Manipulating the Rectifying Contact between Ultrafine Ru Nanoclusters and N-Doped Carbon Nanofibers for High-Efficiency pH-Universal Electrocatalytic Hydrogen Evolution

The rational design of ingenious strategies to boost the intrinsic activity and stability of ruthenium (Ru) is of great importance for the substantial progression of water electrolysis technology. Based on Mott–Schottky effect, electronic regulation within a metal/semiconductor hybrid electrocatalyst represents a versatile strategy to boost the electrochemical performance. Herein, a typical Mott–Schottky hydrogen evolution reaction (HER) electrocatalyst composed of uniform ultrafine Ru nanoclusters in situ anchored on N-doped carbon nanofibers (abbreviated as Ru@N-CNFs hereafter) through a feasible and scalable “phenolic resin-bridged” strategy is reported. Both spectroscopy analyses and density functional theory calculations manifest that such rectifying contact can induce the spontaneous electron transfer from Ru to N-doped carbon nanofibers to generate a built-in electric field, thus enormously promoting the charge transfer efficiency and HER intrinsic activity. Moreover, the seamless immobilization of Ru nanoclusters on the substrate can prevent the active sites from unfavorable migration, coarsening, and detachment, rendering the excellent structural stability. Consequently, the well-designed Ru@N-CNFs afford prominent pH-universal HER performances with small overpotentials of 16 and 17 mV at 10 mA cm⁻² and low Tafel slopes of 31.8 and 28.5 mV dec⁻¹ in acidic and alkaline electrolytes, respectively, which are superior to the state-of-the-art commercial Pt/C and Ru/C benchmarks.     

Development of a Ru catalyst supported on HY zeolite for the oxidative decomposition of NH3 triggered at room temperature

On-site hydrogen production from the oxidative decomposition of NH₃ with a catalyst is highly required in the countryside where external heat is hardly supplied. In this study, Ru-based zeolite catalysts were prepared by impregnation and subsequent washing using RuCl₃·3H₂O and HY zeolite or H-MOR zeolite for the oxidative decomposition of NH₃. The H-MOR-supported Ru catalyst could not be self-heated by feeding 80% NH₃/20% O₂ to the catalyst bed at room temperature. By contrast, the HY-supported Ru catalyst underwent self-heating to approximately 773 K upon feeding the reactants owing to the heat released by NH₃ adsorption and oxidation, leading to excellent performance for the oxidative decomposition of NH₃ during five cycles of start-up tests. Characterization results indicated that the Cl-free Ru/HY catalyst exhibited self-heating due to the presence of small well-dispersed Ru metal particles and a large amount of surface acidic sites.     

L-cysteine-protected ruthenium nanoclusters on CdS as efficient and reusable photocatalysts for hydrogen production

Nanocluster-modified semiconductor-based photocatalysts have been identified as a vital area of research in the area of photocatalytic hydrogen evolution from water. However, the existing ligand protection strategy for synthesizing ultrasmall metal nanoclusters remains confined to a few metals, including Au, Ag, Cu, and their alloys. In this investigation, we describe a facile solution-phase reduction synthesis method for the production of L-cysteine-protected Ru nanoclusters. Our findings demonstrate that these novel Ru nanoclusters function as cocatalysts, which notably increase the photocatalytic activity and photostability of CdS photocatalysts. Moreover, the hybrid CdS photocatalyst modified with Ru nanoclusters exhibits superior activity and stability relative to photoinduced Ru nanoparticles/CdS composite photocatalysts. The simplicity of the synthesized metal nanocluster cocatalyst and its effectiveness in enhancing photocatalyst activity, while reducing the use of precious metals, present new avenues for the development of advanced photocatalysts.     

Hydroxyl-Binding Energy-Induced Kinetic Gap Narrowing between Acidic and Alkaline Hydrogen Oxidation Reaction on Intermetallic Ru3Sn7 Catalyst

Developing highly efficient catalysts toward alkaline hydrogen oxidation reaction (HOR) and narrowing the kinetic gap between acidic and alkaline electrolytes are of great importance for the practical application of alkaline exchange membrane fuel cell . Herein, ordered Ru₃Sn₇/C intermetallic compound has been developed for the HOR under alkaline and acidic conditions. The authors demonstrate that the ordered intermetallic Ru₃Sn₇/C shows much enhanced HOR activity, stability, and CO-tolerance compared with its disordered RuSn solid solution alloy counterpart. More importantly, the authors find that the kinetic gap of HOR between acidic and alkaline media is significantly narrowed in the as-synthesized intermetallic Ru₃Sn₇/C catalysts. Combined experiment results and theoretical calculations, the authors understand that promoted hydroxyl-binding energy on Ru₃Sn₇/C derived from the intermetallic-induced strong electron interaction is responsible for the accelerated alkaline HOR performance and narrowed kinetic gap.     

