David Santos-Carballal

University of Leeds · School of Chemistry

The renewed interest in magnetite (Fe₃O₄) as a major phase in different types of catalysts has led us to study the oxidation-reduction behaviour of its most prominent surfaces. We have employed computer modelling techniques based on the density functional theory to calculate the geometries and surface free energies of a number of surfaces at differ...

Reactive iron sulfide compounds that are formed at hydrothermal vents are implicated as catalysts in Origin of Life theories, which suggestion is lent credence by their widespread presence as redox centres in contemporary enzymes – thereby also suggesting their potential as benign modern-day catalysts for CO₂ conversion. These applications highligh...

4'-substituted neutral/protonated furfurylidenanilines and trans-styrylfurans are able to exist in two different conformations related to the rotation around the furan ring-bridge double bond. In this work, the equilibrium geometry and the corresponding rotational barrier of the benzene ring for each furan derivative conformation were calculated by...

Greigite (Fe₃S₄) and its analogue oxide, magnetite (Fe₃O₄), are natural minerals with an inverse spinel structure whose atomic-level properties may be difficult to investigate experimentally. Here, [D. Rickard and G. W. Luther, Chem. Rev. 107, 514 (2007)] we have calculated the elastic constants and other macroscopic mechanical properties by applyi...

Rotational barriers were calculated for 4'-substituted neutral and protonated furfurylidenanilines (FA) by DFT methods and the corresponding equilibrium geometries were identified. Neutral FA have equilibrium dihedral angle values sensitive to the substituent. ¹H and ¹³C Substituent Induced Shifts in FA were calculated from shielding tensors and co...

ABO4-type materials have shown significant potential for applications as luminescence and photocatalytic materials, and the orthorhombic FeNbO4 (o-FeNbO4) material has also shown excellent promise in catalytic electrodes, unlike other common ABO4 materials. However, little computational work has been carried out on the o-FeNbO4 structure, potential...

Cationic doping has played an important role in the improvement and development of more efficient cathode materials for secondary lithium-ion batteries. In lithium manganese oxides, it was recommended as one of the most effective methods of reducing the number of trivalent manganese (Mn 3+) ions that undergo disproportionation reaction. In the ques...

Greigite (Fe3S4), with its ferredoxin-like 4Fe-4S redox centres, is a naturally occurring mineral capable of acting as a catalyst in the conversion of carbon dioxide (CO2) into low molecular-weight organic acids (LMWOAs), which are of paramount significance in several soil and plant processes as well as in the chemical industry. In this paper, we r...

Monitoring volatile organic compounds (VOCs) in harsh environments, especially for safety applications, is a growing field that requires specialized sensor structures. In this work, we demonstrate the sensing properties toward the most common VOCs of columnar Al2O3/ZnO heterolayer-based sensors. We have also developed an approach to tune the sensor...

Surface coating is one of the techniques used to improve the electrochemical performance and enhance the resistance against decomposition of cathode materials in lithium-ion batteries. Despite several experimental studies addressing the surface coating of secondary Li-ion batteries using α-Al2O3, the reactivity of the material toward the electrolyt...

Nanomedicine has grown structurally complex in order to perform multiple tasks at a time. However, their unsatisfied reliability, uniformity and reproducibility account for the high rates of attrition in translational research. So far, most studies have been one-sidedly focused on the treatment efficacy of inorganic nanoparticles as cancer therapeu...

Heterojunctions are used in solar cells and optoelectronics applications owing to their excellent electrical and structural properties. Recently, these energy-efficient systems have also been employed as sensors to distinguish between individual gases within mixtures. Through a simple and versatile functionalization approach using noble metal nanop...

The Fischer-Tropsch (FT) process consists of the reaction of a synthesis gas (syngas) mixture containing carbon monoxide (CO) and hydrogen (H₂), which are polymerised into liquid hydrocarbon chains, often using a cobalt catalyst, although the mechanistic pathway is not yet fully understood. Here, we have employed unrestricted density functional the...

Increasing carbon dioxide (CO2) emissions, resulting in climate change, have driven the motivation to achieve the effective and sustainable conversion of CO2 into useful chemicals and fuels. Taking inspiration from biological processes, synthetic iron-nickel-sulfides have been proposed as suitable catalysts for the hydrogenation of CO2. In order to...

We have employed density functional theory (DFT) calculations to investigate the adsorption of molecular oxygen and hydrogen on 3d transition metal (TM) surfaces with varying ordered magnetic structures in the bulk, namely ferromagnetic Fe(110), Co(0001), Ni(111) and diamagnetic Cu(111). The trend observed in the energies of adsorption was compared...

