NiRu Alloy Research Articles

Microstructures and hydrogen evolution reaction performance of Ru-M(M=Cu, Ni and Nb) system by magnetron sputtering: The mixing enthalpy effect

Nanostructured hydrogen evolution reaction (HER) electrocatalysts were prepared by magnetron sputtering. With increasing sputtering power of the Ru target, the catalytic performance of Cu-Ru system improved. Pure Ru sample shows the best performance, due to the larger electrochemical surface area, better hydrophily and smaller electron transfer impedance. No Cu-Ru interaction to improve the catalytic property was observed. This can be attributed to the formation of Cu and Ru nanograins rather than CuRu alloys, due to the repulsive force between Ru and Cu resulted by the positive mixing enthalpy. For Ni-Ru system with a mixing enthalpy close to 0, nanocrystalline NiRu alloys formed. Ru1Ni3 showed a high HER performance close to pure Ru due to the synergistic effect. Nb-Ru also shows synergistic interaction to improve the HER performance. Though the active area is smaller than pure Ru, Nb1Ru1 sample achieves an overpotential of 39 mV at a current density of 10 mA/cm2, lower than that of pure Ru. The main reason can be attributed to the formation of amorphous/crystalline heterojunction due to the negative mixing enthalpy. This promotes the charge transfer at the interface, leading to a smaller electrochemical impedance. The Nb1Ru1 sample also shows better stability for 100 h test with an increasing of only 6 mV of the overpotential at 10 mA/cm2.

Coordinated d-p hybridized hcp@fcc NiRu alloy doped by interstitial atoms for boosting urea-assisted simulated seawater electrolysis at industrial current densities

The production of hydrogen through seawater electrolysis has recently garnered increasing concern. However, hydrogen evolution reaction (HER) by alkaline seawater electrocatalysis is severely impeded by the slow H2O adsorption and H* binding kinetics at industrial current densities. Herein, a face-centered cubic/hexagonal close packed (fcc/hcp) NiRu alloy heterojunction was fabricated on Ni foam (N doped NiRu-inf/NF) by a low-temperature nitrogen plasma activation. Simultaneously, nitrogen atoms are introduced into the alloy to facilitate d-p hybridization. When N doped NiRu-inf/NF is integrated into a dual-electrode cell for urea-assisted seawater electrolysis, it achieves 100 mA cm−2 with an ultra-low voltage of 1.36 V and excellent stability. Density functional theory (DFT) verifies that the robust d-p hybridization among Ni, Ru and N exhibits more energy level matching for H2O molecule adsorption at the Ru sites, while simultaneously reducing the interaction between H* and Ni sites in N-doped NiRu-inf.

In Situ Engineering Multifunctional Active Sites of Ruthenium-Nickel Alloys for pH-Universal Ampere-Level Current-Density Hydrogen Evolution.

Developing robust non-platinum electrocatalysts with multifunctional active sites for pH-universal hydrogen evolution reaction (HER) is crucial for scalable hydrogen production through electrochemical water splitting. Here ultra-small ruthenium-nickel alloy nanoparticles steadily anchored on reduced graphene oxide papers (Ru-Ni/rGOPs) as versatile electrocatalytic materials for acidic and alkaline HER are reported. These Ru-Ni alloy nanoparticles serve as pH self-adaptive electroactive species by making use of in situ surface reconstruction, where surface Ni atoms are hydroxylated to produce bifunctional active sites of Ru-Ni(OH)2 for alkaline HER, and selectively etched to form monometallic Ru active sites for acidic HER, respectively. Owing to the presence of Ru-Ni(OH)2 multi-site surface, which not only accelerates water dissociation to generate reactive hydrogen intermediates but also facilitates their recombination into hydrogen molecules, the self-supported Ru90Ni10/rGOP hybrid electrode only takes overpotential of as low as ≈106mV to deliver current density of 1000mAcm-2, and maintains exceptional stability for over 1000h in 1 m KOH. While in 0.5 m H2SO4, the Ru90Ni10/rGOP hybrid electrode exhibits acidic HER catalytic behavior comparable to commercially available Pt/C catalyst due to the formation of monometallic Ru shell. These electrochemical behaviors outperform some of the best Ru-based catalysts and make it attractive alternative to Pt-based catalysts toward highly efficient HER.

