Enhanced Hydrogen Evolution Reaction in Alkaline Media via Ruthenium-Chromium Atomic Pairs Modified Ruthenium Nanoparticles

Precisely optimizing the electronic metal support interaction (EMSI) of the electrocatalysts and tuning the electronic structures of active sites are crucial for accelerating water adsorption and dissociation kinetics in alkaline hydrogen evolution reaction (HER). Herein, an effective strategy is applied to modify the electronic structure of Ru nanoparticles (RuNPs) by incorporating Ru single atoms (RuSAs) and Ru and Cr atomic pairs (RuCrAPs) onto a nitrogen-doped carbon (N-C) support through optimized EMSI. The resulting catalyst, RuNPs-RuCrAPs-N-C, shows exceptional performance for alkaline HER, achieving a six times higher turnover frequency (TOF) of 13.15 s⁻¹ at an overpotential of 100 mV, compared to that of commercial Pt/C (2.07 s⁻¹). Additionally, the catalyst operates at a lower overpotential at a current density of 10 mA·cm⁻2 (η10 = 31 mV), outperforming commercial Pt/C (η10 = 34 mV). Experimental results confirm that the RuCrAPs modified RuNPs are the main active sites for the alkaline HER, facilitating the rate-determining steps of water adsorption and dissociation. Moreover, the Ru-Cr interaction also plays a vital role in modulating hydrogen desorption. This study presents a synergistic approach by rationally combining single atoms, atomic pairs, and nanoparticles with optimized EMSI effects to advance the development of efficient electrocatalysts for alkaline HER.

Rare-Earth Oxychlorides as Promoters of Ruthenium Toward High-Performance Hydrogen Evolution Electrocatalysts for Alkaline Electrolyzers

Developing efficient electrocatalysts for hydrogen evolution reaction (HER) in alkaline environments is vital for hydrogen production, owing to the extra water dissociation and hydroxyl desorption steps. Here, rare-earth oxychlorides (REOCl) are proposed as innovative promoters for ruthenium as HER electrocatalyst in alkali. The lamellar structure of REOCl with weakly bond [Cl] layers can facilitate the formation of an internal electric field that enhances interphase charge transfer. Taking ruthenium/ neodymium oxychloride (Ru/NdOCl) composites as a case study, sub ≈4 nm Ru nanoparticles are successfully embedded into NdOCl crystals through a rapid self-exothermic process, and the highly-coupled Ru-Cl/O-Nd interfaces are observed as metallic Ru particles with the edge of the NdOCl lamellar layers, where the [Nd2O2] and [Cl] layers act as the negative and positive charge transfer channels, respectively. The enhanced charge transfer between REOCl and Ru makes the highly-coupled Ru/REOCl catalysts show better electrocatalytic activity than both the benchmark Pt and Ru catalysts in alkaline electrolyte. This work will encourage more novel promoters for electrocatalysis and other emerging technologies.

Effect of Nitrogen and Phosphorus Doping of Reduced Graphene Oxide in the Hydrogen Evolution Catalytic Activity of Supported Ru Nanoparticles

Three different cathodic materials for the hydrogen evolution reaction (HER) consisting of Ru nanoparticles (NPs) supported onto a bare and two doped reduced graphene oxides (r-GO) have been studied. Ru NPs have been synthesized in situ by means of the organometallic approach in the presence of each reduced graphene support (bare (rGO), N-doped (NH2-rGO) and P-doped (P-rGO)). (HR)TEM, EDX, EA, ICP-OES, XPS, Raman and NMR techniques have been used to fully characterize the obtained rGO-supported Ru materials. These materials have been deposited onto a glassy carbon rotating disk electrode (GC-RDE) to assess their HER electrocatalytic activity at acidic pH. The results show that all three materials are stable under reductive conditions for at least 12 h, and that the heteroatom-doping of the graphene structure extremely increases the activity of the electrodes, especially for the case of Ru@P-rGO, where the overpotential at -10 mA·cm-2 decreases to only 2 mV. Realistic (based on experimental compositional data) modeling of the three rGO supports combined with DFT computational analysis of the electronic and electrocatalytic properties of the hybrid nanocatalysts allows attributing the observed electrocatalytic performances to a combination of interrelated factors such as the distance of the Ru atoms to the dopped rGO support and the hydride content at the Ru NP surface.

