Despite its presumed chemical stability, acetonitrile in Li–O 2 batteries may participate in parasitic pathways involving Li 2 O 2 and water-derived decomposition products. Glyme-, sulfoxide-, and amine-based solvents may show similar behaviour.

Exploring efficient monometallic or bimetallic supported catalysts to improve CO2 methanation at low temperatures is an important topic in the field of heterogeneous catalysis. In the current research, bimetallic Ru-Cu/ TiO2 catalysts were prepared using the co-deposition-precipitation with urea method. Augmenting the ruthenium content from 0.5 to 1.5 wt% boosted the CO2 conversion and improved the reducibility of the catalysts. Optimal metal loadings were found to be 2.0% copper and 1.5% ruthenium, and the synergistic interaction between Ru and Cu in the bimetallic catalysts was confirmed for CO2 methanation. The Ru, Cu and Ru-Cu catalysts were characterized by X-ray diffraction, BET specific surface area, STEM-EDS microscopy, H2/TPR, CO adsorption DRIFTS, CO oxidation DRIFTS (as a model reaction to observe adsorbed species and reaction intermediates on the Ru, Cu and Ru-Cu catalyst surface), methanation followed by DRIFTS, as well as XPS. The outcomes revealed the strong interaction between Ru and Cu on the TiO2 anatase support, which led to modified metal dispersion when both metals were present. Indeed, the heterogenous charge distribution in the bimetallic structure leads to cooperative nucleophilic and Lewis-acidic sites for CO2 adsorption and bond activation. Additionally, hydrogen spillover in Ru-Cu/TiO2 was observed, which improved CO2 methanation and adsorption capacity. As for the Ru-Cu/TiO2 catalyst, catalytic evaluation confirmed its significantly enhanced activity, selectivity, and stability with respect to the corresponding monometallic Ru and Cu catalysts. XPS and in-situ DRIFTS analyses indicated that metallic Ru0 and Cu0 were the most active species. Furthermore, the bimetallic catalyst demonstrated good reusability, maintaining its activity over repeated reaction cycles.

Despite being long considered inert, the common electrolyte solvent acetonitrile can actively participate in parasitic reactions that dictate Li-O2 battery efficiency. Identifying how solvents interact with discharge products in solution or on the surface is key to mitigating parasitic reactions and extending battery lifetimes. Herein, we present a theoretical mechanistic study on the lithium peroxide degradation products in acetonitrile in the presence of water as a contaminant. Under these conditions, the oxidation of acetonitrile takes place in solution. According to the cluster model, the surface electronic effects are insufficient to initiate the acetonitrile oxidation reaction. Water as a contaminant in Li-O2/ACN cells participates in LiOH formation that decomposes by reacting with intermediates to produce the original discharge product Li2O2, but at the expense of producing the parasitic product acetamide. We proposed a reaction of Li2O2 with water to serve as a prototype for conducting intensive and comprehensive computational analysis aimed at testing different solvents for their use in electrolyte solutions or in surface models for Li-O2 batteries straightforwardly.

In this study, we evaluated a series of bimetallic gold-copper catalysts, synthesized by the sequential deposition-precipitation with urea method, for their performance in the total oxidation of propane. From the tested variables (bimetallic ratio, activation protocol, and support type) the most active catalyst was found to be Au1Cu3/TiO2 (Au:Cu =1:3), which was activated in air atmosphere and exhibited the temperature at which the propane conversion reached 50% (T50%) of 328 degrees C, surpassing the performance of its monometallic counterparts. The characterization using various techniques revealed that the Au1Cu3/TiO2 catalyst comprises highly dispersed nanoparticles predominantly exposing Au0 and Cu delta+ active sites in close interaction. Surface analysis via XPS showed that copper species are mainly in the 1+ oxidation state. An increase in Cu2+ species and Lewis's acid sites were also determined in the bimetallic sample, compared to the copper-only catalyst, thus probably accounting for the observed improvement in the catalytic performance. Through operando DRIFTS-MS analysis we identified various predominant intermediate species, depending on the metal present in the catalyst: enolate for gold, formate and carbonate for copper, and a combination of these intermediates in the bimetallic sample, which probably enhances propane oxidation efficiency. Based on the theoretical results we found that gold incorporation into Cu/TiO2 catalyst enhances copper's oxyphilicity and Lewis's acidity, boosting the propane oxidation by enabling electron-assisted activation of stable propyl sites, which form majorly enolate and fully oxidized products. A cascade charge-reservoir effect is proposed to explain differences in chemical reactivity of gold-copper and copper catalysts. Cu preferentially binds to reduced TiO2, preserving direct contact with the support even in the Au-Cu bimetallic catalyst.