Compressed Ru skin on atomic-ordered hexagonal Ru-Ni enabling rapid Volmer-Tafel kinetics for efficient alkaline hydrogen evolution

Ru-based materials are promising electrocatalysts for hydrogen evolution reaction (HER) owing to their low-cost (one twenty-fifth of Pt) and similar Gibbs free energy of H* adsorption (ΔGH*) to that of Pt. However, the inadequate ability for the water dissociation of Ru catalysts is significantly impeding the water splitting efficiency. In this work, we demonstrate an atomically ordered hexagonal Ru-Ni alloy with compressive-strained Ru skin as a high-performance HER catalyst for significantly boosting the water dissociation. The Ordered Ru-Ni achieves an optimized catalytic activity for alkaline HER with a low overpotential of 23 mV at 10 mA cm−2, Tafel slope of 25.9 mV dec−1 and superior mass activity of 4.83 A mg−1Ru, which is 15.1 times higher than Ru/C. According to DFT calculations, the ordered RuNi core imposes homogeneous compressive strain on the Ru skin, resulting in an optimum binding energy towards H*/OH* intermediates on Ru active sites for rapid Tafel step kinetics. Moreover, the decreased H2O dissociation energy barrier of Ordered Ru-Ni suggests a promoted Volmer-Tafel kinetics is achieved, significantly boosting the overall HER efficiency. This work provides a practical avenue for surface strain engineering of Ru-based catalysts to promote the HER activity.

Ce enhanced RuNi alloy multi-metal synergic hydrotalcite oxide derived catalyst for high performance CO2 methanation

Ni-based methanation catalysts have problems such as low temperature activity and easy sintering. The high cost of supported Ru-based methanation catalysts limits their application in industrialization. In this work, a hydrotalcite precursor Ru-Ni-Ce-Y catalyst was prepared by co-precipitation method, and the hydrotalcite oxide catalyst was prepared by high temperature calcination. The hydrotalcite oxide catalyst was prepared by optimizing the ratio of Ni element and the amount of precious metal and rare earth metal. Compared with the traditional supported catalyst, the activity of Ru1Ni80Ce4Y20 was significantly improved. It is confirmed from the experimental results that the medium basic sites, oxygen vacancies and the synergistic effect between RuNi alloy and Ce are the reasons for the high performance of Ru1Ni80Ce4Y20. It provides a thought for the design of highly active, stable and low cost methanation catalysts in industrial methanation production.

Remodeling the Electronic Structure of Metallic Nickel and Ruthenium via Alloying in a Molecular Template for Sustainable Hydrogen Evolution.

The reasonably constructed high-performance electrocatalyst is crucial to achieve sustainable electrocatalytic water splitting. Alloying is a prospective approach to effectively boost the activity of metal electrocatalysts. However, it is a difficult subject for the controllable synthesis of small alloying nanostructures with high dispersion and robustness, preventing further application of alloy catalysts. Herein, we propose a well-defined molecular template to fabricate a highly dispersed NiRu alloy with ultrasmall size. The catalyst presents superior alkaline hydrogen evolution reaction (HER) performance featuring an overpotential as low as 20.6 ± 0.9 mV at 10 mA·cm-2. Particularly, it can work steadily for long periods of time at industrial-grade current densities of 0.5 and 1.0 A·cm-2 merely demanding low overpotentials of 65.7 ± 2.1 and 127.3 ± 4.3 mV, respectively. Spectral experiments and theoretical calculations revealed that alloying can change the d-band center of both Ni and Ru by remodeling the electron distribution and then optimizing the adsorption of intermediates to decrease the water dissociation energy barrier. Our research not only demonstrates the tremendous potential of molecular templates in architecting highly active ultrafine nanoalloy but also deepens the understanding of water electrolysis mechanism on alloy catalysts.

Ru-Ni alloy nanosheets as tandem catalysts for electrochemical reduction of nitrate to ammonia

Ru-Ni alloy nanosheets as tandem catalysts for electrochemical reduction of nitrate to ammonia

Manipulating the interfacial water structure by electron redistribution for the hydrogen evolution reaction.

