An aqueous synthesis of porous PtPd nanoparticles with reversed bimetallic structures for highly efficient hydrogen generation from ammonia borane hydrolysis

Fine construction of porous bimetallic nanomaterials with tunable components and structures is of great importance for their catalytic performance and durability. Herein, we present a facile and mild one-pot route for the preparation of porous PtPd bimetallic nanoparticles (NPs) with reversed structures in aqueous solution for the first time. To this end, a common ionic liquid (IL) 1-hexadecyl-3-methylimidazolium chloride ([C16mim]Cl) is utilized to direct the growth and assembly of porous structures of PtPd NPs. It is shown that the as-prepared porous Pt25Pd75 NPs have obvious hierarchical structures with nanoflowers as subunits and nanorods as basic units. The elemental components and structures of the porous PtPd NPs can be tuned by the precursor ratio and the [C16mim]Cl concentration. Furthermore, various porous PtPd bimetallic structures from Pd-on-Pt to Pt-on-Pd may be efficiently switched by controlling the concentration of glycine. Owing to their high specific surface area, porous hierarchical structures (including mesopores and micropores), and probable electronic effects between Pt and Pd, the porous Pt25Pd75 NPs (Pd-on-Pt structure) are found to exhibit prominent catalytic activity and high stability for hydrogen production from hydrolysis of ammonia borane.

TiN nanotube supported Ni catalyst Ni@TiN-NTs: experimental evidence of structure–activity relations in catalytically hydrolyzing ammonia borane for hydrogen evolution

With commercial TiO₂ as the precursor, titanium nitride nanotubes (TiN-NTs) were fabricated through a hydrothermal – ammonia nitriding route, and next non-noble metal nanosized Ni particles were evenly and firmly anchored on the surface of the TiN-NTs via a PVP-mediated non-aqueous phase reduction–deposition strategy, to obtain the supported catalyst Ni@TiN-NTs. The X-ray powder diffraction (PXRD), field emission scanning and transmission electron microscopy (FE-SEM/TEM) and specific surface area measurements were used to characterize and analyze the phase composition, surface microstructure and morphological features of the product. The catalytic activity of the Ni@TiN-NTs for hydrolyzing ammonia borane to generate hydrogen (H₂) under different conditions was evaluated systematically. The results reveal that the as-fabricated TiN-NTs are composed of TiN and a small amount of TiN_xO_y with the approximate molar atomic ratio of Ti to N at 1 : 1, existing as hollow microtubules with mean tube diameter of 130 nm and length of about 1 μm. Via in situ reduction and deposition, Ni nanoparticles can be uniformly anchored on the surface of TiN-NTs. The catalytic activities of Ni(x)@TiN-NTs with different Ni loading amounts are all higher than that of single metal Ni nanoparticles. The temperature has a positive effect on the catalytic activity of Ni(20)@TiN-NTs, and its total turnover frequency for hydrolyzing ammonia borane is 11.73 mol(H₂) (mol Ni)⁻¹ min⁻¹, with an apparent activation energy of 52.05 kJ mol⁻¹ at 303 K. After 5 cycles, the Ni(20)@TiN-NTs catalyst still maintains 87% of the initial catalytic activity. It could be suggested that these tactics can also be extended to the fabrication of other metal or alloy catalysts supported by TiN-NTs, with great application potential and development prospects.

Titanium nitride nanotubes (TiN-NTs) were fabricated using a hydrothermal – ammonia nitriding route, and non-noble metal nanosized Ni particles were anchored on the surface via a non-aqueous phase reduction–deposition strategy, to obtain the supported catalyst Ni@TiN-NTs.

Facile Preparation of CuS Nanoparticles from the Interfaces of Hydrophobic Ionic Liquids and Water

In this work, a two-phase system composed of hydrophobic ionic liquid (IL) and water phases was introduced to prepare copper sulfide (CuS) nanoparticles. It was found that CuS particles generated from the interfaces of carboxyl-functionalized IL and sodium sulfide (Na₂S) aqueous solution were prone to aggregate into nanoplates and those produced from the interfaces of carboxyl-functionalized IL and thioacetamide (TAA) aqueous solution tended to aggregate into nanospheres. Both the CuS nanoplates and nanospheres exhibited a good absorption ability for ultraviolet and visible light. Furthermore, the CuS nanoplates and nanospheres showed highly efficient photocatalytic activity in degrading rhodamine B (RhB). Compared with the reported CuS nanostructures, the CuS nanoparticles prepared in this work could degrade RhB under natural sunlight irradiation. Finally, the production of CuS from the interfaces of hydrophobic IL and water phases had the advantages of mild reaction conditions and ease of operation.

Ionic-Liquid-Assisted One-Step Synthesis of CoO Nanosheets as Electrocatalysts for Oxygen Evolution Reaction

The sluggish oxygen evolution reaction (OER) hinders the development of electrocatalytic water splitting for energy conversion and storage. Therefore, it is imperative to explore the cost-effective and highly efficient noble-metal-free electrocatalysts for OER. Herein, we are introducing such OER electrocatalyst based on Co, fabricated through an ionic-liquid-assisted one-step synthesis, where ionic liquid played a dual role as solvent cum structure-directing agent. Besides possessing large-accessible surface area and numerous active sites, the as-prepared stable CoO nanosheets exhibited excellent electrochemical activity through establishing an extensive contact with the electrolyte. Under alkaline conditions, the overpotential to achieve a current density of 10 mA cm^-2 is only 320 mV, and the Tafel slope is as small as 70 mV dec^-1. Thus, our work provides a new pathway for designing and engineering the highly efficient non-noble metal OER electrocatalysts by using ionic liquids.