Hydrophobic Microenvironment Modulation of Ru Nanoparticles in Metal-Organic Frameworks for Enhanced Electrocatalytic N2 Reduction.

The modulation of the chemical microenvironment surrounding metal nanoparticles (NPs) is an effective means to enhance the selectivity and activity of catalytic reactions. Herein, a post-synthetic modification strategy is developed to modulate the hydrophobic microenvironment of Ru nanoparticles encapsulated in a metal-organic framework (MOF), MIP-206, namely Ru@MIP-Fx (where x represents perfluoroalkyl chain lengths of 3, 5, 7, 11, and 15), in order to systematically explore the effect of the hydrophobic microenvironment on the electrocatalytic activity. The increase of perfluoroalkyl chain length can gradually enhance the hydrophobicity of the catalyst, which effectively suppresses the competitive hydrogen evolution reaction (HER). Moreover, the electrocatalytic production rate of ammonia and the corresponding Faraday efficiency display a volcano-like pattern with increasing hydrophobicity, with Ru@MIP-F7 showing the highest activity. Theoretical calculations and experiments jointly show that modification of perfluoroalkyl chains of different lengths on MIP-206 modulates the electronic state of Ru nanoparticles and reduces the rate-determining step for the formation of the key intermediate of N2H2 *, leading to superior electrocatalytic performance.

Discriminating the Active Ru Species Towards the Selective Generation of Singlet Oxygen from Peroxymonosulfate: Nanoparticles Surpass Single-Atom Catalysts.

Singlet oxygen (1O2) is an exceptional reactive oxygen species in advanced oxidation processes for environmental remediation. Despite single-atom catalysts (SACs) representing the promising candidate for the selective generation of 1O2 from peroxymonosulfate (PMS), the necessity to meticulously regulate the coordination environment of metal centers poses a significant challenge in the precisely-controlled synthetic method. Another dilemma to SACs is their high surface free energy, which results in an inherent tendency for the surface migration and aggregation of metal atoms. We here for the first time reported that Ru nanoparticles (NPs) synthesized by the facile pyrolysis method behave as robust Fenton-like catalysts, outperforming Ru SACs, towards efficient activation of PMS to produce 1O2 with nearly 100 % selectivity, remarkably improving the degradation efficiency for target pollutants. Density functional theory calculations have unveiled that the boosted PMS activation can be attributed to two aspects: (i) enhanced adsorption of PMS molecules onto Ru NPs, and (ii) decreased energy barriers by offering adjacent sites for promoted dimerization of *O intermediates into adsorbed 1O2. This study deepens the current understanding of PMS chemistry, and sheds light on the design and optimization of Fenton-like catalysts.

Symmetry-Broken Ru Nanoparticles with Parasitic Ru-Co Dual-Single Atoms Overcome the Volmer Step of Alkaline Hydrogen Oxidation.

Efficient dual-single-atom catalysts are crucial for enhancing atomic efficiency and promoting the commercialization of fuel cells, but addressing the sluggish kinetics of hydrogen oxidation reaction (HOR) in alkaline media and the facile dual-single-atom site generation remains formidable challenges. Here, we break the local symmetry of ultra-small ruthenium (Ru) nanoparticles by embedding cobalt (Co) single atoms, which results in the release of Ru single atoms from Ru nanoparticles on reduced graphene oxide (Co1 Ru1,n /rGO). In situ operando spectroscopy and theoretical calculations reveal that the oxygen-affine Co atom disrupts the symmetry of ultra-small Ru nanoparticles, resulting in parasitic Ru and Co dual-single-atom within Ru nanoparticles. The interaction between Ru single atoms and nanoparticles forms effective active centers. The parasitism of Co atoms modulates the adsorption of OH intermediates on Ru active sites, accelerating HOR kinetics through faster formation of *H2 O. As anticipated, Co1 Ru1,n /rGO exhibits ultrahigh mass activity (7.68 A mgRu -1 ) at 50 mV and exchange current density (0.68 mA cm-2 ), which are 6 and 7 times higher than those of Ru/rGO, respectively. Notably, it also displays exceptional durability surpassing that of commercial Pt catalysts. This investigation provides valuable insights into hybrid multi-single-atom and metal nanoparticle catalysis.