The Construction of Polyphotocage Platform for Anticancer Photochemotherapy

Photocages enable the precise activation of molecular function with light in many research fields, such as anticancer treatment, where remote spatiotemporal control over the release of an active drug is needed. However, the poor physiological stability and tumor accumulation of conventional small molecular photocages are significant obstacles to developing efficient therapy in vivo. In this study, a new concept of “polyphotocage” is proposed through photocage–polymer hybrid macromolecular engineering. Photoresponsive Ru complex photocage is designed and fused with PEGylated polycarbonates, resulting in the polyphotocage. Various anticancer drugs can be readily conjugated to the polyphotocage via coordination linkage, which can be cut off to release drugs by red light. The polyphotocages can self-assemble into nanoparticles, which enhances the stability of the Ru photocage and demonstrates the efficient accumulation in different-sized tumorswith a high signal-to-background ratio. Furthermore, rapid cellular internalization and mitochondrial anchoring capability allowed the polyphotocages to deliver drugs into the mitochondria, which induces mitochondrial dysfunction and cell death. These properties ensure the effective delivery of anticancer drugs to solid tumors and multiple tiny tumors, ultimately inhibiting tumor proliferation. This strategy of polyphotocages provides a new platform for the future design of drug-delivery systems for cancer photochemotherapy.     

Polymorphism-Interface-Induced Work Function Regulating on Ru Nanocatalyst for Enhanced Alkaline Hydrogen Oxidation Reaction

Exploring high-performance Pt-free electrocatalysts for hydrogen oxidation reaction (HOR) in alkaline media is highly imperative for the development of alkaline polymer electrolyte fuel cells. Phase engineering is an effective strategy for boosting the catalytic performance of electrocatalysts; however, the fabrication of unconventional polymorphism-interfaced metal catalysts remains a significant challenge. In this study, a polymorphism-interfaced Ru nanocatalyst with a stable hexagonal close-packed (hcp) phase and a metastableface-centered-cubic (fcc) phase is successfully prepared. Owing to the built-in electric field and stacking fault on the unique polymorphic interface, the fcc-hcp-Ru catalyst exhibits outstanding alkaline HOR performance with a mass activity of 1016 A g_PGM^-1, which is six and three times higher than that of conventional hcp-Ru andcommercial Pt/C, respectively. The regulated electron distribution at the polymorphic interface is attributed to the discrepant work functions, which not only optimize the adsorption energy of hydrogen but also facilitate the water formation step to promote the alkaline HOR process. This study demonstrates that unconventional polymorphism-interfaced engineering is an efficient strategy to regulate the electronic structure of metal catalysts and identifies the prominent role of the work function in alkaline HORs, providing a new avenue for the rational design of highly efficient materials for electrocatalysis.     

Hydrogenation of Citral using Monometallic Pt and Bimetallic Pt‐Ru Catalysts on a Mesoporous Support in Supercritical Carbon Dioxide Medium

Supercritical carbon dioxide was shown to be a suitable reaction medium for the highly efficient hydrogenation of citral using monometallic Pt and bimetallic Pt‐Ru supported on a mesoporous material, MCM‐48, as catalyst. A remarkable change in the product distribution was observed after the addition of Ru to the monometallic Pt catalyst in supercritical carbon dioxide. The monometallic Pt catalyst was found to be highly selective to the unsaturated alcohol (geraniol+nerol) at a temperature of 323 K within 2 h whereas the bimetallic catalyst becomes selective to the partially saturated aldehyde (citronellal) under the same reaction conditions. Phase behavior plays an important role in the product distribution. Highest conversion and high selectivity to citronellal were achieved in the homogeneous phase for the Pt‐Ru catalyst while on the other hand the unsaturated alcohol (geraniol+nerol) was produced in the heterogeneous phase for the monometallic Pt catalyst. An XPS study offers strong evidence of the electronic modification of Pt after the addition of Ru in the bimetallic catalyst. The change in product distribution on the Pt‐Ru bimetallic catalyst may be explained by the appreciable interaction between the medium and the metal particles promoted by the presence of metallic Ru.     

Dynamic hydrogen bubble template electrodeposition of Ru on amorphous Co support for electrochemical hydrogen evolution

Electrolyzing water is an environmentally friendly and renewable way to obtain high purity hydrogen. Ruthenium has strong water dissociation ability and suitable hydrogen adsorption energy, so it is considered as one of the candidates of excellent electrocatalysts for hydrogen evolution in alkaline solution. The dynamic hydrogen bubble template (DHBT) is a good electrodeposition technology, which can obtain the 3D metal foams. However, as far as we know, there is no report on the preparation of Ru electrocatalyst by the DBHT method. In this work, the trumpet-shaped Ru on amorphous cobalt support (T-Ru/a-Co) is prepared by the DHBT electrodeposition for the first time. The defect locations are uniformly distributed on the surface of amorphous cobalt (a-Co), which can effectively lead to the formation of nano-bubble template in the DHBT process. However, this special morphology cannot be obtained on the surface of crystalline Co (c-Co). In addition, the electronic structure of T-Ru/a-Co has also been obviously modified, in which the proportion of Ru⁴⁺/Ru⁰ in T-Ru/a-Co has increased, accompanied by the change of binding energy of Ru. It only needs an overpotential of 49 mV to obtain a current density of 10 mA cm⁻² for the T-Ru/a-Co. The specific activity (SA), turnover frequency (TOF) and mass activity (MA) of T-Ru/a-Co are 0.23 mA cm⁻², 0.48 s⁻¹ and 0.24 A mg⁻¹, which are both higher than those of Pt/C, the disk-shaped Ru on the c-Co support (D-Ru/c-Co) and Ru/C, respectively.