Harvesting Green Hydrogen from the Deep Blue: Seawater-Compatible SnSe-P Decorated Graphene-CNTs Based Electrocatalyst Under Universal pH

Fabrication of cost-effective and robust metal-based electrocatalysts for hydrogen evolution reactions (HER) across the entire pH range has garnered significant attention in harvesting renewable energy. Herein, the fabrication of 3D high-surface Ni Foam-Graphene-Carbon Nanotubes (NGC) decorated with phosphorous-inserted tin selenide (SnSe-P) showcases unprecedented HER activity with minimal overpotentials across all pH ranges (52 mV in acidic, 93 mV in basic, and 198 mV in neutral conditions@10 mA cm-2) and stability at 1 A cm-2 for 72 h. The as-designed catalyst shows a low overpotential of 122 mV@10 mA cm-2 in alkaline seawater, achieved through controlled electronic distribution on Sn site after incorporation of P in NGC-SnSe-P. A stable cell voltage of 1.56 V@10 mA cm⁻2 is achieved for prolonged time in 1 m KOH toward overall water electrolysis. Experimental and theoretical investigation reveals that the insertion of P in layered SnSe enables s orbitals of H* and p orbitals of Sn to interact, favoring the adsorption of the H* intermediate. A renewable approach is adopted by using silicon solar cells (η = 10.66%) to power up the electrolyzer, yielding a solar-to-hydrogen (STH) conversion efficiency of 7.70% in 1 m KOH and 5.65% in alkaline seawater, aiming toward green hydrogen production.

Rapid Synthesis of Ruthenium-Copper Nanocomposites as High-Performance Bifunctional Electrocatalysts for Electrochemical Water Splitting

Development of high-performance, low-cost catalysts for electrochemical water splitting is key to sustainable hydrogen production. Herein, ultrafast synthesis of carbon-supported ruthenium-copper (RuCu/C) nanocomposites is reported by magnetic induction heating, where the rapid Joule's heating of RuCl3 and CuCl2 at 200 A for 10 s produces Ru-Cl residues-decorated Ru nanocrystals dispersed on a CuClx scaffold, featuring effective Ru to Cu charge transfer. Among the series, the RuCu/C-3 sample exhibits the best activity in 1 m KOH toward both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), with an overpotential of only -23 and +270 mV to reach 10 mA cm-2, respectively. When RuCu/C-3 is used as bifunctional catalysts for electrochemical water splitting, a low cell voltage of 1.53 V is needed to produce 10 mA cm-2, markedly better than that with a mixture of commercial Pt/C+RuO2 (1.59 V). In situ X-ray absorption spectroscopy measurements show that the bifunctional activity is due to reduction of the Ru-Cl residues at low electrode potentials that enriches metallic Ru and oxidation at high electrode potentials that facilitates the formation of amorphous RuOx. These findings highlight the unique potential of MIH in the ultrafast synthesis of high-performance catalysts for electrochemical water splitting.

An advanced Ru-based alkaline HER electrocatalyst benefiting from Volmer-step promoting 5d and 3d co-catalysts

In this study, a trimetallic catalyst, NiWRu@NF, is electrodeposited onto nickel foam using chronoamperometry to enhance the hydrogen evolution reaction (HER) in alkaline water electrolysis. The catalyst combines nickel, tungsten, and ruthenium components, strategically designed for efficiency and cost-effectiveness, hydroxyl transfer and water dissociation, and acceleration of hydrogen combination, respectively. Evaluation of NiWRu@NF reveals exceptional performance, with a low overpotential of -50 mV and high current density of -10 mA cm-2, signifying its efficiency in promoting HER. Tafel values further corroborate the catalyst's effectiveness, indicating a rapid reaction rate of hydrogen evolution in such a highly alkaline medium compared to other controls studied along with it. This study underscores the significance of NiWRu@NF in advancing alkaline HER kinetics, paving the way for more efficient electrolysis processes.

Energy-Efficient Electrosynthesis of High Value-Added Active Chlorine Coupled with H2 Generation from Direct Seawater Electrolysis through Decoupling Electrolytes

Direct saline (seawater) electrolysis is a well-recognized system to generate active chlorine species for the chloride-mediated electrosynthesis, environmental remediation and sterilization over the past few decades. However, the large energy consumption originated from the high cell voltage of traditional direct saline electrolysis system, greatly restricts its practical application. Here, we report an acid-saline hybrid electrolysis system for energy-saving co-electrosynthesis of active chlorine and H2. We demonstrate that this system just requires a low cell voltage of 1.59 V to attain 10 mA cm-2 with a large energy consumption decrease of 27.7 % compared to direct saline electrolysis system (2.20 V). We further demonstrate that such acid-saline hybrid electrolysis system could be extended to realize energy-saving and sustainable seawater electrolysis. The acidified seawater in this system can absolutely avoid the formation of Ca/Mg-based sediments that always form in the seawater electrolysis system. We also prove that this system in the half-flow mode can realize real-time preparation of active chlorine used for sterilization and pea sprout production.

