https://hdl.handle.net/10481/81224 2026-04-11T22:31:11Z 2026-04-11T22:31:11Z Bachs-Herrera, Anna Vidal-Daza, Isaac Boz, Emre B. Forner-Cuenca, Antoni Martin Martinez, Francisco J. https://hdl.handle.net/10481/105207 2025-07-11T10:10:22Z

Understanding the role of nitrogen-doping and surface topology in the binding of Fe(III)/Fe(II) to biobased carbon electrodes Bachs-Herrera, Anna; Vidal-Daza, Isaac; Boz, Emre B.; Forner-Cuenca, Antoni; Martin Martinez, Francisco J. Low-cost and high performance electrodes are critical to advance electrochemical energy storage devices that decouple energy supply from demand. At their core, carbon is ubiquitously employed given its availability, chemical and electrochemical stability, electrical conductivity, and affordable cost. However, due to their relative inertness, carbonaceous electrodes suffer from limited wettability and kinetic activity with aqueous electrolytes. A common approach is to introduce heteroatoms, either through post-processing (thermal/acid activation) or by employing different precursors. Specifically, biobased carbons like hydrochar and biochar are rich in heteroatoms that are naturally incorporated through the production process into the electrode structure. However, achieving a fundamental understanding of the interactions between metal ions and carbon surfaces has proven elusive, leading researchers to rely on empirical approaches for heteroatom doping of carbons. To achieve a better understanding of the fundamental mechanisms, we performed density functional theory calculations of a commonly employed iron redox couple, Fe(III) and Fe(II). We investigated binding mechanisms in graphitic carbon model systems with different surface features, and explored the effect of nitrogen doping and surface topology on the binding energy, as well as the effect of ions' spin multiplicity in the carbon-metal coordination mechanisms. Our results suggest that the interactions of Fe(III) and Fe(II) ions with the nitrogen-doped carbon electrodes not only depend on the surface curvature or the nitrogen content and functionality, but also on the spin multiplicity of the metal ion. Iron ions always evolve into an open-shell electronic structure with a high number of unpaired electrons to increase their coordination sphere with the graphitic surface. We hope that our findings can assist the development of fit-for-purpose heteroatom-doped carbon electrodes with a tailored nanostructure for electrochemical devices utilizing the Fe(III)/Fe(II) redox couple.

York, Daniel Vidal-Daza, Isaac Segura, Cristina Norambuena-Contreras, Jose Martin Martinez, Francisco J. https://hdl.handle.net/10481/105206 2025-07-11T10:04:09Z

Data-driven representative models to accelerate scaled-up atomistic simulations of bitumen and biobased complex fluids York, Daniel; Vidal-Daza, Isaac; Segura, Cristina; Norambuena-Contreras, Jose; Martin Martinez, Francisco J. Complex molecular organic fluids such as bitumen, lubricants, crude oil, or biobased oils from biorefineries are intrinsically challenging to model with molecular precision, given the large variety and complexity of organic molecules in their composition. Large scale atomistic simulations have been historically limited by this complexity, which has hampered the bottom-up molecular design of these materials, something especially relevant given the current surge of biobased fluids for sustainable applications and the cost of trial-and-error experimental developments. To address this limitation, we have developed an author-agnostic computational framework to generate data-driven representative models of any complex mixture of organic molecules directly from Gas Chromatography-Mass Spectrometry (GCMS) experimental characterisation, thus reducing human biases in model creation and providing a platform for self-driven digital development of molecular organic fluids. The method proposed generates statistically representative molecular samples that simplify the complexity of the fluid in a limited group of molecules, while capturing the critical chemical features needed to describe the overall properties of the mixture. As a case study, we generated a showcase of data-driven representative models from the GCMS characterisation of a bio-oil from the pyrolysis of pine bark, specially produced for this study. Pyrolytic biomass processing into bio-oils provides a waste valorisation route with applications in biorefinery products like asphalt additives and biofuel precursors. Our case study focuses on complex fluids such as bio-oils for asphalt rejuvenators for self-healing purposes or biofuel upgrading. Nevertheless, the general computational framework developed in this manuscript provides a platform for generating data-driven representative models of any bitumen or biobased organic fluid.

Vidal-Daza, Isaac Sánchez Navas, Antonio Hernández Laguna, Alfonso https://hdl.handle.net/10481/81609 2023-06-05T22:13:52Z

Compressional behavior of the aragonite-structure carbonates to 6 GPa Vidal-Daza, Isaac; Sánchez Navas, Antonio; Hernández Laguna, Alfonso The behaviors of aragonite (CaCO3 ), strontianite (SrCO3 ), cerussite (PbCO3 ), and witherite (BaCO3 ) at increasing pressure have been studied up to 6 GPa using density functional theory with plane waves. A parallelism of the orthorhombic carbonates with the closed-packed AsNi structure is considered in our analysis, being the CO2−3 groups not centered in the interstice of the octahedron. The decomposition of the unit-cell volume into atomic contributions using the Quantum Theory of Atoms in Molecules has allowed the analysis of the bulk modulus in atomic contributions. The bulk, axes, interatomic distances, and atomic compressibilities are calculated. The largest compression is on the c crystallographic axis, and the c linear modulus has a linear function with the mineral bulk modulus (K0 ). Many of the interatomic distances moduli of the alkaline earth (AE) carbonates show linear functions with the bulk modulus; however, the whole series (including cerussite) only gives linear functions when K0 is related either with the CC distances modulus or the modulus of the distances of the C to the faces of the octahedron perpendicular to c. These last distances are the projections of the Metal–Oxygen (MO) distances to the center of the octahedron. K0AE carbonates also show linear functions with the atomic moduli of their cations. However, the whole series show a linear relation with the atomic modulus of C atoms. Therefore, the whole series highlight the importance of the C atoms and their interactions in the mechanism of compression of the orthorhombic carbonate series. Supplementary Information The online version contains supplemen- tary material available at https://doi.org/10.1007/s00269-023-01237-6.