Hazardous reactive dyes can cause serious environmental problems, as they are difficult to remove from water using conventional adsorbents due to their large molecular sizes and bulky structures. Sustainable mesoporous carbons derived from alginic acid demonstrated promising adsorbent capacity for several representative industrial bulky reactive dye molecules that account for almost 30% of the global textile dye market: Procion Yellow H-XEL (PY), Remazol Black (RB), Procion Crimson H-XEL (PC) and Procion Navy H-XEL (PN). These new adsorbents showed high mesoporosity (>90%) and large pore diameters (>20 nm) facilitating more straightforward and efficient adsorption and desorption processes when compared with predominately microporous activated carbon (AC), Norit, of similar surface chemistry, or with Silica gel (Sgel) that shows good mesoporosity but is hydrophilic. Their adsorption capacity was also significantly higher than that of both AC and Sgel, verifying suitability for bulky dye elimination from wastewater. Adsorption kinetic studies showed a best fit with the Elovich model, indicating a heterogeneous surface adsorption process. The adsorption isotherm data was best represented via the Toth model for almost all adsorbent/dye systems (R² ≥ 0.98), validating the results of the Elovich model whereby the adsorbent is structurally heterogenous with multilayer dye coverage. From thermodynamic analysis, the derived parameters of ΔG (-11.6 ∼ -6.2 kJ/mol), ΔH and ΔS demonstrate a spontaneous, enthalpy controlled adsorption process that was exothermic for RB (-10.0 kJ/mol) and PC (-23.9 kJ/mol) and endothermic for PY (3.9 kJ/mol) and PN (13.2 kJ/mol). Overall these alginic acid based mesoporous carbons are cost-effective, sustainable and efficient alternatives to current predominantly microporous adsorbent systems.

Given the pressing climate and sustainability challenges, shifting industrial processes towards environmentally friendly practices is imperative. Among various strategies, the generation of green, flexible materials combined with efficient reutilization of biomass stands out. This review provides a comprehensive analysis of the hydrothermal carbonization (HTC) process as a sustainable approach for developing carbonaceous materials from biomass. Key parameters influencing hydrochar preparation are examined, along with the mechanisms governing hydrochar formation and pore development. Then, this review explores the application of hydrochars in supercapacitors, offering a novel comparative analysis of the electrochemical performance of various biomass-based electrodes, considering parameters such as capacitance, stability, and textural properties. Biomass-based hydrochars emerge as a promising alternative to traditional carbonaceous materials, with potential for further enhancement through the incorporation of extrinsic nanoparticles like graphene, carbon nanotubes, nanodiamonds and metal oxides. Of particular interest is the relatively unexplored use of transition metal dichalcogenides (TMDCs), with preliminary findings demonstrating highly competitive capacitances of up to 360 F/g when combined with hydrochars. This exceptional electrochemical performance, coupled with unique material properties, positions these biomass-based hydrochars interesting candidates to advance the energy industry towards a greener and more sustainable future.

Eco-friendly supercapacitor electrodes were synthesised using HTC and pyrolysis, yielding capacitance values > 275 F g⁻¹ and power densities ≈ 3000 W kg⁻¹ that were linked to near ideal pore size matching to the electrolyte sulphate ion diameter.

