Excessive Se on RuSe2 nanocrystals to accelerate water dissociation for the enhanced electrocatalytic hydrogen evolution reaction

Ru incorporated into Se vacancy-containing CoSe2 as an efficient electrocatalyst for alkaline hydrogen evolution

In alkaline media, slow water dissociation leads to poor overall hydrogen evolution performance. However, Ru catalysts have a certain water dissociation performance, thus regulating the Ru-H bond through vacancy engineering and accelerating water dissociation. Herein, an excellent Ru-based electrocatalyst for the alkaline HER has been developed by incorporating Ru into Se vacancy-containing CoSe2 (Ru-VSe-CoSe2). The results from X-ray photoelectron spectroscopy, kinetic isotope effect, and cyanide poisoning experiments for four catalysts (namely Ru-VSe-CoSe2, Ru-CoSe2, VSe-CoSe2, and CoSe2) reveal that Ru is the main active site in Ru-VSe-CoSe2 and the presence of Se vacancies greatly facilitates electron transfer from Co to Ru via a bridging Se atom. Thus, electron-rich Ru is formed to optimize the adsorption strength between the active site and H*, and ultimately facilitates the whole alkaline HER process. Consequently, Ru-VSe-CoSe2 exhibits an excellent HER activity with an ultrahigh mass activity of 44.2 A mgRu-1 (20% PtC exhibits only 3 A mgRu-1) and a much lower overpotential (29 mV at 10 mA cm-2) compared to Ru-CoSe2 (75 mV), VSe-CoSe2 (167 mV), CoSe2 (190 mV), and commercial Pt/C (41 mV). In addition, the practical application of Ru-VSe-CoSe2 is illustrated by designing a Zn-H2O alkaline battery with Ru-VSe-CoSe2 as the cathode catalyst, and this battery shows its potential application with a maximum power density of 4.9 mW cm-2 and can work continuously for over 10 h at 10 mA cm-2 without an obvious decay in voltage.

RuSe2 and CoSe2 Nanoparticles Incorporated Nitrogen-Doped Carbon as Efficient Trifunctional Electrocatalyst for Zinc-Air Batteries and Water Splitting

The development of affordable, highly active, and stable trifunctional electrocatalysts is imperative for sustainable energy applications such as overall water splitting and rechargeable Zn-air battery. Herein, we report a composite electrocatalyst with RuSe2 and CoSe2 hybrid nanoparticles embedded in nitrogen-doped carbon (RuSe2CoSe2/NC) synthesized through a carbonization-adsorption-selenylation strategy. This electrocatalyst is a trifunctional electrocatalyst with excellent hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) activities. An in-depth study of the effect of Se on the electrocatalytic process was conducted. Notably, the incorporation of Se moderately adjusted electronic structure of Ru and Co, enhancing all three types of catalytic performance (HER, η10 = 31 mV; OER, η10 = 248 mV; ORR, E1/2 = 0.834 V) under alkaline condition with accelerated kinetics and improved stability. Density functional theory (DFT) calculation reveals that the (210) crystal facet of RuSe2 is the dominant HER active site as it exhibited the lowest ΔGH* value. The in situ Raman spectra unravel the evolution process of the local electronic environment of Co-Se and Ru-Se bonds, which synergistically promotes the formation of CoOOH as the active intermediate during the OER. The superior catalytic efficiency and remarkable durability of RuSe2CoSe2/NC as an electrode for water splitting and zinc-air battery devices demonstrate its great potential for energy storage and conversion devices.

Multi-d Electron Synergy in LaNi1-x Cox Ru Intermetallics Boosts Electrocatalytic Hydrogen Evolution

Despite the fact that d-band center theory links the d electron structure of transition metals to their catalytic activity, it is yet unknown how the synergistic effect of multi-d electrons impacts catalytic performance. Herein, novel LaNi1-x Cox Ru intermetallics containing 5d, 4d, and 3d electrons were prepared. In these compounds, the 5d orbital of La transfers electrons to the 4d orbital of Ru, which provides adsorption sites for H*. The 3d orbitals of Ni and Co interact with the 5d and 4d orbitals to generate an anisotropic electron distribution, which facilitates the adsorption and desorption of OH*. The synergistic effect of multi-d electrons ensures efficient catalytic activity. The optimized LaNi0.5 Co0.5 Ru has an overpotential of 43mV at 10 mA cm-2 for alkaline electrocatalytic hydrogen evolution reaction. Beyond offering a variety of new electrocatalysts, this work reveals the multi-d electron synergy in promoting catalytic reaction.