In Situ Synthesis of Ru/TiO2- x @TiCN Ternary Heterojunctions for Enhanced Sonodynamic and Nanocatalytic Cancer Therapy.

Albeit nanozymes-based tumor catalytic therapy (NCT) relies on endogenous chemical reactions that could achieve tumor microenvironment (TME)-specialized reactive oxygen species (ROS) production, the unsatisfactory catalytic activity of nanozymes accompanied by complex TME poses a barrier to the therapeutic effect of NCT. Herein, a one-step in situ synthesis strategy is reported to construct ternary Ru/TiO2- x @TiCN heterojunctions through oxidative conversion of TiCN nanosheets (NSs) to TiO2- x NSs and reductive deposition of Ru3+ to Ru nanoparticles. The narrow bandgap and existence of heterojunctions enhance the ultrasound-activated ROS generation of Ru/TiO2- x @TiCN because of the accelerated electron transfer and inhibits electron-hole pair recombination. The augmented ROS production efficiency is achieved by Ru/TiO2- x @TiCN with triple enzyme-like activities, which amplifies the ROS levels in a cascade manner through the catalytic decomposition of endogenous H2 O2 to relieve hypoxia and heterojunction-mediated NCT, as well as depletion of overexpressed glutathione. The satisfactory therapeutic effects of Ru/TiO2- x @TiCN heterojunctions are achieved through synergetic sonodynamic therapy and NCT, which achieve the complete elimination of tumors without recurrence. This strategy highlights the potential of in situ synthesis of semiconductor heterojunctions as enhanced sonosensitizers and nanozymes for efficient tumor therapy.

Reinforcing the Efficiency of Photothermal Catalytic CO2 Methanation through Integration of Ru Nanoparticles with Photothermal MnCo2O4 Nanosheets.

Carbon dioxide (CO2) hydrogenation to methane (CH4) is regarded as a promising approach for CO2 utilization, whereas achieving desirable conversion efficiency under mild conditions remains a significant challenge. Herein, we have identified ultrasmall Ru nanoparticles (∼2.5 nm) anchored on MnCo2O4 nanosheets as prospective photothermal catalysts for CO2 methanation at ambient pressure with light irradiation. Our findings revealed that MnCo2O4 nanosheets exhibit dual functionality as photothermal substrates for localized temperature enhancement and photocatalysts for electron donation. As such, the optimized Ru/MnCo2O4-2 gave a high CH4 production rate of 66.3 mmol gcat-1 h-1 (corresponding to 5.1 mol gRu-1 h-1) with 96% CH4 selectivity at 230 °C under ambient pressure and light irradiation (420-780 nm, 1.25 W cm-2), outperforming most reported plasmonic metal-based catalysts. The mechanisms behind the intriguing photothermal catalytic performance improvement were substantiated through a comprehensive investigation involving experimental characterizations, numerical simulations and density functional theory (DFT) calculations, which unveiled the synergistic effects of enhanced charge separation efficiency, improved reaction kinetics, facilitated reactant adsorption/activation and accelerated intermediate conversion under light irradiation over Ru/MnCo2O4. A comparison study showed that, with identical external input energy during the reaction, Ru/MnCo2O4-2 had a much higher catalytic efficiency compared to Ru/TiO2 and Ru/Al2O3. This study underscores the pivotal role played by photothermal supports and is believed to engender a heightened interest in plasmonic metal nanoparticles anchored on photothermal substrates for CO2 methanation under mild conditions.

Spatially Formed Tenacious Nickel-Supported Bimetallic Catalysts for CO2 Methanation under Conventional and Induction Heating.

