metal promoters (Co, Mo, Cu, and Ru) were synthesized via the co-impregnation method and employed to investigate effects of these metals on the physico-chemical properties and catalytic behavior of Fe/NS catalyst during the Fischer-Tropsch synthesis (FTS). The prepared catalysts were characterized before the FTS reaction by various techniques, such as BET surface area, X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), temperature programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), differential thermal analysis (DTA) and thermogravimetric analysis (TGA). The FTS performance of the prompted catalysts was examined in a quartz fixed-bed microreactor (H2/CO of 2:1, 230 °C and atmospheric pressure) and the products trapped and analyzed by gas chromatography (GC) and GC-mass spectrometry (GC–MS) to determine CO conversion and reaction selectivity. The characterization results obtained indicated that the promotion of Fe/NS catalyst with Co, Mo, Cu and Ru oxides enhanced the catalytic activity of Fe/NS catalyst. The catalytic performance over Ru-Fe/NS, Co-Fe/NS, Mo-Fe/NS and Cu-Fe/NS catalysts at the same conditions showed that CO conversion was 93.3%, 43.6%, 82.4% and 56.3%, respectively. The C6-C16 liquid hydrocarbon selectivity was 41.1%, 30.1%, 25.4% and 33.8%, respectively. The addition of promoters led to an increase in the selectivity towards olefins instead of aromatics over the non-promoted Fe/NS catalyst. Finally, it was found that the Ru, Co, MO and Cu promoters proved to have a significant effect on selectivity towards desired products namely paraffins and olefins.

The Enhancement of Hydrogen Oxidation Activity and the Optimization of Alloy Composition in PdRu Nanoparticle Catalysts

Fuel cells are believed as promising power sources with many advantages including their high efficiency and environment-friendliness. Proton exchange membrane fuel cells (PEMFCs), of which usage can be expected as power sources as automobiles and so on, have yet several problems to resolve for the commercialization. Among them, the high price due to the scarcity of Pt, which is used as anode and cathode catalysts, is one of the most serious issues. Pd is a natural choice to replace Pt because the hydrogen oxidation reaction (HOR) activity of Pd is the next to that of Pt, and Pd is at least fifty times more abundant on earth than Pt. Pd is a more attractive substitute for Pt because of its higher intrinsic CO tolerance than Pt, especially as HOR catalysts for PEMFC where the tolerance of CO, a major impurity of hydrogen fuel, is crucial. Although Pd has comparable HOR activity to Pt, the exclusive use of Pd as anode catalysts of PEMFC has not been satisfactory for the replacement of Pt. We confirmed in our previous report (K. Kwon et al., Catal Today, 232 (2014) 175) that the insufficient HOR activity of Pd could be supplemented by coupling with other elements or compounds such as Ru and tungsten oxide. To investigate the effect of alloying with Ru thoroughly, the calculation of hydrogen binding energy was performed on the basis of spin polarized density functional theory. Pure Pd(001) and Ru(001), Pd monolayer on Ru, and Pd bilayer on Ru are considered as model systems in the calculation. Strain and ligand effects are only applicable to bimetallic models (Pd monolayer on Ru and Pd bilayer on Ru). The negative sign of strain and ligand effects stands for a decrease in binding energy for PdRu alloy. Meanwhile, instead of making an effort to turn the model alloy systems into nanoparticles of Pd mono/bilayer on Ru, which would not be realistic in a few nm dimension, the actual confirmation of HOR enhancement at the level of half cell and PEMFC single cell was obtained by fabricating homogeneous PdRu alloy nanoparticles on carbon support. PdRu nanoparticles of different Pd:Ru atomic ratios of 1:0, 9:1, 1:9, and 0:1 were characterized with TEM and XRD, and compared with a commercial state-of-the-art Pt-based anode catalyst (PtRu1.5/C) in electrochemical experiments. The PdRu9 catalyst shows the highest HOR activity among the PdRu samples, which is comparable to the PtRu catalyst, even though the respective Pd and Ru have lower activity than PtRu. The highest HOR activity of the Ru-richest PdRu nanoparticles could be in line with the highest HOR activity of the Ru-richest PdRu model system (Pd monolayer on Ru).

