Haut PDF Electrocatalytic water splitting with ruthenium nanoparticles

Electrocatalytic water splitting with ruthenium nanoparticles

Electrocatalytic water splitting with ruthenium nanoparticles

- 62 - 3.0 Preface As previously mentioned in the general introduction, H2 can be produced from water through the Water Splitting (WS) process which involves two successive semi- reactions, namely Oxygen Evolution and Hydrogen Evolution reactions (OER and HER, respectively). 1 Electrochemically, these two reactions need to be catalyzed to make the whole process efficient, meaning operating at low overpotential and in fast kinetic conditions. The discovery of highly effective and stable electrocatalysts is thus extremely desired for both reactions. Regarding HER, among the various catalysts tested, Pt-based ones are considered as the best systems for this reaction. 2,3 However, the prohibitive price and scarcity of platinum make it unsuitable for large scale commercial application. Therefore, the development of efficient and cheaper species that could operate at low overpotentials with a high stability is extremely required. Whereas ruthenium has been one of the most studied transition metals to develop catalysts for the OER showing high electrocatalytic activity, the performance of this metal for the HER had not been much investigated. 4 However, in the last few years, several works described Ru-based nanomaterials as efficient Hydrogen Evolution Catalysts (HECs) either in acidic or alkaline conditions. 5,6,7 For instance, Z. Peng et al. reported the preparation and electrocatalytic performance in the HER of two- dimensional Ru nanostructures. 6 The observed improved kinetics of this system when compared to Ru black powder is attributed to the greater specific area of the former due to its 2D structure. This hypothesis is supported by the fact that materials possessing a large surface area should display more active sites. The use of such materials seems thus to be a promising strategy to enhance the catalytic activity. The best performing Ru-systems are composite materials made of RuNPs embedded into carbon matrices that strongly affect their catalytic behavior and do not permit to finely tune the active sites. The followed synthetic protocols lead to barely defined structures, disabling a proper correlation between the characteristics of the nanospecies and their catalytic properties even if it is a key-point to optimize a catalytic reaction. The design of finely controlled metal NPs should offer interesting perspectives to better understand the crucial parameters to develop nanostructured catalysts with increased performance, both in terms of efficiency and stability.
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Development of ruthenium nanoparticles as catalyst models for the splitting of water : combination of experimental and theoretical chemistry approaches

Development of ruthenium nanoparticles as catalyst models for the splitting of water : combination of experimental and theoretical chemistry approaches

For this purpose, we started studying the surface properties of RuNPs stabilized by carboxylic acids as model systems. Alkyl chains with different lengths are considered. On the experimental side, RuNPs were synthesized following the organometallic approach using ethanoic (EtAc), pentanoic (PentAc) and octanoic acid (OcAc) as stabilizers. TEM characterization revealed small NPs with a homogeneous morphology and good dispersion. The surface state of these RuNPs was probed by analytical techniques such as IR, WAXS, NMR, etc., leading to a trustful mapping of their surface. Once the optimal ligand ratio to get RuNPs of similar sizes and their synthetic conditions were established, it was possible to determine the influence of the alkyl chain length of the carboxylic acid ligands on the surface properties of the NPs.
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Ruthenium Nanoparticles for Catalytic Water Splitting

Ruthenium Nanoparticles for Catalytic Water Splitting

least six times- than that of Pt. These characteristics all together have boosted the re-birth of Ru metal as a HER electrocatalyst in the last five years, particularly when it is in the form of NPs. This review focuses on the most remarkable Ru-based NP systems reported as HER/OER (electro)catalysts for the water splitting process and highlights the key factors that rule the catalytic performance of these nanomaterials. Given the crucial role of benchmarking for the objective assessment of the reported systems, a forefront section dedicated to this end has been included. Finally, future research directions are also discussed.
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Impact of three different TiO2 morphologies on hydrogen evolution by methanol assisted water splitting: Nanoparticles, nanotubes and aerogels

Impact of three different TiO2 morphologies on hydrogen evolution by methanol assisted water splitting: Nanoparticles, nanotubes and aerogels