Supported mono and bimetallic Au catalysts have evidenced to be overly effective catalyzing the CO oxidation at low temperature. The bimetallic Au-Pd and Au-Ir catalysts with small amounts of Au, Pd or Ir (1 wt%) displayed homogeneously distributed particles (average metal particle size between 1 and 2 nm), and strong metal-metal interactions, which exerted a fundamental effect on the CO oxidation at low temperature. These bimetallic nanostructures afforded a stable CO oxidation at low temperatures (from-5 degrees C to 25 degrees C). DRIFTS analyses revealed different interactions between CO and the metals, suggesting a different degree of interaction between Au and Ir, Pd, Pt or Ru. Through DFT calculations, it was found that Pd induced high fluxionality on the supported bimetallic catalysts and that Ir produced greater distortion over the TiO2 surface upon adsorption; then, both effects could have been contributing to the high catalytic activity displayed by these materials.

A key intermediate on the reaction mechanism on the Au cluster is found and characterized as perester-type species. This is essential given that by calling this intermediate by its name evidences its chemical nature and explains the high catalytic activity of gold-based nanoparticles in the CO oxidation reaction. In contrast for Au-Ru cluster the CO oxidation reaction proceeded through oxygen dissociative adsorption in the first stage. Au8Ru5 is found to be a stable bimetallic cluster in which gold transfers charge to ruthenium. The electronic state influenced O2 activation mode, thus impacting in O2 adsorption by dissociation. The most stable structure of both O2 and CO adsorption over the cluster involving Ru and Au sites does not lead to the lowest oxidation barrier. Ru sites facilitated the reaction. The interface is the preferred energetically reaction site on the second oxidation stage. The oxidized phase of ruthenium in the bimetallic structure facilitated the oxidation reaction even more than the gold reference catalyst. The present study provided further insight into the origin of the synergistic effect of these metals on their catalytic activity and shed light on the nature of relevant intermediates as a guide for studying these systems in heterogeneous phase.

Quantum chemistry calculations were performed to elucidate the reaction sites and degradation routes of dexamethasone. Flow Injection Analysis Electrospray Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry (FIA-ESI-FTCIR-MS) was used to identify dexamethasone and its byproducts in Mexico City's wastewater, guided by results from ab-initio calculations on the bond energy analysis and thus propose possible degradation routes. Products of hydroxylation/reduction, decarbonylation/formylation and defluorination reactions were identified. The results of this study contribute to the identification of the degradation products of drugs commonly used in the treatment of COVID-19 in urban areas. Through wastewater analysis and computationally assisted Mass-Spectrometry techniques, an alternative approach is presented to identify byproducts in complex matrices when analytical standards are unavailable or in case of limited understanding on the stability of the degradation byproducts in aqueous medium. Identification of degradation byproducts of dexamethasone with the analysis in the sewage water flow of Mexico City by computationally assisted FIA-ESI-FTCIR-MS technique. image

The electronic structure and derived optical properties of five synthesized metal-dicyanoaurate(i), (K)M[Au(CN)2], (M = Mn, Co, Ni, Zn and Cd), coordination polymers are described from a combined experimental analysis and theoretical study based on density functional theory. In this sense, the topological features that influence the electronic structure, which in turn give rise to electronic transitions associated with the band gap energy, are studied from first principles calculations (with hybrid HSE06 and GGA-PBE density functionals) and electronic spectroscopy. The impact of gold (through spin-orbit coupling) and aurophilic interactions on the electronic transitions that gives rise to optical properties is described. The calculated projected density of states and band dispersion diagrams shed light on the molecular orbital distribution and the role of a dicyanoaurate(i) molecular block as the origin of the optical properties. Infrared, Raman and ultraviolet-visible spectroscopic analyses reveal the effect that charge transfer interactions, of a metal -> ligand and metal -> metal nature, have on the electronic behavior within the solids through association with the polarizing power of transition metals and gold atoms. The electronic structure and optical response of five metal-dicyanoaurates(i), (K)M[Au(CN)2] (M = Mn, Co, Ni, Zn and Cd), are described from a combined experimental and theoretical study

