This interdisciplinary work combines the use of shape-and size-defined Pd nanocrystals (cubes of 10 and 18 nm, and octahedra of 37 nm) with in situ techniques and DFT calculations to unravel the dynamic phenomena with respect to Pd reconstruction taking place during acetylene hydrogenation. Notably, it was found that the reacting Pd surface evolved at a different pace depending on the shape of the Pd nanocrystals, due to their specific propensity to form carbides under reaction conditions. Indeed, Pd cubes (Pd(100)) reacted with acetylene to form a PdC 0.13 phase at a rate roughly 6-fold higher than that of octahedra (Pd(111)), resulting in nanocrystals with different degrees of carburization. DFT calculations revealed changes in the electronic and geometric properties of the Pd nanocrystals imposed by the progressive addition of carbon in its lattice.

The catalytic dehydration of propan-2-ol over H-Y and H-ZMS-5 aluminated\ud zeolite models, mimicking both internal cavities and external surfaces, was\ud studied by DFT calculations to investigate the reaction mechanism. After the adsorption of propan-2-ol on the zeolite, the dehydration mechanism starts with alcohol protonation, occurring by one acidic –OH group of the zeolite fragment, followed by a concerted b-elimination to give propene. The catalytic activity is\ud affected by the size of the zeolite cavity, which is larger in the H-Y than in the H-ZMS-5 zeolite. The adsorption energy of the reagent, as an example, decreases in the order: H-Y cavity = H-ZMS-5 > surface H-ZMS-5 cavity, pointing that the adsorption process should preferentially occur either on open surface or inside larger cavity. More interestingly, confinement effects play a twofold role in driving the reaction pathway, resulting in two different effects on the reaction outcomes. The thermodynamic stability, evaluated by the standard free energy difference of\ud the products (water and propene) with respect to the reactant (propan-2-ol), would indeed suggest that the reaction more smoothly could occur for the systems: H-ZMS-5 surface > non-catalyzed > H-Y cavity > H-ZMS-5 cavity. The activation standard free energy of the process conversely decreases in the order: non-catalyzed > H-ZMS-5 surface > H-ZMS-5 cavity > H-Y cavity, suggesting that the reaction is faster inside zeolite cavities. Experimental and computational results are in agreement, giving confidence on the atomistic-level insights provided

In the frame of DFT paradigms, the adsorption of 2-methyl-3-butyn-2-ol (MBY) and 2-methyl-3-buten-2-ol (MBE) on a Pd30 cluster, including both {100} and {111} faces, was studied along with the pathways involved in the hydrogenation, taking place on plane and low coordination (corner/edge) sites of given MBY/Pd30 and MBE/Pd30 surface configurations. The calculated energetics, further validated by gas-phase and water-assisted gas-phase MBY and MBE hydrogenation, performed on well-defined size and shape-controlled Pd nanoparticles supported on SiO2, were able to explain the origin of the structure sensitivity and the high selectivity characterizing the title reaction when occurring in aqueous solution. The CC moiety of the MBY surface species indeed seemed to be mostly activated by plane sites instead of corner/edge atoms, whereas the MBE species appeared to have a different behavior, with their CC moieties typically being activated by low coordination sites. DFT studies excluded that the overhydrogenation paths could be affected by the site topologies; hence, the role of plane, edge, or corner atoms should not be influential in setting the surface reaction mechanism, which as a consequence could be controlled by the adsorption energy, actually distinguished by different values on sites of different topology. The role of water in the selectivity to MBE, which characterizes the catalytic overhydrogenation of MBY on Pd nanoparticles, was also inferred.

A periodic, self‐consistent planewave DFT study was carried out to explore the potential use of Pd6 clusters supported on a boron nitride sheet as a catalyst for the selective decomposition of formic acid (HCOOH) to CO2 and H2. The competition between formate (HCOO) and carboxyl (COOH) paths on catalytic sites, with different proximities to the support, was studied. Based on energetics alone, the reaction may mainly follow the HCOO route. Slightly lower activation energies were found at the lateral sites of the cluster as compared to top face sites. This is particularly true for the bidentate to monodentate HCOO conversion. Through comparison of results with similar studies on HCOOH decomposition on extended Pd surfaces, it was demonstrated that the existence of undercoordinated sites in the sub‐nanometer cluster could play a key role in preferentially stabilizing HCOO over COOH, which is a common CO precursor in this reaction. A hydrogen spillover mechanism was also investigated; migration toward the boron nitride support is not favorable, at least in the early stages of the reaction. However, hydrogen diffusion on the cluster has low barriers compared to those involved in formic acid decomposition.

Biomass-based feedstocks are often oxygenated compounds characterized by large amounts of hydroxyls. As an example, polyols and sugar alcohols are largely employed as reactants for different chemical catalytic transformations such as oxidation, dehydration, and hydrodeoxigenation, which usually occur in aqueous medium. With the goal of gaining new insights into processes that could be industrially relevant, the adsorption of the OH groups on metal surfaces and in the presence of water has to be correctly reproduced and described, within a chosen theoretical framework. Toward this goal, several tests were performed on the catalytically relevant metal Ru, Pd, and Re, benchmarking their bulk and surfaces properties in the frame of the DFT paradigm and employing numerical atomic orbitals, joined with different exchange-correlation vdW-DF functionals. In particular, methanol, ethylene glycol, glycerol, and erythritol adsorption processes on Ru (0001), Pd (111), and Re (0001) surfaces were investigated, as well as their coadsorption with water