Pure Ru Research Articles

Intrinsic 77 K Phosphorescence Characteristics and Computational Modeling of Ru(II)-(Bidentate Cyclometalated-Aromatic Ligand) Chromophores: Their Relatively Low Nonradiative Rate Constants Originating from Low Spin-Orbit Coupling Driven Vibronic Coupling Amplitudes between Emitting and Ground States.

We investigated the photoinduced relaxation of Kasha-type emitting ruthenium-(bidentate cyclometalated aromatic ligand), Ru-CM, chromophores of [Ru(pzpy)2(CM)]+ ions (CM = 1-phenylisoquinoline, 2,3-diphenylpyrazine, and 1,4-diazatriphenylene and pzpy = 2-pyrazol-1-yl-pyridine). This is the first report of the phosphorescence behavior of pure Ru-(bidentate CM) chromophores. The 77 K photoinduced relaxation characteristics of phosphorescence chromophores showed emission quantum yields higher than those of reference Ru-bpy (bpy = 2,2'-bipyridine) chromophores in the emission region of 670-900 nm. This phenomenon of the Ru-CM chromophores could be attributed to their unusually low magnitudes for 77 K nonradiative rate constants (kNRD), although their radiative rate-constants (kRAD) are not remarkable. In order to examine the 77 K photoinduced behavioral relaxation difference between Ru-CM and Ru-bpy chromophores, we used computational simulation, applying the fundamental formalism of kRAD and temperature-independent kNRD equations, which included calculated spin-orbit coupling values.

One-step corrosion inducing the amorphous/crystalline-Co0.8Ru0.2/RuCoOx heterostructures for urea-assisted water decomposition at ampere-level current density

It is challenging to directionally construct the amorphous/crystalline (a/c)-alloy/oxide heterostructures with exceptional bifunctional electrocatalytic performances via a facile method. With these in mind, the a/c-RuCo NWs/NF electrode with the unique hollow structure and a/c-Co0.8Ru0.2/RuCoOx heterostructure was constructed by cleverly controlling the corrosion time. As expected, the well-designed a/c-RuCo NWs/NF||a/c-RuCo NWs/NF only needs 1.46 V to reach an industrial-grade current density of 1 A cm−2, outperforming other advanced electrodes. Strikingly, density functional theory (DFT) and in-situ Raman reveal that the Ruδ+-Ru0 dual-sites and Coδ+ at the a/c-Co0.8Ru0.2/RuCoOx heterointerface act as active species for alkaline HER and UOR, synergistically promoting urea-assisted water splitting. Surprisingly, the unique Co0.8Ru0.2 alloy exhibits the potential to surpass the pure Ru metal in optimizing d-band centers and the adsorption of reaction intermediates. Overall, the a/c-alloy/oxide bifunctional electrode with Ruδ+-Ru0-Coδ+ multi-active sites was constructed by one-step corrosion, providing a new idea for designing efficient a/c-alloy/oxide electrodes and realizing industrial urea-assisted water splitting.

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.

Modulating the Hydrogenation Mechanism of Electrochemical CO2 Reduction Using Ruthenium Atomic Species on Bismuth

AbstractThe conversion of CO2 into formate through electrochemical methods is emerging as an elegant approach for industrial‐scale CO2 utilization in the near future. Although Bismuth (Bi)‐based materials have shown promise thank to their excellent selectivity, their limited reactivity remains a challenge. Herein, this study demonstrates a significant enhancement in the CO2‐to‐formate efficiency of Bi by incorporating ruthenium (Ru) atomic species. Ru single atom doped Bi exhibited a nearly twofold higher partial current density compared with pure Bi and Ru clusters doped Bi, while over 95% Faradaic efficiency (FE) is maintained. Through comprehensive investigations using a combined approach of electrochemical techniques, operando spectroscopy, and theoretical calculations, this study elucidates that the presence of Ru single atom promotes H2O dissociation and H* migration to Bi sites for CO2‐to‐formate conversion by significantly reducing the energy barrier via a H* spillover path. Besides, it is constructed Ru–Bi bridge sites for efficient CO2 hydrogenation via a non‐spillover path, which served as the major mechanism for CO2‐to‐formate conversion in Ru single atom doped Bi.

A Sustainable Route to Ruthenium Phosphide (RuP)/Ru Heterostructures with Electron-Shuttling of Interfacial Ru for Efficient Hydrogen Evolution.

