RuO2 Nanoparticles Research Articles

Synergistic Engineering of Dopant and Support of Ru Oxide Catalyst Enables Ultrahigh Performance for Acidic Oxygen Evolution

AbstractActive and robust electrocatalysts for acidic oxygen evolution reaction (OER) are of crucial importance for efficient proton exchange membrane water electrolyzer (PEM‐WE). Ruthenium (Ru) oxide has attracted considerable attention due to its high activity. However, the unsatisfying stability of Ru oxide in acidic OER environments hinders the application. Here, Ce‐doped RuO2 nanoparticles are designed and supported on Co─N─C material (Ce@RuO2/CoNC) for acidic OER. It is demonstrated that Ce@RuO2/CoNC delivers a super low overpotential of 150 mV and an excellent stability of 1000 h at 10 mA cm−2, outperforming most previously reported Ru‐based catalysts. The mass activity is estimated as 2365.5 AgRu−1 at 1.5 V (vs RHE), representing ≈2× advance compared to the best prior study. Furthermore, applied in a single‐cell PEM‐WE device, it can steadily operate for 1000 h at 200 mA cm−2. The studies show that Ce‐doping and Co─N─C support synergistically enhance the activity and stability of Ru oxide by optimizing the free energies of OER intermediates and suppressing the dissolution of Ru.

Trace RuO2 nanoparticles loaded nickel-coated multi-walled carbon nanotubes to boost hydrogen evolution reaction under acidic and alkaline media

Developing low-cost catalysts with high activity for the Hydrogen Evolution Reaction (HER) is a main challenge to reduce the dependence on precious metals while maintaining the catalytic activity. In this study, nickel-plated multi-walled carbon nanotubes (Ni-MWCNTs) with a large number of active sites were selected, and Ni-MWCNTs electrocatalysts loaded with trace amounts of RuO2 nanoparticles were prepared by annealing treatment, which exhibited excellent HER performances in both acidic and alkaline media. The RuO2 nanoparticles loaded nickel-coated multi-walled carbon nanotubes (RuO2@Ni-MWCNTs) had a small electrochemical impedance spectrum (EIS) and a large electrochemically active surface area (ECSA). Notably, RuO2@Ni-MWCNTs with less than 1 % Ru content exhibited excellent catalytic activities in both acidic and alkaline solutions. The results showed that the overpotentials of RuO2@Ni-MWCNTs were 20.2 mV (alkaline) and 73.7 mV (acidic), respectively. After stabilization at 20 mA cm−2 for 90 h, the evaluation results showed that RuO2@Ni-MWCNTs could maintain their catalytic efficiency without significant degradation.

Influence of the presence of RuO2 on the reactivity of Fe2O3 in the artificial photosynthesis reaction

Surface Plasmonic Resonance (SPR) is the oscillation of free electrons on the surface of a metal or metallic particle upon irradiation with light of a certain frequency. The incorporation of Fe2O3 (a H2O oxidising photocatalyst) with plasmonic RuO2 nanoparticles to form a composite is studied. XRD results show that RuO2 is formed in the rutile phase while Fe2O3 is rhombohedral and also suggests doping of the Fe2O3 lattice with Ru atoms in the composite. UV-Vis spectroscopy shows that RuO2 exhibits a plasmon peak at 511 nm, and CO2-TPD experiments show that RuO2 adsorbs and desorbs CO2. TEM also shows that the RuO2 particles are spherical, as are the Fe2O3 particles with some irregular polyhedra present, too. The composite is a mixture of these two morphologies. The effect of composite formation on the activity of the materials in the artificial photosynthesis reaction is dramatic. Neither RuO2 nor Fe2O3 alone produce significant quantities of gaseous CH4 or CO products. However, the composite material produces both (as well as generating levels of unidentified adsorbed hydrocarbonaceous species). This reactivity is ascribed to the generation of a heterojunction in the composite material. It is suggested that the generation of holes in Fe2O3 is used to provide protons (from H2O oxidation), and the decay of an SPR response on RuO2 provides hot electrons, which together with the protons reduce CO2 to produce CH4, CO and adsorbed hydrocarbonaceous species.