The paper introduces spatially stable Ni-supported bimetallic catalysts for CO2 methanation. The catalysts are a combination of sintered nickel mesh or wool fibers and nanometal particles, such as Au, Pd, Re, or Ru. The preparation involves the nickel wool or mesh forming and sintering into a stable shape and then impregnating them with metal nanoparticles generated by a silica matrix digestion method. This procedure can be scaled up for commercial use. The catalyst candidates were analyzed using SEM, XRD, and EDXRF and tested in a fixed-bed flow reactor. The best results were obtained with the Ru/Ni-wool combination, which yields nearly 100% conversion at 248 °C, with the onset of reaction at 186 °C. When we tested this catalyst under inductive heating, the highest conversion was observed already at 194 °C.

Self-deposited ultrasmall Ru nanoparticles on carbon nitride with high peroxidase-mimicking activity for the colorimetric detection of alkaline phosphatase.

Carbon nitride (C3N4) nanosheets are known as peroxidase mimics, but the low activity hinders their further application. Embedding active metal nanoparticles onto the C3N4 nanosheets is expected to break this limitation. Herein, highly dispersed ultrasmall Ru nanoparticles are anchored onto the C3N4 through spontaneous redox reaction. The as-obtained Ru-C3N4 exhibits excellent peroxidase-like activity, which can be further regulated by adjusting the loading of Ru nanoparticles on C3N4. Using Ru-C3N4 as a mimetic peroxidase, a colorimetric sensing method for alkaline phosphatase (ALP) detection is developed based on the inhibitory effect of ascorbic acid produced by hydrolysis of ALP and l-ascorbic acid 2-phosphate (AAP) on the color development reaction of TMB catalyzed by Ru-C3N4. The sensor exhibits wide linear range and low detection limit for the ALP sensing. Finally, the assay is applied to ALP detection in human serum and satisfactory results are obtained, which provides a promising strategy for colorimetric sensing of ALP.

Ultrasound-assisted green synthesis of Ru supported on LDH-CNT composites as an efficient catalyst for N-ethylcarbazole hydrogenation.

N-ethylcarbazole/dodecahydro-N-ethylcarbazole (NEC/12H-NEC) is one of the most attractive LOHCs, and it is of great significance to develop catalysts with high activity and reduce the hydrogen storage temperature. Layered double hydroxides-carbon nanotubes composites (LDH-CNT) were synthesized by a simple in-situ assembly method. Due to the introduction of CNT, a strong interaction occurred between LDH and CNT, which effectively improved the electron transfer ability of LDH-CNT. Ru/LDH-CNT catalysts were prepared via ultrasound-assisted reduction method without adding reducing agents and stabilizers. Under the cavitation effect of ultrasound, the hydroxyl groups on the surface of LDH were excited to generate hydrogen radicals (•H) with high reducibility, which successfully reduced Ru3+ to Ru NPs. Ru/LDH-3.9CNT-(300-1) catalyst was of 1.63 nm average Ru particle size with CNT amount of 3.9 wt% and the ultrasonic power of 300 W at 1 h, and its electron transfer resistance was less than that of Ru/LDH-(300-1). The synergy of ultrafine Ru NPs and fast electron transfer made it exhibit exceptional catalytic performance in NEC hydrogenation. Even if the reaction temperature was lowered to 80 °C, its hydrogenation performance was better than that of commercial Ru/Al2O3 catalyst at 120 °C. The ultrasound-assisted method is efficient, green and environmentally friendly, and the operation process is simple and economical. It is expected to be used in practical industrial production, which provides a reference for the preparation of high-activity and low-temperature hydrogen storage catalysts.

Highly Dispersed Ru-Co Nanoparticles Interfaced With Nitrogen-Doped Carbon Polyhedron for High Efficiency Reversible Li-O2 Battery.

