Catalytic properties of Ru nanoparticles embedded on ordered mesoporous carbon with different pore size in Fischer-Tropsch synthesis

A series of 3 wt% Ru embedded on ordered mesoporous carbon （OMC） catalysts with different pore sizes were prepared by autoreduction between ruthenium precursors and carbon sources at 1123 K. Ru nanoparticles were embedded on the carbon walls of OMC. Characterization technologies including power X-ray diffraction （XRD）, nitrogen adsorption-desorption, transmission electron microscopy （TEM）, and hydrogen temperature-programmed reduction （H2-TPR） were used to scrutinize the catalysts. The catalyst activity for Fischer-Tropsch synthesis （FTS） was measured in a fixed bed reactor. It was revealed that 3 wt% Ru-OMC catalysts exhibited highly ordered mesoporous structure and large surface area. Compared with the catalysts with smaller pores, the catalysts with larger pores were inclined to form larger Ru particles. These 3 wt% Ru-OMC catalysts with different pore sizes were more stable than 3 wt% Ru/AC catalyst during the FTS reactions because Ru particles were embedded on the carbon walls, suppressing particles aggregation, movement and oxidation. The catalytic activity and C5＋ selectivity were found to increase with the increasing pore size, however, CH4 selectivity showed the opposite trend. These changes may be explained in terms of the special environment of the active Ru sites and the diffusion of products in the pores of the catalysts, suggesting that the activity and hydrocarbon selectivity are more dependent on the pore size of OMC than on the Ru particle size.

Electronic engineering of Co-Ru diatomic sites and Ru nanoparticles for synergistic promotion of hydrogen evolution

The coexistence of multi-component active sites like single-atom sites,diatomic sites(DAS)and nanoclusters is shown to result in superior performances in the hydrogen evolution reaction(HER).Metal diatomic sites are more complex than single-atom sites but their unique electronic structures can lead to significant enhancement of the HER kinetics.Although the synthesis and identification of DAS is usually challenging,we report a simple access to a diatomic catalyst by anchoring Co-Ru DAS on nitrogen-doped carbon supports along with Ru nanoparticles(NPs).Experimental and theoretical results revealed the atomic-level characteristics of Co-Ru sites,their strong electronic coupling and their synergy with Ru NPs within the catalyst.The unique electronic structure of the catalyst resulted in an excellent HER activity and stability in alkaline media.This work provides a valuable insight into a widely applicable design of diatomic catalysts with multi-component active sites for highly efficient HER electrocatalysis.

Ligand-controlled synthesis of high density and ultra-small Ru nanoparticles with excellent electrocatalytic hydrogen evolution performance

Ultra-small size metal nanoparticles(u-MNPs)have broad applications in the fields of catalysis,biomedicine and energy conversion.Herein,by means of a ligand-controlled synthesis strategy,series of Ru-based NPs with high dispersity and ultra-small size(marked as u-Ru/C),or sparse and aggregated state(marked as a-Ru/C)anchored on the surface of hollow porous carbon shells are prepared.Systematical in-situ thermogravimetry-mass spectrometry-Fourier transform infrared spectra tests suggest that the different ligands in these Ru-based precursors can regulate the nucleation,growth and fixation of metal sites during the pyrolysis process,thus contributing to Ru NPs with various size and dispersity.As a result,when applied to hydrogen evolution reaction,the u-Ru-1/C catalyst displays a low Tafel slope of 26 mV dec-1,overpotential of 31 mV(at 10 mA cm^(-2))and a large exchange current density of 1.7 mA cm^(-2) in 1.0 M KOH,significantly better than that of the a-Ru-2/C,hollow carbon and even commercial 20%Pt/C.This is mainly because that the u-Ru-1/C sample owns both smaller particle size,more electrochemical active sites,higher intrinsic activity and optimized surface H adsorption ability than that of the a-Ru-2/C counterpart.Such ligand-modulated growth strategy is not only applicable to Ru,but also can be extended to other similar metals,offering a step forward in the design and synthesis of highly dispersed u-MNPs.

