Multi-scale modeling and experimental investigation of oxidation behavior in platinum nanoparticles

Understanding the impact of oxidation on the reactivity and performance of Pt nanoparticles (NPs) is crucial for developing durable and efficient catalysts. In this study, we investigate the oxidation process of a realistic Pt NP using a multistep approach combining computational methods (ReaxFF, MACE-MP-0, and DFT) with experimental techniques (XRD, TEM, and EXAFS). Our workflow aims to measure oxidation extent, compare different computational models, analyze electronic structure changes, and provide guidance for selecting appropriate computational models in catalytic atomistic studies. We perform hybrid MD-MC simulations using ReaxFF which reveal significant oxidation with oxygen penetrating deep into the core at high oxygen partial pressure, with the formation of detached small cluster oxide Pt6O8 species. We investigate the plausibility of these configurations and possible degradation mechanism by carrying out XRD, TEM, and EXAFS measurements on samples of various average particle sizes. Experimental measurements show partial agreement with our simulations in terms of coordination numbers, bond distances, oxygen fractional occupancy and onset/place-exchange potentials. Despite these agreements, we find poor matches between the binding energies calculated by ReaxFF and DFT, casting doubt on the predictive power of ReaxFF and the existence of Pt6O8 species. In contrast, the universal MACE-MP-0 model shows significant improvement in the prediction of energetics. Comparing these force fields with DFT calculations on oxidized and non-idealized systems is essential for understanding the limitations of such models in predicting catalytically relevant properties at high potentials and was previously unexplored in the literature. Our study provides a foundation for understanding the complex interplay between nanoparticle structure, oxidation state, and catalytic performance, aiming to guide the rational design of advanced catalytic materials through atomistic modeling.

Pt nanoparticles under oxidizing conditions - implications of particle size, adsorption sites and oxygen coverage on stability

Platinum nanoparticles are efficient catalysts for different reactions, such as oxidation of carbon and nitrogen monoxides. Adsorption and interaction of oxygen with the nanoparticle surface, taking place under reaction conditions, determine not only the catalytic efficiency but also the stability of the nanoparticles against oxidation. In this study, platinum nanoparticles in oxygen environment are investigated by systematic screening of initial nanoparticle-oxygen configurations and employing density functional theory and a thermodynamics-based approach. The structures formed at low oxygen coverages are described by adsorption of atomic oxygen on the nanoparticles whereas at high coverages oxide-like species are formed. The relative stability of adsorption configurations at different oxygen coverages, including the phase of fully oxidized nanoparticles, is investigated by constructing p-T phase diagrams for the studied systems.

Strain effects in core-shell PtCo nanoparticles: a comparison of experimental observations and computational modelling

Strain in Pt nanoalloys induced by the secondary metal has long been suggested as a major contributor to the modification of catalytic properties. Here, we investigate strain in PtCo nanoparticles using a combination of computational modelling and microscopy experiments. We have used a combination of molecular dynamics (MD) and large-scale density functional theory (DFT) for our models, alongside experimental work using annular dark field scanning transmission electron microscopy (ADF-STEM). We have performed extensive validation of the interatomic potential against DFT using a Pt₅₆₈Co₁₈ nanoparticle. Modelling gives access to 3 dimensional structures that can be compared to the 2D ADF-STEM images, which we use to build an understanding of nanoparticle structure and composition. Strain has been measured for PtCo and pure Pt nanoparticles, with MD annealed models compared to ADF-STEM images. Our analysis was performed on a layer by layer basis, where distinct trends between the Pt and PtCo alloy nanoparticles are observed. To our knowledge, we show for the first time a way in which detailed atomistic simulations can be used to augment and help interpret the results of ADF-STEM strain mapping experiments, which will enhance their use in characterisation towards the development of improved catalysts.

Photo/electrocatalysis and photosensitization using metal nanoclusters for green energy and medical applications

Owing to the rapidly increasing demand for sustainable technologies in fields such as energy, environmental science, and medicine, nanomaterial-based photo/electrocatalysis has received increasing attention. Recently, synthetic innovations have allowed the fabrication of atomically precise metal nanoclusters (NCs). These NCs show potential for green energy and medical applications. The present article primarily focuses on evaluation of the recent developments in the photo/electrocatalytic and photosensitizing characteristics of metal and alloy NCs. The review comprises two sections: (i) photo/electrocatalysis for green energy and (ii) photosensitization for biomedical therapy applications. Finally, the challenges associated with the use of metal NCs are presented on the basis of current developments.

Recent advancements in Pt-nanostructure-based electrocatalysts for the oxygen reduction reaction

A comprehensive evaluation of Pt-nanostructure-based electrocatalysts for the oxygen reduction reaction.

Trends in water-promoted oxygen dissociation on the transition metal surfaces from first principles

Dissociation of O₂ into atomic oxygen is a significant route for O₂ activation in metal-catalyzed oxidation reactions. In this study, we systematically investigated the mechanisms of O₂ dissociation and the promoting role of water on nine transition metal (Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, and Au) surfaces. It was found that on clean metal surfaces, the dissociation of O₂ was most favorable on Co(0001) and most difficult on Au(111), according to the free energy barriers of Co (0.03 eV) < Rh (0.20 eV) < Ni (0.26 eV) < Cu (0.45 eV) < Ir (0.62 eV) < Pd (0.65 eV) < Pt (0.92 eV) < Ag (1.07 eV) < Au (2.50 eV). With the involvement of water, O₂ and H₂O formed an O₂H₂O complex via hydrogen bonding interactions, being accompanied by an increased co-adsorption free energy of 0.17-0.52 eV and a more activated O-O bond. More importantly, the introduction of water reduced the barriers of O₂ dissociation on all the nine metal surfaces, with the reduction of the free energy barrier ranging from 0.03 eV on Co(0001) to 1.05 eV on Au(111). The intrinsic reasons for the promotional role of water are attributed to the hydrogen bonding effect between O₂ and H₂O and the electronic modification effect induced by the water-surface interaction. These results provide a fundamental understanding of the catalytic role of water in O₂ dissociation on the transition metal surfaces and may be helpful in the rational design of new efficient catalysts for the oxidation reactions using molecular oxygen or air.

Ethanol, O, and CO adsorption on Pt nanoparticles: effects of nanoparticle size and graphene support

DFT calculations reveal aspects of size and support effects for Pt nanoparticles on graphene interacting with O, CO and ethanol.

Oxide-based nanomaterials for fuel cell catalysis: the interplay between supported single Pt atoms and particles

Nanomaterials coated with atomically dispersed platinum on ceria are structurally dynamic and show high potential for applications in fuel cells.

Decoupling strain and ligand effects in ternary nanoparticles for improved ORR electrocatalysis

Ternary Pt–Au–M (M = 3d transition metal) nanoparticles show reduced OH adsorption energies and improved activity for the oxygen reduction reaction (ORR) compared to pure Pt nanoparticles, as obtained by density functional theory.

The oxygen reduction reaction (ORR) on reduced metals: evidence for a unique relationship between the coverage of adsorbed oxygen species and adsorption energy

The ORR current follows a volcano-like dependence on the coverage of oxygen species that adsorb upon exposure to dissolved oxygen and on their adsorption energy.