Semiconductors are essential for modern life since they are the basis of many current technologies that are related to better living standards. Some of them, characterized by the periodic assembling of metal cyanides with filled d-shell (nd10 ) constitute an interesting series of cyanide-based coordination polymers with physical properties such like anomalous anisotropic thermal expansion and quantum confinement effects related to the polymer's width that can be exploited for technological applications. Herein, the electronic structure of nd10 metal cyanide-based systems were studied both experimentally and through Density Functional Theory. The band gap found for one-dimensional (1D) -M-C≡N- (M=Cu, Ag, Au) and tetrahedral M-(C≡N)2 (M=Zn, Cd, Hg) systems can be attributed to Laporte-allowed π →${\to }$ π* (Metal to Ligand Charge Transfer mechanism) combined with metal center (d →${\to }$ s,p) electronic transitions. Aurophilic bonding was found on the AuCN structure, and a new forbidden electronic transition associated to its band gap is reported. Computed effective and reduced masses from carriers revealed that carrier mobility and quantum confinement effects are greater in 1D systems.

Transition metal hexacyanocobaltates(III) correspond to coordination polymers that present physical properties that can be used for technological applications. In this sense, properties like spin-crossover under different physical stimuli (light, temperature, pression, etc) or the colossal mechanical negative thermal expansion has been reported as astonishing properties of these materials (Goodwin et al., 2008; Goodwin et al., 2008; Avila et al., 2022) [1–3]. In this contribution, the electronic properties of hexacyanocobaltates(III) that contain Zn2+, Cd2+ and Ag1+ as metal ions, with a closed d-shell electronic configuration, are studied by means of combined UV–Vis spectroscopy and ab-initio calculations. The influence of the outer metals (Zn, Cd, Ag) when forming the coordination polymers as well as the effect of the inner octahedral moiety [Co(CN)6]3- have on the macroscopic electronic properties is discussed. Metal to ligand charge transfer transitions that produce the optical behavior are also clarified. Furthermore, the origin of the band gap transitions for Zn and Cd hexacyanocobaltates(III) is reported for the first time and supported by ab-initio calculations. New optical band gap energy values are proposed from a combined Urbach and Tauc analysis. Finally, the effects of metal substitution in Prussian blue analogues and the structural phase shift towards a zeolite-like phase on the band gap are analyzed.

Ruthenium is a robust catalyst for a variety of applications in environmental heterogeneous catalysis. The catalytic performance of Ru/TiO2 materials, synthesized by using the deposition precipitation with urea method, was assessed in the catalytic oxidation of C3H8, varying the ruthenium loading. The highest catalytic reactivity was obtained for a Ru loading of 2 wt.

Theelectronic structure of cyanide-based Zn[M(CN)(4)](M = Ni, Pd, and Pt) coordination polymers is studied by means ofspectroscopic techniques and DFT-based computational calculations.The observed different & nu;(CN) band shifts to higher frequencieswhen the inner metal from the tetracyanate moiety [M(CN)(4)] changes from Ni to Pt and Ni to Pd as a consequence of the chargedistribution produced by the & pi; back-bonding phenomena and thecompetition between the polarization powers from M and Zn. This isevidenced by infrared, Raman, and UV-vis spectroscopic techniquesin conjunction with hybrid HSE06 calculations. The sample characterizationwas completed from XPS spectra and HR-TEM images. The electronic structurewas also studied by the computed lm-decomposed density of states andband dispersion diagrams. The nature of the valence band top and conductionband bottom is described by d-M, p-M, p-nitrogen, and c-carbon hybridizedorbitals. The electronic behavior of the former solids strongly differsfrom that of the isolated square-planar tetracyanates, but the HOMO-LUMOelectronic transitions are still dominated by the tetracyanate [M(CN)(4)] and & pi;-& pi;* interactions in the three cases.Band gap energy values are reported for the three studied semiconductors,and the internal metal effect is analyzed. The indirect nature ofthe electronic transitions associated with the gap is discussed, andthe values of the effective and reduced masses are reported.