The band gap of NP150 has not surprisingly been estimated to 3.2 eV after reflectance data treatment, assuming an indirect band gap [19-22] (figure 4a). The assumption of a direct band gap, reported by some authors for nanoparticles [23] or crystals [24], would give, with this determination protocol on our materials, a value of 3.45 eV which is inconsistent with literature data reported for anatase particles [25, 26]. Such a large value could have been considered, due to the very small size of the particles. However, the assumption of an indirect bandgap is confirmed by the determination of that of NP250 (figure 4b), made up of larger particles (3.2 eV for an indirect bandgap also). Tolbert et al reported that the quantum behaviour does not depend on the nature of the bandgap (direct or indirect)
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Morphological and Structural Evolution of Co3O4 Nanoparticles Revealed by in Situ Electrochemical Transmission Electron Microscopy during Electrocatalytic Water Oxidation

Morphological and Structural Evolution of Co3O4 Nanoparticles Revealed by in Situ Electrochemical Transmission Electron Microscopy during Electrocatalytic Water Oxidation

detected, typical of lamellar phases like CoOOH and Co(OH) 2 (Figure S12). Some areas from the surrounding phase showed no evidence of structuration, thus suggesting that the matrix is again amorphous, as in basic medium. Chemical mapping did not evidence the presence of phosphorus (Figure S13). Thus, the matrix is an amorphous cobalt (oxyhydr)oxide-like phase, as in the alkaline KOH electrolyte. When using the same KPi electrolyte but under cyclic voltammetry (Figure 6E), morphological changes are less apparent, with no significant change in the particle size. Some 1-2 nm crystalline domains were nevertheless observed with d- spacing typical of CoOOH. They are embedded by a 3 nm-thick amorphous layer. These TEM observations complete the structural information reported by Bergmann et al. 23 under cyclic
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Ruthenium Nanoparticles Supported on Carbon Microfibers for Hydrogen Evolution Electrocatalysis

Ruthenium Nanoparticles Supported on Carbon Microfibers for Hydrogen Evolution Electrocatalysis

Abstract: Four different cathodes for the hydrogen evolution reaction (HER) have been developed by the decoration of commercial carbon microfibers with Ru nanoparticles (Ru NPs). Two types of carbon fibers have been used: pristine, as-received, carbon fibers (pCF) and carbon fibers modified by an oxidative treatment that led to the functionalization of their surface with carboxylic groups (fCF). The decoration of these CFs with Ru NPs has been performed by two different methodologies based on the organometallic approach: direct synthesis of Ru NPs on top of the CFs (in-situ Ru NPs) or impregnation of the CFs with a colloidal solution of preformed Ru NPs stabilized with 4-phenylpyridine (RuPP NPs; ex-situ Ru NPs). The electrocatalytic performance of these four cathodes (ex-situ RuPP@pCF and RuPP@fCF; in-situ Ru@pCF and Ru@fCF) for the HER has been studied in acidic conditions. The results obtained show that both the nature of the NPs and of the carbon fibers play a key role on the stability and activity of the hybrid electrodes: ex-situ prepared Ru NPs afford better activities at lower overpotentials and better stabilities than those formed in-situ. Among the two ex-situ systems, an enhancement of the stability with pCF is observed, that may arise from more effective π-interactions between 4-phenylpyridine ligand and the surface of these carbon fibers. This interaction is somehow disfavoured with fCF due to the presence of the surface carboxylic groups.
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Activity and stability of cobalt phosphides for hydrogen evolution upon water splitting

Activity and stability of cobalt phosphides for hydrogen evolution upon water splitting

