A DFT Study on the O2 Adsorption Properties of Supported PtNi Clusters

O2 activation by AuAg clusters on a defective (100)MgO surface

In the present work, we discuss the electronic properties of supported dispersed bimetallic clusters with respect to their size, geometry, and Au_n/Ag_m (n + m = 6) composition. We have studied with supercell-density functional theory calculations the role of the charge transfer from the MgO defective support toward the cluster in the activation of O₂ by Au_nAg_m clusters. We first considered gas-phase clusters with different atomic compositions; then, we deposited all of them on a pristine (100)MgO surface and finally on a more realistic (100)MgO F-center. We performed a global and unrestricted search of the (cluster + surface) geometry. The Mexican enhanced genetic algorithm has been used to exhaustively explore the potential energy surface. Our results show that O₂ activation depends on the Au_n/Ag_m ratio. It has been found that both metals involved play different and important roles toward (a) the actual O₂ dissociation and (b) weakening of the oxygen-cluster bond, which, in turn, may promote the possibility of a catalytic process to take place, such as the oxidation process of CO and NO_x among others.

Correlating Oxygen Reduction Reaction Activity and Structural Rearrangements in MgO-Supported Platinum Nanoparticles

We develop a multi‐scale approach towards the design of metallic nanoparticles with applications as catalysts in electrochemical reactions. The here discussed method exploits the relationship between nanoparticle architecture and electrochemical activity and is applied to study the catalytic properties of MgO(100)‐supported Pt nanosystems undergoing solid‐solid and solid‐liquid transitions. We observe that a major increment in the activity is associated to the reconstruction of the interface layers, supporting the need for a full geometrical characterisation of such structures also when in‐operando.

Structural properties of sub-nanometer metallic clusters

At the nanoscale, the investigation of structural features becomes fundamental as we can establish relationships between cluster geometries and their physicochemical properties. The peculiarity lies in the variety of shapes often unusual and far from any geometrical and crystallographic intuition clusters can assume. In this respect, we should treat and consider nanoparticles as a new form of matter. Nanoparticle structures depend on their size, chemical composition, ordering, as well as external conditions e.g. synthesis method, pressure, temperature, support. On top of that, at finite temperatures nanoparticles can fluctuate among different structures, opening new and exciting horizons for the design of optimal nanoparticles for advanced applications. This article aims to overview geometrical features of transition metal clusters and of their various rearrangements.

A genomic characterisation of monometallic nanoparticles

A “genomic” description of monometallic nanoparticles could help to design more efficient nanocatalysts.

Origin of enhanced stability and oxygen adsorption capacity of medium-sized Pt-Ni nanoclusters

Understanding the stability and adsorption properties of O atom can be considered as the first step to understand the mechanism of the oxygen reduction reaction on Pt-Ni nanoclusters. In this work, the equilibrium structures, stability, adsorption properties and deformation energies of medium-sized Pt-Ni nanoclusters are studied by global optimization method and density functional theory calculations. It is found that Pt-Ni nanoclusters are of more stable structure and larger oxygen adsorption energy than Pt nanoclusters, and the enhanced stability and oxygen adsorption capacity of Pt-Ni nanoclusters originate from both the strain and electronic factors. Based on the strain effect, the local pressures are on average much better equilibrated on Pt-Ni nanoclusters, bringing about the more stable structure. The elongation of the metal-metal bond distances results in the increase of adsorption energy of the O atom on Pt-Ni nanoclusters. Considering the electronic effect, the charge interaction between the LDOS (d orbital) of metal atoms adjacent to the adsorbed O atom and the DOS (p orbital) of the O atom gives rise to the increase of oxygen adsorption capacity on Pt-Ni nanoclusters. Simultaneously, the charge density difference analysis shows that the Ni atoms doping is conducive for O atom adsorption. In addition, the diffusion of O atom from surface to interior is difficult due to the high diffusion energy barriers. Our results show that both strain and electronic factors are of important effects on the stability and adsorption properties of nanoalloys.

CO2 adsorption on gas-phase Cu4−xPtx (x = 0–4) clusters: a DFT study

Transition and noble metal clusters have proven to be critical novel materials, potentially offering major advantages over conventional catalysts in a range of value-added catalytic processess such as carbon dioxide transformation to methanol.