RuO2 Loading Research Articles

Solar-driven thermo-photocatalytic CO2 methanation over a structured RuO2:TiO2/SBA-15 nanocomposite at low temperature

A new hybrid catalyst composed of mesostructured silica SBA-15 functionalized with TiO2 and further loaded with RuO2 was developed to efficiently promote thermo-photocatalytic CO2 hydrogenation into methane at low temperatures. The catalytic activity was assessed with respect to TiO2:RuO2 loading, catalyst dosage, illumination source (polychromatic sunlight and monochromatic LEDs) and power, [H2]:[CO2] molar ratio, temperature, and catalyst reusability. The best methanation yields were attained for the RuO2(6.4%):TiO2(16.9%)/SBA-15 nanocomposite at 150 ºC, under simulated sunlight (0.21 W) and stoichiometric [H2]:[CO2] molar ratio, reaching: a specific CH4 production rate of 13.6 mmol gcat-1 h-1; 99.8 % selectivity; 96.8 % CO2 conversion (110-min; 40 mL); and apparent photonic efficiency/quantum yield of 39.5 %/42.1 %. Considering only the active RuO2:TiO2 photocatalyst mass (23.3 %), the CH4 production rate increased to 58.6 mmol gactive_cat-1 h-1. Besides, this highly-active photocatalyst featured excellent UV-Vis-IR light absorbance, high surface area, and stability for reuse when moist gas was removed between cycles.

Dimensionally stable anodes for the oxygen evolution reaction: Ruthenium dioxide on a nickel metal substrate

Dimensionally stable anodes (DSA) for the oxygen evolution reaction (OER) gradually passivate under operating conditions due to the formation of insulating TiO2 at the interface of the Ti-metal substrate and the catalytically active metal oxide layer (typically a mixture of ruthenium and iridium oxides). The incorporation of a catalytically active, yet stable, interfacial buffer layer or substrate is a potential means of promoting the overall performance. Here, we prepared DSA-like RuO2 on Ni films by the thermal decomposition method and contrast their OER activity with an analogous RuO2 on Ti-metal film. The fabrication process resulted in the presence of NiO and Ni oxides/(oxy)hydroxides at the surface of the rutile RuO2 layer. Along with RuO2, the former species were active in the water splitting reaction under the testing conditions. Ni–RuO2 films showed lower OER overpotentials relative to Ti–RuO2 suggesting a synergistic effect between Ni- and Ru-oxides and the Ni layer between Ti and RuO2 to improve overall performance. Further studies should optimize the NiO–RuO2 loading levels, understand the NiO–RuO2 synergy toward catalytic performance and determine the stability under accelerated testing conditions.

A ternary composite RuO2@SWCNT/graphene for high performance electrochemical capacitors

A hybrid nanostructure of hydrous RuO2 nanoparticles deposited on the surface of SWCNT/graphene (S/G) composite has been prepared through a sol-gel process and low-temperature annealing. Benefiting from the combined advantages of graphene, SWCNTs and hydrous RuO2, the hybrid electrode material (RuO2@S/G-60 of 58.53% RuO2 loading) has a high specific capacitance of 988 F/g at a current density of 1 A/g and excellent rate performance. The results show that S/G is very suitable as a carbon skeleton of hydrous RuO2.

Effect of different RuO2 contents on selective catalytic oxidation of ammonia over RuO2-Fe2O3 catalysts

A series of RuO2-Fe2O3 catalysts varied in RuO2 loading were prepared by sol-gel method and used for selective catalytic oxidation of ammonia to nitrogen. The results indicated that all the RuO2-Fe2O3 catalysts showed an excellent low-temperature catalytic activity and the RuO2 loading played a key role in catalytic activity of ammonia oxidation. Moreover, the characterizations of BET, XRD, H2-TPR and DRIFTS were employed to investigate the relation between the physicochemical property of catalysts and catalytic activity. The research results elucidated that the introduction of RuO2 increased the surface area. The synergistic effect between RuO2 and Fe2O3 enhanced the redox property and the catalytic activity of ammonia oxidation. Meanwhile, the RuO2 loading gave the significant effect on surface acidity of catalysts. Lewis acid sites were predominant on the catalyst surface.

