The methanol economy is an attractive approach to tackle the current concerns over the depletion of natural resources and the global warming intrinsically associated with the use of fossil fuels. This can be achieved by hydrogenation of carbon dioxide to produce methanol, a liquid fuel with potential use in civil transportation. In this study, we aim to pinpoint the intermediates that are involved in the catalytic CO2 conversion into methanol on pure zirconia (ZrO2), Cu and Cu/ZrO2 systems. To accomplish this, we make use of infrared (IR) spectroscopy measurements and quantum chemical simulations within the hybrid density functional theory (DFT) framework. At 250 degrees C and p similar to 30 bar, the main species formed on the partially hydroxylated ZrO2 is bidentate formate, whereas the co-production of bicarbonate is relevant upon cooling to T=25 degrees C. On pure Cu, the IR fingerprints of methanol and carbon dioxide indicate their presence in the gas phase and surface environment, albeit formate/formic acid and methoxy species are also detected at these experimental conditions. The production of methanol on Cu/ZrO2 is mostly dependent on the Cu catalyst, but the higher amount of the methoxy intermediate can be correlated with the consumption of formate adsorbed on ZrO2 or at the Cu/ZrO2 interface. On the Cu/ZrO2 mixture, the reaction mechanism is likely to involve formate as the main intermediate, instead of CO which would result from the reverse water-gas shift reaction. Ultimately, the higher activity shown by the Cu/ZrO2 mixture might be associated with the extra-production of methoxy/methanol catalyzed by ZrO2 in the presence of Cu.

Porphyrins constitute a class of attractive materials for harvesting sunlight and promote chemical reactions following their natural activity for the photosynthetic process in plants. In this work, we employ an in-silico design strategy to propose novel porphyrin-based materials as photocatalysts for hydrogen evolution reaction (HER). More specifically, a set of meso-substituted porphyrins with donor-acceptor architecture are evaluated within the density functional theory (DFT) framework, according to these screening criteria: i) broad absorption spectrum in the ultraviolet–visible (UV–Vis) and near infrared (NIR) range, ii) suitable redox potentials to drive the uphill reaction that lead to molecular hydrogen formation, iii) low exciton binding free energy (E_b), and iv) low hydrogen binding free energy (ΔG_H), a quantity that should present low HER overpotentials, ideally ΔG_H = 0. The outcomes indicate that the Se-containing compound, where the donor ligands are attached to the porphyrin core by the spacer, outstands as the most promising candidate that is presented in this work. It displays a broad absorption in the visible and NIR regions to up to 1000 nm, suitable catalytic power, low E_b (in special in high dielectric constant environment, such as water) and the lowest ΔG_H = +0.082 eV. This is comparable, in absolute values, to the value exhibited by platinum (ΔG_H = −0.10 eV), one of the most efficient catalysts for HER.

In recent decades, indium nitride (InN) has been attracting a great deal of attention for its potential applicability in the field of light-emitting diodes (LEDs) and high-frequency electronics. However, the contribution from adsorption- and reaction- related processes at the atomic scale level to the InN growth has not yet been unveiled, limiting the process optimization that is essential to achieve highly crystalline and pure thin films. In this report, we investigate the reaction pathways that are involved in the crystal growth of InN thin film in atomic layer deposition (ALD) techniques from trimethylindium (TMI) and ammonia (NH3) precursors. To accomplish this task, we use a solid-state approach to perform the ab-initio calculations within the Perdew–Burke–Ernzerhof functional (PBE) level of theory. The results clarify the activation role from the N-rich layer to decrease the barrier for the first TMI precursor dissociation from Δ‡H= +227 kJ/mol, in gas phase, to solely +16 kJ/mol, in the surface environment. In either case, the subsequent CH3 release is found to be thermo- and kinetically favored with methylindium (MI) formed at the hcp site and ethane (C2H6) as the byproduct. In the following step, the TMI physisorption at a nearby occupied hcp site promotes the sequential hydrogen removal from the N-rich layer at the minimum energy cost of Δ‡H < +105 kJ/mol with methane (CH4) release. An alternative mechanism involving the production of CH4 is also feasible upon dissociation in gas phase. Furthermore, the high concentration of CH3 radicals, from precursor dissociation, might be the origin of the carbon impurities in this material under the experimental conditions of interest. Finally, the passivation methodology is not found to affect the evaluation of the surface-related processes, whereas the inclusion of spin-polarization is demonstrated to be essential to the proper understanding of the reaction mechanism.