Ultrasensitive xylene sensor based on RuO2-modified BiVO4 nanosheets

Two-dimensional (2D) BiVO4 nanosheets (NSs), featuring distinctive chemical properties and dangling-bond-rich surfaces, are promising for developing high-performance gas sensors. However, the previously reported 2D BiVO4 NSs-based devices suffer from a low responsivity and poor selectivity. In this work, we introduce RuO2 nanoparticles to boost the gas sensing properties of 2D BiVO4 NSs-based sensor. Intriguingly, the RuO2-decoration changes the selectivity of the corresponding gas sensor from acetone to xylene. Compared to the pristine BiVO4 sensor, the RuO2-BiVO4 sensor displays a reduced optimal operating temperature of 260℃ and exhibits a response of 19.0–5 ppm xylene, reaching a five-fold enhancement. Simultaneously, the RuO2-BiVO4 sensor also exhibits a rapid response and recovery time of 10 and 25 s respectively, as well as robust long-term stability with less than 5 % variation in response after a storage of 60 days. The improvement in sensing performance can be attributed to the RuO2-decoration from three aspects: heterojunction construction, surface state modulation and gas oxidation catalysis on the surface. This work not only provides a high-performance xylene sensing material but also provides insightful comprehension regarding the modification effects of RuO2.

In situ enhanced chlorine oxide radical generation on a novel space-confined photoanode and its application for ammonia oxidation: Structure, performance, and mechanism

Oxidizing ammonia to nitrogen is a challenge in wastewater treatment. For this challenge ammonia oxidation via chlorine oxide radicals has been proved to be a potential method. In this study, a space-confined photoanode was designed and prepared by loading RuO2 nanoparticles on TiO2/WO3 nanowires for in situ enhancing the generation of chlorine oxide radical. Scanning electron microscopy characterization confirmed that RuO2 nanoparticles were uniformly deposited on TiO2/WO3 nanowires. The generation of chlorine oxide radical was markedly boosted, and its steady-state concentration reached 2.76 × 10−12 M. This value was 3 times that of the traditional bifacial electrode (a type of electrode that has been widely used for chlorine oxide radical-related research). As a result, ammonia oxidation was greatly enhanced. In 90 min, 31.9 mg/L ammonia nitrogen could be degraded, yet only 0.94 mg/L nitrate was accumulated. In addition, the space-confined photoanode exhibited good performance for real wastewater treatment, and 41.0 mg/L ammonia nitrogen could be oxidized in 135 min. During photoelectrocatalysis, a synergistic index (47.7 %) was obtained. Besides the synergistic effect between photocatalysis and electrocatalysis, the unique morphology and structural design (TiO2/WO3 and RuO2 were mainly responsible to hydroxyl radical generation and free chlorine production, respectively) also synergistically promoted the generation of chlorine oxide radical, thereby improving ammonia oxidation. The mechanism for ammonia oxidation via chlorine oxide radicals over the space-confined photoanode was proposed based on experimental results and theoretical calculations.

Carbon Nanotube Support, Carbon Loricae and Oxygen Defect Co-Promoted Superior Activities and Excellent Durability of RuO2 Nanoparticles Towards the pH-Universal H2 Evolution.

This work reports a strategy that integrates the carbon nanotube (CNT) supporting, ultrathin carbon coating and oxygen defect generation to fabricate the RuO2 based catalysts toward the pH-universal hydrogen evolution reaction (HER) with high efficiencies. Specifically, the CNT supported RuO2 nanoparticles with ultrathin carbon loricae and rich oxygen vacancies at the surface (C@OV-RuO2/CNTs-325) have been synthesized. The C@OV-RuO2/CNTs-325 shows superior activities and excellent durability for the HER. It only requires overpotentials of 36.1, 18.0, and 19.3mV to deliver -10mA cm-2 in the acidic, neutral, and alkaline media, respectively. Its HER activities are comparable to that of the Pt/C in the acidic media but higher than those of the Pt/C in the neutral and alkaline media. The C@OV-RuO2/CNTs-325 shows excellent HER durability with no activity losses for > 500h in the acidic, neutral or alkaline media at -250mA cm-2. The density-functional-theory calculations indicate that the CNT supporting, the carbon coating, and the OVs can modulate the d-band centers of Ru, increasing the HER activities of C@OV-RuO2/CNTs-325, and stabilize the Ru atoms in the catalyst, increasing the durability of the C@OV-RuO2/CNTs-325. More interestingly, the C@OV-RuO2/CNTs-325 shows great potential for practical applications toward overall seawater splitting.