The lithium-oxygen (Li-O2 ) battery with high energy density of 3860 Wh kg-1 represents one of the most promising new secondary batteries for future electric vehicles and mobile electronic devices. However, slow oxygen reduction/oxygen evolution (ORR/OER) reaction efficiency and unstable cycling performance restrain the practical applications of the Li-O2 battery. Herein, Ru-modified nitrogen-doped porous carbon-encapsulated Co nanoparticles (Ru/Co@CoNx -C) are synthesized through reduction of Ru on metal-organic framework (MOFs) pyrolyzed derivatives strategies. Porous carbon polyhedra provide channels for reactive species and stable structure ensures the cyclic stability of the catalyst; abundant Co-Nx sites and high specific surface area (353 m2 g-1 ) provide more catalytically active sites and deposition sites for reaction products. Theoretical calculations further verify that Ru/Co@CoNx -C can regulate the growth of Li2 O2 to improve reversibility of Li-O2 batteries. Li-O2 batteries with Ru/Co@CoNx -C as cathode catalyst achieve small voltage gaps of 1.08 V, exhibit excellent cycle stability (205 cycles), and deliver high discharge specific capacity (17050 mAh g-1 ). Furthermore, pouch-type Li-O2 batteries that maintain stable electrochemical performance output even under conditions of bending deformation and corner cutting are successfully assembled. This study demonstrates Ru/Co@CoNx -C catalyst's great application potential in Li-O2 batteries.

Ru nanoparticles anchored on porous N-doped carbon nanospheres for efficient catalytic hydrogenation of Levulinic acid to γ-valerolactone under solvent-free conditions.

The catalytic transformation of the biomass platform compound levulinic acid (LA) to γ-valerolactone (GVL) is a vital reaction to produce related renewable chemicals and fuels. Developing stable catalysts with highly dispersed and accessible ultrafine metal nanoparticle (NP) active sites for the hydrogenation of LA under solvent-free conditions is still a major challenge. Herein, a versatile nano-emulsion self-assembly method was employed to fabricate N-doped carbon nanospheres with a high specific surface area and hierarchically porous structure. Ultrafine Ru NPs were successfully anchored on the hierarchal porous N-doped carbon nanospheres (HPNC) with high dispersion. The obtained Ru/HPNC catalyst exhibited excellent catalytic performance for LA hydrogenation to GVL under solvent-free conditions with outstanding reusability. In contrast, Ru NPs embedded in other supports (including activated carbon and carbon nanotubes) were observed to be less effective under the same reaction conditions. The superior catalytic performance of the Ru/HPNC catalyst is due to the hierarchically porous catalyst structure, and accessible ultrafine Ru active sites which can promote the activation of CO bonds and H2 absorption during the catalytic process. The reaction pathway of LA hydrogenation to GVL is clearly researched by theoretical calculations. Thus, the current work provides a facile strategy for the synthesis of highly dispersed ultrafine metal NP-based catalysts for an important biomass transformation.

Boosted CO2 photoreduction performance on Ru-Ti3CN MXene-TiO2 photocatalyst synthesized by non-HF Lewis acidic etching method.

Photocatalytic CO2 reduction to produce value-added products is considered a promising solution to solve the global energy crisis and the greenhouse effect. In this study, Ti3CN MXene was synthesized using a Lewis acidic etching method without the usage of toxic hydrofluoric acid (HF). Ti3CN MXene was then used as a support for the in situ hydrothermal growth of TiO2 and Ru nanoparticles. In the presence of 0.5 wt% Ru, Ru-Ti3CN-TiO2 shows CO and CH4 production rates of 99.58 and 8.97 µmol/g, respectively, in 5 h under Xenon lamp irradiation, more than 20.5 and 9.3 times that of commercial P25. The enhancement in photocatalytic activity was attributed to the synergy between the in-situ growth of TiO2 on Ti3CN MXene and Ru nanoparticles. It was proven experimentally that Ti3CN MXene can provide abundant pathways for electron transfer. The separation and transfer of the photo-induced charge were further increased with the help of Ru and Ti3CN MXene, leaving more electrons to participate in the subsequent CO2 reduction reaction. We believe that this work will encourage more attention to designing environment-friendly MXene-based photocatalysts for CO2 photoreduction using the non-HF method.