IrO2 Decorated Self-Doped TiO2 Nanotube Arrays: A Binder-Free and More Stable Electrode for Oxygen Evolution Reaction in Acid Condition

The effective, stable and low cost anodic catalyst or electrode for OER is still a big challenge for water electrolysis in acid condition. Many efforts were devoted to develop suitable supports for depositing Ir and Ru metal or oxides to obtain an enhanced activity or stability for OER. In this work, self-doped TiO2 nanotube arrays (sTNTA) which has a higher electrical conductivity than TNTA was chosen as the support, it was fabricated by a simple electrochemical reduction of TNTA in neutral electrolyte. Then IrO2 nano particles were deposited on it by electrochemical pulse deposition method to form an OER electrode. The cyclic voltammetric behavior, electrical conductivity and micro structure of sTNTA prepared under different reduction potential were characterized to obtain an optimal performance for depositing IrO2, the OER activity and stability of new electrode were also determined. The obtained sTNTA shows an increased current in CV test than TNTA, which is due to the increased carrier density. As the reduction potential move to more negative level (from -1.5V to -1.9V vs. Ag/AgCl), the carrier density was found increased for 3 order of magnitudes, and XPS characterization confirm the existence of Ti3+ which formed in electrochemical reduction process, and sTNTA prepared under -1.9V shows the best electrochemical performance. After depositing IrO2, IrO2/sTNTA exhibited higher OER activity than IrO2/TNTA, according to the CV and EIS test, this can be ascribed to the enhanced electrical conductivity of support, which results in more active sites and lower charge transfer resistance of the electrode. The OER stability of IrO2/sTNTA was tested under constant current of 5mA/cm2, IrO2/TNTA and IrO2/Ti which prepared by electrochemical deposition on Ti foil were also tested for comparison. A higher stability of IrO2/sTNTA electrode was observed than the other two electrodes, and this may be due to the interaction between the IrO2 and sTNTA. XPS studies show a clear peak shift of Ir4f in IrO2/sTNTA, indicating a possible lower valence of Iridium, and such lower oxidation state of Iridium may be response for the enhanced OER stability. In summary, our studies have demonstrated the possibility of self-doped TNTA as a potential anodic support for OER. Comparing with the TNTA, the high electrical conductivity of sTNTA facilitate the charge transfer rate and thus improve the OER activity. Additionally, a higher OER stability was observed for IrO2/sTNTA electrode, and this may be due to possible catalyst-support interactions between IrO2 and self-doped TNTA. Figure 1

(Invited) Electrochemical Methods for Surface Composition Determination of Alloy and Core/Shell Nanoparticles

The surface characteristics of metallic nanoparticles (NPs), especially the atomic percent and distribution of each component, is critical to their catalytic and electrocatalytic behavior. Therefore, efforts are underway to design NP catalysts with full control of their composition, both in the bulk and at the surface. In our work, Pt-Ru and Pt-Ir NPs, either in alloy or core@shell forms, are of great interest, due to their suitability for a wide range of electrocatalytic and sensing applications, such as for the oxidation of formic acid, alcohols, and ammonia, for oxygen evolution and reduction in regenerative fuel cells, in the reduction of hydrogen peroxide, and as an electron mediating matrix in glucose biosensors 1–8. In the present work, PtxIry alloys, Ircore@Ptshell, Rucore@Ptshell, and Rucore@Pt-Irshell NPs were synthesized using the simple and controllable polyol method 9. In the case of PtxIry alloy NPs, two sequential heating steps were employed to minimize the possibility of surface enrichment of Pt or Ir during NP formation. In the case of Ircore@Ptshell and Rucore@Ptshell NPs, the Ptshell, with a coverage of between 0.1 and 2 monolayers (MLs), was controllably deposited on the surface of the Ircore and Rucore NPs, while for the Rucore@Pt-Irshell NPs, one ML of the PtxIry alloy shell, containing different Pt:Ir ratios, was deposited on the Rucore. Wavelength dispersive X-ray spectroscopy (WDS) and energy dispersive X-ray spectroscopy, coupled with high-resolution transmission electron microscopy (EDS/HRTEM) and powder X-ray diffraction (PXRD), were then used to determine the bulk composition and homogeneity of the NPs. To determine the outer surface composition of these NPs, the underpotential deposition/stripping of Cu and oxalic acid oxidation have been used previously, e.g., for Pt-Ru NPs 10–12. However, the effect of NP size, Pt-Ru interactions at the surface, and the degree of Ru oxidation on the catalytic activity have not been determined. In other prior work 13, CO stripping was used to establish the stability of PtRu NPs by tracking the changes in the surface composition. In the present work, several electrochemical fingerprinting methods were developed (underpotential deposition/removal of H atoms, CO stripping, and surface oxide reduction) to determine the precise coverage and thickness (fraction of MLs) of the Ptshell on the Ircore@Ptshell and Rucore@Ptshell, NPs and the Pt:Ir ratio at the surface of the PtxIry alloy and Rucore/Pt-Irshell NPs, as well as the real surface area of the exposed metals. Figure 1 1,14,15 shows the CO stripping voltammetry of the NPs under study here as an example of how the peak potential and splitting correlate with the NP surface composition. A comparison will be given between the surface areas and compositions obtained by each of the electrochemical methods used here, as well as with what can be inferred from TEM imaging methods.