2 TOC Abstract Late transition metal phosphides have been reported to have high activity for catalyzing hydrogen evolution reaction (HER), yet their active site and stability are not well-understood. Here we report systematic activity and stability study of CoP for HER by combining electrochemical measurements for CoP nanoparticles (NPs) with ex situ and in situ synchrotron X-ray absorption (XAS) spectroscopy at phosphorus and cobalt K edges, as well as density functional theory (DFT) calculations. Colloidally synthesized CoP NPs showed high HER activity in both acid and base electrolytes, comparable to previous work, where no significant pH dependence was observed. Transmission electron microscopy-energy dispersive spectroscopy study of CoP NPs before and after exposure to potentials in the range from 0 to 1.4 V vs. the reversible hydrogen electrode (RHE) revealed that the P/Co ratio reduced with increasing potential in the potentiostatic measurements prior to HER measurements. The reduced P/Co ratio was accompanied with the emergence of (oxy)phosphate(s) as revealed by XAS, and reduced specific HER activity, suggesting the important role of P in catalyzing HER. This hypothesis was further supported by DFT calculations of HER on the most stable (011) surface of CoP and voltage dependent intensities of both phosphide and phosphate components from P-K edge X-ray spectroscopy. This work highlights the need of stabilizing metal phosphides and optimizing their surface P sites in order to realize the practical use of metal phosphides to catalyze HER in electrochemical and photoelectrochemical devices.
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Synthesis and Chemical and Morphological Characterization of Ruthenium-Based Nanoparticles

Synthesis and Chemical and Morphological Characterization of Ruthenium-Based Nanoparticles

The increase of environmental pollution challenges, fossil fuel depletion, the fluctuation of oil prices, and climbing global energy demand necessitate the alternative of efficient energy- converting devices, instead of fossil fuel. Over the last few years, this demand has been satisfied, to some extent, by using fuel cells, which are recognized as clean, silent, power sources with high efficiencies. These fuel cells have been proposed as appropriate power generators, which convert the chemical energy of fuel (such as hydrogen, methanol, ethanol, etc.) into electrical energy with minimal environmental pollution [8-10]. There are five different main categories of fuel cells, in which their classification is generally based on the electrolytes used. One of the best known, and used, is the proton exchange membrane fuel cell (PEMFC). This fuel cell uses hydrogen as a fuel and oxygen from the air as an oxidant. PEMFCs have high energy conversion efficiencies, good performance capabilities, and quick startup at low temperatures, which make them the most promising candidates for portable and transportation applications [10, 11]. The main components of fuel cells are anode, cathode, and electrolyte. In PEMFCs, at the anode, catalyst causes the hydrogen to split into H + and electrons. The positively charged hydrogen ions and electrons reach to the cathode by passing through the proton exchange membrane electrolyte and an external circuit, respectively. At the cathode, the electrons and H + combine with oxygen to produce water as the only final product [12]. The electrochemical reactions in both anode and cathode, along with the overall reaction are:
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Earth-Abundant Molecular Z-Scheme Photoelectrochemical Cell for Overall Water-Splitting

Earth-Abundant Molecular Z-Scheme Photoelectrochemical Cell for Overall Water-Splitting

Compared to photoanodes, photocathodes are much less developed. These include III-V semiconductors, 5 p-silicon, 5-6 metal oxides 5 and dye-sensitized transparent conducting oxides (DS- TCO). 7 III-V, silicon and metal oxide photocathodes generally exhibit relatively negative photocurrent onset potentials, which in an unbiased system, must be provided by the photoanode. It is also difficult to tune the materials toward desired absorption spectra and redox potentials. III- V photovoltaics are expensive and due to poor stability in aqueous conditions, involve an additional cost for protection layers, a case that also holds for silicon. DS-TCO based systems 8-18 operate in aqueous environments without protection layers and can be low-cost due to cheap TCO substrates and simple dyeing procedures. 19 The molecular components can be designed and synthesised with atomic precision, which allows precise tuning of the absorption spectrum and redox potentials. Molecular catalysts generally show good selectivity, which is important in the presence of oxygen. 20-21 DS-TCOs show promise as components for unbiased PEC cells for solar fuel production. 22-23 However, there are very few reports of unbiased DS-TCO Z-scheme water splitting cells, the most efficient reported so far produced H2 with 55% Faradaic efficiency and a steady- state photocurrent of approximately 15 A cm −2 ( > 400 nm, LED, 100 mW.cm −2 ). 24-25 The system was reliant on ruthenium, which in the long term may not be cost-effective for scale up. Another report utilized a DS-TCO for CO2 reduction within an unbiased PEC cell. 26
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Hollow Cobalt Phosphide with N-Doped Carbon Skeleton as Bifunctional Electrocatalyst for Overall Water Splitting