Ru@Carbon Nanotube Composite Microsponge: Fabrication in Supercritical CO2 for Hydrogenation of p-Chloronitrobenzene.

Novel heterogeneous catalysts are needed to selectively anchor metal nanoparticles (NPs) into the internal space of carbon nanotubes (CNTs). Here, supercritical CO2 (SC-CO2) was used to fabricate the Ru@CNT composite microsponge via impregnation. Under SC-CO2 conditions, the highly dispersive Ru NPs, with a uniform diameter of 3 nm, were anchored exclusively into the internal space of CNTs. The CNTs are assembled into a microsponge composite. The supercritical temperature for catalyst preparation, catalytic hydrogenation temperature, and time all have a significant impact on the catalytic activity of Ru@CNTs. The best catalytic activity was obtained at 100 °C and 8.0 MPa: this gave excellent selectivity in the hydrogenation of p-chloronitrobenzene at 100 °C. This assembly strategy assisted by SC-CO2 will be promising for the fabrication of advanced carbon composite powder materials.

Boron-induced activation of Ru nanoparticles anchored on carbon nanotubes for the enhanced pH-independent hydrogen evolution reaction.

As a promising dopant, electron deficient B atom not only tunes the electronic structure of electrocatalysts for improving their intrinsic catalytic activities, but also combines with hydroxy radical as strong adsorption sites for accelerating the water dissociation during the hydrogen evolution reaction (HER). In this paper, we report an electrocatalyst based on boron-modified Ru anchored on carbon nanotubes (B-Ru@CNT) that shows impressive HER activity in acidic and alkaline media. The boron-rich closo-[B12H12]2- borane was selected as a moderately strong reductant for the in situ reduction of a Ru salt, which yielded B-doped Ru nanoparticles. The experimental and theoretical results indicate that the incorporation of B not only weakens the Ru-H bond and downshifts the d-bond centre of Ru from the Fermi level by reducing the electron density at Ru but also accelerates the water dissociation reaction by providing B sites, which strongly adsorb OH* intermediates, and nearby Ru sites, which act as sites for the adsorption of the H* intermediate, thus boosting the HER performance and enhancing the HER kinetics. As a result of the tuning of the electronic structure via B doping, B-Ru@CNT showed excellent HER performance, yielding overpotentials of 17 and 62 mV at a current density of 10 mA cm-2 in alkaline and acidic solutions, respectively. These results indicate that our synthetic method is a promising route to B-doped metallic Ru with enhanced pH-independent HER performance.

Fabrication of hierarchical Ru/PEDOT:PSS/Ti3C2Tx nanocomposites as electrochemical sensing platforms for highly sensitive Sudan I detection in food.

In our paper, a promising electrochemical sensing platform was fabricated with titanium carbide (Ti3C2Tx), poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), and ruthenium nanoparticles (RuNPs). First, the Shandong pancake structural PEDOT:PSS/Ti3C2Tx was prepared by physical stirring. PEDOT:PSS as the dispersant was embedded into the Ti3C2Tx nanosheets, increasing the degree of dispersion of the Ti3C2Tx nanosheets and further improving the specific surface area of the composite material. Then, RuNPs were supported on the surface of PEDOT:PSS/Ti3C2Tx to form the hierarchical ternary nanocomposite of Ru/PEDOT:PSS/Ti3C2Tx. The prepared Ru/PEDOT:PSS/Ti3C2Tx nanocomposite exhibited promising electrochemical sensing properties toward Sudan I detection with a wide detection range of 0.01 âˆ¼ 100 µM and a high sensitivity of 482.43 µA mM-1 cm-2. Moreover, the Ru/PEDOT:PSS/Ti3C2Tx sensing platform has been successfully applied for Sudan I detection in ketchup and chili paste, implying the promising application prospect of Ru/PEDOT:PSS/Ti3C2Tx in food safety testing.