Ruthenium (Ru) is a promising electrocatalyst for the hydrogen evolution reaction (HER), despite suffering from low activity in non-acidic conditions due to the high kinetic energy barrier of H2O dissociation. Herein, the synthesis of carbon nanosheet-supported RuP/Ru heterostructures (RuP/Ru@CNS) from a natural polysaccharide is reported and demonstrates its behavior as an effective HER electrocatalyst in non-acidic conditions. The RuP/Ru@CNS exhibits low overpotential (106mV at 200 mA·cm-2) in alkaline electrolyte, exceeding most reported Ru-based electrocatalysts. The electron shuttling between Ru atoms at the RuP/Ru interface results in a lowered energy barrier for H2O dissociation by electron-deficient Ru atoms in the pure Ru phase, as well as optimized H* adsorption of electron-gaining Ru atoms in the neighboring RuP. A low H* spillover energy barrier between Ru atoms at the RuP/Ru interface further boosts HER kinetics. This study demonstrates a sustainable method for the fabrication of efficient Ru-based electrocatalysts and provides a more detailed understanding of interface effects in HER catalysis.

Breaking linear scaling relationships in NRR with hydrogen bonding in confined space: A case study of g-C3N4 covered Ru(001) system

The electrochemical nitrogen reduction reaction (NRR) is a very efficient method for sustainable NH3 production under mild conditions, but it requires effective catalysts to expedite the NRR kinetics. However, the linear scaling relationships between the energies of elementary steps in NRR severely limit the rates of thermally catalysis reactions. Using density functional theory calculations, we demonstrate that these scaling relations can be circumvented by introducing hydrogen bonding and confinement field in g-C3N4/Ru(Rh) catalysis. Specially, the adsorption strength of key intermediate *N2H can be enhanced on the g-C3N4/Ru(Rh) own to the formation of H···N hydrogen bonding, while the adsorption of N2 is weakened due to the steric confinement field of the covered g-C3N4, resulting a significantly decrease of the energy barrier for the potential-limiting step in g-C3N4/Ru(Rh) system compared that in pure Ru(Rh) surface. Moreover, the hydrogen bonding strength between g-C3N4 and *NxHy increases with increasing of H atoms, which lower the energy barrier for the following protonation steps. Our results provide guidance for optimizing catalysts for application with hydrogen bonding and steric confinement.

Modulating the electronic structure of VS2via Ru decoration for an efficient pH-universal electrocatalytic hydrogen evolution reaction.

High-efficiency water electrolysis over a broad pH range is desirable but challenging. Herein, Ru-decorated VS2 on carbon cloth (Ru-VS2/CC) has been in situ synthesized, which features the regulated electronic structure of VS2 by introducing Ru. It is remarkable that the optimal Ru-VS2/CC displays excellent electrocatalytic hydrogen evolution activity with overpotentials of 89 and 87 mV at -10 mA cm-2 in 0.5 M H2SO4 and 1.0 M KOH, respectively. Theoretical calculations and electrocatalytic measurements have demonstrated that introducing Ru induces an enhanced charge density around the Fermi level, facilitating charge transfer and speeding up the electrocatalytic HER kinetics. The Gibbs free energy of the hydrogen intermediate (ΔGH*) of Ru-VS2/CC (0.23 eV) is much closer to zero than that of pure VS2 (0.51 eV) and Ru (-0.37 eV), demonstrating an easier hydrogen adsorption and desorption process for Ru-VS2/CC. The more favorable ΔGH*, differential charge density and the d-band center endow Ru-VS2 with enhanced intrinsic electrocatalytic activity. This study presents a feasible strategy for enhancing electrocatalytic HER activity by the regulation of the electronic structure and the rational integration of dual active components.

Ti3C2Tx nanosheets with uniformly anchored Ru nanoparticles for efficient acidic and basic hydrogen evolution reaction

Developing an efficient and stable electrocatalyst for hydrogen evolution reaction (HER) remains critically significance for renewable hydrogen production. Herein, a facile electrochemical reduction method was proposed to fabricate Ru nanoparticles (NPs) evenly anchored on Ti3C2Tx nanosheets (Ti3C2Tx-NS) electrocatalyst (Ru@Ti3C2Tx-NS). Interestingly, owing to the interaction between Ru NPs and Ti3C2Tx-NS, the resultant Ru@Ti3C2Tx-NS electrocatalyst performed a Pt-like electrocatalytic property for HER under the acidic solution with an ultra-low overpotential of 46.75 mV to reach −10 mA/cm2, a small Tafel slope of 30.6 mV/dec, and long-term stability. Simultaneously, the Ru@Ti3C2Tx-NS also displayed splendid HER electrocatalytic performance in the basic condition. Furthermore, Ru@Ti3C2Tx-NS showed a lower value of Gibbs free energy for HER (−0.21 eV) than either pure Ru or Ti3C2Tx-NS from the theoretical calculation results. It is expected that such a promising approach would be extended to design and fabricate other noble metal NPs anchored MXene nanosheets for HER application.

