Sustainable solid-state synthesis of uniformly distributed PdAg alloy nanoparticles for electrocatalytic hydrogen oxidation and evolution

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.

Nano-Ag: Environmental applications and perspectives

Silver nanoparticles (AgNPs) are promising bactericidal agents and plasmonic NPs for environmental applications, owing to their various favorable properties. For example, AgNPs enables reactive oxygen species (ROS) generation, surface plasmon resonance (SPR), and specific reaction selectivities. In fact, AgNPs-based materials and their antimicrobial, optical, and electrical effects are at the forefront of nanotechnology, having applications in environmental disinfection, elimination of environmental pollutants, environmental detection, and energy conversions. This review aims to comprehensively summarize the advanced applications and fundamental mechanisms to provide the guidelines for future work in the field of AgNPs implanted functional materials. The state-of-art terms including (photo)(electro)catalytic reactions, heterojunction formation, the generation and attacking of ROS, genetic damage, hot electron generation and transfer, localized surface plasmon resonance (LSPR), plasmon resonance energy transfer (PERT), near field electromagnetic enhancement, structure-function relationship, and reaction selectivities have been covered in this review. It is expected that this review may provide insights into the rational development in the next generation of AgNPs-based nanomaterials with excellent performances.

Nano-Sized PtRu/C Electrocatalyst With Separated Phases and High Dispersion Improves Electrochemical Performance of Hydrogen Oxidation Reaction

Alloys and core-shell nanoparticles have recently received enormous attention which opened up new avenues for highly active catalysts. Despite considerable advances in this field, the majority of proposed approaches suffer from either complicated procedures or unstable structures, severely hindering their practical applications. Here, we successfully synthesized alloy electrocatalyst with separated phases, PtRu alloy nanoparticles robustly supported by carbon matrix (PtRu/C), using a convenient two-step solvothermal method. The constructed PtRu/C at different NaOH contents (0–1.25 mmol) were compared and electrochemical activity were evaluated by the hydrogen oxidation reaction (HOR). In contrast, the homogeneous distribution and minimum average size of Ru and Pt nanoparticles on carbon, appeared at approximately 4 nm, proving that PtRu/C-0.75 possessed abundant accessible active sites. The catalytic activities and the reaction mechanism were studied via electrochemical techniques. PtRu/C-0.75 has excellent activity due to its unique electronic structure and efficient charge transfer, with the largest j₀ value of 3.68 mA cm⁻² in the HOR.

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.

Strong electrostatic adsorption-engaged fabrication of sub-3.0 nm PtRu alloy nanoparticles as synergistic electrocatalysts toward hydrogen evolution

Alloying of Pt with Ru to form ultrafine and well-defined PtRu alloy nanoparticles (NPs) for synergistically electrocatalytic hydrogen evolution is highly desirable but remains a synthetic challenge. Here, we report a strong electrostatic adsorption (SEA)-assisted fabrication of ultrafine and homogeneously distributed PtRu alloy NPs using ethylenediaminetetraacetic acid tetrasodium-derived carbon (EC) as a matrix. The O, N-rich EC with a hierarchically macro/meso/microporous structure and the SEA-assisted formation of the [Ru(bpy)₃][PtCl₆] complex ensure the successful generation of ultrasmall PtRu alloy NPs (2.93 nm in diameter) with high dispersion. The optimal PtRu/EC-700 delivers excellent electrocatalytic properties with an ultralow overpotential (η₁₀ = 18 mV), robust durability and good long-term stability for the alkaline hydrogen evolution reaction (HER). The ultrasmall PtRu alloy NPs with rich surface sites, the synergistic catalysis effect between Pt and Ru and the hierarchically macro/meso/microporous structure of O, N-rich EC cooperatively enhance the HER performance of PtRu/EC-700. This study provides an easy but effective way to construct metal alloy NPs with an ultrafine size and high dispersity for catalytic applications.

Ultrafine Pd Nanoparticles Supported on Soft Nitriding Porous Carbon for Hydrogen Production from Hydrolytic Dehydrogenation of Dimethyl Amine-Borane

Simple and efficient synthesis of a nano-catalyst with an excellent catalytic property for hydrogen generation from hydrolysis of dimethyl amine-borane (DMAB) is a missing piece. Herein, effective and recycled palladium (Pd) nanoparticles (NPs) supported on soft nitriding porous carbon (NPC) are fabricated and applied for DMAB hydrolysis. It is discovered that the soft nitriding via a low-temperature urea-pretreatment induces abundant nitrogen-containing species on the NPC support, thus promoting the affinity of the Pd precursor and hindering the agglomeration of formed Pd NPs onto the NPC surface during the preparation process. Surface-clean Pd NPs with a diameter of sub-2.0 nm deposited on the NPC support (Pd/NPC) exhibit an outstanding catalytic performance with a turnover frequency (TOF) of 2758 h^-1 toward DMAB hydrolysis, better than many previous reported Pd-based catalysts. It should be emphasized that the Pd/NPC also possesses a good stability without an obvious decrease in catalytic activity for DMAB hydrolysis in five successive recycling runs. This study provides a facile but efficient way for preparing high-performance Pd catalysts for catalytic hydrogen productions.