Hollow Cobalt Phosphide with N-Doped Carbon Skeleton as Bifunctional Electrocatalyst for Overall Water Splitting

on ZIF-67 nanocrystals,40,41 leading to the formation of surface wrinkles in the product (Figures 1c,d and S2). The PDA coating can be further verified by the high-resolution TEM (HRTEM) image Figure 1e−g)), in which an amorphous layer of ca. 5 nm in thickness can be found in the product. The formation of PDA coating can be further confirmed by the following experimental results: (1) The Raman spectrum of the product shows no characteristics peaks of their ZIF-67 precursors (Figure S3; 175 and 257 cm−1 for the stretching of Co−N, 682 cm−1 for imidazole ring puckering and C−H out of plane bend,1140 cm−1 for the stretching of C−N),42,43 which indicates the complete hydrolysis of ZIF- 67 and the complete removal of the N-containing organic ligands of 2-methylimidazolate. (2) The energy-dispersive spectroscopy (EDX) line scans clearly verify the existence of N and C (Figure 1h,i), which thus can only be attributed to the N and C atoms of PDA layers rather than the 2- methylimidazolate ligands. Accompanied by the formation of PDA coating, the decomposition of ZIF- 67 into Co-LDH nanosheets is simultaneously induced in the slight basic buffer solution,44 as confirmed by the PXRD patterns (Figures S4 and S5), selected-area electron diffraction (SAED) pattern (Figure S6), and EDX line scans showing the distribution of Co and O elements (Figure 1i).35,44−47 TEM image also reveals that Co-LDH possesses a hollow nanostructure (H-Co-LDH), with thin shells of ca. 55 nm (Figure 1d). Careful examination of a typical H-Co-LDH particle under HRTEM indicates that the shell consists of a large amount of small nanoparticles with average diameter of ca. 12 nm (Figure 1e). The lattice spacing of 0.274 and 0.164 nm in these small nanoparticles can be assigned to the (012) and (110) planes of Co-LDH,45 respectively, thus further confirming that the small nano-particles are Co-LDH (Figure 1(f, g)). Moreover, the distribution of Co and O is in line with that of N and C in the EDX line scans of H-Co-LDH, suggesting the formation of H-Co-LDH particles with homogeneous PDA coating (denoted as H-Co-LDH@PDA). It is worth noting here that although PDA and MOFs have been used together to synthesize hollow PDA nanocapsules40 or porous hybrid nanostructures,48−50 a synthetic approach based on the subtle coupling of PDA coating and MOF conversion processes has not been reported before. Our synthetic approach reported here thus provides new insights into the development of PDA based complex nanostructures.
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Carboxylic acid-capped ruthenium nanoparticles: experimental and theoretical case study with ethanoic acid

Carboxylic acid-capped ruthenium nanoparticles: experimental and theoretical case study with ethanoic acid

Yannick (b) ; Lecante, Pierre (c) ; Amiens, Catherine (b) ; del Rosal, Iker (a) ; Philippot, Karine ?(b) ; Poteau, Romuald ?(a) Given the properties of metal nanoparticles (NPs) depend on several parameters (namely, mor- phology, size, surface composition, crystalline structure, etc.) a computational model that brings a better understanding of structure/properties relationship at the nanoscale is a significant plus in order to explain the surface properties of metal NPs and also their catalytic viability, in particular when envisaging a new stabilizing agent. In this study we combined experimental and theoretical tools to obtain a mapping of the surface of ruthenium NPs stabilized by ethanoic acid as a new capping ligand. For that purpose, the organometallic approach was applied as synthesis method. The morphology and crystalline structure of the obtained particles was characterized by state- of-the art techniques (TEM, HRTEM, WAXS) and their surface composition was determined by various techniques (solution and solid-state NMR, IR, chemical titration, DFT calculations). DFT calculations of the vibrational features of model NPs and of the chemical shifts of model clusters allowed to secure the spectroscopic experimental assignations. Spectroscopic data as well as DFT mechanistic studies showed that the ethanoic acid lies on the metal surface as ethanoate, together with hydrogen atoms. The optimal surface composition determined by DFT calculations appeared to be ca. [0.4-0.6] H/Ru surf and 0.4 ethanoate/Ru Surf , which was corroborated by exper- imental results. Moreover, for such a composition, an hydrogen adsorption Gibbs free energy in the range -2.0 to -3.0 kcal.mol -1 was calculated, which makes these ruthenium NPs a promising nanocatalyst for the hydrogen evolution reaction in the electrolysis of water.
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Catalysis with Colloidal Ruthenium Nanoparticles