DFT–kMC Analysis for Identifying Novel Bimetallic Electrocatalysts for Enhanced NRR Performance by Suppressing HER at Ambient Conditions Via Active-Site Separation

As an alternative to the traditional Haber-Bosch process for ammonia synthesis under high temperature and pressure, the electrochemical nitrogen reduction reaction (NRR) under ambient conditions has been getting attention. Although ruthenium (Ru) is considered the holy-grail catalyst for the NH3 process, it suffers from low selectivity due to the competition between NRR and hydrogen evolution reaction. Experimental screening of new candidate catalysts that can circumvent this challenge is highly resource-intensive, requiring significant labor and expensive precursors. To address this challenge, we have combined density functional theory and kinetic Monte Carlo to shortlist high-performing NRR catalysts. Specifically, this framework utilizes a combination of thermodynamic, electronic, and kinetic analyses to investigate different bimetallic catalysts (i.e., RuTi, RuV2, Ru3W, RuZn3, and RuZr) with specially designed separate active sites for N2 and H adsorption to enhance NRR performance. Our investigations revealed that the newly suggested RuV2 has superior NRR activity with decreased thermodynamic overpotential and increased reaction rates that surpass those of Ru. Notably, RuV2 shows a high N2 selectivity by significantly reducing H poisoning on the catalyst surface and increasing the amount of NH3 with a turnover frequency of 1.1 × 10–4 s–1 under mild conditions (300 K and 1 bar), which is 1 000 times greater than that of a pure Ru electrocatalyst. Given these key observations, we believe our framework can play a pivotal role in elucidating the role of different active sites for NRR and can be extended to other high-impact metallic catalyst families in the future.

Modulating CoFeOX Nanosheets Towards Enhanced CO2 Photoreduction to Syngas: Effect of Calcination Temperature and Mixed-Valence Multi-Metals.

CoFeOX nanosheets were synthesized by a facile coprecipitation and calcination method. The effect of calcination temperature on the crystal texture, morphology and surface areas of CoFeOX were fully explored. CoFeOX sample calcined at 600 °C (CoFeOX -600) showed superior catalytic performance for the reduction of CO2 under visible light. Compared with the pure Ru(bpy)3 2+ -sensitized CO2 reduction system, the CoFeOX -added system achieved 19-fold enhancement of CO production (45.7 μmol/h). The mixed valence state and nanosheet-like structure of CoFeOX cocatalyst support its ultra-high charge transfer and abundant CO2 active adsorption sites exposure, which promote the separation of photogenerated charges, and thus improve the photocatalytic CO2 reduction activity. Carbon source of CO from CO2 was verified by 13 CO2 isotopic labelling experiment. Repeated activity experiments confirmed the good stability of CoFeOX in the CO2 photoreduction system. This work would provide prospective insights into developing novel cost-effective, efficient, and durable non-precious metal cocatalysts to improve the efficiency of photocatalytic reduction of CO2 .

Highly efficient RuTe2/C electrocatalyst for oxygen reduction reaction in proton exchange membrane fuel cells