Low-Temperature Wastewater Electrolysis for H2 and Clean Water Generation

Water electrolysis represents a sustainable approach to produce green hydrogen (H2); however, the high energy cost (H2O → 2H+ + 2e- + ½O2, ∆H° = 275 kJ/mol H2, E° = −1.18 V) associated with water electrolysis and electricity cost (>$50/MWh) results in a minimum H2 selling price ≈$4/kg H2. Hence, we need to find alternative process to generate H2 to meet the current U.S. Department of Energy's (DOE's) Energy Earthshots of $1/kg H2 in one decade.Wastewater electrolysis represents an alternative approach to generate H2 with renewable sources by electrochemically oxidizing organic molecules to generate H2 (e.g., CH3COOH + 2H2O → 2CO2 + 8e- + 8H+, ∆H° = 53 kJ/mol, E° = −0.02 V,) which has up to 5 times lower energy requirement than water electrolysis. As opposed to water electrolysis that requires clean water streams, wastewater electrolysis uses readily available waste streams that need cleanup anyway to generate H2; hence, integrating a second application in addition to H2 generation.1-3 In this work, we compare the performance of heterogeneous electrocatalysts for the electrocatalytic oxidation (ECO) of organic molecules present in wastewater as well as electrocatalysts for the H2 evolution reaction (HER) at room temperature. ECO electrocatalysts were developed and tested using real wastewaters derived from several sources including the hydrothermal liquefaction (HTL) of food waste. We synthesized the ECO electrocatalysts using both platinum-group metals (PGM) as well as base-group metals (BGM) with equimolar loadings and tested them as a function of half-cell potential. Our results show that both PGM- and BGM-based bimetallics improve the activity and stability compared to the baseline RuO2-based catalysts4-6. We performed a preliminary techno-economic analysis and showed that the levelized costs of using this technology to process the wastewater alone is equivalent to that of traditional wastewater processing. The sale of the produced H2 co-product will decrease the levelized processing cost below that of current wastewater processing. References Andrews, E.; Lopez-Ruiz, J. A.; Egbert, J. D.; Koh, K.; Sanyal, U.; Song, M.; Li, D.; Karkamkar, A. J.; Derewinski, M. A.; Holladay, J.; Gutiérrez, O. Y.; Holladay, J. D., Performance of Base and Noble Metals for Electrocatalytic Hydrogenation of Bio-Oil-Derived Oxygenated Compounds. ACS Sustainable Chemistry & Engineering 2020, 8 (11), 4407-4418.Lopez-Ruiz, J. A.; Qiu, Y.; Andrews, E.; Gutiérrez, O. Y.; Holladay, J. D., Electrocatalytic valorization into H2 and hydrocarbons of an aqueous stream derived from hydrothermal liquefaction. Journal of Applied Electrochemistry 2021, 51 (1), 107-118.Lopez-Ruiz, J. A.; Andrews, E.; Akhade, S. A.; Lee, M.-S.; Koh, K.; Sanyal, U.; Yuk, S. F.; Karkamkar, A. J.; Derewinski, M. A.; Holladay, J.; Glezakou, V.-A.; Rousseau, R.; Gutiérrez, O. Y.; Holladay, J. D., Understanding the Role of Metal and Molecular Structure on the Electrocatalytic Hydrogenation of Oxygenated Organic Compounds. ACS Catalysis 2019, 9 (11), 9964-9972.Qiu, Y.; Lopez-Ruiz, J. A.; Zhu, G.; Engelhard, M. H.; Gutiérrez, O. Y.; Holladay, J. D., Electrocatalytic decarboxylation of carboxylic acids over RuO2 and Pt nanoparticles. Appl. Catal. B-Environ. 2022, 305, 121060.Lopez-Ruiz, J. A.; Qiu, Y.; Andrews, E.; Gutiérrez, O. Y.; Holladay, J. D., Electrocatalytic valorization into H2 and hydrocarbons of an aqueous stream derived from hydrothermal liquefaction. J. Appl. Electrochem. 2021, 51 (1), 107-118.Qiu, Y.; Lopez-Ruiz, J. A.; Sanyal, U.; Andrews, E.; Gutiérrez, O. Y.; Holladay, J. D., Anodic electrocatalytic conversion of carboxylic acids on thin films of RuO2, IrO2, and Pt. Appl. Catal. B-Environ. 2020, 277, 119277. Figure 1