The sluggish dissociation of water in alkaline electrolytes significantly hinders the kinetics of the hydrogen evolution reaction (HER), particularly on surfaces of Ru-based catalysts. The structure of water at the water-catalyst interface influences this dissociation process, yet controlling the configuration of water molecules is challenging due to their random distribution. In this study, a NiRu alloy supported on nitrogen-doped carbon (NiRu/NC) is selected as a model catalyst to investigate the electron distribution of the catalyst manipulating the adsorption configuration and orientation of water molecules. The introduction of Ni leads to charge transfer from Ni to Ru atoms within the NiRu alloy, causing a notable redistribution of charge that strengthens the local electric fields surrounding the NiRu alloy. These electron-rich Ru sites attract K+ cations to the surface, resulting in an increased presence of K+ cation-hydrated water molecules, which is an H-down configuration with a reduced Ru-H distance. This phenomenon is confirmed by in situ Raman spectroscopy. Consequently, NiRu/NC exhibits outstanding HER performance, achieving low overpotentials of 16 and 344 mV at current densities of 10 and 1000 mA cm-2, respectively.

The ex situ exsolved Ni–Ru alloy from nickel–ruthenium co-doped SrFeO3−δ perovskite as a potential catalyst for CC and CO hydrogenation

The Ni–Ru alloy dispersed on the brownmillerite support efficiently hydrogenates biomass model component furfural into furfuryl alcohol, a value-added chemical.

Partially oxidized inter-doped RuNi alloy aerogel for the hydrogen evolution reaction in both alkaline and acidic media.

A facile reduction and doping process is employed with the supercritical ethanol drying method to form RuNi alloy aerogels. The optimized heterostructure comprising RuNi metal, RuO2, and NiO phases is synthesized through partial oxidation. When applied to the surface of Ni foam, the multiphase aerogels form a morphology of highly porous 0D colloidal aerogel networks on the surface. RuNi alloy-Ni foam oxidized at 350 °C (RuNi-350@NF) has an overpotential of 89 and 61 mV in 1 M KOH and 0.5 M H2SO4 media at 50 mA cm-2, as well as satisfactory long-term stability. Additionally, the Tafel slopes in alkaline and acidic media are found to be 34 and 30.9 mV dec-1, respectively. Furthermore, it exhibits long-term stability (35 h) in alkaline and acidic media at high current densities of 50 mA cm-2, respectively. This study presents a novel strategy for developing exceptionally efficient and free-standing 3D porous aerogel electrocatalysts with potential applications in hydrogen production.

Ultrathin core–shell Au@RuNi nanowires for superior electrocatalytic hydrogen evolution

Ultrathin core–shell Au@RuNi nanowires have been synthesized via the epitaxial growth of uniform fcc-structured RuNi alloy layer on the surface of ultrathin Au NWs, demonstrating remarkable alkaline HER performance and outstanding stability.

Specific Hydrogen Spillover Pathways Generated on Graphene Oxide Enabling the Formation of Non-Equilibrium Alloy Nanoparticles.

The phenomenon of hydrogen spillover is investigated as a means of realizing a hydrogen-based society for over half a century. Herein, a graphene oxide having a precisely tuned architecture via calcination in air to introduce ether groups onto basal planes along with carbon defects is reported. This material provides specific pathways for the spillover of atomic hydrogen and has practical applications with regard to the synthesis of non-equilibrium solid-solution alloy nanoparticles. A combination of experimental work and simulations confirmed that the presence of ether groups associated with carbon defects facilitated hydrogen spillover within the basal planes of this graphene oxide. This enhanced hydrogen spillover ability, in turn, enables the simultaneous reduction of Ru3+ and Ni2+ ions to form RuNi alloy nanoparticles under hydrogen reduction conditions. Energy dispersive X-ray and X-ray absorption near edge structure simulations establish that this strategy forms unique alloy nanoparticles each comprising a Ru core with a RuNi solid-solution shell having a hexagonal close-packed structure. These non-equilibrium RuNi alloy nanoparticles exhibit greater catalytic activity than monometallic Ru nanoparticles during the hydrolysis of ammonia borane.

High-Stability RuNi/C Electrocatalyst for Efficient Hydrogen Oxidation Reaction in Alkaline Condition.

The Ru-based catalyst for hydrogen oxidation reaction (HOR) with remarkable activity and reliability at high potential range remains a formidable challenge. Herein, the RuNi/C nanoparticles are customized, in which NiRu alloy is tightly wrapped with a carbon layer, delivering 2.2-fold and 8.3-fold enhancement in kinetic current density than that of commercial Pt/C and Ru/C, respectively. Notably, the current density maintains 2.93mAcm-2 disk at 0.6 V vsRHE, which effectively improves the stability of Ru-based catalysts at high voltage. The NiRu alloy triggers electron redistribution between two metal elements and regulates the surface adsorption performance, coupled with a tightly wrapped outer carbon layer which is in situ formed with alloy as a good conductor of electronic and protection from the electrolyte. This work not only provides a novel electrocatalyst for efficient HOR with its potential for industrial application but also opens up a new avenue for designing highly active catalytic systems.

