Pascal Buskens

This study evaluates CuFeO2 and CuFe2O4 as promising catalysts for photothermal CO2 conversion and their ability to form plasmonic Cu nanoparticles in situ. A straightforward, reproducible, aqueous citrate-based solution-gel method with high stoichiometric control was developed to synthesize both catalysts from the same starting materials. XRD, Raman, and ICP-OES confirmed nearly phase-pure materials with appropriate bandgaps (1.13 eV for CuFeO2 and 1.55 eV for CuFe2O4), determined by UV–vis spectroscopy. SEM and BET analyses showed a dense morphology for CuFeO2 and a slightly more porous CuFe2O4 architecture. The catalysts were tested in a photoreactor, where they selectively form CO via the reverse water–gas shift reaction. The combination of light and heat causes exsolution of copper onto the surface. These nanoparticles exhibit the localized surface plasmon resonance effect (LSPR), which facilitates CO2 conversion. The CuFeO2 catalyst produces 62 mmol of CO gcatalyst–1 h–1, and CuFe2O4 produces 65 mmol of CO gcatalyst–1 h–1, both using a combination of reactor heating and catalyst illumination. The key advancements are the development of a universal aqueous solution-gel route to structurally distinct copper iron oxides and the identification of an in situ Cu exsolution mechanism that converts these materials from pre-catalysts into active photothermal catalysts.

Vanadium is a transition metal widely used in steel production, batteries, and catalysis. It is a critical material and its disposal poses significant environmental challenges, making recovery and reuse a necessity. This study presents an innovative approach for the recovery and reuse of vanadium from spent catalysts, transforming it into high-purity V2O5 as the precursor for advanced VO2-based thermochromic coatings for smart windows. A multistep process comprising reductive acid leaching, oxidation, and selective precipitation was employed to develop two recovery pathways, resulting either in high-purity vanadium pentoxide (total metallic impurities of 2.14 ppm; extraction yield = 26%) or in a high extraction yield of 72% (total metallic impurities = 1.78%). The material was subsequently converted to monoclinic VO2 and applied for the production of a thermochromic solar control coating for smart windows. Optical measurements revealed a visible transmittance of 55% and a solar modulation of 4.4%, consistent with values for state-of-the-art VO2 coatings prepared by chemical reduction of virgin V2O5. This process demonstrates the technical feasibility of recovering vanadium from spent catalysts and reuse it in functional materials for smart windows, contributing to resource efficiency and environmental sustainability.

Copper niobate metal oxides have gained significant attention in the field of CO2 reduction because of their great potential to address current energy and environmental challenges. Conventional solid-state synthesis methods generally suffer from poor cation homogeneity, whereas sol–gel processes facilitate molecular-scale mixing of precursors and enhanced compositional uniformity. However, many conventional sol–gel routes employ harmful or nonsustainable complexing agents, limiting their sustainability and scalability. Here, we report a facile citrate-complex aqueous solution–gel route for the controlled synthesis of CuNb2O6 and Cu3Nb2O8 phases. Citric acid functions as a chelating and polymerizing agent, facilitating the homogeneous complexation of Cu and Nb cations in aqueous solution while simultaneously promoting molecular-level mixing prior to gelation. The used precursor solution chemistry enables thermal decomposition and crystallization, leading to the reproducible formation of well-defined copper–niobate phases. The phase formation and purity of the target phases were confirmed using in situ high-temperature X-ray diffraction (HT-XRD), Raman spectroscopy, scanning electron microscopy (SEM), and UV–vis spectroscopy. The synthesized materials were further evaluated as precatalysts for photothermal CO2 hydrogenation, where CO was identified as the sole reaction product.

Building-integrated photovoltaics (BIPV) have achieved a high level of technical maturity. In spite of that, the installed capacity remains limited. To stimulate the integration of solar panels in the built environment, aesthetical features like color and freedom in size and shape are of key importance for architects and building owners. Multilayer interference coatings are an attractive coloring technique for solar panels, as they are known for their high solar transmission and tuneable reflection peak. The latter gives rise to an intense metallic reflection color. In this study, the outdoor performance of colored versus non-colored BIPV panels was investigated, and a method has been developed to measure the color variation of the solar panels with respect to outdoor conditions, viewing angles and tilt angles of the setup. A limited performance loss of 15% was measured for colored solar panels compared to their black counterparts, caused by a reduction in generated photocurrent due to light loss. Outdoor color measurements showed that the cloudiness of the sky and the tilt angle of the setup are key parameters causing a color variation from yellow-green to blue-green. In addition, the developed method and tailored measurement setup have proven their value in quantifying color appearance of colored BIPV in realistic and varying outdoor conditions.

The size dependency of octahedron-shaped magnetite particles on their magnetic properties near the multi-domain limit for inductive heating applications is studied, demonstrating thermoplastic adhesive composite melting for (de)bonding applications.

The transition to a sustainable energy system is crucial to meet climate targets and reduce fossil fuel dependence. Solar hydrogen systems offer a promising route for renewable hydrogen production. This study presents a techno-economic assessment of hydrogen production using integrated solar hydrogen panels combined with balance-of-plant equipment such as compressors. The analysis combines detailed Aspen Plus process design with an hourly solar model to capture the impact of system scale and hydrogen storage under intermittent operation. Results show that large-scale integrated systems can achieve costs comparable to photovoltaic–electrolyzer setups, suggesting a feasible and streamlined alternative. System scale is the dominant factor influencing the levelized cost of hydrogen (LCOH). At a small scale (1000 panels), the LCOH is about 49 €/kg. Including hydrogen storage reduces costs by up to 40% through better utilization of capital-intensive components. At larger scales, costs decrease substantially: 100,000 panels yield an LCOH of 9.1 €/kg, and 10 million panels reach 7.3 €/kg. In these large systems, storage slightly increases costs because added capital expenditures outweigh operational gains. If solar-to-hydrogen efficiency improves to 23% and panel costs drop to 120 €/m², hydrogen could be produced at around 3.8 €/kg. These findings emphasize the importance of scale, efficiency gains, and cost reduction to enable affordable renewable hydrogen directly from sunlight and water.

This study reports the conversion of CO ₂ and H ₂ to CO and H ₂ O at low temperature and low pressure (up to 203 °C, p = 3.5 bar) using plasmonic Au/CeO _{2− x} photocatalysts, with mildly concentrated sunlight as the sole energy source (up to 9 kW m ⁻² ).

A modular, automated photoreactor system for CO ₂ hydrogenation enables precise conversion into methane or carbon monoxide. The carbon monoxide is subsequently utilized in carbonylation reactions, advancing sustainable synthesis and CO ₂ utilization.