CO oxidation on Ru-Pt bimetallic nanoclusters supported on TiO2(101): The effect of charge polarization.

Pt-based catalyst is widely used in CO oxidation, while its catalytic activity is often undermined because of the CO poisoning effect. Here, using density functional theory, we propose the use of a Ru-Pt bimetallic cluster supported on TiO2 for CO oxidation, to achieve both high activity and low CO poisoning effect. Excellent catalytic activity is obtained in a Ru1Pt7/TiO2(101) system, which is ascribed to strong electric fields induced by charge polarization between one Ru atom and its neighboring Pt atoms. Because of its lower electronegativity, the Ru atom donates electrons to neighboring Pt. This induces strong electric fields around the top-layered Ru, substantially promoting the adsorption of O2/CO + O2 and eliminating the CO poisoning effect. In addition, the charge polarization also drives the d-band center of the Ru1Pt7 cluster to up-shift to the Fermi level. For surface O2 activation/CO oxidation, the strong electric field and d-band center close to the Fermi level can promote the adsorption of O2 and CO as well as reduce the reaction barrier of the rate-determining step. Meanwhile, since O2 easily dissociates on Ru1Pt7/TiO2(101) resulting in unwanted oxidation of Ru and Pt, a CO-rich condition is necessary to protect the catalyst at high temperature.

CO2 Methanation on Co-sputtered Ru–Metal Oxides Catalysts Prepared Using the Polygonal Barrel-Sputtering Method

CO2 methanation catalysts were prepared by co-sputtering with Ru and metal oxides such as TiO2 and ZrO2 using the polygonal barrel-sputtering method. The co-sputtering technique not only resulted in the decrease in the reaction temperature but also maintained the deposition of smaller Ru particles during the reaction at higher temperature.

Diamines as auxiliary ligands for tuning photophysical and electrochemical properties of Ruthenium(II) polypyridyl complexes

The complex with the formula [Ru(bpy)2(2,3-diaminonaphthalene)][PF6] (5) was synthesized and characterized by 1H NMR spectroscopy, mass spectrometry and elemental analysis. A set of previously reported complexes with the formula [Ru(bpy)2(diamine)][PF6]{diamine = 1,2-diaminoethane (2), o-phenylenediamine (3), 1,2-diaminocyclohexane (4) } was synthesized and crystal structures were obtained for complexes 3 and 4. UV–vis absorption spectra of the complexes 2–5 were collected and compared to that of [Ru(bpy)3][PF6]2 (1), showing that the MLCT band is red-shifted upon introducing the diamine ligands in place of bipyridine. Emission spectra, excited-state lifetimes and emission quantum yields were collected at room temperature for the complexes 1–5, showing considerable changes in the photophysical characteristics upon the introductions of the diamine. The emission spectrum of 5 exhibits an intense emission in the far red-NIR region when excited at 510 nm. The cyclic voltammograms of the complexes 1–5 show one oxidation peak between 0.98 V and 1.15 V which is attributed to the Ru(II)/Ru(III) oxidation couple. Calculated HOMO and LUMO energy levels from both electrochemical data and theoretical calculations suggest a lower HOMO energy level for complex 1 than the diamino-containing complexes, presumably due to the stronger ligand field of the bipyridine.