Highly enhanced hydrazine oxidation on bifunctional Ni tailored by alloying for energy-efficient hydrogen production

The low-potential hydrazine oxidation reaction (HzOR) can replace the oxygen evolution reaction (OER) and thus assemble with the hydrogen evolution reaction (HER), consequently achieving energy-saving hydrogen (H2) production. Notably, developing sophisticated bifunctional electrocatalysts for HER and HzOR is a prerequisite for efficient H2 production. Alloying noble metals with eligible non-precious ones can increase affordability, catalytic activity, and stability, alongside rendering bifunctionality. Herein, RuNi alloy deposited onto carbon (RuNi/C) was directly prepared by a simple and highly practical co-reduction method, showing excellent performance for HER and HzOR. Interestingly, to achieve 10 mA cm−2, RuNi/C only required an ultralow potential of 24 mV for HER, on par with commercial 20 wt% platinum in carbon (Pt/C), and −65 mV for HzOR, surpassing most reported counterparts. Moreover, the two-electrode electrolyzer only required small operation voltages of 57.8 and 327 mV to drive 10 and 100 mA cm−2, respectively. Driven by a homemade hydrazine (N2H4) fuel cell and solar panel, appreciable H2 yields of 1.027 and 1.406 mmol h−1 were achieved, respectively, exhibiting the energy-saving advantages alongside robust practicability. Moreover, theoretical calculations revealed that alloying with Ru endows bifunctional Ni sites not only with a lower H2O dissociation barrier but also with more favorable H* adsorption alongside the reduced energy barrier between HzOR intermediates.

Flash synthesis of ultrafine and active NiRu alloy nanoparticles on N-rich carbon nanotubes via joule heating for efficient hydrogen and oxygen evolution reaction

The design and controlled synthesis of high-performance alloy nanoparticles as bifunctional electrocatalysts towards hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is of great industrial importance, but remains a great challenge. However, most of the prepared bimetallic alloys display unsatisfactory catalytic activity. Herein, NiRu alloy nanoparticles well-dispersed on N-rich carbon nanotubes (NiRu-CNTs) with a strong metal-support interaction (SMSI) are prepared through a flash Joule heating method in 0.5 s. Impressively, NiRu-CNTs exhibit remarkable HER activity under 1.0 M KOH solution with quite a small overpotential of 5.1 mV to reach the current density of 10 mA cm−2. In addition, superior HER stability up to 10 h with no noticeable current density degradation is realized. As expected, NiRu-CNTs exhibits excellent OER performance with a small overpotential of 270 mV at 10 mA cm−2, small Tafel slope of 54.1 mV dec−1, and long-term durability over 5000 CV cycles. When used in two-electrode electrolyzer for overall water splitting, NiRu-CNTs displays a low voltage of 1.85 V at 100 mA cm−2. This eco-friendly and cost-effective synthesis approach can be extended to the rational synthesis of various alloy catalysts with different metal species.

Revealing the Crystal Phase-Activity Relationship on NiRu Alloy Nanoparticles Encapsulated in N-Doped Carbon towards Efficient Hydrogen Evolution Reaction.

Adjusting the crystal phase of a metal alloy is an important method to optimize catalytic performance. However, detailed understanding about the phase-property relationship for the hydrogen evolution reaction (HER) is still limited. In this work, the crystal phase-activity relationship of NiRu nanoparticles is studied employing N-doped carbon shell coated NiRu nanoparticles with different phase contents. It is found that the NiRu@NC (mix) with both face-centred cubic (fcc) and thermodynamically unstable hexagonal close-packed (hcp) phase NiRu give the best HER performance. Further activity studies demonstrate that hcp NiRu has better HER performance, and NiRu@NC (mix) with rich (∼70 %) hcp phase presented outstanding performance with an overpotential of only 27 mV @ 10 mA ⋅ cm-2 . The high HER activity of NiRu@NC (mix) is attributed to the formation of hcp phase. This finding indicates that the regulation of crystal structure can provide a new strategy for optimizing HER activity.

Ru-Ni Alloy Nanoparticles Loaded on N-Doped Amphiphilic Mesoporous Hollow Carbon@silica Spheres as Catalyst for the Hydrogenation of α-Pinene to cis-Pinane.