Zeolite-seed-directed Ru nanoparticles highly resistant against sintering for efficient nitrogen activation to ammonia

To stabilize Ru nanoparticles against sintering is an urgent problem in the utilization of Ru-based catalysts for NH3 synthesis.In the present study,we used Ru-containing ZSM-5 as seeds to crystallize ZSM-5,and the resulted Ru@ZSM-5 catalyst is highly resistant against Ru sintering.According to the results of diffuse reflectance infrared fourier transform spectroscopy(DRIFTS)and transmission electron microscopy(TEM)analyses,the average size of Ru nanoparticles is around 3.6 nm,which is smaller than that of Ru/ZSM-5-IWI prepared by incipient wetness impregnation.In NH3 synthesis(N2:H2=1:3)at 400℃and 1 MPa,Ru@ZSM-5 displays a formation rate of 5.84 mmolNH3 gcat^-1 h^-1,which is much higher than that of Ru/ZSM-5-IWI(2.13 mmolNH3 gcat^-1 h^-1).According to the results of TEM,N2-temperatureprogrammed desorption(N2-TPD),X-ray photoelectron spectroscopy(XPS)and X-ray absorption fine structure(XAFS)studies,it is deduced that the superior performance of Ru@ZSM-5 is attributable to the small particle size and the ample existence of metallic Ru0 sites.This method of zeolite encapsulation is a feasible way to stabilize Ru nanoparticles for NH3 synthesis.

Double spatial confinement on ruthenium nanoparticles inside carbon frameworks as durable catalysts for a quasi-solid-state Li–O_(2) battery

The rational design of large-area exposure,nonagglomeration,and longrange dispersion of metal nanoparticles(NPs)in the catalysts is critical for the development of energy storage and conversion systems.Little attention has been focused on modulating and developing catalyst interface contact engineering between a carbon substrate and dispersed metal.Here,a highly dispersed ultrafine ruthenium(Ru)NP strategy by double spatial confinement is proposed,that is,incorporating directed growth of metal–organic framework crystals into a bacterial cellulose templating substrate to integrate their respective merits as an excellent electrocatalytic cathode catalyst for a quasi-solid-state Li–O_(2) battery.The porous carbon matrix with highly dispersed ultrafine Ru NPs is well designed and used as cathode catalysts in a Li–O_(2) battery,demonstrating a high discharge areal capacity of 6.82 mAh cm^(–2) at 0.02 mA cm^(–2),a high-rate capability of 4.93 mAh cm^(–2) at 0.2 mA cm^(–2),and stable discharge/charge cycling for up to 500 cycles(2000 h)with low overpotentials of~1.4 V.This fundamental understanding of the structure–performance relationship demonstrates a new and promising approach to optimize highly efficient cathode catalysts for solid-state Li–O_(2) batteries.

Accelerating the Activation of NO_(x)^(−)on Ru Nanoparticles for Ammonia Production by Tuning Their Electron Deficiency

Stable and portable ammonia(NH3)is a promising,low-cost,and environment-friendly medium for energy storage.How to achieve the rapid production of NH3 from reducing NO_(x)^(−)in aqueous systems and industrial wastewater via electrochemical methods remains the main challenge for practical application on a large scale.The corresponding electrocatalysts as the key materials in electrochemical devices suffer from low activity,especially in neutral systems.In this work,we successfully elevated the activity of the bench-mark Ru electrocatalysts to more than 30 times via construction of rectifying contact of Ru metals and noble carbons.We theoretically predicted and then rationally designed a new type of P-O rich carbon with large work functions as“noble”supports to attract a pronounced number of electrons from Ru metals at the rectifying interface.The resulting electron deficiency of Ru metals largely promotes the pre-adsorption and activation of NO_(x)^(−)anions,providing high Faradaic efficiencies(>96%)and record-high turnover frequency values for universal NO_(2)^(−)and NO_(3)^(−)reduction in neutral solution.

Ru Nanoparticles Supported on Co-Embedded N-Doped Carbon Nanotubes as Efficient Electrocatalysts for Hydrogen Evolution in Basic Media

A challenging but urgent task is to construct efficient and robust hydrogen evolution reaction(HER)electrocatalysts for practically feasible and sustainable hydrogen production through alkaline water electrolysis.Herein we report a simple and mild pyrolysis method to synthesize the efficient Ru nanoparticles(NPs) supported on Co-embedded N-doped carbon nanotubes(Ru/Co-NCNTs)catalyst for HER in basic media.The Ru/Co-NCNTs display remarkable performance with a low overpotential of only 35mV at 10mA/cm^2,a small Tafel slope(36mV/dec),and a high mass activity in 1mol/L KOH,which is superior to commercial 20% Pt/C catalyst.This excellent performance is benefited from the enhanced conductivity of N-doped carbon nanotubes(NCNTs)and high intrinsic activity triggered by synergistic coupling between Ru NPs and Co-embedded N-doped carbon nanotubes(Co-NCNTs).

