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Nanocatalyst-by-design promises to empower the next generation of electrodes for energy devices. However, current numerical methods consider individual and often geometrical closed-shell nanoparticles, neglecting how the coexistence of several and structurally diverse isomers in a sample affect the activity of the latter. Here, we present a multiscale numerical approach to calculate, in a fast and high-throughput fashion, the current density and mass activity of individual isomers, as well as predict the activity of morphologically diverse but size-selected samples. We propose specific design rules of platinum nanosamples for the electrochemical reduction of molecular oxygen, identifying the size range up to 5.5 nm as the one where isomerization of individual nanoparticles and the morphological composition of the sample cannot be neglected. We confirm a peak of the activity of defected and concave polyhedra at 2–3 nm while spherical but amorphous isomers become the most active in the range of 3–5 nm, with an astonishing mass activity of 2.7 A/mg. We provide a possible explanation to rationalize the discrepancies in the measured mass activity of size-selected samples, in terms of the different distributions of Pt isomers in each specimen.

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., Communication is key! We discuss the results of a multi‐scale approach to probe the interplay between structural rearrangements of supported Pt nanoparticles for electrochemical oxygen reduction reaction and their catalytic activity.

With a focus on platinum nanoparticles of different sizes (diameter of 1-9 nm) and shapes, we sequence their geometrical genome by recording the relative occurrence of all the non equivalent active site, classified according to the number of neighbours in their first and second coordination shell. The occurrence of sites is morphology and size dependent, with significant changes in the relative occurrence up to 9 nm. Our geometrical genome sequencing approach is immediately transferable to address the effects of the morphological polydispersivity in size-selected samples and the influence of temperature, including ionic vibrations and thermal activated processes. The proposed geometrical genome forecasts an enhancement of the catalytic reduction of molecular oxygen on stellated and anisotropic platinum twinned nanoparticles, with their shortest axes of ~2 nm, and an irreversible disruption of the Pt nanocatalyst's structure above 1000 K., 13 pages 7 Figures

Small metallic nanoparticles supported on transition metal carbides exhibit an unexpected high activity towards a series of chemical reactions. In particular, the Au/TiC system has proven to be an excellent catalyst for SO 2 decomposition, thiophene hydrodesulfurization, O 2 and H 2 dissociation and the water gas shift reaction. Recent studies have shown that Au/TiC is a very good catalyst for the reverse water–gas shift (CO 2 + H 2 → CO + H 2 O) and CO 2 hydrogenation to methanol. The present work further expands the range of applicability of this novel type of systems by exploring the catalytic activity of Au/TiC towards the hydrogenation of CO or CO 2 with periodic density functional theory (DFT) calculations on model systems. Hydrogen dissociates easily on Au/TiC but direct hydrogenation of CO to methanol is hindered by very high activation barriers implying that, on this model catalyst, methanol production from CO 2 involves the hydrogenation of a HOCO-like intermediate. When dealing with mixtures of syngas (CO/CO 2 /H 2 /H 2 O), CO could be transformed into CO 2 through the water gas shift reaction with subsequent hydrogenation of CO 2 to methanol.

To elucidate the effect of the architecture of supported bimetallic nanocatalysts, we developed a new lattice kinetic Monte Carlo based on the classifying and counting adsorption sites with respect to their generalized coordination number. We employed this tool to estimate the activity of MgO-supported PtNi nanoalloys for oxygen reduction. We demonstrated that the presence of Ni atoms in contact with the substrate massively enhances their activity with at least a 7-order of magnitude increase in the turnover of water production with respect to the case where only Pt lay at the interface. We further discussed how the nanoalloy shape affects the activity showing that truncated octahedra are 102 more active than cuboctahedra of similar size. We explained our results in terms of their distinct distribution and occurrence of the most active sites for oxygen reduction leading to the stabilization of different chemical species during the reaction dynamics. Our results suggest that engineering multifaceted and long edge PtNi-nanoalloys with a certain chemical ordering at the support interface would improve their catalytic performance for the oxygen reduction reaction.

Au atoms in contact with TiC(001) undergo significant charge polarization. Strong metal–support interactions make Au/TiC(001) an excellent catalyst for the low-temperature water–gas shift (WGS), with turnover frequencies orders of magnitude larger than those observed for conventional metal/oxide catalysts. DFT calculations indicate that the WGS reaction follows an associative mechanism with HOCO as a key intermediate.

Periodic density functional theory (DFT) calculations have been used to study the stability of five different C-terminations of the Mo2C(001) surface in the most stable orthorhombic (β) phase of this important material. The different terminations all have similar values of the work function or atomic charges, indicating a similar electronic structure, although the analysis of the cleavage energy suggests that the non polar C-terminated surfaces will be the extended terminations seen under thermodynamic equilibrium. Nevertheless, the calculated DFT cleavage energy values together with statistical arguments indicate that different C-terminated motifs are likely to coexist even at temperatures just below annealing conditions.

The interaction of Au, Cu, and Ni metal atoms with the δ-MoC(001) surface was studied using periodic density functional (DF) calculations to analyze adsorption energies and equilibrium geometries, work functions, atomic charges, projected density of states (PDOS), and shifts of the transition metal d-band center. The atomic adsorption is found to cause an in-plane distortion of the surface, and, besides, the interaction strength turns to be coverage dependent. A lower coverage allows for a better accommodation of the adsorbate, alongside causing a d-band center shift to more negative energies, as shown by plots of the PDOS. Regardless of the coverage, interaction strength diminishes following the order Ni > Cu > Au. Adatom chemical activity can be inferred based on the calculated d-band center; Ni being the most active metal, followed by Cu, and then Au for every coverage studied. This result well correlates with experiments on other transition metal carbides. Atomic adsorption also diminishes surface work function.

The adsorption of CO at regular and defect sites of the TiC surface has been studied by means of density functional theory (DFT) based calculations and temperature programmed desorption experiments (TPD) using TiC nanopowders as substrate whose structure and morphology have been characterized by X-ray diffraction and both scanning and transmission electron microscopy. The results obtained confirm previous work indicating that the nature of CO adsorption is strongly dependent on surface coverage due to the distortion of the surface induced by the adsorbate and also allows one to resolve an apparent anomaly between theory and experiment. Calculations and TPD experiments show that CO adsorption strength at regular sites is rather large with an adsorption energy of about − 1.60 eV which is consistent with a main desorption peak at ~ 500 K. Adsorption at low coordinated sites is even stronger and in agreement with desorption experiments indicating that CO continues to desorb at temperatures as high as 600 K.

Our experimental and theoretical investigation focuses on the role of magnetism on the structures and energetics of nanoclusters of the important 3d antiferromagnetic (AFM) semiconductor, manganese sulphide (MnS). Our cluster beam mass spectra for both (MnS)n and (MnSe)n show a pronounced “magic” abundance, at n = 13, in accord with results for other nonmagnetic chalcogenide clusters (e.g., CdS, CdSe, ZnS, ZnSe). Using global optimization and ab initio calculations we focus on cluster isomers of (MnS)13 and its two neighboring compositions, (MnS)12 and (MnS)14, and show that the magic status of the former is fully compatible with the high relative energetic stability of the n = 13 ground state with respect to those for n ± 1. We demonstrate a strong symbiosis between cluster structure and spin ordering, which leads to a particular type of AFM spin-ordered ground-state cluster structure being energetically selected for all cluster sizes and which enhances the magic stability of (MnS)13. This nanomagnetostr...

The interaction of CO with the bare TiC(001) surface and with Aun (n = 4, 9, 13) nanoparticles supported on the same TiC(001) surface has been studied by means of periodic density functional theory...