N-doped mesoporous carbon spheres (NHMC@mSiO2 ) encapsulated in silica shells were prepared by emulsion polymerization and domain-limited carbonization using ethylenediamine as the nitrogen source, and Ru-Ni alloy catalysts were prepared for the hydrogenation of α-pinene in the aqueous phase. The internal cavities of this nanomaterial are lipophilic, enhancing mass transfer and enrichment of the reactants, and the hydrophilic silica shell enhances the dispersion of the catalyst in water. N-doping allows more catalytically active metal particles to be anchored to the amphiphilic carrier, enhancing its catalytic activity and stability. In addition, a synergistic effect between Ru and Ni significantly enhances the catalytic activity. The factors influencing the hydrogenation of α-pinene were investigated, and the optimum reaction conditions were determined to be as follows: 100 °C, 1.0 MPa H2 , 3 h. The high stability and recyclability of the Ru-Ni alloy catalyst were demonstrated through cycling experiments.

Hydrodeoxygenation of Anisole by Using a Ruthenium‐Containing Nickel‐Iron Hydrotalcite‐Based Catalyst

AbstractRuthenium‐loaded nickel‐iron (Ni−Fe) hydrotalcite materials were synthesized via the co‐precipitation method. The physicochemical properties of the synthesized materials were characterized by spectroscopic and analytical methods. The highly crystalline nature of Ni−Fe HT (NiFe‐0.5) hydrotalcite material was evident from powder XRD studies. The presence of uniformly dispersed ruthenium in its NiRu alloy form was evident from the TPR studies. The synthesized materials show promising catalytic performance for the hydrodeoxygenation (HDO) of anisole under ambient reaction conditions (190 °C, 20 bar H2). The catalyst prepared with a nickel‐to‐iron molar ratio of 2 : 1 (NF0.5 A) exhibited a good hydrotalcite structure and moderate catalytic activity for the hydrotreatment of anisole. The catalytic activity was improved by the introduction of 4 wt. % ruthenium on the surface of Ni−Fe hydrotalcite (NF0.5Ru), which shows 98 % anisole conversion with the selective formation of toluene as the major product. Catalytic activity remained for several consecutive runs. The recycled catalyst showed a similar conversion with the formation of toluene and methylcyclohexane as the major products. The variation in the selectivity might be due to the re‐dispersion of Ni−Ru active sites.

Pyrochlore Oxide Decorated with Exsolved Metal Nanoparticles for Enhanced Water Splitting Reaction

Recently, we reported hybrid catalysts consist of metal nanoparticles on a metal oxide support for water splitting reaction, which is synthesized through an in situ exsolution process of metallic nanoparticles on pyrochlore oxide material.1,2 Specifically, we prepared Ni substituted lead ruthenate pyrochlore oxide (Pb2Ru1.6Ni0.4O6.5) via sol-gel crystallization and reduce the samples at different temperatures. Ni nanoparticles supported pyrochlore oxide catalyst significantly accelerate the conversion of Ni to NiOOH due to favorable electron transfer during the oxygen evolution reaction. The hybrid catalyst of pyrochlore oxide with NiRu alloy nanoparticles exhibits superior hydrogen evolution reaction performance, resulting from the bifunctional reaction mechanism, modified electronic structure, and efficient electron transport. Consequently, remarkable water electrolysis performance with superior long-term stability was obtained at the hybrid catalysts.

Carbon supported NiRu nanoparticles as effective hydrogen evolution catalysts for anion exchange membrane water electrolyzers

Establishing anion exchange membrane water electrolysis (AEMWE) as a new technology for efficient hydrogen production requires cost-effective and high-performance catalyst materials. Here, we report the synthesis and comprehensive characterization of carbon supported NiRu alloy nanoparticles as a cost-effective hydrogen evolution reaction catalyst for AEMWEs. Different NiRu catalysts were synthesized using a facile and scalable impregnation method. Half-cell results showed the ‘NiRu’ catalyst with ca. 10 wt.% Ru to exhibit an increased noble metal mass activity and slightly decreased Tafel slope compared to a commercial Pt/C catalyst with 60 wt.% Pt. Further, we report the application of NiRu/C as a cathodic catalyst in AEMWE full cell for the first time. In full cell tests, the synthesized catalysts exhibit 2 A cm−2 at 1.95 V with a low loading of 0.1 mgPGM cm−2 at the cathode.