Facet modulation of nickel-ruthenium nanocrystals for efficient electrocatalytic hydrogen evolution

Constructing highly active electrocatalysts towards hydrogen evolution reaction (HER) in both alkaline and acidic media is essential for achieving a sustainable energy economy. Here, a facile ethylene glycol reduction strategy was employed to design the nickel-ruthenium nanocrystals (Ni-Ru NC) with an exposed highly active Ru (101) facet as an efficient electrocatalyst for HER. Testings show Ni-Ru NC outperforms the benchmark catalyst Pt/C by delivering extraordinarily low overpotentials of 21.1 and 70.9 mV to drive 10 mA cm^-2 in acidic and alkaline solutions, respectively. The results of experimental and theoretical studies suggest that Ni can modulate the electronic structure of the Ru NC and optimize the hydrogen adsorption free energy on Ru's surface, which accelerates the charge transfer kinetics and enhances the HER performance. The study support the potential application of facet-modulated Ru-based HER eleccatalyst in an alkaline environment.

Recent advances in understanding and design of efficient hydrogen evolution electrocatalysts for water splitting: A comprehensive review

An unsustainable reliance on fossil fuels is the primary cause of the vast majority of greenhouse gas emissions, which in turn lead to climate change. Green hydrogen (H₂), which may be generated by electrolyzing water with renewable power sources, is a possible substitute for fossil fuels. On the other hand, the increasing intricacy of hydrogen evolution electrocatalysts that are presently being explored makes it more challenging to integrate catalytic theories, catalytic fabrication procedures, and characterization techniques. This review will initially present the thermodynamics, kinetics, and associated electrical and structural characteristics for HER electrocatalysts before highlighting design approaches for the electrocatalysts. Secondly, an in-depth discussion regarding the rational design, synthesis, mechanistic insight, and performance improvement of electrocatalysts is centered on both the intrinsic and extrinsic influences. Thirdly, the most recent technological advances in electrocatalytic water-splitting approaches are described. Finally, the difficulties and possibilities associated with generating extremely effective HER electrocatalysts for water-splitting applications are discussed.

Review of the Design of Ruthenium-Based Nanomaterials and Their Sensing Applications in Electrochemistry

In this review, ruthenium nanoparticles (Ru NPs)-based functional nanomaterials have attractive electrocatalytic characteristics and they offer considerable potential in a number of fields. Ru-based binary or multimetallic NPs are widely utilized for electrode modification because of their unique electrocatalytic properties, enhanced surface-area-to-volume ratio, and synergistic effect between two metals provides as an effective improved electrode sensor. This perspective review suggests the current research and development of Ru-based nanomaterials as a platform for electrochemical (EC) sensing of harmful substances, biomolecules, insecticides, pharmaceuticals, and environmental pollutants. The advantages and limitations of mono-, bi-, and multimetallic Ru-based nanocomposites for EC sensors are discussed. Besides, the relevant EC properties and analyte sensing approaches are also presented. On the basis of these insights, we highlighted recent results for synthesizing techniques and EC environmental pollutant sensors from the perspectives of diverse supports, including graphene, carbon nanotubes, silica, semiconductors, metal sulfides, and polymers. Finally, this work overviews the modern improvements in the utilization of Ru-based nanocomposites on the basis for electroanalytical sensors as well as suggestions for the field's future development.

Rational Design of Better Hydrogen Evolution Electrocatalysts for Water Splitting: A Review

The excessive dependence on fossil fuels contributes to the majority of CO2 emissions, influencing on the climate change. One promising alternative to fossil fuels is green hydrogen, which can be produced through water electrolysis from renewable electricity. However, the variety and complexity of hydrogen evolution electrocatalysts currently studied increases the difficulty in the integration of catalytic theory, catalyst design and preparation, and characterization methods. Herein, this review first highlights design principles for hydrogen evolution reaction (HER) electrocatalysts, presenting the thermodynamics, kinetics, and related electronic and structural descriptors for HER. Second, the reasonable design, preparation, mechanistic understanding, and performance enhancement of electrocatalysts are deeply discussed based on intrinsic and extrinsic effects. Third, recent advancements in the electrocatalytic water splitting technology are further discussed briefly. Finally, the challenges and perspectives of the development of highly efficient hydrogen evolution electrocatalysts for water splitting are proposed.