Uniformly Dispersed Ru Nanoparticles Constructed by In Situ Confined Polymerization of Ionic Liquids for the Electrocatalytic Hydrogen Evolution Reaction.

Design and development of cost-effective electrocatalysts with high efficiency and stability for scalable and sustainable hydrogen production through water splitting is still challenging. Herein, with the aid of divinyl functionalized ionic liquids, uniformly distributed Ru nanoparticles (NPs) on nitrogen-doped carbon frameworks are obtained via an in situ confined polymerization strategy. Attributed to the unique lamellar structure and confinement effect of carbon supports, the optimized homo-PIL-Ru/C-600 (with Ru 10 wt%) catalyst exhibits superior catalytic efficiency for the hydrogen evolution reaction with the overpotential of only 16 mV at a current density of 10 mA cm-2 and the corresponding Tafel slope of only 42 mV dec-1 . Moreover, the performance can be well reserved even after 10 000 cycles, demonstrating excellent stability and promising potentials for industrial application. This work not only provides a facile approach for the preparation of highly efficient Ru-based catalysts, but also guides the synthesis of other highly dispersed metallic NPs for special applications.

Ultrasound-excited hydrogen radical from NiFe layered double hydroxide for preparation of ultrafine supported Ru nanocatalysts in hydrogen storage of N-ethylcarbazole.

Highly active Ru nanoparticles (Ru NPs) supported on NiFe layered double hydroxide (Ru/NiFe-LDH) are prepared easily using ultrasound-assisted reduction method without chemical reductants and stabilizers. The plentiful hydroxyls on NiFe-LDH are excited into hydrogen radicals (H) under the action of ultrasound for reducing Ru3+ to Ru0. Ru NPs with an average particle size of 1.26 nm highly disperse on the mesopore-like surface of NiFe-LDH, which improve the catalytic performance for N-ethylcarbazole (NEC) hydrogenation. The experimental results show that 5Ru/NiFe-LDH-300-60 exhibits the best catalytic performance with 100% conversion of NEC, 98.88% yield of dodecahydro-N-ethylcarbazole (12H-NEC) and 5.77 wt% mass hydrogen storage capacity under the reaction conditions of 110 ℃, 6 MPa and mRu:mNEC = 0.15 wt% for 80 min. The kinetics study shows that the apparent activation energy is only 25.15 kJ/mol, which is the lowest in the reported literatures. Ru complexes with O-contained groups on NiFe-LDH, improving the catalytic stability in NEC hydrogenation.

Ethylene Glycol Electrochemical Reforming Using Ruthenium Nanoparticle-Decorated Nickel Phosphide Ultrathin Nanosheets.

In this work, ruthenium nanoparticle-decorated ultrathin nickel phosphide nanosheets on nickel foam substrate (Ru/Ni2P/NF) nanocomposites are synthesized conveniently by a cyanogel-NaBH4 method and a subsequent phosphating process, which displays excellent electroactivity for both the hydrogen evolution reaction (HER) and ethylene glycol electro-oxidation reaction (EGEOR) in an alkaline solution. Concretely, at Ru/Ni2P/NF nanocomposites, only 1.37 and -0.13 V potentials are required to obtain a current density of 100 mA cm-2 for EGEOR and HER, respectively. Meanwhile, Ru/Ni2P/NF nanocomposites also exhibit pre-eminent electrocatalytic performance of the long-running process for both EGEOR and HER. Density functional theory calculations demonstrate that the introduction of Ru nanoparticles results in an optimization of the surface adsorption energy and construction of a synergistic catalysis interface, which improve the electrocatalytic performance of nickel phosphide nanosheets. Notably, a symmetric Ru/Ni2P/NF||Ru/Ni2P/NF ethylene glycol electrolyzer needs only 1.14 V electrolysis voltage to obtain 10 mA cm-2 for hydrogen production, which effectively eliminates the H2/O2 explosion risk and highlights an energy-saving mode for electrochemical hydrogen production.

Effective Ru/CNT Cathode for Rechargeable Solid-State Li-CO2 Batteries.

