Deposition Of Ru Research Articles

Effect of Ru Deposition on the Mechanism of Photocatalytic Water Splitting by GaZnNO Solid Solution

Effect of Ru Deposition on the Mechanism of Photocatalytic Water Splitting by GaZnNO Solid Solution

Selective surface deposition of trace amount of ruthenium onto a freestanding, fibrous carbon monolith for pH-universal hydrogen evolution reaction

Among various hydrogen evolution reaction (HER) catalysts, ruthenium (Ru)-based catalysts exhibit excellent pH-universal activity, whereas the presence of inaccessible active sites buried in dense layers inevitably leads to excessive use of Ru. In addition, intentional formation of Ru nanoparticles in addition to single atoms to optimize HER activity further increases the Ru mass loading.In this study, the direct deposition of trace amount of Ru onto pre-assembled fibrous carbon monolith leads to highly efficient pH-universal HER activity with only 0.32 wt% of ultralow Ru content. The selective deposition of Ru onto only accessible active sites in three-dimensional carbon monolith suppresses the formation of buried active sites. Despite the low content, the selective deposition pathway to only accessible sites result in the formation of Ru nanoparticles, which synergize with coexisting single atoms to optimize pH-universal HER activity. The presence of Co single atoms in the fibrous carbon matrix further optimizes the deposition and HER activity of Ru species. The prepared monolithic catalyst exhibits highly efficient pH-universal HER activity with the drastically low overpotential values of 14/15/54 mV and the Tafel plots of 19/17/46 mV dec-1 in 1 M KOH alkaline, 0.5 M H2SO4 acidic, and 1 M PBS neutral electrolytes, respectively. It also exhibits a high durability during 10,000 cycles under an accelerated reaction conditions. Differentiated from conventional powdered catalysts that typically require a ruthenium content of ∼ 20%, this study suggests a novel strategy for simultaneously improving the HER activity of the catalytic electrode and reducing the use of Ru.

Atomic layer deposited Ru/Mo2C heterostructure for efficient nitrogen reduction and nitrogen evolution in Li-N2 battery

Li-N2 battery is a promising platform for integrating N2 fixation and electrochemical energy storage. However, the low activity and poor stability of cathode catalysts lead to undesirable electrochemical performance of Li-N2 batteries. Herein, a Ru/Mo2C heterostructure was controllably fabricated on N-doped carbon nanotubes (NCNTs) by atomic layer deposition technique. The Li-N2 battery with Ru/Mo2C-NCNTs cathode catalyst exhibits large specific capacity, high cycling stability and enhanced reversibility. This excellent performance derives from the formation of unique Ru/Mo2C heterostructure by the preferential deposition of Ru on Mo2C supports with a controlled number of ALD-cycles, which could enrich the active sites, improve the structural stability and modulate the electronic transfer behavior to facilitate N2 reduction reaction and N2 evolution reaction on the cathode. This work may provide a new direction or strategy for the development of efficient cathode electrocatalysts for Li-N2 batteries.

Photoactivated Ru chemical vapor deposition using (η3-allyl)Ru(CO)3X (X = Cl, Br, I): From molecular adsorption to Ru thin film deposition

We have investigated photoassisted chemical vapor deposition (PACVD) of Ru on functionalized alkanethiolate self-assembled monolayers (SAMs) using (η3-allyl)Ru(CO)3X (X = Cl, Br, I) precursors. Three SAMs were employed with —CH3, —OH, or —COOH terminal groups. Our data show that (η3-allyl)Ru(CO)3Cl molecularly adsorbs on the functionalized SAMs and no Ru(0) is deposited in either the dark or under UV light. Similarly, (η3-allyl)Ru(CO)3I molecularly adsorbs on all substrates studied. For (η3-allyl)Ru(CO)3Br at longer deposition times under UV light, Ru(0) and RuOx are deposited on —CH3- and —OH-terminated SAMs. In contrast for —COOH-terminated SAMs, little or no Ru is deposited, which is attributed to the formation of Ru-carboxylate complexes that block further deposition. Density Functional Theory calculations show that the different deposition behaviors observed are not due to the primary photoprocess, which is the loss of a carbonyl ligand, but rather can be attributed to the energy required to lose a second carbonyl ligand, a secondary photoprocess. Together, these data suggest that PACVD can be employed for area selective deposition.

