Escalating environmental concerns have dictated the need to develop innovative methods for efficiently desulfurizing marine fuels (heavy fuel oils). In this work, the oxidative desulfurization method using deep eutectic solvents (DESs) was applied to reduce the sulfur content in a commercially available heavy fuel oil (HFO) below 0.5 wt.%, as current regulations demand. Initially, the S-compounds in the fuel were oxidized using an oxidative mixture of H₂O₂ with carboxylic acid (either acetic or formic acid). Subsequently, the oxidized S-compounds were extracted from the fuel using a series of environmentally friendly deep eutectic solvents (DESs), the best of which was proven to be a mixture of choline chloride with ethylene glycol at a 1/2 molar ratio. The process was optimized by investigating the effect of several process parameters on the desulfurization efficiency, namely, the H₂O₂/S molar ratio, the H₂O₂/acid molar ratio, the acid type, the oxidation temperature and oxidation time, the solvent/fuel mass ratio, the extraction time, and the extraction temperature. A desulfurization efficiency of 75.7% was achieved under the optimized conditions, reducing the S content in the fuel to 0.33 wt.%. Furthermore, different methods to recycle the DESs were investigated, and consecutive desulfurization and solvent regeneration cycles were performed. The most efficient recycling method was determined to be the anti-solvent addition of excess water, which resulted in 89.5% DES purification by causing precipitation of the dissolved solids. After three cycles of desulfurization and regeneration using different recycling routes, it was found that the regeneration degree declines gradually; however, it is more than 79.3% in all cases.

The advancement of catalytic materials is critical to improving the performance, reducing the cost and enhancing the sustainability of Proton Exchange Membrane (PEM) fuel cells and electrolyzers. Although Platinum Group Metal (PGM)-based electrocatalysts exhibit high electrochemical activity, their limited availability and the environmentally intensive extraction pose significant challenges. This study aims to demonstrate the direct reuse of recycled impure platinum (Pt) precursors for the synthesis of effective Pt/C electrocatalysts as a viable step toward circular hydrogen economy implementation. A low-cost and eco-friendly chlorine-based hydrometallurgical method was successfully employed to recycle over 99% of Pt from End-of-Life (EoL) Membrane Electrode Assemblies (MEAs), with an industrial perspective. Recycled metal precursor was used without purification to synthesize Pt/C electrocatalyst via a scalable and sustainable method. The catalyst was structurally and chemically characterized, and their electrochemical performance towards the Oxygen Reduction Reaction (ORR) was conducted under conditions simulating real operating environments. The recycled-metal-derived catalyst demonstrated comparable activity toward ORR (170 A/gPt) relative to a commercial catalyst, indicating its potential as viable alternative to conventional PGM-based catalysts. By integrating energy-efficient recycling with advanced material design, this work supports the development of cost-effective and green solutions for clean energy technologies aligned with a circular hydrogen economy model.

A single-step impregnation approach is investigated as a synthetic route for photocatalyst synthesis active under visible light. The as-derived photocatalysts exhibited very high degradation rates towards methylene blue (MB) decolorization under visible light despite the high concentration of the initial MB solution concentration. The TiO₂-based photocatalysts were prepared using nitrate precursor compounds for copper and silver; thus, Ag/TiO₂ and Cu/TiO₂ photocatalysts were prepared. The photocatalyst’s physicochemical properties were determined by XRF, BET, and XRD analysis. The metal nature of the titania substrate, the titania matrix effect, and the metal concentration parameters were studied, while the catalyst concentration in the MB initial solution was optimized.

The European Union’s ambitions for climate neutrality and digital leadership rely on secure access to CRMs, essential for green and digital technologies but supply risks and geopolitical challenges. The CRUSADE project develops a sustainable, integrated recycling approach targeting underutilized waste streams from ELVs, including PCBs, catalytic converters, batteries and automotive fuel cells. CRUSADE proposes a universal hydrometallurgical process treating up to 500 tonnes of waste annually and recovering approximately 40 tonnes of CRMs at commercial purity. At the core of the process is a MWAL technology that enables a 15–80 % reduction in CO₂ emissions compared to conventional leaching methods, depending on feedstock composition. The process integrates AI-based automation for sorting and treatment, advanced downstream recovery and material traceability via digital tools, aligning with Industry 4.0 principles. Currently, the project is progressing toward scaling up these technologies to a modular pilot unit at TRL7, targeting 15 % faster processing time and 15 % lower product cost relative to current practices. CRUSADE aims to close material loops within the automotive and micromobility sectors, contributing to Europe’s circular economy objectives, raw material independence and climate mitigation goals under the European Green Deal.