Nobel-metal based bimetallic nanoparticles (BNPs) are composed of two different metals presenting heteroatom interactions. In these nanomaterials it is possible to tune the relative composition that allows for the modulation of electronic and catalytic properties. They are of great interest for their technological and industrial applications due to their catalytic properties which may exceed those of their monometallic analogue structures. A theoretical perspective on the electronic, stability and reactivity related properties of gold, ruthenium and Au-Ru nanoparticles is presented herein. This analysis considered the use of first-principles methods and the cluster approach to get a physical insight into the novel properties that arise from the combination of two metals in the nano and sub-nano scale. Au-Ru BNPs may present a higher catalytic efficiency than the monometallic structures due to the synergy between the metals in the CO oxidation reaction. However, the effect of Ru over the Au-based NPs on their enhanced catalytic activity is not well understood. A density functional theory (DFT) study of one Au-Ru cluster model was performed to analyze its electronic properties and to gain a better understanding in the stability of structures with various metal compositions. Based on the computed mixing enthalpy, the Au-Ru cluster with a core-shell type morphology and a relative composition close to 1:0.75 was determined as the most stable one. Finally, a CO oxidation reaction pathway different from that determined for Au-NPs was presented for the free particle occurring in the Au-Ru interface. O2 may undergo adsorption on a Ru site through a dissociative process. The computed CO oxidation barrier height is lower than that found for the monometallic Ru clusters but is higher than that determined for Au clusters. This study will guide further research on this kind of model nanostructures in heterogeneous catalysis.

Au/TiO2, Pd/TiO2, Pt/TiO2 and Rh/TiO2 catalysts were synthesized by the deposition–precipitation with urea (DPU) and sol–gel (SG) methods to elucidate the influence of the preparation method on the catalytic activity in the CO oxidation at low temperature. In all cases, the metal loading was 1 wt%. The effect of the synthesis method was remarkable for the Au/TiO2 and Pd/TiO2 materials and less important for the Pt/TiO2 and Rh/TiO2 materials. However, for the four materials, the DPU method revealed the most active materials at 0 °C with respect to the sol–gel method. Au/TiO2 and Rh/TiO2, obtained by the DPU method, were active at temperatures below 0 °C and showed outstanding catalytic activity in comparison with the Pd/TiO2 and Pt/TiO2 catalysts. Density Functional Theory based calculations on M13/TiO2 (M = Au, Pd, Pt or Rh) structures revealed a superior charge transfer from a defective support to Au, while Rh triggered O2 bond scission in the oxygen vacancy site located in the metal-support interface.

The photocatalytic activity of titanium dioxide in visible range is a great target in material science. In order to promote visible solar radiation absorption by this semiconductor, its structure needs to be modified. A theoretical study of TiO2 anatase phase (TiO2-a) has been studied under some modifications: oxygen vacancies (TiO2-OV); oxygen vacancies mediated by atomic hydrogen (TiO2-H); nitrogen doped (TiO2-N); sulfur doped (TiO2-S) and; fluorine doped (TiO2-F). The results of band structures, density of states, band gap, conductivity and optical properties are analyzed for those different conditions.