The Importance of Decarbonylation Mechanisms in the Atomic Layer Deposition of High-Quality Ru Films by Zero-Oxidation State Ru(DMBD)(CO)3.

Achieving facile nucleation of noble metal films through atomic layer deposition (ALD) is extremely challenging. To this end, η4 -2,3-dimethylbutadiene ruthenium(0) tricarbonyl (Ru(DMBD)(CO)3 ), a zero-valent complex, has recently been reported to achieve good nucleation by ALD at relatively low temperatures and mild reaction conditions. The authors study the growth mechanism of this precursor by in situ quartz-crystal microbalance and quadrupole mass spectrometry during Ru ALD, complemented by ex situ film characterization and kinetic modeling. These studies reveal that Ru(DMBD)(CO)3 produces high-quality Ru films with excellent nucleation properties. This results in smooth, coalesced films even at low film thicknesses, all important traits for device applications. However, Ru deposition follows a kinetically limited decarbonylation reaction scheme, akin to typical chemical vapor deposition processes, with a strong dependence on both temperature and reaction timescale. The non-self-limiting nature of the kinetically driven mechanism presents both challenges for ALD implementation and opportunities for process tuning. By surveying reports of similar precursors, it is suggested that the findings can be generalized to the broader class of zero-oxidation state carbonyl-based precursors used in thermal ALD, with insight into the design of effective saturation studies.

RuS2-modified NiW/Al2O3 catalysts for refractory 4,6-dimethyl-dibenzothiophene hydrodesulfurization

Al2O3-supported noble metal (NM)-modified hydrodesulfurization (HDS) catalysts (W 15.8 wt% and Ni 3.5 wt%) were applied in refractory 4.6-dimethyl-dibenzothiophene elimination. Corresponding Ru-doped (0.5 and 0.7 wt%) materials were either dried (120 °C) or dried followed by calcining (400 °C) after NM deposition prior to activation (400 °C, 15/85H2S/H2 mixture). In solid at 0.5 wt% NM calcined after Ru deposition ruthenium was less dispersed (XRD and TPR) than over corresponding just dried one. Also, WS2 had higher dispersion (HR-TEM) on the latter. However, “NiWS” phase was enhanced (XPS) on the former material. NM-doped catalysts annealed before activation showed significantly enhanced activity (x2.4 and x1.6, solids with 0.5 and 0.7 wt% Ru, respectively) in refractory dibenzothiophene (DBT) HDS, as to that of pristine NiW/Al2O3. Enhanced hydrogenating properties of the former materials improved S elimination from sterically-hindered DBT. Conversely, Ru-doping was detrimental on NiW/alumina when non-annealed prior to activation. Unreduced Run+ and decreased pyrite-like RuS2 species (XPS) on those catalysts could be related to their strongly diminished HDS activity.

Effect of preparation method and reaction parameters on catalytic activity for ammonia synthesis

MgO–CeO2 support was prepared by three different methods and impregnated by 1% Ru. These mixed oxides supported Ru catalysts were applied to ammonia (NH3) synthesis. NH3 synthesis activity was highly dependent on the H2/N2 ratio, temperature, pressure conditions, and physical characteristics of the catalysts. NH3 synthesis increased using a higher H2 concentration in reactant stream at a relatively higher temperature and pressure conditions, while lower H2 concentration was suitable at lower temperatures. Likewise, the effect of increasing pressure was more dominant at a higher temperature for higher H2 concentration. Physical characteristics of the catalysts strongly influenced NH3 synthesis activity, which varied for different methods. Increased surface area, high dispersion of Ru and CeO2, and preferential deposition of Ru on CeO2 were responsible for higher NH3 synthesis activity of the catalyst prepared from the co-precipitation method.

Nickel Foam Supported NiO@Ru Heterostructure Towards High-Efficiency Overall Water Splitting.