Ultralow Ru Single Atoms Confined in Cerium Oxide Nanoglues for Highly-Sensitive and Robust H2 O2 -Related Biocatalytic Diagnosis

Exploring highly efficient, portable, and robust biocatalysts is a great challenge in colorimetric biosensors. To overcome the challenging states in creating single-atom biocatalysts, such as insufficient activity and stability, here, this work has engineered a unique CeO2 support as nanoglue to tightly anchor the Ru single-atom sites (CeO2 -Ru) with strong electronic coupling for achieving highly sensitive and robust H2 O2 -related biocatalytic diagnosis. The morphology and chemical/electronic structure analysis demonstrates that the Ru atoms are well-dispersed on CeO2 surface to form high-density active sites. Benefiting from the unique structure, the prepared CeO2 -Ru exhibits outstanding peroxidase (POD) like catalytic activity and selectivity to H2 O2 . Steady-state kinetic study results show that the CeO2 -Ru presents the highest Vmax and turnover number than the state-of-the-art POD-like biocatalysts. Consequently, the CeO2 -Ru discloses a high efficiency, good selectivity, and robust stability in the colorimetric detection of L-cysteine, glucose, and uric acid. Notably, the limit of detection (LOD) can reach 0.176 × 10-3 m for the L-cysteine, 0.095 × 10-3 m for the glucose, and 0.088 × 10-3 m for the uric acid via cascade reaction. This work suggests that the proposed unique CeO2 nanoglue will offer a new path to create single-atom noble metal biocatalysts and take a step closer to future biotherapeutic and biocatalytic applications.

Amorphizing Metal Selenides-Based ROS Biocatalysts at Surface Nanolayer toward Ultrafast Inflammatory Diabetic Wound Healing

The microenvironments with high reactive-oxygen-species (ROS) levels, inflammatory responses, and oxidative-stress effects in diabetic ulcer wounds, leading to poor proliferation and differentiation of stem cells, severely inhibit their efficient healing. Here, to overcome the unbalanced multielectron reactions in ROS catalysis, we develop a cobalt selenide-based biocatalyst with an amorphous Ru@CoSe nanolayer for ultrafast and broad-spectrum catalytic ROS-elimination. Owing to the enriched electrons and more unoccupied orbitals of Ru atoms, the amorphous Ru@CoSe nanolayer-equipped biocatalyst displays excellent catalase-like kinetics (maximal reaction velocity, 23.05 μM s^-1; turnover number, 2.00 s^-1), which exceeds most of the currently reported metal compounds. The theoretical studies show that Ru atoms act as "regulators" to tune the electronic state of the Co sites and modulate the interaction of oxygen intermediates, thus improving the reversible redox properties of active sites. Consequently, the Ru@CoSe can efficiently rescue the proliferation of mesenchymal stem cells and maintain their angiogenic potential in the oxidative stress environment. In vivo experiments reveal the superior ROS-elimination ability of Ru@CoSe on the inflammatory diabetic wound. This study offers an effective nanomedicine for catalytic ROS-scavenging and ultrafast healing of inflammatory wounds and also provides a strategy to design biocatalytic metal compounds via bringing amorphous catalytic structures.

Three-Dimensional Strawlike MoSe2-Ni(Fe)Se Electrocatalysts for Overall Water Splitting

The development of efficient and low-cost transition-metal electrocatalysts is of great significance for hydrogen production from water splitting. Herein, we synthesized three-dimensional strawlike MoSe₂-NiSe composed of microrods on nickel foam (NF) by a one-step hydrothermal reaction. The as-prepared MoSe₂-NiSe/NF exhibited effective hydrogen evolution reaction (HER) activity (low overpotential of 79 mV at 10 mA cm^-2 and stability of 21 h in 1 M KOH), benefiting from the large electrochemically active area provided by strawlike structures, proper Se content, and synergistic effect of active phases. The enhanced oxygen evolution reaction (OER) activity (the low overpotential of 217 mV at 10 mA cm^-2 and maintaining stability for 47 h in 1 M KOH) was further observed for Fe-doped MoSe₂-NiSe/NF (MoSe₂-NiFeSe/NF) prepared by facile soaking, which can be mainly ascribed to optimized active phases formed on the OER process after Fe doping. The two-electrode system (MoSe₂-NiSe/NF||MoSe₂-NiFeSe/NF) requires a low cell voltage of 1.54 V to obtain a current density of 10 mA cm^-2 in 1 M KOH, which provides an interesting idea for constructing an effective overall water splitting system.