Metal organic frameworks-derived porous carbons/ruthenium oxide composite and its application in supercapacitor

In this study, we employed traditional method to synthesize zeolitic imidazolate framework-8 crystals (ZIF-8), one of the well-known metal organic frameworks (MOFs) with zeolite-like pore structure. Then, ZIF-8 crystal was served as a sacrificial template and carbon resource to prepare nanoporous carbons material (PCs) with high specific surface area (1230 m2 g−1) and abundant pore structure (average pore diameter is 2.8 nm). Finally, we used conventional reflux and subsequent thermal treatment to achieve composites, in which the PCs exploited as a substrate to grow ruthenium oxide (RuO2) nanoparticles on its surface. The resulting RuO2/PCs composite with 70.7 wt % RuO2 loading revealed excellent electrochemical performances in terms of high specific capacitance (539.6 F g−1 at 1 A g−1) and good rate capability (capacitance retain 81.5% at 200 A g−1 as compared to that of 1 A g−1) in three electrode system. Furthermore, the symmetric supercapacitor based on RuO2/PCs electrodes delivered a high energy density of 23.38 Wh kg−1 at a power density of 600 W kg−1, indicating a potential application prospect.

Ruthenium doped carbon aerogel with CO2 surface activation for enhanced electrochemical capacitance

With the aim of enhancement of electrochemical capacitance, CO2 activation of carbon aerogel (CA) prepared by polycondensation of resorcinol with formaldehyde was performed to obtain activated carbon aerogel (ACA) having improved surface area properties. Ruthenium oxide nano-particles were loaded by impregnation method for utilizing pseudo-capacitive property of ruthenium oxide (RuO2) and the effect of activation treatment was studied. RuO2 loading of 20% by weight was accomplished in CA and ACA to synthesize RuO2 doped carbon aerogel (CA/RuO2) and activated carbon aerogel (ACA/RuO2). While the specific capacitance of carbon aerogel improved from 95 to 153 F/g on activation, RuO2 loading further led to enhancement in capacitance and specific capacitance of 308 F/g was obtained for ACA/RuO2. The studies being important for Ru economy, showed the influence of surface area enhancement of base matrix in achieving high specific capacitance.

Enhancement of p-type gas-sensing performances of NiO nanoparticles prepared by precipitation with RuO2 impregnation

In this work, 0–1.00wt% Ru-loaded nickel oxide nanoparticles were synthesized by the chemical precipitation/impregnation methods and systematically characterized for gas-sensing applications. Characterizations by electron microscopy, X-ray diffractometry, X-ray photoemission spectroscopy showed that primary particles were face-centered-cubic structure of NiO and RuO2 nanoparticles were dispersed within larger NiO NPs. Nitrogen adsorption studies also revealed that specific surface area of RuO2/NiO nanoparticles increased with increasing Ru content. Gas-sensing measurement showed that increasing Ru loading content considerably improved C2H5OH response and selectivity against H2S, NO2, SO2, H2, and NH3 at an operating temperature of 350°C. In particular, the NiO sensor with the highest Ru content of 1.00wt% showed a high p-type sensor response of 35.9–2000ppmC2H5OH at 350°C, which was about three times as high as that of unloaded one. Therefore, RuO2 loading by impregnation is an effective mean to improve the gas-sensing performances of p-type NiO-based gas sensors.

Advanced RuO2/PEDOT Architecture for Flexible and Transparent Supercapacitors

The ever-increasing development of smart electronics requires powerful energy storage devices, in particular supercapacitors with flexible and transparent properties. Increasing the mass loading of active material promotes the specific capacity (or capacitance) at the expense of transparency and flexibility of the supercapacitor electrodes. Therefore in order to maintain high transmittance, thin films which constitute of pseudocapacitive material and conductive network would be highly desirable. Here we report on a RuO2/PEDOT hybrid thin film by a simple aerosol-jet spray technique. It was found that RuO2 loading and electrode thickness have great effects on the transmittance and sheet resistance of the thin film, which could be well explained and fitted via the percolation theory.1,2 By loading 40 wt.% RuO2, the hybrid thin film demonstrated a transmittance of 94%, a lowest sheet resistance and a highest areal capacitance (1.4 mF cm-2) among other hybrid films. The solid-state symmetric supercapacitor was assembled, which demonstrated fast-rate response and retained 100% of initial capacitance after 10000 cycles. When pairing up the hybrid thin film positive electrode with the PEDOT thin film negative electrode, the solid-state asymmetric supercapacitors exhibited a voltage window of 1.2 V and a transmittance of 84%. Furthermore, thin films with large area (100 cm2) was also sprayed and assembled into asymmetric solid-state supercapacitor, demonstrating its scalability.