Electrocatalytic water splitting for hydrogen production from renewable energy requires the innovation of electrocatalysts with high activity and low cost. In this work, densely packed NiO@Ru nanosheets were fabricated on the surface of Ni foam through a two-step method of Ni(OH)2 growth followed by Ru deposition. Through pair distribution function analysis from selected-area electron diffraction and X-ray photoelectron spectroscopy, the interface structure feature is revealed as a thin layer of perovskite NiRuO3 sandwiched between NiO and Ru. The electrode exhibits high activity and durability for HER and OER, delivering a current density of 10 mA cm-2 at a voltage of 1.55 V for overall water splitting in 1 M KOH. The excellent performance can be attributed to the intimate interface contact of NiO and Ru in addition to low charge transfer resistance and super-hydrophilic surface structure, as verified by the electrochemical impedance spectroscopy and contact-angle measurement.

Atomic Layer Deposition of Ru for Replacing Cu-Interconnects

Atomic Layer Deposition of Ru for Replacing Cu-Interconnects

Efficient Photocatalytic CO2 Reformation of Methane on Ru/La‐g‐C3N4 by Promoting Charge Transfer and CO2 Activation**

AbstractArtificial photosynthesis, in which solar energy drives CO2 to produce hydrocarbon fuels, is considered an effective way to solve the increasingly serious energy crisis and mitigate the greenhouse effect. Herein, layered porous Ru‐loaded and La‐doped g‐C3N4 nanosheets (Ru‐LGCNs) were prepared by one‐step calcination, followed by in situ photoreduction deposition of Ru. The layered Ru‐LGCN showed excellent photocatalytic CO2 reformation of methane performance under visible light, and the generation rates of CO, CH3CH3, CH3OH and CH3CH(OH)CH3 were 133, 154, 251 and 133 μmol h−1 g−1, respectively. The reason for the enhanced photocatalytic activity of Ru‐LGCN is the synergistic effect of bimetallic Ru and La. It is worth noting that the doped La can provide a good channel for charge transfer between LGCNs and CO2. This change in the charge behavior of the transport path is beneficial to break the C=O bonds on the active site La and generate methyl radicals on Ru, resulting in the generation of C2+ hydrocarbons.

Ru/Ce/Ni Metal Foams as Structured Catalysts for the Methanation of CO2

The development of highly conductive structured catalysts with enhanced mass- and heat-transfer features is required for the intensification of the strongly exothermic catalytic hydrogenation of CO2 in which large temperature gradients should be avoided to prevent catalyst deactivation and to control selectivity. Therefore, in this work we set out to investigate the preparation of novel structured catalysts obtained from a commercial open cell Ni foam with high pore density (75 ppi) onto which a CeO2 layer was deposited via electroprecipitation, and, eventually, Ru was added by impregnation. Composite Ru/Ce/Ni foam catalysts, as well as simpler binary Ru/Ni and Ce/Ni catalysts were characterized by SEM-EDX, XRD, cyclic voltammetry, N2 physisorption, H2-temperature programmed reduction (TPR), and their CO2 methanation activity was assessed at atmospheric pressure in a fixed bed flow reactor via temperature programmed tests in the range from 200 to 450 °C. Thin porous CeO2 layers, uniformly deposited on the struts of the Ni foams, produced active catalytic sites for the hydrogenation of CO2 at the interface between the metal and the oxide. The methanation activity was further boosted by the dispersion of Ru within the pores of the CeO2 layer, whereas the direct deposition of Ru on Ni, by either impregnation or pulsed electrodeposition methods, was much less effective.

In operando activation of alkaline electrolyzer by ruthenium spontaneous deposition

Conventional alkaline electrolyzers used for water splitting can considerably increase their efficiency upon modification of the surface of the electrode. Here we present in operando evidence of activation of a conventional alkaline electrolyzer using nickel electrodes modified by spontaneous deposition of ruthenium (1 × 10−5 M in 30% w/v KOH electrolyte). Surface modifications were analyzed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. Conventional electrochemical techniques were used to establish the kinetic and thermodynamic parameters of hydrogen generation before and after the spontaneous deposition of Ru. Changes on the nickel electrodes by direct modification of the electrolyte allowed to reduce the potential at minimum current from 1.64 to 1.00 V under the same operating conditions. That is, a considerable increase in the electrolysis efficiency was attained by reducing the activation overvoltage. Thus, using a simple, inexpensive, and reproducible method, it is possible to increase the efficiency of conventional electrolyzers.