Catalysis with Colloidal Ruthenium Nanoparticles

117 dehydrogenation of ammonia borane by hydrolysis (due to its simplicity and green character as well as efficiency), interesting results were also obtained by methanolysis or dehydrocoupling. These last approaches merit more efforts, at least at the fundamental level, in order to get mechanism insights, enable the development of more performant catalytic systems and improve hydrogen productivity. If numerous kinetics parameters are available and allow comparing the efficiency of the Ru nanocatalysts reported for the dehydrogenation of amine boranes in water, there is no clear insight explaining the high activity generally observed. What about the real effect of particle size, Ru crystal structure, surface area, stabilizer and/or support nature on the catalytic performances? Answers to these questions remain to be found in most cases. Moreover, the catalytic lifetime parameter has received a quite low attention until now, whereas NPs are not thermodynamically stable entities and can be readily deactivated, which may harm their long-term performance. If AB solvolytic dehydrogenation is a promising hydrogen generation system (in particular for cases that require a convenient and reliable hydrogen source) the decomposition of AB results in a contamination of released H 2 by NH 3 and borazine which is a major problem for application in
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C-H bond activation catalyzed by Ruthenium nanoparticles

C-H bond activation catalyzed by Ruthenium nanoparticles

161 4 Experimental section 4.1 Reagents and General Procedures All reactions were carried out in a Fischer-Porter glassware. Commercially substrates were used without any further purification. Other phenylpyridines were synthesized by 2-bromopyridine and corresponding boronic acids according to reported literature. 111 All work-up and purification procedures were carried out with reagent-grade solvents. Toluene was purchased from VWR Chemicals (BDH Prolabo) and used without further purification. Flash column chromatography was performed using Merck silica gel 60 (0.040-0.063 mm). 1 H NMR (400 MHz), 13 C NMR (100 MHz) spectra were recorded on a Bruker Avance 400 MHz spectrometer. Chemical shifts are reported in parts per million (ppm) downfield from residual solvent peaks and coupling constants are reported in Hertz (Hz). Splitting patterns are designated as singlet (s), doublet (d), triplet (t). Splitting patterns that could not be interpreted or easily visualized are designated as multiplet (m). Electrospray mass spectra were recorded using an ESI/TOF Mariner Mass Spectrometer. UV-visible spectra were recorded on a Cary 400 (Agilent) double-beam spectrometer using a 10 mm path quartz cell. Emission spectra were measured on a Fluoromax-3 (Horiba) spectrofluorimeter. A right-angle configuration was used. High- resolution mass spectra (HRMS) were performed on a Bruker maXis mass spectrometer by the "Fédération de Recherche" ICOA/CBM (FR2708) platform.
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Balanced Splitting and Rebalanced Splitting

