Paula Sánchez

The growing demand for sustainable and energy-efficient materials has positioned aerogels as promising candidates for advanced insulation applications. Among them, polyurethane (PU) aerogels are attracting increasing interest due to their thermal insulation properties and mechanical versatility. However, their development commonly relies on trial-and-error experimentation, which is time-consuming and resource-intensive. This study presents a Digital Twin (DT) framework to support PU aerogel design and reduce the experimental workload. A pilot-scale DT was developed using data from 21 synthesis experiments, including process configuration, parameter mapping, model development, and process analysis. Two predictive models were evaluated, with the Support Vector Regression (SVR) model showing good agreement with the experimental data (R² = 0.964) and being selected to estimate aerogel density within the parameter range studied. The DT framework enabled the identification of synthesis conditions associated with lower density, which may contribute to improved thermal insulation performance. These results illustrate the potential of DT-assisted modelling to support material development, improve process understanding, and guide more efficient experimentation in PU aerogel synthesis. Overall, this work highlights a data-driven approach for advancing sustainable and scalable aerogel manufacturing.

A systematic study on the competitive oxidation of glucose (Glc), xylose (Xyl), and 5-hydroxy­methyl­fur­fural (HMF) vs the oxygen evolution reaction (OER) was performed by coupling H-cell electrochemical experiments with in situ O₂ monitoring in the anodic chamber using an activated Ni foam as the anode. At a substrate concentration of 10 mM, multipotential steps showed similar OER onset potential values for Glc and Xyl (1.49 V_RHE), while the value for HMF was slightly lower (1.47 V_RHE). Chronoamperometry tests at 1.6 V_RHE (30 min) with varying concentrations showed that both Glc and Xyl oxidation reactions fully suppressed the OER at 30 mM, while 100 mM was required for HMF. A Langmuir–Hinshelwood analysis of the current–substrate concentration dependence revealed the slower kinetics and inhibitory effects impacting HMF oxidation, which account for the significant difference in performance with respect to both aldoses. Given its relevance as both a model and a promising substrate for membraneless electrolysis operation, Glc was further investigated in a long-term chronoamperometry experiment with in situ O₂ monitoring (15 h at 1.6 V_RHE, 30 mM Glc). The results suggested the feasibility of sustaining OER-free operational conditions for approximately 4 h from an initial Glc concentration of 100 mM. HPLC analysis indicated the presence of formate as the main coproduct of hydrogen via glucose electrolysis.

This study aims to systematically evaluate the competition between the oxygen evolution reaction (OER) and glucose oxidation reaction (GOR) in order to find the working conditions of a membrane-less glucose electrolyzer. For this purpose, a H electrochemical cell (H-cell) has been used to isolate the cathodic and anodic compartments. In the latter, in situ O₂ measurements were performed by an optical sensor during different kinds of electrochemical experiments. As the glucose concentration increased, a progressive decrease in the O₂ production rate was observed during the chronoamperometry step at 1.7 V vs RHE. At a glucose concentration of 40 mM, the OER can be entirely replaced by glucose oxidation on the Ni-based anodic catalyst. On the other hand, onset potentials for real O₂ production were obtained at different glucose concentrations in order to maximize the electrocatalytic activity without any O₂ production on the electrolyzer. During the operation of the electrolyzer at the selected conditions, instead of O₂, added value chemicals were obtained in the anodic compartment of the cell. These products were determined by ¹H and ¹³C NMR, and the results showed that formic acid was the main product after 46 h of the electrolysis experiment (1.5 V vs RHE). Other products such as lactic acid and gluconic acid were also identified. The innovative experimental approach used in this study can be extended to other conditions, organic molecules, and catalysts. Furthermore, it serves as a starting point to establish a roadmap to a membrane-less electrolyzer to produce hydrogen and added value products.

Graphene-based catalysts are emerging as promising alternatives to reduce reliance on metal-based catalysts in the hydrogen evolution reaction (HER). This study introduces a novel family of metal-free graphene-based materials codoped with nitrogen and phosphorus (GNP). These materials were synthesized, characterized, and evaluated for HER performance as glucose-tolerant cathodes for biomass electrolysis in a soft alkaline medium, referred to as Mixed Electrolyte (ME): 0.1 M NaOH + 1.0 M Na₂SO₄. It was found that the calcination time directly affects the catalytic properties of the final catalysts, with longer calcination times enhancing HER activity. This was attributed to the effective incorporation of nitrogen (N pyrrolic, N quaternary) and phosphorus (P graphitic) into the graphitic network, along with increased catalyst mesoporosity, which significantly improves mass and electron transfer. Furthermore, chronopotentiometry tests revealed substantial electrochemical activation of HER catalytic performance, stemming from the removal of heteroatoms from the carbon framework. This process, confirmed by XPS and Raman Spectroscopy, led to the formation of topological 5- and 7-membered carbon rings, which serve as the main active sites for the reaction. This significantly accelerates the water dissociation activity, leading to improved catalytic performance with a final overpotential (η₁₀) of −0.386 V in ME. Notably, the exceptional stability and electrochemical activity under various alkaline media, along with its tolerance in the presence of glucose, make this new cathodic catalyst a suitable candidate for a membrane-less biomass electrolyzer.

A systematic study on the electrochemical reforming of monosaccharides (fructose, glucose, and xylose) using Pt-based anodic electrocatalysts is here presented for the first time to completely optimize the anodic catalyst and electrolyzer operating conditions. First, the electro-oxidation of each molecule was studied using a monometallic (Pt) and two bimetallic (PtNi and PtCo) anodic electrocatalysts supported on graphene nanoplatelets (GNPs). Tests in a three-electrode cell showed superior electrochemical activity and durability of PtNi/GNPs, especially at potentials higher than 1.2 V vs RHE, with the highest electrocatalytic activity in d-xylose electro-oxidation. Then, monometallic (Pt and Ni) and bimetallic electrocatalysts with different Pt:Ni mass ratios (1:1 and 2:1) were studied for d-xylose electro-oxidation, with the 2:1 mass ratio presenting the best results. This electrocatalyst was selected as the most suitable for scale-up to an anion-exchange membrane electrolyzer, where the optimal operating potential was determined. Additionally, stable operating conditions of the electrolyzer were achieved by cyclic H₂ production and cathodic regeneration polarization steps. This led to suitable and reproducible H₂ production rates throughout the production cycles for renewable hydrogen production from biomass-derived streams.

A potential method of storing and transporting hydrogen safely in a cost-effective and practical way involves the utilization of molecules that contain hydrogen in their structure such as ammonia. Because of its high hydrogen content and carbon-free molecular structure, as well as the maturity of related technology (easy liquefaction), ammonia has gained attention as a “hydrogen carrier” for the generation of energy. Unfortunately, hydrogen production from ammonia requires an efficient catalyst to achieve high conversion at low reaction temperatures. Recently, very attractive results have been obtained with low-surface-area materials. This review paper is focused on summarizing and comparing recent advances in novel, economic and active catalysts for this reaction, paying particular attention to materials with low surface area such as silicon carbide (SiC) and perovskites (ABO₃ structure). The effects of the supports, the active phase and the addition of promoters in such low-porosity materials have been analyzed in detail. Advances in adequate catalytic systems (including support and active metal) benefit the perspective of ammonia as a hydrogen carrier for the decarbonization of the energy sector and accelerate the “hydrogen economy”.