Enhanced hydrogen evolution in neutral media via proximity effect of Ru/RuO2-TiO2 nanocatalysts

Ru-based nanomaterials have been demonstrated to be highly active electrocatalysts for hydrogen evolution reaction (HER), yet weak water adsorption and splitting ability in neutral media thus it is rather difficult for the intermediates to adsorb on the active site. Herein, we introduce a concept of the proximity effect, comprising adjacent Ru and RuO2 nanoparticles coupled on TiO2 (Ru/RuO2-TiO2), for the synergic promotion of water molecule adsorption and splitting, significantly enhancing HER electrocatalysis performance. The in-situ spectroscopy experiments and density function theory (DFT) simulations demonstrated that the proximity effect between the adjacent Ru nanoparticles and RuO2 nanoparticles can accelerate water adsorption and splitting. As a result, the as-made Ru/RuO2-TiO2 only need overpotentials of 52.7, 16.0, and 16.4 mV to achieve the current density of 10 mA cm–2 in neutral, acid, and alkaline media, respectively. The mass activity of Ru/RuO2-TiO2 in neutral media is 320 and 117 times higher than that of commercial Ru/C and Pt/C at the overpotential of 100 mV, respectively. This work emphasizes the proximity effect for activation of reactants which can be extended to other electrocatalytic reactions.

Investigation and Comparative Studies on Charge Storage Performance in Nanostructured RuO2, NiO and Co3O4 Nanoparticles for High Dense Energy Storage

Investigation and Comparative Studies on Charge Storage Performance in Nanostructured RuO2, NiO and Co3O4 Nanoparticles for High Dense Energy Storage

Bovine Serum Albumin Template-Mediated Fabrication of Ruthenium Dioxide/Multiwalled Carbon Nanotubes: High-Performance Electrochemical Dopamine Biosensing in Human Serum.

The presence of abnormal dopamine (DA) levels may cause serious neurological disorders, therefore, the quantitative analysis of DA and its related research are of great significance for ensuring health. Herein, the bovine serum albumin (BSA) template method has been proposed for the preparation of catalytically high-performance ruthenium dioxide/multiwalled carbon nanotube (RuO2/MWCNT) nanocomposites. The incorporation of MWCNTs has improved the active surface area and conductivity while effectively preventing the aggregation of RuO2 nanoparticles. The outstanding electrocatalytic performance of RuO2/MWCNTs has promoted the electro-oxidation of DA at neutral pH. The electrochemical sensing platform based on RuO2/MWCNTs has demonstrated a wide linear range (0.5 to 111.1 μM), low detection limit (0.167 μM), excellent selectivity, long-term stability, and good reproducibility for DA detection. The satisfactory recovery range of 94.7% to 103% exhibited by the proposed sensing podium in serum samples signifies its potential for analytical applications. The aforementioned results reveal that RuO2/MWCNT nanostructures hold promising aptitude in the electrochemical sensor to detect DA in real samples, further offering broad prospects in clinical and medical diagnosis.

A TiO2 nanotube photoanode (blue TiO2 nanotube/RuO2/BiVO4) for efficient acetaminophen degradation and nitrogen removal