Area-Selective Deposition of Ruthenium by Area-Dependent Surface Diffusion

Area-selective deposition (ASD) enables the growth of materials on target regions of patterned substrates for applications in fields ranging from microelectronics to catalysis. Selectivity is often achieved through surface modifications aimed at suppressing or promoting the adsorption of precursor molecules. Here, we show instead that varying the surface composition can enable ASD by affecting surface diffusion rather than adsorption. Ru deposition from (carbonyl)-(alkylcyclohexadienyl)Ru and H2 produces smooth films on metal nitrides, and nanoparticles on SiO2. The latter form by surface diffusion and aggregation of Ru adspecies. Kinetic modeling shows that changing the surface termination of SiO2 from -OH to -CH3, and thus its surface energy, leads to larger and fewer nanoparticles because of a 1000-fold increase in surface diffusion rates. Kinetic Monte Carlo simulations show that even surface diffusion alone can enable ASD because adspecies tend to migrate from high- to low-diffusivity regions. This is corroborated by deposition experiments on three-dimensional (3D) TiN-SiO2 nanopatterns, which are consistent with Ru migrating from SiO2 to TiN. Such insights not only have implications for the interpretation of experimental results but may also inform new ASD protocols, based on chemical vapor and atomic layer deposition, that take advantage of surface diffusion.

Single-Step Synthesis of Platinoid-Decorated Phosphorene: Perspectives for Catalysis, Gas Sensing, and Energy Storage.

The originality of phosphorene is suppressed by its structural defects, irreproducibility, and sensitivity to the ambient environment. To preserve phosphorene's essential characteristics, for example, influencing the charge redistribution and generating the formation of active centers, noble-metal decoration is found to be an efficient approach. Herein, we demonstrate a single-step electrochemical synthesis of platinoid-decorated few-layer phosphorene (FP). The material's structure and effects of metal (Ru, Rh, and Pd) deposition on the FP nanosheets were first explored by numerous analytical techniques and theoretical calculations. Platinoid-decorated FPs demonstrate high quality and consist of one to five layers modified with round- and heptagon-shaped metal nanoparticles with the most intense distribution of Pd. The high-rate Rh deposition provides the enhanced electrocatalytic efficiency for hydrogen evolution (79 mV·dec-1-Tafel slope) and almost 20 times increased capacity for the Li-ion batteries in comparison to bare and Ru-decorated FP. The chemosensing of platinoid-decorated FP indicates a response to methanol plus ethanol and shows inertness to acetone. The incorporation of Ru and Rh nanoparticles increases FP's selectivity toward methanol. This research provides a new approach for the in situ FP functionalization during top-down synthesis and thus broadens the material's feasibility for advanced nanotechnology.

Monolithic Integration and Analysis of Vertical, Partially Encapsulated Nanoelectrode Arrays

This study reports on the development of vertical, partially encapsulated nanoelectrodes for electrically contacting the interior of electrogenic cells with microelectronics. Intracellular electrical stimulation and recording with single cell resolution enables new insights into the electrophysiology of cells embedded in a complex multicellular network, providing detailed understanding of fundamental processes affecting cell to cell communication and thereby paving the way for novel applications including pharmacological studies and other neuromodulation techniques like focused ultrasound and electroceuticals. In order to minimize the influence of the measurement system, an approach based on nano-sized hollow electrodes, achieving an adhesion based intracellular access, is used. The focus of the presented work is on the novel fabrication technology and the characterization of the resulting nanoelectrodes. In CMOS compatible processes, the hollow geometry is achieved using a sacrificial layer technique combining deep reactive ion etching and atomic layer deposition of Ru. For decoupling the extracellular milieu, a partial passivation of the nanoelectrodes by Ta2O5 is realized. The monolithic integration allows an application specific fine-tuning of geometry and placement of the nanoelectrodes. A discrete microelectrode array was designed to electrically and electrochemically characterize the nanoelectrodes. Resistance measurements, cyclic voltammetry and electrochemical impedance spectroscopy show the feasibility of the developed electrodes as an electronic interface to electrochemical fluids. Specifically, an electrode resistance of 2.92 $\text{k}\Omega $ and charge delivery capacitance of $748.13~\frac {\mu \text {C}}{\text {cm}^{2}}$ were observed. Confocal microscopy analyses of neural cells interfaced with the nanoelectrodes indicate an adhesion based intracellular access as well as biostability and biocompatibility. [2020-0224]