In this study, we have developed solid-state models of platinum and palladium bimetallic catalysts, Pt3Pd2 and Pt2Pd3, which are rapidly thermally annealed at 800 °C. These models were constructed by determining all the unique atomic configurations in a 2x2x1 supercell, using the program Site-Occupation Disorder (SOD), and optimized with the Genera...

Cobalt nanoparticles play an important role as a catalyst in the Fischer-Tropsch synthesis. During the reaction process, cobalt nanoparticles can become oxidized leading to the formation of two phases: CoO rock-salt and Co3O4 cubic spinel. Experimentally, it is possible to evaluate the phase change and follow the catalyst degradation by measuring t...

LiMn2O4 spinel is a promising cathode material for secondary lithium-ion batteries. Despite showing a high average voltage of lithium intercalation, the material is structurally unstable, undergoing lowering of the crystal symmetry due to Jahn-Teller distortion of the six-fold Mn3+ cations. Although Ni has been proposed as a suitable substitutional...

Platinum has been widely used as the catalyst of choice for the production of hydrogen in the hybrid sulphur (HyS) cycle. In this cycle, water (H2O) and sulphur dioxide (SO2) react to form sulphuric acid and hydrogen. However, the surface reactivity of platinum towards H2O and SO2 is not yet fully understood, especially considering the competitive...

LiMn 2 O 4 spinel is a promising cathode material for secondary lithium-ion batteries. However, although showing a high average voltage of lithium intercalation, the material is structurally unstable, suffering lowering of the crystal symmetry lowering due to Jahn-Teller distortion of the six-fold Mn ³⁺ cations. Although Ni has been proposed as a s...

In the present study, the competitive adsorption geometries for arsenate and phosphate on magnetite surfaces over a pH range of 4-9 was investigated using in situ attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) and two-dimensional correlation analysis (2D-COS). The adsorption energies and infrared vibrational frequen...

In the present study, the competitive adsorption geometries for arsenate and phosphate on magnetite surfaces over a pH range of 4-9 was investigated using in situ attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) and two-dimensional correlation analysis (2D-COS). The adsorption energies and infrared vibrational frequen...

Atomistic molecular dynamics (MD) and steered MD simulations in combination with umbrella sampling methodology were utilized to study the general anesthetic propofol and the opioid analgesic fentanyl and their interaction with lipid bilayers, which is not yet fully understood. These molecules were inserted into two different fully hydrated phosphol...

Given the importance of SO2 as a pollutant species in the environment and its role in the hybrid sulphur (HyS) cycle for hydrogen production, we carried out a density functional theory study of its interaction with the Pt (001), (011), and (111) surfaces. First, we investigated the adsorption of a single SO2 molecule on the three Pt surfaces. On bo...

For a fast and reliable monitoring of hazardous environments, the discrimination and detection of volatile organic compounds (VOCs) in the low ppm range is highly demanded and requires the development...

Acetic acid (CH3–COOH) is an important commodity chemical widely used in a myriad of industrial processes, whose production still largely depends on homogeneous catalysts based on expensive rare metals. Here, we report a computational study on the formation of CH3–COOH from carbon dioxide (CO2) as an alternative chemical feedstock on the {111} surf...

Understanding the surface reactivity of the commercial cathode material LiMn2O4 towards the electrolyte is important to improve the cycling performance of secondary lithium-ion batteries and to prevent manganese dissolution. In this work, we have employed spin-polarized density functional theory calculations with on-site Coulomb interactions and lo...

Platinum is a noble metal that is widely used for the electrocatalytic production of hydrogen, but the surface reactivity of platinum toward water is not yet fully understood, even though the effect of water adsorption on the surface free energy of Pt is important in the interpretation of the morphology and catalytic properties of this metal. In th...

Platinum is a noble metal that is widely used for the electro-catalytic production of hydrogen, but the surface reactivity of platinum towards water is not yet fully understood, even though the effect of water adsorption on the surface free energy of Pt is important in the interpretation of the morphology and catalytic properties of this metal. In...

Nanomaterials – magnetic nanoparticles in particular have been shown to have significant potential in cancer theranostics, where iron oxides are commonly the materials of choice. While biocompatibility presents an advantage, the low magnetisation is a barrier to their widespread use. As a result, highly magnetic cobalt nanoparticles are attracting...

Nanomaterials for highly selective and sensitive sensors towards specific gas molecules of volatile organic compounds (VOCs) are most importantly for developing the new generation detector devices e.g. used as biomarkers for diseases, as well as for continuous air quality monitoring. Here, we present an innovative preparation approach for engineeri...