Colloidal Dispersion of Nano-Ru/SiO_2 in PEG and its Application for Hydrogenation of Benzene

Colloidal dispersion of nano-Ru/SiO2 in PEG （polyethylene glycol, M.W.=400） was used for benzene hydrogenation. The system has the features of easy catalyst＇s recycling and high catalyst stability.

Ru particle size effect in Ru/CNT-catalyzed Fischer-Tropsch synthesis

Carbon nanotube （CNT）-supported Ru nanoparticles with mean sizes ranging from 2.3 to 9.2 nm were prepared by different post-treatments and studied for Fischer-Tropsch （FT） synthesis. The effects of Ru particle size on catalytic behaviors were investigated at both shorter and longer contact times. At shorter contact time, where the secondary reactions were insignificant, the turnover frequency （TOF） for CO conversion was dependent on the mean size of Ru particles; TOF increased with the mean size of Ru particles from 2.3 to 6.3 nm and then decreased slightly. At the same time, the selectivities to C5＋ hydrocarbons increased gradually with the mean size of Ru particles up to 6.3 nm and then kept almost unchanged with a further increase in Ru particle size. At longer contact time, C10-C20 selectivity increased significantly at the expense of C21＋ selectivity, suggesting the occurrence of the selective hydrocracking of C21＋ to C10-C20 hydrocarbons.

Development of Ru-Decorated Carbon Nanotubes-Supported Catalyst for a Microchannel Methanation Reactor

In this study, MWNT and alumina nanopowder were used as a ruthenium catalyst support for the conversion of carbon monoxide to methane. Metal foam structures were employed to support such catalytic systems, offering interesting possibilities for commercial applications due to low-pressure drop; excellent flow characteristic and heat transfer properties. Prior to the ruthenium impregnation, the MWNT surface was initially modified by means of metal cation activation and surface adsorption of anionic surfactant. The decoration processes using both surface modifications promoted the deposition of ruthenium with a mean 2 nm diameter. The use of nickel as a nucleating center enhanced the Ru nanoparticle density on the CNT surface compared to the Ru/CNT catalyst prepared by excess solution impregnation. As a reducing agent, ethylene glycol completely converted Ru2＋ to Ru0as confirmed by an EDS/TEM analysis. Among the prepared catalysts, Ru/AI203-CNTs prepared by Ni2＋ activation showed the best performance for the hydrogenation reaction. This is interpreted in terms of the higher ruthenium nanoparticle exposure on the nanostructured catalyst, as a result of the better MWNT dispersion in the MWNT/Al2O3 mixture.

Graphdiyne scaffold anchored highly dispersed ruthenium nanoparticles as an efficient cathode catalyst for rechargeable Li-CO_(2) battery

Lithium (Li)-CO_(2) battery is rising as an attractive energy-storage system with the competence of CO_(2) conversion/fixation. However, its practical development is seriously hindered by the high overpotential. Herein, a rational design on a highly catalytic Li-CO_(2) battery electrode built by graphdiyne powder as a multi-functional laminar scaffold with anchored highly dispersed Ru nanoparticles is explored. The strong interaction between the abundant acetylenic bond sites of graphdiyne scaffold and Ru nanoparticles can effectively promote the electrochemical progress and reduce the voltage polarization. The unique channels architecture of the cathodic catalyst with enough space not only accelerates CO_(2) diffusion and electrons/Li+ transport, but also allows a large amount of accommodation for discharged product (Li2CO3) to assure an advanced capacity. The corresponding Li-CO_(2) battery displays an advanced discharged capacity of 15,030 mAh/g at 500 mA/g, great capacity retention of 8873 mAh/g at 2 A/g, high coulombic efficiency of 97.6% at 500 mA/g and superior life span for 120 cycles with voltage gap of 1.67 V under a restricted capacity of 1000 mAh/g at 500 mA/g. Ex/in-situ studies prove that synergy between Ru nanoparticles and acetylene bonds of GDY can boost the round-trip CO_(2)RR and CO_(2)ER kinetics.