It is desirable but challenging for ruthenium (Ru)-based chalcogenides to achieve high activity and good durability toward oxygen reduction reaction (ORR) in fuel cell applications. In this work, a facile microwave route followed by heat treatment was utilized to synthesize carbon supported ruthenium tellurium (RuTe2/C) catalysts, and the effects of heat treatment temperature on crystal structure, microstructure, chemical state, electrocatalytic activity, and fuel cell performance were studied. The mixed phase of predominant orthorhombic RuTe2 and minor hexagonal Ru was identified as dual active sites for RuTe2/C catalysts. Density functional theory calculations demonstrated that orthorhombic RuTe2 exhibits enhanced intrinsic activity relative to pure Ru due to the weakened absorption energies of oxygen intermediates. Because of the smallest nanoparticle size and complete formation of an orthorhombic RuTe2 structure, the best ORR performance was achieved with the RuTe2/C catalyst heat treated at 400 °C, showing a maximum half-wave potential of 0.70 V and only a 70 mV drop (10.0% loss) after 6000 potential cycles. In a H2/O2 fuel cell test, the best-performed RuTe2/C catalyst delivered a maximum power density of 672 mW⋅cm−2 using a low cathode Ru loading of 0.18 mg·cm−2, which is the best performance ever achieved for the Ru-based catalysts. After 6000 cycles of rigorous accelerated degradation test, the cell performance decayed by 55.4% because of the migrations of Te and Ru from the cathode side to the anode side and the growth of the RuTe2/C nanoparticles.

Ferromagnetism in Pr-rich binary Pr7Ru3 intermetallic compound

We present the synthesis and experimental characterization of the binary intermetallic compound Pr7Ru3. The polycrystalline sample was prepared by arc melting pure Pr and Ru, followed by homogenization at 500 °C and 600 °C for 48 and 89 h, respectively. Powder x-ray diffraction confirms that Pr7Ru3 crystallizes in an orthorhombic crystal structure (Pnma, space group no. 62) with the lattice parameters: a = 7.3606(7) Å, b = 23.120(1) Å and c = 6.5959(5) Å. Magnetization, resistivity, and heat capacity measurements reveal a ferromagnetic transition in Pr7Ru3 with the Curie temperature TC ∼ 24.5 K. The bulk transition is confirmed by a large λ-shape anomaly observed in the specific heat measurement. The magnetic susceptibility above the transition obeys the modified Curie-Weiss law with a positive Curie-Weiss temperature ϴCW = 30(1) K and an effective magnetic moment of 3.39(1) μB/Pr. Resistivity data for Pr7Ru3 reveals metallic-like behavior with a clear anomaly at the transition temperature which is smeared by an applied magnetic field. We also synthesized high-quality nonmagnetic analog La7Ru3 for which superconducting transition is observed with Tc = 1.95 K, in agreement with the literature.

Temperature-controlled synthesis of heterostructured Ru-Ru2P nanoparticles embedded in carbon nanofibers for highly efficient hydrogen production

Developing highly efficient, cost-effective, and stable electrocatalysts for hydrogen evolution reaction (HER) is of considerable importance but remains challenging. Herein, we report the fabrication of a robust Ru-based electrocatalyst, which comprises heterostructured Ru-Ru2P nanoparticles that are embedded in the N,P-codoped carbon nanofibers (CNFs), through a synthetic strategy involving electrospinning and temperature-controlled pyrolysis treatment. The as-prepared Ru-Ru2P catalyst (Ru-Ru2P@CNFs) shows excellent HER catalytic activities with low overpotentials of 11 and 14 mV in acidic and alkaline media, respectively, to achieve a current density of 10 mA cm−2, which are superior to the individual components of pure Ru and Ru2P catalysts. Density functional theory calculations demonstrate the existence of electronic coupling effect between Ru and Ru2P at the heterointerfaces, leading to a well-modulated electronic structure with optimized hydrogen adsorption strength and enhanced electrical conductivity for efficient HER electrocatalysis. In addition, the overall synthetic strategy can be generalized for the synthesis of a series of transitional metal phosphide-based nanofibers, thereby holding a remarkable capacity for various potential applications.

A trace of Pt can significantly boost RuO2 for acidic water splitting

The development of highly potential electrocatalysts for acidic water electrolysis is particularly desirable for many energy-related processes. Herein, we demonstrated a versatile strategy to activate and stabilize RuO2-based electrocatalyst for acidic water splitting by a trace of Pt, where Pt plays an essential role in promoting oxygen evolution reaction (OER), and can simultaneously act as the active site for hydrogen evolution reaction (HER). Compared with pure Ru oxide nanosheet assemblies (Ru ONAs), the “5%Pt-containing” Ru ONAs (5%Pt-Ru ONAs) achieve much enhanced OER activity in 0.5 and 0.05 mol/L H2SO4, with much lower overpotentials of 227 and 234 mV at 10 mA cm−2, respectively. Experimental and theoretical analyses reveal that the atomically dispersed Pt incorporating into RuO2 lattice is conducive to increasing the concentration of O vacancies, which effectively enhances the interaction with reaction intermediate and thus lowers the energy barrier for the formation of OOH*. Moreover, benefited from the presence of Pt, the formation of RuO2 is more achievable when proper annealing is applied. In addition to OER, due to the presence of active Pt, the HER performance of 5%Pt-Ru ONAs can also be ensured, thereby realizing efficient acidic overall water splitting. Finally, the excellent activity can also be achieved without sacrificing stability. This work highlights an attractive strategy for designing active and stable RuO2-based electrocatalysts for acidic overall water splitting.