Model Operational Matrix for the Betterment of Ruthenium As a Catalyst for the Electrochemical Nitrogen Reduction Reaction to Ammonia in Aqueous Electrolytes

Ammonia (NH3), as a green energy carrier, potential transportation fuel and chemical for fertilizer synthesis, plays an indispensable role in the agricultural, plastic, pharmaceutical and textile industries1. Industrially, NH3 manufacturing is dominated by the Haber–Bosch (HB) process, which consumes more than 2% of the global energy supply, and releases 1.87 tons of greenhouse gas, carbon dioxide (CO2), per 1 ton of NH3 2. This energy-intensive process is also inefficient and relatively low conversion ratio are achieved due to unfavorable chemical equilibrium 3. Hence, it is of great significance to develop alternative routes for more efficient N2 fixation under milder conditions. Recently, a worldwide gold rush has been triggered, and many pioneering methods are being investigated to convert N2 to NH3, including biological catalysis 4, photocatalysis 5,6and electrocatalysis 2,7. Particularly, electrochemical reduction of N2 to NH3 is thermodynamically predicted to be more energy efficient than the HB process by about 20% 7,8 . An electrochemical process could also provide the benefit of reducing greenhouse gas emission as the source of H2 is the electrolysis of water molecules instead of natural gas. With this scenario, ammonia would be synthesized in a carbon-neutral manner if renewable electrical energy is used.In the electrochemical N2 reduction reaction (NRR) system, though electrocatalysts are the paramount components, a rational cell design, synthesize and operation conditions are very vital 4. Most of recent studies have looked on a single parameter (or two) such as catalyst morphology, catalyst deposition and loading, nitrogen reduction potential or type, temperature, pressure and components of cell and electrolytes. However, the fact that NRR and catalyst deposition is a multistep process, sampled parameters study might not provide sufficient information about the actual electrocatalytic process. Therefore, our group tried to determine the best working conditions and ways of designing NRR experiments in order to draw conclusions on the process efficiency in terms of charge used and NH3 yield. In the present study, electrochemically deposited Ru metal catalysts have been investigated. It is found that in ambient reaction conditions and in highly concentrated electrolytes, a Faradic Efficiency as high as 1.2 % can be reached by optimizing the Ru deposition morphology and deposition time (loading), as well as the NRR potential, nature of cation/anion exchange membranes and size of the counter cations in the electrolyte. This is a 4-fold improvement compared to the maximum efficiency reported 4 with the same catalyst (< 0.3 %).

Optimization of ruthenium as a buffer layer for non-collinear antiferromagnetic Mn3X films

Two thin film deposition routes were studied for the growth of high quality single crystalline Ru (0001) epitaxial films on c-Al2O3 substrates using radio frequency-magnetron sputtering. Such films are very important as buffer layers for the deposition of epitaxial non-collinear antiferromagnetic Mn3X films. The first route involved depositing Ru at 700 °C, leading to a smooth 30 nm thick film. Although, high resolution x-ray diffraction revealed twinned Ru film orientations, in situ post-annealing eliminated one orientation, leaving the film orientation aligned with the substrate, with no in-plane lattice rotation and a large lattice mismatch (13.6%). The second route involved the deposition of Ru at room temperature followed by in situ post-annealing at 700 °C. Transmission electron microscopy confirmed a very high quality of these films, free of crystal twinning, and a 30° in-plane lattice rotation relative to the substrate, resulting in a small in-plane lattice mismatch of –1.6%. X-ray reflectivity demonstrated smooth surfaces for films down to 7 nm thickness. 30 nm thick high quality single-crystalline Mn3Ga and Mn3Sn films were grown on top of the Ru buffer deposited using the second route as a first step to realize Mn3X films for antiferromagnetic spintronics applications.

