Rita Carvalho Veloso

New sustainable energy solutions are needed, and oceans—covering more than 70% of Earth's surface—can become a key asset in achieving this objective. Rechargeable seawater batteries (SWBs) use the almost infinite supply of Na ions present in natural seawater as the catholyte. Nevertheless, to obtain high performance, scalable and effective electrocatalysts must be added. The use of readily available carbon‐rich biowaste has become a widely advanced approach in scaling up new energy storage technologies. Furthermore, the tunable and porous characteristics inherent to bio‐waste precursors can enhance capacitive behavior, enabling hybrid performance. In this work, a peanut‐shell bio‐waste activated carbon—originally designed for supercapacitor electrodes, leveraging its high surface area and capacitive potential—is synthesized through an easy, affordable, and eco‐friendly process, and applied as an electrocatalyst in a SWB cathode. Notably, the bio‐waste coating on the immersed electrode exhibited remarkable enhancements over a thermally treated commercial carbon felt electrode. These improvements included a capacitance increase of nearly 166% and reduced voltage gaps (averaging a 59% decrease) in a full‐cell configuration. This enhanced electrochemical performance results from a synergy between capacitive effects and improved oxygen reaction efficiency, supporting sustainable supercapacitor‐like capacitive electrodes in SWB technology.

The global environmental crisis necessitates reliable, sustainable, and safe energy storage solutions. The current systems are nearing their capacity limits due to the reliance on conventional liquid electrolytes, which are fraught with stability and safety concerns, prompting the exploration of solid-state electrolytes, which enable the integration of metal electrodes. Solid-state sodium-ion batteries emerge as an appealing option by leveraging the abundance, low cost, and sustainability of sodium. However, low ionic conductivity and high interfacial resistance currently prevent their widespread adoption. This study explores polyvinyl-based polymers as wetting agents for the NASICON-type NZSP (Na₃Zr₂Si₂PO₁₂) solid electrolyte, resulting in a combined system with enhanced ionic conductivity suitable for Na-ion solid-state full cells. Electrochemical impedance spectroscopy (EIS) performed on symmetric cells employing NZSP paired with different wetting agent compositions demonstrates a significant reduction in interfacial resistance with the use of poly(vinyl acetate)—(PVAc-) based polymers, achieving an impressive ionic conductivity of 1.31 mS cm⁻¹ at room temperature, 63.8% higher than the pristine material, notably reaching 7.36 mS cm⁻¹ at 90 °C. These results offer valuable insights into the potential of PVAc-based polymers for advancing high-performance solid-state sodium-ion batteries by reducing their total internal resistance.

Alkali activated cements (AAC) have been pointed as probably the most promising alternative to traditional Portland cement. There is still significant debate surrounding such claim, as several already identified obstacles have yet to be addressed by most, if not all, the agents involved in the construction industry. However, it appears that some applications of the AAC can be developed and introduced in current practice at a faster rate than, for instance, structural concrete. One of these applications can be the production of materials with thermal valency, based on the capacity of the AAC to expand during the initial reactions. Several techniques capable of producing this expansion have already been tested and developed, contributing to an increasing perception that this is a short-term viable solution for the implementation of AAC. The present paper tested an array of industrial by-products in the production of porous cement pastes, activated with sodium hydroxide and sodium silicate, with the intention of producing façade panels. Two additional by-products were incorporated as thermal damping reinforcements, and the pastes were assessed in terms of flexural and compressive strength, as well as density, after which the most performing were selected for microstructural characterisation (SEM/EDX), environmental behaviour (leaching tests), porosity analyses (MIP testing) and thermal performance (thermal coefficient testing). The results showed that the production of panels for thermal insulation, based on alkali activated industrial by-products, is competitive with traditional materials based on Portland cement and other commercial solutions.

High reflectance materials constitute an attractive idea to reduce cooling loads, which is crucial for attaining the Nearly Zero Energy Buildings goal, also presenting the benefit of broadening the range of colours applicable in building facades. The EnReflect project intended to redesign envelope systems by increasing their solar reflectance through nanotechnology. The main idea was to produce novel nanomaterial-based coatings with high near-infrared (NIR) reflectance by tuning their optical properties and testing their compatibility with typical insulation technologies such as ETICS. As such, this project focused on the synthesis of nanoparticles with improved NIR reflectance, the evaluation of the hygrothermal-mechanical behaviour of thermal insulation systems with the application of the improved coating solutions, the characterization of the more relevant material properties and the durability assessment. One of the main achievements was the development of a facile synthesis of a nanocomposite with improved performance in the NIR region that allowed the reflectance improvement of a darkfinishing coating. Also, the incorporation of such nanoparticles had a positive effect on keeping their optical properties after accelerated ageing cycles. The development of numerical simulations allowed the estimation of the maximum surface temperature in Mediterranean climates under different optical parameters. The study of the hygrothermal behaviour of thermalenhanced façades led to the development of a new durability assessment methodology which contributed to closing a standardization gap.