Determination of optical constants of thin films in the EUV.

The determination of fundamental optical parameters is essential for the development of new optical elements such as mirrors, gratings, or photomasks. Especially in the extreme ultraviolet (EUV) and soft x-ray spectral range, the existing databases for the refractive indices of many materials and compositions are insufficient or are a mixture of experimentally measured and calculated values from atomic scattering factors. Since the physical properties of bulk materials and thin films with thicknesses in the nanometer range are not identical, measurements need to be performed on thin layers. In this study we demonstrate how optical constants of various thin film samples on a bulk substrate can be determined from reflection measurements in the EUV photon energy range from 62 eV to 124 eV. Thin films with thickness of 20 nm to 50 nm of pure Mo, Ni, Pt, Ru, Ta, and Te and different compositions of NixAlx, PtTe, PtxMo, RuxTax, Ru3Re, Ru2W, and TaTeN were prepared by DC magnetron sputtering and measured using EUV reflectometry. The determination optical constants of the different materials are discussed and compared to existing tabulated values.

Origin of Enhanced Ammonia Synthesis on Ru–Co Catalysts Unraveled by Density Functional Theory

Bimetallic Ru–Co catalysts have been reported as promising NH3 production catalysts that are better than various Ru–X alloys, including RuFe and pure Ru, under mild conditions; however, a systematic understanding of their superior activity is still lacking. Here, we report a comprehensive theoretical study on NH3 synthesis of Ru–Co catalysts using density functional theory and microkinetic modeling. Indeed, the RuCo surface enables more facile N2 dissociation than the Ru surface, which results from the manifested Co-induced spin symmetry breaking of Ru. We also investigated the surface phase diagram of RuCo(0001) with partial pressures of H2 and N2 gases and found that the most stable phase of the RuCo surface consists of a fraction of both N and H atoms under experimental Haber–Bosch pressure conditions; however, NH3 can be readily produced on the surfaces without severe surface poisoning issues. Furthermore, this study shows that the spin-symmetry breaking of nonmagnetic surfaces can enhance the catalytic activity for NH3 synthesis, which provides an alternative strategy to catalyst design.

Amorphous/Crystalline Heterophase Ruthenium Nanosheets for pH‐Universal Hydrogen Evolution

To design and synthesize heterophase noble-metal materials is of crucial importance owing to their unique structure and apparent properties. Ruthenium (Ru) is one of the most active candidates for hydrogen evolution reaction because of its low price compared with other precious metals, which is favorable for industrial hydrogen cycle operation. In this study, free-standing amorphous/crystalline Ru nanosheets are facilely synthesized through a controlled annealing method. Charge redistribution occurs at the phase interface because of the work function difference between amorphous and crystalline domains. The resulting structure and property are conductive to the adsorption and dissociation of water molecules, associated with optimized hydrogen interaction and enhanced binding between Ru atoms. Accordingly, electrochemical measurements demonstrate that the amorphous/crystalline heterophase Ru exhibits improved hydrogen evolution efficiency as compared with pure amorphous Ru and pure crystalline Ru, at pH-universal conditions. Specifically, only 16.7mV overpotential is required to reach 10mA cm-2 in 1.0 m KOH. Meanwhile, the heterophase structure displays a higher stability during operation than pure amorphous and crystalline structures. This study demonstrates the importance of phase engineering, broadens the Ru-based material family, and provides more insights for developing efficient metal materials.

Optimizing Hydrogen Binding on Ru Sites with RuCo Alloy Nanosheets for Efficient Alkaline Hydrogen Evolution.