First-Principles Evaluation of fcc Ruthenium for its use in Advanced Interconnects

As the semiconductor industry turns to alternate conductors to replace Cu for future interconnect nodes, much attention as been focused on evaluating the electrical performance of Ru. The typical hexagonal close-packed (hcp) phase has been extensively studied, but relatively little attention has been paid to the face-centered cubic (fcc) phase, which has been shown to nucleate in confined structures and may be present in tight-pitch interconnects. Using \emph{ab initio} techniques, we benchmark the performance of fcc Ru. We find that the phonon-limited bulk resistivity of the fcc Ru is less than half of that of hcp Ru, a feature we trace back to the stronger electron-phonon coupling elements that are geometrically inherited from the modified Fermi surface shape of the fcc crystal. Despite this benefit of the fcc phase, high grain boundary scattering results in increased resistivity compared to Cu-based interconnects with similar average grain size. We find, however, that the line resistance of fcc Ru is lower than that of Cu below 21 nm line width due to the conductor volume lost to adhesion and wetting liners. In addition to studying bulk transport properties, we evaluate the performance of adhesion liners for fcc Ru. We find that it is energetically more favorable for fcc Ru to bind directly to silicon dioxide than through conventional adhesion liners such as TaN and TiN. In the case that a thin liner is necessary for the Ru deposition technique, we find that the vertical resistance penalty of a liner for fcc Ru can be up to eight times lower than that calculated for conventional liners used for Cu interconnects. Our calculations, therefore, suggest that the formation of the fcc phase of Ru may be a beneficial for advanced, low-resistance interconnects.

Area-Selective ALD of Ru on Nanometer-Scale Cu Lines through Dimerization of Amino-Functionalized Alkoxy Silane Passivation Films.

The selective deposition of materials on predefined areas on a substrate is of crucial importance for various applications, such as energy harvesting, microelectronic device fabrication, and catalysis. A representative example of area-confined deposition is the selective deposition of a metal film as the interconnect material in multilevel metallization schemes for CMOS technology. This allows the formation of multilevel structures with standard lithographical techniques while minimizing pattern misalignment and overlay and improving the uniformity of the structures across the wafer. In this work, area-selective deposition of Ru by atomic layer deposition (ALD) is investigated using alkoxy siloxane dielectric passivation layers. In this work, a comparison of several silane organic SAM precursors in terms of Ru ALD ASD performance is reported. The importance of the surface areal concentration of the passivation molecules is demonstrated. According to the in situ X-ray photoelectron spectroscopy film characterization, the ALD blocking layers derived from a (3-trimethoxysilylpropyl) diethylenetriamine (DETA) precursor have the ability to polymerize under ALD-compatible temperatures, such as 250 °C, which leads to a significant inhibition of Ru growth up to 400 ALD cycles. At the same time, the DETA layer can be selectively removed from the oxidized Cu surface by rinsing in acetic acid, which allows selective deposition of ca. 14 nm of Ru on Cu with no Ru detected on the DETA-coated surface by RBS. The approach is successfully tested on 50 nm half-pitch patterned SiO2/Cu lines.

Ruthenium Electrodeposition from Water-in-Salt Electrolytes and the Influence of Tetrabutylammonium

The use of water-in-salt electrolytes is evaluated for the electrodeposition of metallic ruthenium. The mechanisms of proton reduction inhibition by concentrated LiCl and dilute tetrabutylammonium is evaluated. Concentrated LiCl is found to disrupt the hydrogen bonding network within the solution bulk, whereas TBA is found to adsorb onto the electrode surface, blocking proton access. Ruthenium exists as a different complexed species in water-in-salt electrolytes vs dilute aqueous electrolytes, leading to a −300 mV shift in the deposition onset potential. Greater current efficiencies of Ru deposition can be obtained when depositing at proton overpotentials by the use of water-in-salt electrolytes, and TBA can offer further improvements. The grain structure and resistivities of Ru thin films are studied.