Hollow-structured amorphous Cu(OH)x nanowires doped with Ru for wide pH electrocatalytic hydrogen production

Developing efficient and stable catalysts for electrocatalytic hydrogen evolution reaction (HER) with low overpotential is the key point to realizing large-scale hydrogen commercialization. Herein, Ru doped amorphous hollow copper hydroxide nanowires on copper foam (Ru-Cu(OH)_x/CF) is prepared by surface chemical oxidization and following solvothermal process. The hollow 3D nanowire structure can provide abundant accessibility active sites, promote electrolyte in filtration and facilitate gas diffusion in the process of the electrochemical reaction. Then, the as-synthesized Ru-Cu(OH)_x/CF electrocatalyst exhibits impressive electrocatalytic performance for HER with 45, 80 and 50 mV to drive 10 mA cm^-2 in 1.0 M KOH, 1.0 M phosphate-buffered saline (PBS) and 0.5 M H₂SO₄, respectively, with remarkable long-term stability. Moreover, sustainable energies can power the two-electrode setup with amounts of hydrogen generation. The strategy may be particularly beneficial to explore simple synthesis and high-performance catalysts for HER.

Increased crystallinity of RuSe2/carbon nanotubes for enhanced electrochemical hydrogen generation performance

Ru-Based catalysts are significant in the green hydrogen generation via the electrochemical water-splitting reaction. Herein, it is found that the increased crystallinity of cubic RuSe₂ nanoparticles anchored over carbon nanotubes (RuSe₂/CNTs) could largely increase the hydrogen generation performance both in acidic and alkaline electrolytes. The freshly prepared RuSe₂/CNTs with low crystallinity had a very low catalytic performance for the HER, while the catalytic ability could be largely boosted by facile thermal annealing at 650 °C in an N₂ atmosphere, resulting from the increased crystallinity and electronic effect. The crystal structure enhancement of the RuSe₂ nanoparticles was well supported by the X-ray diffraction technique and the lattice fringes in the high-resolution transmission electron microscopy images. As a result, the catalyst exhibited largely improved catalytic performance compared to the freshly prepared RuSe₂/CNTs; specifically, the overpotentials of 48 and 64 mV were required to drive 10 mA cm^-2 in alkaline and acidic media when loaded on a glassy carbon electrode, much less than those of 109 and 120 mV for the freshly prepared RuSe₂/CNTs; the catalytic performance in the alkaline electrolyte was even close to that of the commercial Pt/C catalyst. Correspondingly, the improved catalytic stability, catalytic kinetics, charge transfer ability and catalytic efficiency of the active sites were also observed. The current work shows an effective approach and important understanding for catalytic performance enhancement via increased crystallinity by facile thermal annealing.

Synergistic phase and crystallinity engineering in cubic RuSe2 catalysts towards efficient hydrogen evolution reaction

Herein, cubic RuSe2 electrocatalysts with different 1T phase ratios (ranging from 20.53% to 64.97%) and crystallinities (ranging from 1.72% to 89.10%) were developed by a fast and efficient microwave-assisted synthesis method.

