CO₂ Capture by TiO₂ Anatase Surfaces: A Combined DFT and FTIR Study

In this work, by combining FTIR results with periodic DFT calculations, we highlight the role of different anatase surface sites in the CO₂ adsorption and in the subsequent reactions. It is shown that CO₂ is mainly adsorbed in linear form at the (101) surface, while the formation of a variety of surface carbonates is occurring at the (001) one. The role of coadsorbed water in the formation of surface bicarbonates is also investigated. All the structures identified by FTIR spectroscopy were modeled by DFT, and the adsorption geometries and the energy of formation for the surface species were carefully analyzed. For the most stable structures we also performed the calculation of the vibrational frequencies that were compared with the FTIR data

Surface Properties of ZnS Nanoparticles: A Combined DFT and Experimental Study

Carbon monoxide adsorption on nanosize ZnS has been investigated by FTIR spectroscopy and periodic DFT calculations. FTIR experiments show that CO adsorption on the zinc sulfide nanoparticles gives rise to a single main ν­(CO) band indicating that the majority of the exposed sites are on the same surface. Computed adsorption energies (−0.244/–0.207 eV for the low and high coverage, respectively) and stretching frequencies (2182/2172 cm^–1) of CO adsorbed at the most stable (110) ZnS surface are in excellent agreement with observations (ν­(CO) = 2190/2168 cm^–1). CO is weakly bound to the Zn²⁺ Lewis acid surface site mainly through electrostatic interaction and a small contribution from σ donation. The strength of surface Lewis sites in ZnS is lower with respect to ZnO

Ab Initio Simulation of ZnO/LaMnO₃ Heterojunctions: Insights into Their Structural and Electronic Properties

Layered oxide heterostructures show interesting properties that encompass those of the standalone moieties; hence, a detailed understanding of the interface is key to the development and use of such materials. In this work, we have performed quantum-chemical ab initio calculations to give a complex description of structural and electronic properties of epitaxial growth ZnO/LaMnO₃ (ZnO/LMO) interfaces. The Crystal code, which uses a local (Gaussian) basis set, is used to design and characterize ZnO/LMO heterostructures including (112̅0) and (101̅0) nonpolar overlayers of ZnO on LMO(001), supported from simpler formulation to hybrid functionals of density functional theory. The applied structural models and coincidence cells are described and illustrated in detail. We discuss the impact of different termination of LMO through stability (computed strain and adhesion energies) and structural and electronic properties (density of states and 3D charge density differences). The ZnO(112̅0) overlayer shows the lesser structural distortion and the most stable configuration with LaO termination of LMO. These important findings enable us to propose novel hybrid composites for electrochemical devices

Systematic Life Cycle Environmental Impact Comparison of Alternative Synthetic Strategies for Ti₃C₂T_<i>x</i> MXene

The need for more environmentally sustainable MXene syntheses was ranked by the MXene community among the top research challenges for the upcoming decades. This means that both well-established synthetic protocols and newly proposed ones need to be assessed and compared in terms of their associated environmental impacts. Despite the various number of existing synthetic methods for MXenes, only one synthesis of Ti3C2Tx has been assessed from an environmental perspective, by applying the life cycle assessment (LCA) methodology. This work proposes for the first time a systematic life cycle environmental impact comparison among seven different synthetic pathways of the same Ti3C2Tx MXene. Starting from the first reported synthesis, the further approaches assessed differ in terms of MAX phase precursors, etching, and delamination procedures adopted. An uncertainty analysis was also performed to determine the reliability of the obtained results, which were also used in conjunction with those related to the measured bulk electrical conductivity of the MXene produced together with the obtained density values of opportunely prepared Ti3C2Tx freestanding films. This allows accounting for the necessary different quality of the obtained products, highlighting the better trade-off solutions between low environmental impacts, high electrical conductivity, and low weight of the potentially developed Ti3C2Tx MXene-based devices

Stability and Formation of the Li₃PS₄/Li, Li₃PS₄/Li₂S, and Li₂S/Li Interfaces: A Theoretical Study

Solid electrolytes have shown superior behavior and many advantages over liquid electrolytes, including simplicity in battery design. However, some chemical and structural instability problems arise when solid electrolytes form a direct interface with the negative Li-metal electrode. In particular, it was recognized that the interface between the β-Li3PS4 crystal and lithium anode is quite unstable and tends to promote structural defects that inhibit the correct functioning of the device. As a possible way out of this problem, we propose a material, Li2S, as a passivating coating for the Li/β-Li3PS4 interface. We investigated the mutual affinity between Li/Li2S and Li2S/β-Li3PS4 interfaces by DFT methods and investigated the structural stability through the adhesion energy and mechanical stress. Furthermore, a topological analysis of the electron density identified preferential paths for the migration of Li ions

Work Function of Oxide Ultrathin Films on the Ag(100) Surface

Theoretical calculations of the work function of monolayer (ML) and bilayer (BL) oxide films on the Ag(100) surface are reported and analyzed as a function of the nature of the oxide for first-row transition metals. The contributions due to charge compression, charge transfer and rumpling are singled out. It is found that the presence of empty d-orbitals in the oxide metal can entail a charge flow from the Ag(100) surface to the oxide film which counteracts the decrease in the work function due to charge compression. This flow can also depend on the thickness of the film and be reduced in passing from ML to BL systems. A regular trend is observed along first-row transition metals, exhibiting a maximum for CuO, in which the charge flow to the oxide is so strong as to reverse the direction of rumpling. A simple protocol to estimate separately the contribution due to charge compression is discussed, and the difference between the work function of the bare metal surface and a Pauling-like electronegativity of the free oxide slabs is used as a descriptor quantity to predict the direction of charge transfer