An electrochemiluminescent magneto-immunosensor for ultrasensitive detection of hs-cTnI on a microfluidic chip

Sensitive detection and precise quantitation of trace-level crucial biomarkers in a complex sample matrix has become an important area of research.For example,the detection of high-sensitivity cardiac troponin I (hs-cTnI) is strongly recommended in clinical guidelines for early diagnosis of acute myocardial infarction.Based on the use of an electrode modified by single-walled carbon nanotubes (SWCNTs) and a Ru(bpy)32+-doped silica nanoparticle (Ru@SiO2)/tripropylamine (TPA) system,a novel type of electrochemiluminescent (ECL) magnetoimmunosensor is developed for ultrasensitive detection of hs-cTnI.In this approach,a large amount of[Ru(bpy)3]2+is loaded in SiO2(silica nanoparticles) as luminophores with high luminescent efficiency and SWCNTs as electrode surface modification material with excellent electrooxidation ability for TPA.Subsequently,a hierarchical micropillar array of microstructures is fabricated with a magnet placed at each end to efficiently confine a single layer of immunomagnetic microbeads on the surface of the electrode and enable 7.5-fold signal enhancement In particular,the use of transparent SWCNTs to modify a transparent ITO electrode provides a two-order-of-magnitude ECL signal amplification.A good linear calibration curve is developed for hs-cTnI concentrations over a wide range from 10 fg/ml to 10 ng/ml,with the limit of detection calculated as 8.720 fg/ml (S/N=3).This ultrasensitive immunosensor exhibits superior detection performance with remarkable stability,reproducibility,and selectivity.Satisfactory recoveries are obtained in the detection of hs-cTnI in human serum,providing a potentia analysis protocol for clinical applications.

Fischer-Tropsch reaction within zeolite crystals for selective formation of gasoline-ranged hydrocarbons

Product selectivity control is attractive in Fischer-Tropsch(F-T)synthesis but it is still a challenge,because the F-T products follow the Anderson-Schulz-Flory(ASF)distribution with maximized gasoline-ranged(C_(5)-C_(11))hydrocarbon selectivity at 45%.Herein,we report a strategy by optimizing the gasoline selectivity to outperform the ASF limitation.The key to this success is fixation of the metal nanoparticles within zeolite crystals(metal@zeolite),where the zeolite micropore adjusts the product selectivity.For example,the Ru@NaY exhibited the gasoline selectivity 64.3% in the F-T reaction,which is significantly higher than the ASF limitation and about 2 times of that(32.8%)over conventionally supported Ru catalyst(Ru/NaY).This investigation might offer an alternative route for the direct transformation of syngas to liquid fuels with controllable selectivities.

Direct aerobic oxidation of monoalcohol and diols to acetals using tandem Ru@MOF catalysts

The aerobic oxidation of monoalcohols and diols to acetals is an important academic and industrial challenge for the production of fine chemicals and intermediates.The existing methods usually rely on a two-step process in which alcohols are first oxidized to aldehydes over metal catalysts(Ru,Pt,Pd)and then acetalized using acids.Due to the instability of aldehydes,how to avoid over-oxidation to their respective carboxylic acids and esters is a long-standing challenge.For this reason,certain non-conjugated dialdehydes have never been successfully produced from diol oxidation.Hereby we report a Ru@metal-organic framework(MOF)tandem catalyst containing ultra-fine Ru nanoparticles(<2 nm)for direct alcohol to acetal conversion of monoalcohol and diols with noformation of carboxylic acids.Mechanistic study reveals that the presence of Lewis acid sites in the MOF work in concert with Ru active sites to promptly convert aldehydes to acetals thereby effectively suppressing the formation of over-oxidation byproducts.

Switching of CO_(2)hydrogenation selectivity via chlorine poisoning over Ru/TiO_(2)catalyst

It is fascinating to explore the distribution of CO_(2)hydrogenation products regulated by heterogeneous catalysts,as both the chemical state of surface metals and structure of the support itself of the supported catalysts may affect the performance of CO_(2)hydrogenation.Herein,the complete switching of CO_(2)hydrogenation products from CH4 to CO can be realized by induction of Cl into Ru/TiO_(2)catalyst.Density functional theory(DFT)calculations indicated that Cl ions were mainly located on the Ru metal sites of Ru/TiO_(2)catalysts.Bader charge analysis and Ru 3p X-ray photoelectron spectra(XPS)results suggested that electrons transferred from Ru to Cl,resulting in the decrease of electron density of Ru.In situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)of CO_(2)hydrogenation and CO adsorption proved that with the increase of the Cl ion content,the adsorption of CO on the catalyst surface was significantly weakened,and resulted in the high CO selectivity.Our work demonstrates the role of Cl ions in regulating the distribution of CO_(2)hydrogenation products,and provides new ideas for regulating other catalytic processes.