Ruthenium Oxide/Reduced Graphene Oxide Nanoribbon Composite and Its Excellent Rate Capability in Supercapacitor Application

AbstractChemical oxidation is used to cut and unzip multi‐walled carbon nanotubes in the transverse direction and the axial direction to form graphene oxide nanoribbon (GONR). Ruthenium oxide/reduced graphene oxide nanoribbon composite (RuO2/rGONR) with a 72.5 wt% RuO2 loading is synthesized through an aqueous‐phase reaction, in which GONR is served as starting material, followed by mild thermal treatment in ambient air. The resulting RuO2/rGONR composite achieves specific capacitance up to 677 F·g−1 at the current density of 1 A·g−1 in three‐electrode system using 1 mol·L−1 H2SO4 as electrolyte. The resultant electrode exhibits an excellent rate capability (91.8% retention rate at 20 A·g−1). Especially, the symmetric supercapacitor assembled on the basis of RuO2/rGONR electrode delivers high energy density (16.2 Wh·kg−1) even at the power density of 9885 W·kg−1, which is very essential for supercapacitors.

New Insights into the Photocatalytic Properties of RuO2/TiO2 Mesoporous Heterostructures for Hydrogen Production and Organic Pollutant Photodecomposition

Photocatalytic activities of mesoporous RuO2/TiO2 heterojunction nanocomposites for organic dye decomposition and H2 production by methanol photoreforming have been studied as a function of the RuO2 loading in the 1–10 wt % range. An optimum RuO2 loading was evidenced for both kinds of reaction, the corresponding nanocomposites showing much higher activities than pure TiO2 and commercial reference P25. Thus, 1 wt % RuO2/TiO2 photocatalyst led to the highest rates for the degradation of cationic (methylene blue) and anionic (methyl orange) dyes under UV light illumination. To get a better understanding of the mechanisms involved, a comprehensive investigation on the photogenerated charge carriers, detected by electron spin resonance (ESR) spectroscopy in the form of O–, Ti3+, and O2– trapping centers, was performed. Along with the key role of superoxide paramagnetic species in the photodecomposition of organic dyes, ESR measurements revealed a higher amount of trapped holes in the case of the 1 wt % RuO2/T...

Amorphous RuO2 coated on carbon spheres as excellent electrode materials for supercapacitors

Significant enhancement in supercapacitor performances was achieved by the first fabrication of amorphous RuO2 hybrid by utilising carbon spheres as templates. The as-prepared carbon spheres (Cs)/RuO2 and reduced carbon spheres (rCs)/RuO2 composites exhibit high specific capacitances of 387 F g−1 (44.2 wt% RuO2 loading) and 614 F g−1 (72.6 wt% RuO2 loading) at a current density of 1 A g−1 at 2 mg cm−2 loading mass, showing remarkable rate capability with capacitances of 336 F g−1 and 491 F g−1 at a current density of 20 A g−1 and excellent cycling stability with capacity retention of 97.7% and 90.8% for 5000 cycles. The enhanced electrochemical performances could be attributed to the unique structure of the resulted composites as well as the high utilization of well-dispersed RuO2 nanoparticles on the carbon surface. These results demonstrate the great potential of carbon sphere-based composites in the development of high-performance electrode materials for supercapacitors.

Synthesis of RuO2 decorated quasi graphene nanosheets and their application in supercapacitors

Multiwalled carbon nanotubes (MWCNTs) are split along the longitudinal direction to form quasi graphene oxide (QGO) by modified Hummers method and quasi graphene nanosheet/RuO2 (QGN/RuO2) composites with 40.0 wt% RuO2 loading are prepared by a one-step hydrothermal synthesis without any reducing agent. The characterization of morphology and structure shows that the amorphous RuO2 nanoparticles are uniformly dispersed on all the surfaces of QGN. The electrochemical measurements show that the QGN/RuO2 composites exhibit good capacitive properties compared to pure RuO2 and pure QGN in acidic, alkaline and even in neutral electrolytes. The specific capacitances of QGN/RuO2 in 1 M KOH, 1 M H2SO4, and 1 M Na2SO4 are 453.7, 415.7, 287.5 F g−1. Significantly, the QGN/RuO2 composites can achieve a high voltage window of 1.6 V and greatly increase the energy density (102.2 W h kg−1) and power density (1600 W kg−1) of supercapacitors in 1 M Na2SO4 (1 A g−1). These results demonstrate that the QGN/RuO2 composites are a promising material for high-performance supercapacitors.