Platinum nanowires (NWs) have been reported to be catalytically active towards the oxygen reduction reaction (ORR). The edge modification of Pt NWs with metals M (M = Au, Ag or Pd) may have a positive impact on the overall ORR activity by facilitating diffusion of adsorbed oxygen Oads and hydroxyl groups OHads between the {001} and {111} terraces....

Nanomaterials – magnetic nanoparticles in particular have been shown to have significant potential in cancer theranostics, where iron oxides are commonly the materials of choice. While biocompatibility presents an advantage, the low magnetisation is a barrier to their widespread use. As a result, highly magnetic cobalt nanoparticles are attracting...

The development of affordable bifunctional platinum alloys as electrode materials for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) remains one of the biggest challenges for the transition towards renewable energy sources. Yet, there is very little information on the optimal ratio between platinum and the transition metal...

A new strategy based on the functionalization and doping of semiconducting oxides was proposed for tuning their properties. A considerable increase in the gas sensing ability of Fe-doped ZnO (ZnO:Fe) films is achieved via functionalization using oxidized silver nanoparticles (AgO/Ag NPs) with a diameter of ~7 nm. AgO/Ag-decorated ZnO:Fe (Ag/ZnO:Fe)...

Greigite and other iron sulfides are potential cheap, earth-abundant electrocatalysts for the hydrogen evolution reaction (HER), yet little is known about the underlying surface chemistry. Structural and chemical changes to a greigite (Fe3S4) modified electrode were determined at −0.6 V vs. SHE at pH 7, under conditions of the HER. In situ X-ray Ab...

The unbridled emissions of gases derived from the use of fossil fuels have led to an excessive concentration of carbon dioxide (CO2) in the atmosphere with concomitant problems to the environment. It is therefore imperative that new cost-effective catalysts are developed to mitigate the resulting harmful effects through the activation and conversio...

The spinel-structured lithium manganese oxide (LiMn₂O₄) is a material currently used as cathode for secondary lithium-ion batteries, but whose properties are not yet fully understood. Here, we report a computational investigation of the inversion thermodynamics and electronic behaviour of LiMn₂O₄ derived from spin-polarised density functional theor...

The growing environmental, industrial and commercial interests in understanding the processes of carbon dioxide (CO 2 ) capture and conversion have led us to simulate, by means of density functional theory calculations, the application of different iron oxide and sulfide minerals to capture, activate and catalytically dissociate this molecule. We h...

This contribution reports the synthesis, crystal structure, and related properties of six new zeolite-like hexacyanometallates of formula unit T3(H3O)2[M(CN)6]2.uH2O where T=Co2+, Zn2+ and M= RuII, OsII. Their crystal structure was solved and refined from X-ray powder diffraction patterns assisted by IR and UV-vis-NIR spectroscopic data. Both, the C...

We have studied the adsorption of three organic molecules onto different surfaces of goethite α−FeO(OH) using atomistic simulation techniques. New interatomic potentials for the interaction between goethite and the organic molecules were developed. In the majority of cases the organic molecules were found capable of forming a coordinate bond via th...

Greigite (Fe₃S₄), the sulfide counterpart of the spinel-structured oxide material magnetite (Fe₃O₄), is a mineral widely identified in anoxic aquatic environments and certain soils, which can be oxidised, thereby producing extremely acid solutions of sulfur-rich wastewaters, so-called acid mine drainage (AMD) or acid rock drainage (ARD). Here we re...

Thorium dioxide is of significant research interest for its use as a nuclear fuel, particularly as part of mixed oxide fuels. We present the results of a DFT study of uranium-substituted thorium dioxide, where we found that increasing levels of uranium substitution increases the covalent nature of the bonding in the bulk ThO₂ crystal. Three low Mil...

FeM₂X₄ spinels, with the magnetite structure, where M is a transition metal and X is oxygen or sulfur, are candidate materials for spin filters, one of the key devices in spintronics.We present here a computational study of the inversion thermodynamics and the electronic structure of these (thio)spinels for M = Cr, Mn, Co, Ni, using calculations ba...

This thesis presents the results of ab initio based simulation studies of magnetite (Fe₃O₄) and related FeM₂X₄ (thio)spinels with M = Cr, Mn, Fe, Co and Ni and X = O and S. Using density functional theory with long-range dispersion correction and on-site Coulomb interactions (DFT + U – D2), we have investigated a number of properties of these mater...