Neodymium-decorated graphene as an efficient electrocatalyst for hydrogen production

Rare earth (RE) materials such as neodymium (Nd) and others consist of unique electronic configurations which result in unique electronic, electrochemical, and photonic properties. The high temperature (>1100 °C) growth and low active surface areas of REs hinder their use as an efficient electrocatalyst. Herein, different morphologies of Nd were successfully fabricated in situ on the surface of graphene using a double-zone chemical vapor deposition (CVD) method. The morphology of the Nd material on graphene is controlled, which results in the significant enhancement of the large specific surface area and electrochemical active area of the composite material due to the spatial morphology of Nd, thereby improving the hydrogen evolution reaction (HER) performance in an alkaline medium. The significantly enhanced HER activity with an overpotential of 75 mV and a Tafel slope of 95 mV dec^-1 at a current density of 10 mA cm^-2 is observed in Nd-GF. Mainly, a high specific surface area of ∼2217 cm² g^-1 and the porosity of graphene play major roles in the enhancement of activity. Thus, the present work provides a new strategy for the neodymium engineering synthesis of efficient rare earth-graphene composite electrocatalysts with a high electrochemical active area.

Industrially promising NiCoP nanorod arrays tailored with trace W and Mo atoms for boosting large-current-density overall water splitting

Nanoarray catalysts supported on substrates provide an opportunity for industrially promising overall water splitting at large current densities. However, most of the present electrocatalysts show high overpotentials at a large current density, inducing a low efficiency for industrial water electrolysis. Herein, using the classic NiCoP nanorod arrays as the basic catalyst model, we presented a trace W and Mo co-doped strategy to boost the overall water splitting electrocatalysis at an industrial current density. After a trace amount of W and Mo atoms was doped, the constructed W and Mo co-doped NiCoP nanorod arrays (W,Mo-NiCoP/NF) show a low overpotential of 249 mV towards the hydrogen evolution reaction (HER) at a very large current density of 1000 mA cm^-2. We deduce that the regulation of the electronic structure caused by the trace W and Mo atoms, as well as the intrinsic features of nanoarrays leads to enhanced catalytic activity. In addition, a significant enhancement towards the oxygen evolution reaction (OER) was also achieved by this co-doped strategy. Finally, an overall water splitting device using W,Mo-NiCoP/NF as both the anode and cathode was assembled to exhibit a low cell voltage of 1.85 V at a large current density of 500 mA cm^-2 and an excellent long-term stability within 50 h, better than most of the state-of-the-art bifunctional electrocatalysts yet reported. Our results highlight the significance of trace-doping engineering in industrial water electrolysis.

Interface- and Surface-Engineered PdO-RuO2 Hetero-Nanostructures with High Activity for Hydrogen Evolution/Oxidation Reactions

Active catalysts for HER/HOR are crucial to develop hydrogen-based renewable technologies. The interface of hetero-nanostructures can integrate different components into a single synergistic hybrid with high activity. Here, the synthesis of PdO-RuO₂ -C with abundant interfaces/defects was achieved for the hydrogen evolution reaction (HER) and hydrogen oxidation reaction (HOR). It exhibited a current density of 10 mA cm^-2 at 44 mV with a Tafel slope of 34 mV dec^-1 in 1 m KOH. The HER mass activity was 3 times higher in base and comparable to Pt/C in acid. The stability test confirmed high HER stability. The catalyst also exhibited excellent HOR activity in both media; in alkaline HOR it outperformed Pt/C. The exchange current density i_0,m of PdO-RuO₂ /C was 522 mA mg^-1 in base, which is 58 and 3.4 times higher than those of Pd/C and Pt/C. The HOR activity of PdO-RuO₂ /C was 22 and 300 times higher than those of PdO/C in acid and base. Improvement of HER/HOR kinetics in different alkaline electrolytes was observed in the order K⁺ <Na⁺ <Li⁺ , and increase of HER as well decrease of HOR kinetics was observed with increasing Li⁺ concentration. It was proposed that OH_ad -M⁺ -(H₂ O)_x in the double-layer region could influence HER/HOR activity in base. Based on the hard and soft acid and base (HSAB) theory, the OH_ads -M⁺ -(H₂ O)_x could help to remove more OH_ads into the bulk, leading to increase in HER/HOR activity in alkaline electrolyte (K⁺ <Na⁺ <Li⁺ ) and increasing the HER with increasing Li⁺ concentration. The decrease of HOR activity of PdO-RuO₂ /C with increasing M⁺ was due to M⁺ -induced OH_ads destabilization through the bifunctional mechanism. The high HER/HOR activity of PdO-RuO₂ /C could be attributed, among other factors, to interface engineering and strong synergistic interaction. This work provides an opportunity to design oxide-based catalysts for renewable energy technologies.