The oxidation of propane to CO2 was performed by means of Pt-Pd nanoparticles supported on TiO2. The catalyst activities were evaluated through conversion versus temperature, where propane conversion profiles and reac-tion rates followed the order Pt-Pd/TiO2 > Pt/TiO2 > Pd/TiO2. It is proposed that the oxidation of propane on Pt-Pd/TiO2 catalysts occurs not only on Pt0 and Pd0 sites but also on Pt2+, Pd2+ and Ti3+ones, improving the oxidation pathway of propane as shown by Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) and X-ray Photoelectron Spectroscopy (XPS). Propane uptake and Lewis and Bro center dot nsted acidity type on the Pt-Pd/TiO2 catalyst were four times higher than on Pt/TiO2 and Pd/TiO2 as observed by FTIR-pyridine thermo-desorption. Ab-initio calculations showed that Pt enhanced the Bro center dot nsted acidity of the interface favor-ing a dissociative oxygen adsorption, whereas the bimetallic system presented more acidic Lewis sites which correlate with the catalytic activity. Then, hydrogen adsorption could be considered as a chemical reactivity descriptor for the oxidation of propane. Likewise, the higher activity of the Pt-Pd/TiO2 catalyst was explained by considering that the Pt-Pd catalyzed reduction of Ti4+ to Ti3+created oxygen vacancies that enhanced the mobility of lattice oxygen of the TiO2 support and its transfer to the propane species adsorbed on the Pt-Pd bimetallic nanoparticles.

The optical bandgap (E-g) of transition metal nitroprussides remains practically undocumented, probably because these materials are usually considered wide bandgap solids, characterized by a strong metal-ligand charge-transfer band below 500 nm. In this contribution, we are reporting experimental and DFT computed data for both, 3D and 2D phases of Zn and Cd nitroprussides to get physical insight into the metal and structure effect on the optical bandgap (E-g) of these materials. 3D Ag nitroprusside, an analog solid for which the E-g value has been reported, was included for comparison. E-g values were obtained from both, UV-vis-NIR spectra and DFT calculations. The solids under study show a direct bandgap with diverse Urbach tails, which was ascribed to the presence of structural defects. Metal to ligand charge transfer within nitroprusside ion dominates the electronic structure in the valence-gap-conduction region for the 3D systems. Both, the outer metal, and the incorporation of 1-Methyl-2-pyrrolidone as an organic pillar molecule between adjacent layers for the 2D analogs, influence the electronic structure and consequently, the E-g values obtained. In these materials, the polarizing power of outer metal has a relevant role in the observed E-g value.

Transition metal nitroprussides have an n-type semiconductor electronic behavior whose optical response remains scarcely documented. Experimentally, their electronic structure is dominated by Metal to Ligand Charge Transfer (MLCT) type transition that arises from the nitroprusside moiety, [Fe(CN)(5)NO](2-). In addition to that optical transition, these materials can absorb light from d-d and band-band transitions. In this contribution, the electronic structure of monovalent, Hg-2[Fe(CN)(5)NO].2H(2)O, and divalent mercury, Hg[Fe(CN)5NO] is studied using ab-initio calculations and experimental results. Results from UV-Vis, IR, and Raman spectroscopies revealed the nature of the electronic transitions that explain the optical response of mercury nitroprusside systems. For the studied systems, the wide optical bandgap is revisited, and new values are reported. The influence of the valence of the mercury ion on the electronic structure and its changes according to the structural features are analyzed. The employed Meta-GGA functional SCAN and SCAN + rVV10 proved to be accurate methods to describe the structure and electronic properties of the studied mercury nitroprusside-based materials at a reasonable computational cost.

A density functional theory + U systematic theoretical study was performed on the geometry, electronic structure, and energies of properties relevant for the chemical reactivity of TiO2 anatase. The effects of D3(BJ) dispersion correction and the Hubbard U value over the energies corresponding to the TiO2/Ti2O3 reduction reaction, the oxygen vacancy formation, and transition-metal doping were analyzed to attain an accurate and well-balanced description of these properties. It is suggested to fit the Hubbard correction for the metal dopant atom by taking as reference the observed low spin-high spin (HS) energy difference for the metal atom. PBEsol-D3 calculations revealed a distinct electronic ground state for the yttrium-doped TiO2 anatase surface depending upon the type of doping and interstitial or substitutional defects. Based on the calculations, it was found that a HS state explains the observed ferromagnetism in cobalt-substituted TiO2 anatase. The results presented herein might be relevant for further catalytic studies on TiO2 anatase using a large surface model that would be worthwhile for heterogeneous catalysis simulations.