To simultaneously remove organic carbon and nitrogen, especially from wastewater containing organic amine compounds, a nanotube photoanode was prepared by depositing RuO2 and BiVO4 nanoparticles in and on a blue TiO2 nanotube substrate (BTNT/RuO2/BiVO4). The synthesized materials were systematically characterized by scanning electron microscope, energy-dispersive X-ray, X-ray diffraction, X-ray photoelectron spectroscopy, and electrochemical tests. Acetaminophen, a commonly used pharmaceutical with an amine group, was used as the model pollutant to examine the performance of the prepared electrodes. The results indicated that acetaminophen could be degraded by 100 % in 180 min over BTNT/RuO2/BiVO4 with a rate constant of 0.0338 min−1, which was 25.0 and 1.1 times higher than those obtained over BTNT/BiVO4 and BTNT/RuO2, respectively. Meanwhile, 81.3 % of total nitrogen could be removed. Compared with BTNT/BiVO4 and BTNT/RuO2, BTNT/RuO2/BiVO4 had a significant synergistic effect, and the synergy index reached to 47.7 %. Additionally, BTNT/RuO2/BiVO4 exhibited good stability, high current efficiency (63.2 %) and low energy consumption (0.020 kWh·g COD−1). The good performance of BTNT/RuO2/BiVO4 was mainly attributed to the enhanced formation of ClO· resulted from the synergistic interaction between RuO2 and BiVO4 due to the spatial confinement effect. Lastly, a possible reaction mechanism via ClO· over BTNT/RuO2/BiVO4 was proposed.

Visible light photocatalysis enhancement by Ag3PO4 decorated with RuO2 nanoparticles

In this study, we employed the precipitation method to synthesize nanoparticles of silver phosphate doped with ruthenium, utilizing synthesized silver phosphate and ruthenium trichloride trihydrate as precursors. The investigation of structural, chemical, and morphological characteristics was conducted through X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and photoluminescence spectroscopy. The degradation of the methylene blue dye in aqueous solutions at room temperature was catalyzed by the synthesized ruthenium-doped silver phosphate nanoparticles. When the process was conducted without the photocatalyst or light, the photodegradation of dyes was minimal. The photocatalytic activity of ruthenium-doped silver phosphate nanoparticles was assessed and contrasted with that of its control counterpart, pure silver phosphate. The obtained ruthenium-doped silver phosphate nanoparticles exhibit a significant improvement in dye degradation rate, compared to pure silver phosphate, which is evidenced by the increased visible light absorption brought on by the presence of ruthenium in silver phosphate crystallite sites, which produced well-separated photo-generated electron and hole pairs when illuminated by visible light.

Interfacial Ru centers coupling with oxygen vacancies in VO-RuO2@CA hybrid aerogel boosts acidic water oxidation

The exploitation of highly active, cheap cost and durable electrocatalyst for acidic water oxidation reaction still presents a major technological and scientific challenge in proton exchange membrane water electrolysers (PEMWEs). Herein, a hybrid aerogel of oxygen defect-rich RuO2 nanoparticles coupling with carbon (VO-RuO2@CA) was designed to promote their activity and stability during acid water oxidation. The optimized VO-RuO2@CA achieves an ultralow overpotential of 207 mV at 10 mA cm−2 for acidic water oxidation and sustains a prominent long-term stability during the 30 h chronopotentiometry test in 0.5 M H2SO4. Furthermore, VO-RuO2@CA exhibits high mass activities of 186.5 mA mgRu−1 and TOF values of up to 2.07 s−1 at an overpotential of 300 mV, being 17.7 and 4.8 times higher than commercial RuO2, respectively. Theory calculations and experimental results verify that the oxygen vacancies (VO) could significantly weaken the binding energy of O* with respect to OOH* for the interfacial Ru centers between RuO2 and carbon, rendering the increase of the intrinsic water oxidation activity and resistance to over-oxidation for RuO2. This research provides a novel pathway to explore remarkably efficient 3D porous hybrid aerogel electrocatalysts toward anodic electrocatalysts applications in PEMWEs.

High-temperature planar heating elements using RuO2 nanosheets

Planar heating elements employ carbon nanotubes, graphene, and metals. However, the high-temperature (300–500 °C) applications of heating elements based on metallic and organic materials are limited because they oxidize at high temperatures. Oxide materials such as RuO2 are promising alternatives. The electrical conductivity of heating elements are strongly dependent on the aspect ratios of fillers; thus, RuO2 nanosheets are suitable fillers for high-temperature planar heating elements because RuO2 remains stable at high temperatures, and RuO2 nanosheets have high aspect ratios of over 1000, as the lateral sizes and thicknesses of the RuO2 nanosheets are 2∼5 μm and 1–3 nm, respectively. Consequently, the electrical conductivity of planar heating elements using RuO2 nanosheets as fillers is 940 times higher than that of heating elements using conventional granular RuO2 nanoparticles. Therefore, the RuO2 nanosheet-based heating elements will be suitable in various applications requiring high temperatures and high uniformity.