Ruthenium (Ru)‐based catalysts, with considerable performance and desirable cost, are becoming highly interesting candidates to replace platinum (Pt) in the alkaline hydrogen evolution reaction (HER). The hydrogen binding at Ru sites (Ru−H) is an important factor limiting the HER activity. Herein, density functional theory (DFT) simulations show that the essence of Ru−H binding energy is the strong interaction between the 4dz2 orbital of Ru and the 1s orbital of H. The charge transfer between Ru sites and substrates (Co and Ni) causes the appropriate downward shift of the 4dz2 ‐band center of Ru, which results in a Gibbs free energy of 0.022 eV for H* in the RuCo system, much lower than the 0.133 eV in the pure Ru system. This theoretical prediction has been experimentally confirmed using RuCo alloy‐nanosheets (RuCo ANSs). They were prepared via a fast co‐precipitation method followed with a mild electrochemical reduction. Structure characterizations reveal that the Ru atoms are embedded into the Co substrate as isolated active sites with a planar symmetric and Z‐direction asymmetric coordination structure, obtaining an optimal 4dz2 modulated electronic structure. Hydrogen sensor and temperature program desorption (TPD) tests demonstrate the enhanced Ru−H interactions in RuCo ANSs compared to those in pure Ru nanoparticles. As a result, the RuCo ANSs reach an ultra‐low overpotential of 10 mV at 10 mA cm−2 and a Tafel slope of 20.6 mV dec−1 in 1 M KOH, outperforming that of the commercial Pt/C. This holistic work provides a new insight to promote alkaline HER by optimizing the metal‐H binding energy of active sites.

Optimizing Hydrogen Binding on Ru Sites with RuCo Alloy Nanosheets for Efficient Alkaline Hydrogen Evolution

AbstractRuthenium (Ru)‐based catalysts, with considerable performance and desirable cost, are becoming highly interesting candidates to replace platinum (Pt) in the alkaline hydrogen evolution reaction (HER). The hydrogen binding at Ru sites (Ru−H) is an important factor limiting the HER activity. Herein, density functional theory (DFT) simulations show that the essence of Ru−H binding energy is the strong interaction between the orbital of Ru and the 1s orbital of H. The charge transfer between Ru sites and substrates (Co and Ni) causes the appropriate downward shift of the ‐band center of Ru, which results in a Gibbs free energy of 0.022 eV for H* in the RuCo system, much lower than the 0.133 eV in the pure Ru system. This theoretical prediction has been experimentally confirmed using RuCo alloy‐nanosheets (RuCo ANSs). They were prepared via a fast co‐precipitation method followed with a mild electrochemical reduction. Structure characterizations reveal that the Ru atoms are embedded into the Co substrate as isolated active sites with a planar symmetric and Z‐direction asymmetric coordination structure, obtaining an optimal modulated electronic structure. Hydrogen sensor and temperature program desorption (TPD) tests demonstrate the enhanced Ru−H interactions in RuCo ANSs compared to those in pure Ru nanoparticles. As a result, the RuCo ANSs reach an ultra‐low overpotential of 10 mV at 10 mA cm−2 and a Tafel slope of 20.6 mV dec−1 in 1 M KOH, outperforming that of the commercial Pt/C. This holistic work provides a new insight to promote alkaline HER by optimizing the metal‐H binding energy of active sites.

Strong Electron Coupling of Ru and Vacancy-Rich Carbon Dots for Synergistically Enhanced Hydrogen Evolution Reaction.

The exploitation of ingenious strategies to improve the activity and stability of ruthenium (Ru) is crucial for the advancement of Ru-based electrocatalysts. Vacancy engineering is a typical strategy for modulating the catalytic activity of electrocatalysts. However, creating vacancies directly into pure metallic Ru is difficult because of the extremely stringent conditions required and will result in instability because the integrity of the crystal structure is destroyed. In response, a compromise tactic by introducing vacancies in a Ru composite structure is proposed, and vacancy-rich carbon dots coupled with Ru (Ru@CDs) are elaborately constructed. Specifically, the vacancy-rich carbon dots (CDs) serve as an excellent platform for anchoring and trapping Ru nanoparticles, thus restraining their agglomeration and growth. As expected, Ru@CDs exhibited excellent catalytic performance with a low overpotential of 30 mV at 10 mA cm-2 in 1 m KOH, a small Tafel slope of 22 mV decade-1 , and robust stability even after 10000 cycles. The low overpotential is comparable to those of most previously reported Ru-based electrocatalysts. Additionally, spectroscopic characterizations and theoretical calculations demonstrate that the rich vacancies and the electron interactions between Ru and CDs synergistically lower the intermediate energy barrier and thereby maximize the activity of the Ru@CDs electrocatalyst.