Designing Nanoparticles and Nanoalloys with Controlled Surface and Reactivity

Nickel Phosphide: The Effect of Phosphorus Content on the Activity and Stability toward Oxygen Evolution Reaction in Alkaline Medium

In this work a systematic study of the effect of the metal to phosphorus ratio in Ni-P nanoparticles on their catalytic activity with respect to the OER is reported. To this end, nickel phosphide nanoparticles are synthesized through two different synthesis routes, one involving in-situ phosphidation and one involving ex-situ phosphidation. In-situ phosphidation is performed via two steps route in a one-pot synthesis, in which Ni nanoparticles are formed at 220 °C, but not isolated, and then transformed to phase-pure either Ni12P5 or Ni2P nanocrystallites. In the second synthesis method (ex-situ phosphidation), nickel nanoparticles with an excess amount of trioctylphosphine (TOP) as a capping agent are synthesized and separated from the solution, then subsequently annealed in three different atmospheres, leading to the formation of three types of NixPy viz. [NixPy-H2/Ar], [NixPy-Ar], and [NixPy-air]. [NixPy-air] nanoparticles shows the best electrocatalytic activity among the annealed nanoparticles in Ar and H2/Ar but lower than Ni12P5 nanoparticles. However, [NixPy-air] shows very high stability in comparison with other synthesized nanoparticles. Moreover, the effect of the adventitious and spiked Fe in the electrolyte is studied on the electrocatalytic activity of all synthesized nanoparticles.

Nanometal Thermocatalysts: Transformations, Deactivation, and Mitigation

Nanometals have been proven to be efficient thermocatalysts in the last decades. Their enhanced catalytic activity and tunable functionalities make them intriguing candidates for a wide range of catalytic applications, such as gaseous reactions and compound synthesis/decomposition. On the other hand, the enhanced specific surface energy and reactivity of nanometals can lead to configuration transformation and thus catalytic deactivation during the synthesis and catalysis, which largely undermines the activity and service time, thereby calling for urgent research effort to understand the deactivating mechanisms and develop efficient mitigating methods. Herein, the recent progress in understanding the configuration transformation-induced catalytic deactivation within nanometals is reviewed. The major pathways of configuration transformations, and their kinetics controlled by the environmental factors are presented. The approaches toward mitigating the transformation-induced deactivation are also presented. Finally, a perspective on the future academic approaches toward in-depth understanding of the kinetics of the deactivation of nanometals is proposed.

Ultra-Fast High-Precision Metallic Nanoparticle Synthesis using Laser-Accelerated Protons

Laser-driven proton acceleration, as produced during the interaction of a high-intensity (I > 1 × 1018 W/cm2), short pulse (<1 ps) laser with a solid target, is a prosperous field of endeavor for manifold applications in different domains, including astrophysics, biomedicine and materials science. These emerging applications benefit from the unique features of the laser-accelerated particles such as short duration, intense flux and energy versatility, which allow obtaining unprecedented temperature and pressure conditions. In this paper, we show that laser-driven protons are perfectly suited for producing, in a single sub-ns laser pulse, metallic nanocrystals with tunable diameter ranging from tens to hundreds of nm and very high precision. Our method relies on the intense and very quick proton energy deposition, which induces in a bulk material an explosive boiling and produces nanocrystals that aggregate in a plasma plume composed by atoms detached from the proton-irradiated surface. The properties of the obtained particles depend on the deposited proton energy and on the duration of the thermodynamical process. Suitably controlling the irradiated dose allows fabricating nanocrystals of a specific size with low polydispersity that can easily be isolated in order to obtain a monodisperse nanocrystal solution. Molecular Dynamics simulations confirm our experimental results.

Describing inorganic nanoparticles in the context of surface reactivity and catalysis

Fabrication of inorganic nanoparticles is now a mature field. However, further advances, in particular in the field of catalysis, require a more accurate description of their surface and of the transformations occurring beneath the surface in the environment of use. Through a selection of case studies, this feature article proposes a journey from surface science to nanoparticle design, while illustrating state-of-the-art spectroscopies that help provide a relevant description of inorganic nanoparticles in the context of surface reactivity.