Heterointerface engineering of Ru/RuS_(2) on N/S-doped hollow mesoporous carbon for promoting alkaline hydrogen evolution

Alkaline hydrogen evolution reaction (HER) suffers from a sluggish kinetic,which requires the elaborate catalytic interface and micro-nanoscale architecture engineering of the electrocatalysts to accelerate the water dissociation and hydrogen evolution.Herein,the heterointerface engineering was proposed for promoting the alkaline HER by constructing the highly exposed Ru/RuS_(2) heterostructures homogeneously distributed on hollow N/S-doped carbon microspheres (Ru/RuS_(2)@h-NSC).Benefited from the synergistic effect of heterointerfacial Ru/RuS_(2),the high accessibility of the active sites on both inner and outer surface of mesoporous shells and the efficient mass transport,Ru/RuS_(2)@h-NSC affords a remarkable catalytic performance with an overpotential of 26 mV@10 mA/cm^(2) for alkaline HER,outperforming most of the state-of-the-art catalysts.Further applying Ru/RuS_(2)@h-NSC and its oxidized derivate for the overall alkaline water splitting,the required cell voltage is much lower than that of the commercial Pt/C||RuO_(2)pair to achieve the same current density.Our study may allow us to guide the design of micro-nanoreactors with optimal catalytic interfaces for promising electrocatalytic applications.

Micropore-confined Ru nanoclusters catalyst for efficient pHuniversal hydrogen evolution reaction

Pt-based catalysts are used commercially for the hydrogen evolution reaction(HER),even though the low earth abundance and high cost of platinum hinder scale-up applications.Ru metal is a promising alternative catalyst for HER owing to its lower cost but similar metal-hydrogen bond strength to Pt.However,designing an efficient and robust Ru-based electrocatalyst for pHuniversal HER is challenging.Herein,we successfully synthesized N-doped carbon(NC)supported ruthenium catalysts with different Ru sizes(single-atoms,nanoclusters and nanoparticles),and then systematically evaluated their performance for HER.Among these catalysts,the Ru nanocluster catalyst(Ru NCs/NC)displayed optimal catalytic performance with overpotentials of only 14,30,and 32 mV(at 10 mA·cm^(-2))in 1 M KOH,1 M phosphate buffer saline(PBS),and 0.5 M H_(2)SO_(4),respectively.The corresponding mass activities were 32.2,12.1 and 8.1 times higher than those of 20 wt.%Pt/C,and also much better than those of the Ru single-atoms(Ru SAs/NC)and Ru nanoparticle(Ru NPs/NC)catalysts,at an overpotential of 100 mV under alkaline,neutral and acidic conditions,respectively.Density functional theory(DFT)calculations revealed that the outstanding HER performance of the Ru NCs/NC catalyst resulted from a strong interaction between the Ru nanoclusters and the N-doped carbon support,which downshifted the d-band center and thus weakened the*H adsorption ability of Ru sites.

Three-in-one Fe-porphyrin based hybrid nanosheets for enhanced CO_(2)reduction and evolution kinetics in Li-CO_(2)battery

Efficient cathode-catalysts with multi-functional properties are essential for Li-CO_(2)battery,while the construction of them with simultaneously enhanced CO_(2)reduction and evolution kinetics is still challenging.Here,a kind of hybrid nanosheets based on Ru nanoparticles,Fe-TAPP and grapheme oxide(GO)has been designed through a one-pot self-assembly strategy.The Ru,Fe-porphyrin and GO based hybrid nanosheets(denoted as Ru/Fe-TAPP@GO)with integrated multi-components offer characteristics of ultrathin thickness(~4 nm),high electro-redox property,uniformly dispersed morphology,and high electrical conductivity,etc.These features endow Ru/Fe-TAPP@GO with ultra-low overpotential(0.82 V)and fully reversible discharge/charge property with a high specific-capacity of 39,000 m Ah/g within 2.0-4.5 V at 100 m A/g,which are much superior to Ru@GO and Fe-TAPP@GO.The achieved performance was presented as one of the best cathode-catalysts reported to date.The synergistically enhanced activity originated from the integrated hybrid nanosheets may provide a new pathway for designing efficient cathode-catalysts for Li-CO_(2)batteries.