Chemistry of the Interaction and Retention of Tc and Tc Species at the FeO(001) Surface.

The pertechnetate ion TcO is a nuclear fission product whose major issue is the high mobility in the environment. Experimentally, it is well known that FeO can reduce TcO to Tc species and retain such products quickly and completely, but the exact nature of the redox process and products is not completely understood. Therefore, we investigated the chemistry of TcO and Tc species at the FeO(001) surface through a hybrid DFT functional (HSE06) method.

Improving the Oxygen Evolution Reaction on FeO(001) with Single-Atom Catalysts.

Doping magnetite surfaces with transition-metal atoms is a promising strategy to improve the catalytic performance toward the oxygen evolution reaction (OER), which governs the overall efficiency of water electrolysis and hydrogen production. In this work, we investigated the FeO(001) surface as a support material for single-atom catalysts of the OER. First, we prepared and optimized models of inexpensive and abundant transition-metal atoms, such as Ti, Co, Ni, and Cu, trapped in various configurations on the FeO(001) surface.

Effect of Surface Functionalization on the Magnetization of FeO Nanoparticles by Hybrid Density Functional Theory Calculations.

Surface functionalization is found to prevent the reduction of saturation magnetization in magnetite nanoparticles, but the underlying mechanism is still to be clarified. Through a wide set of hybrid density functional theory (HSE06) calculations on FeO nanocubes, we explore the effects of the adsorption of various ligands (containing hydroxyl, carboxylic, phosphonic, catechol, and silanetriol groups), commonly used to anchor surfactants during synthesis or other species during chemical reactions, onto the spin and structural disorder, which contributes to the lowering of the nanoparticle magnetization. The spin-canting is simulated through a spin-flip process at octahedral Fe ions and correlated with the energy separation between O 2p and Fe 3d states.

Multiscale simulations of the hydration shells surrounding spherical FeO nanoparticles and effect on magnetic properties.

Iron oxide magnetic nanoparticles (NPs) are excellent systems in catalysis and in nanomedicine, where they are mostly immersed in aqueous media. Even though the NP solvation by water is expected to play an active role, the detailed structural insight at the nanostructure oxide/water interface is still missing. Here, based on our previous efforts to obtain accurate models of dehydrated Fe3O4 NPs and of their magnetic properties and through multiscale molecular dynamics simulations combining the density functional tight binding method and force field, we unravel the atomistic details of the short range (chemical) and long range (physical) interfacial effects when magnetite nanoparticles are immersed in water.

Parametrization of the Fe-O cross-interaction for a more accurate FeO/water interface model and its application to a spherical FeO nanoparticle of realistic size.

The accurate description of iron oxides/water interfaces requires reliable force field parameters that can be developed through comparison with sophisticated quantum mechanical calculations. Here, a set of CLASS2 force field parameters is optimized to describe the Fe-O cross-interaction through comparison with hybrid density functional theory (HSE06) calculations of the potential energy function for a single water molecule adsorbed on the FeO (001) surface and with density functional tight binding (DFTB+U) molecular dynamics simulations for a water trilayer on the same surface. The performance of the new parameters is assessed through the analysis of the number density profile of a water bulk (12 nm) sandwiched between two magnetite slabs of large surface area.

Insight into the interface between FeO (001) surface and water overlayers through multiscale molecular dynamics simulations.

In this work, we investigate the FeO (001) surface/water interface by combining several theoretical approaches, ranging from a hybrid functional method (HSE06) to density-functional tight-binding (DFTB) to molecular mechanics (MM). First, we assess the accuracy of the DFTB method to correctly reproduce HSE06 results on structural details and energetics and available experimental data for adsorption of isolated water, dimers, and trimers up to a water monolayer. Second, we build two possible configurations of a second and a third overlayer and perform molecular dynamics simulations with DFTB, monitoring the water orientation, the H-bond network, and the ordered water structure formation.