An effective Ru/CNT electrocatalyst plays a crucial role in solid-state lithium-carbon dioxide batteries. In the present article, ruthenium metal decorated on a multi-walled carbon nanotubes (CNTs) is introduced as a cathode for the lithium-carbon dioxide batteries with Li1.5Al0.5Ge1.5(PO4)3 solid-state electrolyte. The Ru/CNT cathode exhibits a large surface area, maximum discharge capacity, excellent reversibility, and long cycle life with low overpotential. The electrocatalyst achieves improved electrocatalytic performance for the carbon dioxide reduction reaction and carbon dioxide evolution reaction, which are related to the available active sites. Using the Ru/CNT cathode, the solid-state lithium-carbon dioxide battery exhibits a maximum discharge capacity of 4541 mA h g-1 and 45 cycles of battery life with a small voltage gap of 1.24 V compared to the CNT cathode (maximum discharge capacity of 1828 mA h g-1, 25 cycles, and 1.64 V as voltage gap) at a current supply of 100 mA g-1 with a cutoff capacity of 500 mA h g-1. Solid-state lithium-carbon dioxide batteries have shown promising potential applications for future energy storage.

Laser conversion of biomass into porous carbon composite under ambient condition for pH-Universal electrochemical hydrogen evolution reaction.

It is highly desirable to develop durable and advanced electrocatalysts for pH-universal hydrogen evolution reaction (HER). While it makes much progress so far, the development of an environmental-friendly and cost-effective method to upgrade earth-abundant biomass into high value-added products still remains a major challenge. Thermal pyrolysis method which requires high pyrolysis temperature and long synthesis period is considered as a general method for preparation of carbon-based electrocatalysts. In view of this, ruthenium, nitrogen co-doped porous carbon (Ru@CN) is synthesized by laser conversion method at room temperature using cheap and renewable biomass honey as green carbon source. By controlling the loading of Ru and laser power, the electrocatalytic activities of as-prepared electrocatalysts can be adjusted effectively. Because of the advantage of rich Ru0 and Ru-N sites, the synthesized 0.04-Ru@CN-6 with Ru loading amount of 2.66 wt% exhibits a preferable electrocatalytic activity toward HER under all-pH conditions. Especially in alkaline solution, the optimal 0.04-Ru@CN-6 exhibits a small overpotential (11 mV) at 10 mA cm-2 current density, which is even much better than commercial 20 wt% Pt/C (37 mV). This strategy reported here may be a feasible and unique approach to synthesis and design of high-performance as well as cost-effective all-pH HER electrocatalyst.

Hierarchical Architectures Based on Ru Nanoparticles/Oxygen-Rich-Carbon Nanotubes for Efficient Hydrogen Evolution.

Highly active and durable electrocatalysts are essential for producing hydrogen fuel through the hydrogen evolution reaction (HER). Here, a uniform deposition of Ru nanoparticles strongly interacting with oxygen-rich carbon nanotube architectures (Ru-OCNT) through ozonation and hydrothermal approaches has been designed. The hierarchical structure of Ru-OCNT is made by self-assembly of oxygen functionalities of OCNT. Ru nanoparticles interact strongly with OCNT at the Ru/OCNT interface to give excellent catalytic activity and stability of the Ru-OCNT, as further confirmed by density functional theory. Owing to the hierarchical structure and adjusted surface chemistry, Ru-OCNT has an overpotential of 34 mV at 10 mA cm-2 with a Tafel slope of 27.8 mV dec-1 in 1 M KOH, and an overpotential of 55 mV with Tafel slope of 33 mV dec-1 in 0.5 M H2 SO4 . The smaller Tafel slope of Ru-OCNT than Ru-CNT and commercial Pt/C in both alkaline and acidic electrolytes indicates high catalytic activity and fast charge transfer kinetics. The as-proposed chemistry provides the rational design of hierarchically structured CNT/nanoparticle electrocatalysts for HER to produce hydrogen fuel.