Synergistic Interfacial Effect of Ru/Co3O4 Heterojunctions for Boosting Overall Water Splitting.

Low-cost bifunctional electrocatalysts capable of efficiently driving the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are needed for the growth of a green hydrogen economy. Herein, a Ru/Co3O4 heterojunction catalyst rich in oxygen vacancies (VO) and supported on carbon cloth (RCO-VO@CC) is prepared via a solid phase reaction (SPR) strategy. A RuO2/Co9S8@CC precursor (ROC@CC) is first prepared by loading Co9S8 nanosheets onto CC, following the addition of RuO2 nanoparticles (NPs). After the SPR process in an Ar atmosphere, Ru/Co3O4 heterojunctions with abundant VO are formed on the CC. The compositionally optimized RCO-VO@CC electrocatalyst with a Ru content of 0.55wt.% exhibits very low overpotential values of 11 and 253mV at 10mA cm-2 for HER and OER, respectively, in 1m KOH. Further, a low cell voltage of only 1.49V is required to achieve a current density of 10mA cm-2. Density functional theoretical calculations verify that the outstanding bifunctional electrocatalytic performance originates from synergistic charge transfer between Ru metal and VO-rich Co3O4. This work reports a novel approach toward a high-efficiency HER/OER electrocatalyst for energy storage and conversion.

Structural characterization and dielectric properties of ternary polyaniline/berlin blue/ruthenium dioxide nanocomposite

ABSTRACT A ternary nanocomposite composed of polyaniline/berlin blue/ruthenium dioxide, i.e. PANI/BB/RuO2 was synthesized through a one-pot process using ammonium persulfate as a strong oxidizing agent in H2SO4 medium. The structure, morphology, thermal and optical properties of unary PANI, BB, RuO2, and ternary PANI/BB/RuO2 nanomaterials were analyzed through FTIR, XRD, FESEM, TGA, and UV-Vis techniques. The FTIR and XRD studies confirmed the formation of ternary nanocomposite. FESEM analysis revealed the homogenous structure with uniform distribution of PANI, BB, and RuO2 nanoparticles in the ternary nanocomposite. From UV-Vis studies, a low optical band gap value was obtained for PANI/BB/RuO2 nanocomposite in comparison to PANI nanoparticles. Further, the dielectric behavior of the unary and ternary nanomaterials was analyzed through various parameters such as dielectric constant, dielectric loss, real and imaginary parts of electric modulus in the frequency range of 10 Hz−1 MHz by varying the temperature. It was found that ternary PANI/BB/RuO2 nanocomposite exhibits high dielectric constant and electric modulus (150°C) compared to unary nanoparticles. Hence, PANI/BB/RuO2 can serve as a suitable dielectric material for energy storage devices such as in solid-state capacitors.

Enhanced electrocatalytic activity in hydrogen evolution reaction using 2D/2D nanohybrids of ruthenate nanoflakes and graphitic carbon nitride.

Photoelectrochemical and electrochemical water splitting was examined using ruthenate nanoflake (RuNF) and graphitic carbon nitride (g-C3N4) hybrids. A two-dimensional and visible-light-responsive photocatalyst g-C3N4 was hybridized with the RuNFs that we recently synthesized via a bottom-up process in aqueous solution, yielding 2D/2D nanocomposites. The influence of the 2D/2D nanocomposites on oxygen and hydrogen evolution during photoelectrochemical and electrochemical water splitting was investigated. First, electrolysis of a Na2SO4 aqueous solution was conducted with intermittent photo-irradiation. Both the g-C3N4 electrode and the RuNF/g-C3N4 hybrid electrode provided anodic and cathodic photocurrents at high and low potentials, respectively; however, the copresence of RuNFs decreased the photocurrents, probably because the RuNFs retarded the light absorption by g-C3N4. Moreover, the use of RuNF/g-C3N4 hybrids as electrodes facilitated both the oxygen and hydrogen evolution reactions without photo-irradiation. However, for the oxygen evolution reaction, the effect of the RuNFs was similar to that of RuO2 nanoparticles, indicating that the influence of the type and morphology of ruthenium species on the oxygen evolution reaction was small. Conversely, irrespective of the pH of the aqueous solutions in an electrolytic bath, the 2D/2D nanostructure of RuNFs and g-C3N4 decreased the overpotential of the hydrogen evolution reaction. However, the use of RuO2 particles instead of RuNFs did not cause such a phenomenon. Thus, it was revealed that the RuNFs synthesized via a bottom-up process were useful as a co-catalyst for the hydrogen evolution reaction.