Quasi-solid-state pseudocapacitors using proton-conducting gel polymer electrolyte and poly(3-methyl thiophene)–ruthenium oxide composite electrodes

We report the studies on a flexible quasi-solid-state configuration of the redox supercapacitors (pseudocapacitors) assembled with an ionic liquid-based proton conducting non-aqueous gel polymer electrolyte (ILGPE) and composite electrodes of conducting polymer [poly-3-methyl thiophene (pMeT)] and hydrous ruthenium dioxide (RuO2.xH2O). The presence of RuO2.xH2O in the composite electrodes has been confirmed by X-ray diffraction and thermogravimetric analysis. The ILGPE films, prepared with the solution of an ionic liquid (1-ethyl 3-methyl imidazolium trifluoromethanesulfonate) and a salt ammonium trifluoromethanesulfonate entrapped in a host polymer poly(vinylidene fluoride-co-hexafluoropropylene), have been characterized. The symmetrical pseudocapacitors have been assembled and characterized using electrochemical impedance spectroscopy, cyclic voltammetry, and charge–discharge tests. The composite electrodes with the ∼13 wt.% hydrous RuO2 loading in pMeT film has shown a maximum specific capacitance value of ∼118 F g−1 (of the composite electrode material). The corresponding maximum specific energy and power density have been found to be ∼12.8 W kg−1 and ∼513 W kg−1, respectively. With further increase in the content of RuO2.xH2O, a slight decrease in specific capacitance value has been observed, which indicates the reduction in utilization rate of RuO2.xH2O. The composite electrodes show stable capacitance values up to 5,000 charge–discharge cycles.

Photocatalytic Synthesis of Acetaldehyde by Selective Oxidation of Ethanol on Ruox-vox/tio2

The gas-solid photocatalytic partial oxidation of ethanol to acetaldehyde on monometallic RuOx/TiO2 and bimetallic RuOx-VOx/TiO2 catalysts has been studied in a fluidized bed photoreactor at high illumination efficiency. For RuOx/TiO2, by increasing ruthenium loading ethanol conversion decreased from 60 to 37 %, while acetaldehyde selectivity increased to about 97 % at 0.4 wt % RuO2 loading. With bimetallic RuOxVOx/TiO2 the selective yield to acetaldehyde by monometallic Ru based catalysts is enhanced by the highly active V species, resulting in higher photocatalytic performance. By increasing the vanadium loading, ethanol conversion increased up to 100 % with almost total selectivity to acetaldehyde.

Fabrication and supercapacitive properties of a thick electrode of carbon nanotube–RuO2 core–shell hybrid material with a high RuO2 loading

A core-shell hybrid material of amorphous hydrous RuO2-coated carbon nanotubes (CNT–RuO2) with a RuO2 loading as high as 82.4wt% was prepared by a solution method using RuCl3 and NaHCO3 aqueous solutions. The effect of preparation conditions, especially the dripping speed of the NaHCO3 solution, on the formation of the core-shell structure was investigated, and the corresponding mechanism was discussed. Supercapacitive properties of the CNT–RuO2 and amorphous hydrous RuO2 electrodes with a thickness of over 200μm were studied and the crucial factors to govern their rate capability were analyzed. For the thick CNT–RuO2 electrode, a comparison of its specific capacitance before and after subtracting the effect of the voltage drop of discharge curves caused by the inner resistance of the CNT–RuO2 symmetrical supercapacitor indicates that electronic conductivity is more important than proton diffusion in determining its rate capability.

Titanium–indium oxy(nitride) with and without RuO2 loading as photocatalysts for hydrogen production under visible light from water

Titanium–indium (oxy)nitride composite materials with and without RuO2 loadings were produced by treating TiO2–In2O3 mixed powders with ammonia at high temperature (700–850°C) (Elemental analysis indicated an empirical formula of TiIn0.029O0.63N1.4).We have found that ammonolysis of TiO2 to form Ti (oxy)nitride or In2O3 to form In (oxy)nitride do not give composites active toward methanol–water under visible light, but TiO2 and In2O3 mixed together do give composites active toward methanol–water under visible light. Ti–In (oxy)nitride powders modified by surface loading with RuO2 nanoparticles at 3wt% achieves the highest H2 evolution activity under visible light irradiation. The composite material did not react in the dark, but upon irradiation with visible light, the hydrogen production rate under illumination goes way up to 30μmolh−1 and the turnover number shows that this is a photocatalytic reaction.