Balanced Splitting and Rebalanced Splitting

BALANCED SPLITTING AND REBALANCED SPLITTING ∗ RAYMOND L. SPETH † , WILLIAM H. GREEN † , SHEV MACNAMARA ‡ , AND GILBERT STRANG ‡ Abstract. Many systems of equations fit naturally in the form du/dt = A(u) + B(u). We may separate convection from diffusion, x-derivatives from y-derivatives, and (especially) linear from nonlinear. We alternate between integrating operators for dv/dt = A(v) and dw/dt = B(w). Non- commutativity (in the simplest case, of e Ah and e Bh ) introduces a splitting error which persists even in the steady state. Second-order accuracy can be obtained by placing the step for B between two half-steps of A. This splitting method is popular, and we suggest a possible improvement, especially for problems that converge to a steady state. Our idea is to adjust the splitting at each timestep to [A(u) + c n ] + [B(u) − c n ]. We introduce two methods, balanced splitting and rebalanced splitting, for choosing the constant cn . The execution of these methods is straightforward, but the stability analysis becomes more difficult than for cn = 0. Experiments with the proposed rebalanced splitting method indicate that it is much more accurate than conventional splitting methods as systems ap- proach steady state. This should be useful in large-scale simulations (e.g., reacting flows). Further exploration may suggest other choices for c n which work well for different problems.
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Coupling electrocatalytic CO2 reduction with thermocatalysis enables the formation of a lactone monomer

Coupling electrocatalytic CO2 reduction with thermocatalysis enables the formation of a lactone monomer

Carbonylation. Under an argon atmosphere, a 1 mL vial was filled with 70 µL of propylene oxide, 1 mL of 1,2-dimethoxyethane and 8.3 mg of [TPPCr][Co(CO) 4 ]. This mixture was transferred with a syringe to a carbonylation reactor (CR), immediately purged three times with 10 bar of argon. It was then connected to the PA, gases from the PA were expanded into the CR. The CR was closed, and heated to 50 °C for 2 °h with stirring. The CR was the cooled down to 0 °C and carefully opened to release the pressure. A 500 µL aliquot of the final reaction mixture was sampled, to which CDCl 3 and mesitylene (internal standard) were
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Fluctuation splitting Riemann solver for a non-conservative modeling of shear shallow water flow

Fluctuation splitting Riemann solver for a non-conservative modeling of shear shallow water flow

16 The time instant at which the onset of transverse waves occurs depends upon the value of CFL and hence time-step. These transverse wave structures appears to be an instability phenomenon in the SSWF model triggered by the numerical noise acting as perturbations. A series of computations is performed on the structured quadrangular grid with 1000 × 400 points with different values of CFL = 1, 0.9, 0.8 and 0.7. Hence the values of CFL used here are close to the numerical stability limit (CFL=1). The time-step (∆t) is plotted verses time (t) in Fig. (14) for each simulation. Dynamics in each simulation is accompanied by two decrements in ∆t which can be seen in each curve of Fig. (14). The first of which corresponds to the formation of a quasi-1D roll wave profile, nearly at the time (t = 5 s). The interval of the stability of this quasi-1D wave seems to larger when CFL used is smaller. In such cases the second and sharp decrease in the curve of ∆t appears latter, delaying the appearance of transverse structures. This can be viewed as the system containing transverse waves which are superimposed on the quasi-1D profiles. Depending on the numerical noise (which is larger near the stability limit) transverse waves can be observed earlier. Another feature which can be noted from ∆t curves is that, as CFL decreases fluctuations in the time-steps decrease. For the simulations with higher CFL, unsteady nature of transverse waves cause such fluctuations in the time-step. For small values of CFL stable waves are seen, as shown in Fig. (11), (12) and (13). The results presented above are computed on a fine grid, however similar results are obtained for the coarse grids like the one with 300 × 50 points.
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Silica nanoparticles separation from water: aggregation by cetyltrimethylammonium bromide (CTAB)

Silica nanoparticles separation from water: aggregation by cetyltrimethylammonium bromide (CTAB)

Moreover, it was also observed that all of the satisfying aggre- gation of 30R50 (0.05–0.51%) begin at CTAB = 0.1 mM, whatever their surface zeta potential. This suggests that the ‘‘depletion floc- culation’’ may not only occur at very high zeta values (10 mM CTAB for all three concentrations of 30R50 as mentioned above), but also very low ones (30R50 0.51% with 0.1 mM CTAB corresponding to f  ÿ40 mV). Of course, at the concentration of 0.1 mM CTAB, the formation of micelles from CTAB can be neglected. However, as nanoparticles come closer together, the intercolloidal region con- sists of a region that is depleted in CTAB. The depletion effect ( Shi, 2002 ) is induced by their osmotic pressure, due to the differ- ence of CTAB concentration between the inside and outside re- gions. Solvent between the nanoparticles then tends to diffuse out to reduce the concentration gradient, causing the nanoparticles to aggregate.
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Custom plating of nanoscale semiconductor/catalyst junctions for photoelectrochemical water splitting