As technological advances raise living standards around the globe, the worlds population continues to grow, driving energy demand to levels that conventional power sources can no longer satisfy. These sources are not only limited, but also environmentally harmful, making renewable power the only sustainable solution to cover this demand. However, to fully harness the potential of renewable energy, it is crucial to develop reliable, high-performing energy storage technologies that effectively address the intermittent nature of these energy sources. Furthermore, increased industrial production has intensified environmental pollution. In particular, synthetic dyes, when released into water courses, are responsible for the persistent contamination of millions of litres of water. Unfortunately, conventional water treatment methods are unable to effectively remove these pollutants completely, resulting in severe environmental damage that presents a serious threat to wildlife, ecosystems and human health. This doctoral thesis aims to effectively tackle these global challenges through the development of sustainable, multifunctional biopolymeric materials. Specifically, biomass-derived activated carbons (ACs) were synthesised via hydrothermal carbonisation (HTC), an environmentally friendly, energy-efficient alternative to conventional carbonisation. These materials were further modified through the addition of layered transition metal dichalcogenides (TMDCs), specifically, 2D-WS2 nanosheets, to add functionality and improve conductivity. For energy storage applications, these sustainable ACs (and their WS2-doped counterparts) were assessed as electrodes for electrochemical capacitors, measuring their capacitance, power density and energy density. Remarkably, these materials yielded capacitance values exceeding 270 F/g and power densities close to 5000 W/kg, performance levels that, to date, few biomass-based materials have achieved. Moreover, their applicability as electrocatalysts for the Oxygen Reduction Reaction (ORR), a crucial reaction in fuel cell energy storage was explored. Parameters such as the number of transferred electrons and the concentration of byproducts (specifically, the harmful HO2- ion) were evaluated. Overall, the synthesised ACs displayed competitive results compared to commercial platinum-based catalysts, highlighting the electrocatalytic potential of these materials. Simultaneously, a polymeric scaffold was developed by electrospinning a poly-L-lactic acid (PLLA) solution, which was further reinforced with WS2 nanosheets to enhance mechanical properties. Subsequently, AC was integrated into the polymeric matrix, yielding a hybrid material with excellent surface area, mechanical properties and adsorption capacity. This hybrid adsorbent was further tested for wastewater remediation, specifically for the adsorption of four dyes: two cationic (Methylene Blue, MB, and Rhodamine B, RB) and two anionic dyes (Methyl Orange, MO, and Congo Red, CR). The adsorption mechanism was studied through kinetic modelling and adsorption isotherms. Notably, the hybrid PLLA-WS2-AC adsorbent exhibited excellent adsorption performance with near-complete removal of the dyes, some of which were fully adsorbed in less than 15 minutes. Overall, the sustainably derived materials developed in this thesis exhibit impressive potential to tackle the energy and environmental challenges that will shape our future. Their exceptional performance underscores the importance of innovative, green solutions that pave the way for future advancements in sustainable development and green technology. RESUMEN A medida que los avances tecnológicos mejoran la calidad de vida, la población mundial continúa creciendo, conllevando unos niveles de demanda energética que las fuentes convencionales ya no pueden satisfacer. Estas fuente no solo son limitadas, sino que resultan perjudiciales para el medio ambiente, lo que convierte a la energía renovable en la única solución sostenible para cubrir esta demanda. Sin embargo, para aprovechar plenamente el potencial de la energía renovable, es fundamental desarrollar tecnologías de almacenamiento energético eficientes y seguras que permitan abordar los problemas derivados de la naturaleza intermitente de estas fuentes. Al mismo tiempo, el incremento en la producción industrial ha intensificado la contaminación ambiental. En particular, las tintas sintéticas, al ser vertidas en las masas de agua, contribuyen a la contaminación persistente de toneladas de agua. Por desgracia, los métodos convencionales de tratamiento de aguas no son capaces de eliminar eficazmente la totalidad de estos contaminantes, lo que conlleva graves daños medioambientales que presentan una seria amenaza a la fauna, los ecosistemas y la salud humana. Esta tesis tiene como objetivo abordar de forma efectiva estos desafíos globales mediante el desarrollo de materiales biopoliméricos multifuncionales y sostenibles. Concretamente, se sintetizaron carbones activados (ACs) derivados de biomasa mediante carbonización hidrotermal, una alternativa sostenible más eficiente energéticamente que la carbonización convencional. Estos materiales se modificaron posteriormente con la adición de dicalcogenuros de metales de transición (TMDCs), específicamente nanoláminas de 2D-WS, para añadir funcionalidad y mejorar su conductividad. Para las aplicaciones de almacenamiento de energía, estos ACs sostenibles (y sus versiones dopadas con WS2) se utilizaron como electrodos en condensadores electroquímicos, evaluando su capacitancia, densidad de potencia y densidad energética. Estos materiales alcanzaron valores de capacitancia superiores a 270 F/g y densidades de potencia cercanas a 5000 W/kg, niveles de rendimiento que, hasta la fecha, pocos materiales basados en biomasa han...