The Influence of Ni Addition in the Mechanism of CO2 Electroreduction on Cu Crystals-Mechanistic Insight from DFT Simulations.

We present a DFT analysis of the role of the Cu-Ni synergistic effect for the CO2 reduction to C2H4, in comparison to the pure Cu catalyst. The analysis is focused on the thermodynamic stability of reactive intermediates along the proposed pathway of C2 species formation. We have observed that the potential needed for the reaction decreases with the addition of Ni in the investigated model. In addition, we have observed the differences in the preferred pathway based on the significant differences in stability of the reactive intermediates depending on th Cu:Ni ratio. The results suggest that despite the fact the Cu surface is always exposed, and it is the only one that is able to directly interact with the intermediates, the presence of the Ni in the underlying sections of the crystal is significant enough to change the mechanism of the reaction.

A DFT Study of CO2 Hydrogenation on Faujasite-Supported Ir4 Clusters: on the Role of Water for Selectivity Control.

Reaction mechanisms for the catalytic hydrogenation of CO2 by faujasite-supported Ir4 clusters were studied by periodic DFT calculations. The reaction can proceed through two alternative paths. The thermodynamically favoured path results in the reduction of CO2 to CO, whereas the other, kinetically preferred channel involves CO2 hydrogenation to formic acid under water-free conditions. Both paths are promoted by catalytic amounts of water confined inside the zeolite micropores with a stronger promotion effect for the reduction path. Co-adsorbed water facilitates the cooperation between the zeolite Brønsted acid sites and Ir4 cluster by opening low-energy reaction channels for CO2 conversion.

TiO2-catalyzed synthesis of sugars from formaldehyde in extraterrestrial impacts on the early Earth.

Recent synthetic efforts aimed at reconstructing the beginning of life on our planet point at the plausibility of scenarios fueled by extraterrestrial energy sources. In the current work we show that beyond nucleobases the sugar components of the first informational polymers can be synthesized in this way. We demonstrate that a laser-induced high-energy chemistry combined with TiO2 catalysis readily produces a mixture of pentoses, among them ribose, arabinose and xylose. This chemistry might be highly relevant to the Late Heavy Bombardment period of Earth's history about 4-3.85 billion years ago. In addition, we present an in-depth theoretical analysis of the most challenging step of the reaction pathway, i.e., the TiO2-catalyzed dimerization of formaldehyde leading to glycolaldehyde.

The role of Ir4 cluster in enhancing the adsorption of CO2 on selected zeolites - GCMC simulations.

We have investigated the adsorption of CO2 molecules inside the EMT, SAO, SBS, SBT and IWS zeolites with respect to the influence of the Ir4 clusters on the adsorption capabilities of these materials. We have determined that the capabilities of CO2 adsorption depend on the combined effect of the framework topology and the position of the Ir4 cluster. Adsorption intensifies despite the fact that a fraction of the pore volume is occupied by the Ir4 cluster, and thus, the adsorption is more intense than that on empty zeolite. The pore topology however is also playing a crucial role in the effect, as in certain cases it allows the CO2 molecules to order in such a way they fill the most pore space.

GCMC simulations of CO2 adsorption on zeolite-supported Ir4 clusters.

We have studied the adsorption of CO2 molecules inside the pores of faujasite zeolite and evaluated the influence of the Ir4 clusters on the intensity of the adsorption. The force field designed for CO2 adsorption in zeolites has been extended with the parameters for the CO2/Ir4 interactions, taking the Density Functional Theory (DFT) energies as a reference. We have found that despite the fraction of the pore volume that is occupied by the Ir4 cluster, the adsorption is more intense than that of empty faujasite. The adsorption sites next to the cluster are very characteristic, and the interactions are more intensive due to the interactions of zeolite and the Ir cluster both playing an important role.

DFT modeling of CO2 adsorption on Cu, Zn, Ni, Pd/DOH zeolite.

This study is the analysis of the adsorption process of the CO2 molecule on the cationic sites of the DOH zeolite. Based on the DFT method, we have been able to identify several adsorption sites containing extra-framework cations and evaluate the value of the adsorption energy with respect to the distance from the adsorption site. The zinc cation has been found to cause the strongest interaction with the CO2 molecule. Subsequently, the adsorption process has been investigated by means of the Molecular Dynamics simulations. The results of the MD simulations are consistent with the geometry optimizations, and confirm the activation of CO2 molecule adsorbed in the Zn site.