Custom plating of nanoscale semiconductor/catalyst junctions for photoelectrochemical water splitting

will be discussed later). This also showed that V oc increased with decreasing p and w due to the change in reverse dark current density (j 0,dark ) associated with the increasing n-Si/Ni contact area. This model structure was also used to picture the Si energetics around a Ni pad. Figure 5a,b shows the models as 2D representations of the conduction band (CB) energy for p = 100 µm and extreme w values of 350 and 100 nm, respectively. These data show the considerable impact of w on the band bending profile close to the surface (see the supplementary information for more details). This is also clearly illustrated in Figure 5c, which shows the 1D band bending (conduction and valence bands) below a Ni pad with a p value fixed at 100 µm and varying pad width (100 nm < w < 350 nm). These figures clearly show that shrinking the Ni NW section increases the effective barrier height, which is in good agreement with the literature devoted to the pinch-off phenomenon. 35,44,45 Importantly, the
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Surprising Differences of Alkane C‐H Activation Catalyzed by Ruthenium Nanoparticles: Complex Surface‐Substrate Recognition?

Surprising Differences of Alkane C‐H Activation Catalyzed by Ruthenium Nanoparticles: Complex Surface‐Substrate Recognition?

to a hydroxyl-, carboxy- or an amine group for example, the large alkane fraction in the crude oil would feed the pool of industrial base chemicals. Thus, heterogeneous catalysis has long studied the activation of hydrocarbons on metal surfaces with typical reactions such as alkane hydrogenolysis. In these studies, H/D exchange has been used as a test of reactivity of the hydrocarbons. In this respect, when explicitely mentioned no real difference in reactivity was found for cyclohexane and cyclopentane. [3,4,5,6] In solution, the research
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Electrocatalytic Activity of Small Organic Molecules at PtAu Alloy Nanoparticles for Fuel Cells and Electrochemical Biosensing Applications.

Electrocatalytic Activity of Small Organic Molecules at PtAu Alloy Nanoparticles for Fuel Cells and Electrochemical Biosensing Applications.

The requirement of highly active metal catalysts for fuel cell applications has attracted many interests in developing monodispersed, single component, small-size NPs of Pt and Au, as well as bimetallic PtAu alloy NPs [8]. However, the improvement for fuel cell performance provided by the majority of metal NPs and their alloy-based catalysts is limited to either activity or to stability, not to both at the same time. Pt-group metals have been extensively studied as an effective catalyst for oxidation of small organic fuels such as formic acid and methanol. However, the principal challenge is the poisoning by CO-like intermediate species during the electro-oxidation process. This is the main cause of the low activity in fuel cells. PtAu NPs catalysts possess the capacity to solve this poisoning effect on platinum electrodes. Despite this exciting progress in the fuel cell catalysis, the unsupported PtAu NPs suffers problem of stability towards the oxidation of these organic molecules upon potential cycling. A major concern with electrocatalysis of small organic molecules for fuel cell application is the long-term stability. Due to the harsh environment in fuel cells, only a few materials can withstand these conditions over the time period needed. Carbon supported metal alloys nanoparticles such as graphene [9], carbon black [10,11] as catalyst supports, covered with metal nanoparticles, have shown promising results concerning the long-term stability; therefore, the development of graphene or carbon black supported PtAu alloy NPs should also enhance the electrocatalytic activity. Besides, macroporous carbon supports could be used to eliminate the fierce aggregation of the PtAu colloid NPs over time. Also, fundamental study of the electrode processes under practical fuel cell operating conditions would give firsthand information about performance in real fuel cells and aid in the design of potential catalyst compositions. Also, the prepared unsupported binary PtAu NPs catalysts which were carbon monoxide tolerant can be tested in the fuel cell stack to determine its long term capability. The long term operation tests are important to determine the life time of the catalysts.
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