Co-doped RuO2 nanoparticles with enhanced catalytic activity and stability for the oxygen evolution reaction.

Efficient and durable electrocatalysts for the oxygen evolution reaction (OER) play an important role in the use of hydrogen energy. Rutile RuO2, despite being considered as an advanced electrocatalyst for the OER, performs poorly in stability due to its easy oxidative dissolution at very positive (oxidizing) potentials. Herein, we report a type of Co-doped RuO2 nanoparticle for boosting OER catalytic activity and stability in alkaline solutions. The replacement of Ru by Co atoms with a lower ionic valence and smaller electronegativity can promote the generation of O vacancies and increase the electron density around Ru, thus enhancing the adsorption of oxygen species and inhibiting the peroxidative dissolution of RuO2 during the OER process. It was found that Ru0.95Co0.05Oy exhibited excellent OER performance with overpotentials as low as 217 mV at 10 mA cm-2 and 290 mV at 100 mA cm-2 in 1 M KOH, as well as outstanding stability in continuous testing for 50 h at a current density of 100 mA cm-2, and nearly no significant degradation after the accelerated durability test of 2000 cycles.

Interfacial engineering of RuO2 for electrocatalytic decomposition of Li2CO3 in Li–CO2/O2 battery

Li2CO3, the primary byproduct of Li–CO2/O2 batteries, is challenging to decompose electrochemically and its accumulation cause the short lifespan of the battery. Herein, we report strong interfacial interaction between the intimately interfaced ultrafine RuO2 and Co3O4 nanoparticles, which leads to transfer of electrons from Ru 4d orbital to Co 3d orbital via interfacial Ru–O–Co bridges. Such intense interaction is found to boost the adsorption of CO2 and O2 on the RuO2; more importantly, it can also effectively decrease the energy barrier for the rate determining step of decomposition of Li2CO3. Therefore, both the formation and decomposition kinetics of Li2CO3 during charge and discharge are efficiently enhanced on the Co3O4-interfaced RuO2 compared to the freestanding RuO2. Using such Co3O4-interfaced RuO2 as cathode catalyst, Li–CO2/O2 (V:V = 4:1) batteries depict an overpotential as low as 1.31 V and a cycling stability of 137 cycles under a constant capacity of 1000 mAh g−1, which is significantly better than that with only Co3O4 or RuO2; the enhanced decomposition kinetics of Li2CO3 is also confirmed by monitoring the release of CO2 using in-situ mass spectrum. This work emphasizes the role of interfacial oxygen bridges in enhancing electrocatalytic decomposition of Li2CO3.

H2S-sensing properties of flame-synthesized RuO2-decorated WO3 nanoparticulate spin-coated films

This work aimed to develop effective and reliable H2S gas sensors based on flame-synthesized RuO2-decorated WO3 spin-coated films. Inclusive material characterizations unveiled the decoration of 1–3 nm RuO2 nanoparticles on 10–25 nm WO3 nanoparticles with 0–1 wt% Ru. Sensing layers coated with 1–6 cycles were tested towards 0.25–10 ppm H2S at 200–400 °C under various humidity conditions (0–80 %RH). The sensors with four spin-coated layers and 0.2 wt% Ru presented a reproducibly optimum response of ∼71.0 with a fair response time of ∼ 15.1 s to 10 ppm H2S in dry ambient at 350 °C. Additionally, the optimal sensor exhibited high H2S selectivity with respect to CH3SH, CH3SCH3, C3H6O, C2H5OH, CH3OH, CH2O, C6H6, C8H10, NO2, NO, H2, CH4, CO2, C2H2, HCOOH, CH3COOH, and CH3CHOHCOOH. Furthermore, the sensors displayed decent repeatability and satisfactory medium-term stability of resistance and response. Therefore, flame-synthesized RuO2-loaded WO3 nanoparticles were promising for effective and practical H2S sensing.