BaCeO 3 as a novel photocatalyst with 4f electronic configuration for water splitting

Photocatalytic water splitting properties of BaCeO 3 were investigated experimentally and theoretically. Photocatalytic evaluation results showed that H 2 and O 2 evolved from aqueous solutions containing CH 3OH and AgNO 3 sacrificial reagents, respectively, and overall water splitting was achieved with the aid of RuO 2-loading under ultraviolet light irradiation. Density function theory calculation indicated that the valence band of BaCeO 3 was mainly composed of O 2p orbitals, while the conduction band was dominantly constructed by Ce 4f orbitals.

Promotion effect of nanosized Pt, RuO2 and NiOx loading on visible light-driven photocatalysts K4Ce2M10O30 (M = Ta, Nb) for hydrogen evolution from water decomposition

Metal oxide photocatalysts K4Ce2M10O30 (M = Ta, Nb) capable of responding to visible light were synthesized by conventional high temperature solid-state reaction. The photocatalysts have an appropriate band gap energy ca. 1.8–2.3 eV and excellent chemical potential level to evolve H2 from aqueous solutions containing a sacrificial electron donor (Na2SO3) under visible light irradiation (λ>420 nm) without any co-catalyst. When they were loading with Pt, RuO2 and NiOx, the activities for evolving H2 were prompted markedly. By SEM and TEM investigations, it can be seen that these loading K4Ce2M10O30 (M = Ta, Nb) in diameter of about 10–30nm particles, especially the NiOx loading even formed double layered structure with metal nickel (Ni) and metal oxide (NiO). The reasons for the increasing activities after these loading electron migrating from the conduction band of K4Ce2M10O30 (M =Ta, Nb) to the Pt, RuO2 and NiOx nanoparticles, which function as H2 production sites on the surface of catalysts. The same phenomenon appears on the solid solution K4Ce2Ta10 –xNbxO30 (x = 0–10) with loading RuO2.

Simultaneous determination of chlorine and oxygen evolving at RuO2/Ti and RuO2-TiO2/Ti anodes by differential electrochemical mass spectroscopy

Chlorine and oxygen evolving at RuO2/Ti and RuO2–TiO2/Ti anodes have been simultaneously determined at electrode potentials from 1.0 to about 2V (vs Ag/AgCl) by differential electrochemical mass spectroscopy (DEMS). On the RuO2/Ti anodes, the threshold electrode potential for oxygen evolution increased with a decrease in RuO2 loading, while the chlorine evolution potential was unchanged. Low RuO2 loading anodes gave a high chlorine evolution ratio under various constant electrolysis potentials. On the RuO2–TiO2/Ti anodes, the threshold electrode potential for oxygen evolution increased with an increase in the TiO2 content more remarkably than that for chlorine evolution. High TiO2 content anodes gave a high chlorine evolution ratio at various constant electrolysis potentials. The combination of RuO2 and TiO2 exhibits a remarkable effect with respect to the enhancement of chlorine evolution selectivity.

Doped TiO 2 for solar energy applications

TiO 2 samples were prepared from TiCl 3 solution or TiCl 4 with or without 0.5a/o Cr, 0.5a/o Mn or 0.25a/o of each. The samples were heated under vacuum (for 6 hrs) at 600°C or in H 2/N 2 (for 6.5 hrs) at 500°C. Two Cr-doped samples were loaded with RuO 2 (using RuCl 3 solutions). The reflectance spectra of the powders were recorded using a Perkin Elmer 330 spectrophotometer over the range 200–800 nm. The spectra of the undoped and Cr-doped samples demonstrated the increased visible absorption on doping, with further improvements on heating and after RuO 2-loading. The effects were more marked for the samples prepared from TiCl 3. The Mn-doped samples and the Cr/Mn-doped samples exhibited similar trends of increased absorption. Maximum visible absorption was observed for the Mn-doped or Cr/Mn-doped samples, the improvement surpassing the effect of Ru-loading of Cr-doped samples. The effect of the latter was more pronounced for the sample prepared from TiCl 3 compared to TiCl 4. Little effect on the spectrum resulted from irradiation with visible light. Preliminary work on the reduction of CO 2 solution containing EDTA in a suspension of Pt-loaded TiO 2, demonstrated the formation of HCHO on irradiation with a medium pressure mercury lamp. The latter was determined by gas chromatography and colorimetrically.