Anchoring Co3S4 nanowires on NiCo2O4 nanosheet arrays as high-performance electrocatalyst for hydrogen and oxygen evolution

The development of catalysts which can substitute expensive metals to efficiently split water is currently a hot research topic. Here, multi-layered NF/NiCo2O4/Co3S4 nanocomposite was prepared on 3D porous nickel foam...

Hyperdispersed ruthenium nanoparticles anchored on S/N co-doped carbon nanotubes as an efficient HER electrocatalyst

Hyperdispersed ruthenium nanoparticles anchored on S/N co-doped carbon nanotubes show the same high-performance HER catalytic activity as commercial Pt/C.

Minutely dispersed ruthenium in tremella-like N-doped carbon for enhanced visible-light-driven photocatalytic hydrogen production by CdS quantum dots

The employment of Ru/NC effectively retards the recombination of charge carriers by the storage and consumption of photo-excited electrons, achieving a significantly improved activity for H2 evolution, which is 21 times higher than that of bare CdS QDs.

Rational Construction of Ruthenium-Cobalt Oxides Heterostructure in ZIFs-Derived Double-Shelled Hollow Polyhedrons for Efficient Hydrogen Evolution Reaction

Transition metal oxides (TMOs) and their heterostructure hybrids have emerged as promising candidates for hydrogen evolution reaction (HER) electrocatalysts based on the recent technological breakthroughs and significant advances. Herein, Ru-Co oxides/Co₃ O₄ double-shelled hollow polyhedrons (RCO/Co₃ O₄ -350 DSHPs) with Ru-Co oxides as an outer shell and Co₃ O₄ as an inner shell by pyrolysis of core-shelled structured RuCo(OH)_x @zeolitic-imidazolate-framework-67 derivate at 350 °C are constructed. The unique double-shelled hollow structure provides the large active surface area with rich exposure spaces for the penetration/diffusion of active species and the heterogeneous interface in Ru-Co oxides benefits the electron transfer, simultaneously accelerating the surface electrochemical reactions during HER process. The theory computation further indicates that the existence of heterointerface in RCO/Co₃ O₄ -350 DSHPs optimize the electronic configuration and further weaken the energy barrier in the HER process, promoting the catalytic activity. As a result, the obtained RCO/Co₃ O₄ -350 DSHPs exhibit outstanding HER performance with a low overpotential of 21 mV at 10 mA cm^-2 , small Tafel slope of 67 mV dec^-1 , and robust stability in 1.0 m KOH. This strategy opens new avenues for designing TMOs with the special structure in electrochemical applications.

Ordered Macroporous Superstructure of Nitrogen-Doped Nanoporous Carbon Implanted with Ultrafine Ru Nanoclusters for Efficient pH-Universal Hydrogen Evolution Reaction

The electrochemical hydrogen evolution reaction (HER) is an attractive technology for the mass production of hydrogen. Ru-based materials are promising electrocatalysts owing to the similar bonding strength with hydrogen but much lower cost than Pt catalysts. Herein, an ordered macroporous superstructure of N-doped nanoporous carbon anchored with the ultrafine Ru nanoclusters as electrocatalytic micro/nanoreactors is developed via the thermal pyrolysis of ordered macroporous single crystals of ZIF-8 accommodating Ru(III) ions. Benefiting from the highly interconnected reticular macro-nanospaces, this superstrucure affords unparalleled performance for pH-universal HER, with order of magnitude higher mass activity compared to the benchmark Pt/C. Notably, an exceptionally low overpotential of only 13 mV@10 mA cm^-2 is required for HER in alkaline solution, with a low Tafel slope of 40.41 mV dec^-1 and an ultrahigh turnover frequency value of 1.6 H₂ s^-1 at 25 mV, greatly outperforming Pt/C. Furthermore, the hydrogen generation rates are almost twice those of Pt/C during practical overall alkaline water splitting. A solar-to-hydrogen system is also demonstrated to further promote the application. This research may open a new avenue for the development of advanced electrocatalytic micro/nanoreactors with controlled morphology and excellent performance for future energy applications.

Ruthenium nanoparticles supported on S-doped graphene as an efficient HER electrocatalyst

An efficient HER catalyst was prepared by doping graphene and wrapping ruthenium nanoparticles, and its performance is comparable to that of commercial Pt/C.