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Abstract: Carbon dioxide (CO2) hydrogenation represents a central route for sustainable fuel production and carbon recycling, yet its efficiency is critically dependent on the structural and electronic properties of the catalyst. In practical heterogeneous systems prepared by conventional wet-chemical methods, a distribution of active sites, ranging from atomically dispersed species to subnanometric clusters and nanoparticles, typically coexist in the final catalyst. Here, we investigate how support defect engineering governs this distribution in Ru/TiO2 catalysts with varying metal loadings and oxidative pre-treatments. Comprehensive spectroscopic and imaging analyses, including XPS, HR-STEM, and XAS established a clear correlation between Ru structure and catalytic behavior. Critically low Ru loadings (0.2 wt%) induced a transition from metallic nanoparticles to highly dispersed and single atom species, while oxidative pretreatment generated RuO2 like domains. A fraction of isolated Ru atoms persisted, particularly on defect-rich TiO2, where oxygen vacancies act as anchoring sites, improving stability under redox conditions. Catalytic testing revealed that Ru dispersion and oxidation state jointly determine activity and selectivity: extended metallic Ru or oxidized Ru nanoparticles favor complete hydrogenation to CH4, whereas isolated Ru species promote CO formation via the reverse water–gas shift pathway. The coexistence of these Ru configurations is associated with enhanced low temperature activity, while defect engineered supports improve stability against deactivation. Defect engineering of TiO2 provides an effective strategy to stabilize atomically dispersed Ru and to balance nanoparticles and atomic species, offering a versatile strategy to tune CO2 hydrogenation performance and advance the design of Ru based catalysts for sustainable hydrogenation processes.

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Abstract: The development of efficient recycling processes for lithium-ion battery electrode materials is essential for sustainable battery technologies. TiNb2O7 (TNO) is an attractive high-power anode material, but recycling strategies remain largely unexplored. Here, we report a direct recycling approach for TNO anodes recovered from a cycled TNO/LiNi0.6Mn0.2Co0.2O2 cell. We find that residual lithium in recovered TNO promotes the formation of a lithiated rutile impurity phase and Ti2Nb10O29 during thermal processing, which degrades the electrochemical performance of the recovered TNO. Structural and compositional analyses reveal the origin of these phases and guide the development of a recycling route that combines hydrothermal lithium removal with a subsequent heat treatment, preventing impurity formation. Recycled TNO produced by this method delivers high capacity, excellent rate capability, and stable performance at high current densities, achieving 279 (5) and 261 (10) mA h g−1 at 2 and 4 A g−1, respectively, comparable to commercial TNO. These results demonstrate a viable direct recycling strategy for TNO anodes.

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Abstract: The thermal catalytic hydrogenolysis of polyolefins offers a pathway to convert plastic waste to value-added hydrocarbons. However, the reliance on noble metals such as Ru or Pt remains a significant barrier to large-scale implementation. In this work, we demonstrate that the Zr-containing mixed metal oxides (MMOs), Co0.7Al0.3–xZrx (CAZ), Ni0.7Al0.3–xZrx (NAZ), and Ni0.7Co0.3–xZrx (NCZ), with x = 0, 0.1, 0.2, and 0.3, are highly effective at 250 °C under 20 bar of H2 for virgin isotactic polypropylene (PP) (Mw = 240 kDa) hydrogenolysis to give liquid hydrocarbon products. The catalysts were produced by calcination of the Zr-containing layered double hydroxide (LDH) precursors; [Co0.7Al0.3–xZrx(OH)2][CO3](0.3–x)/2, [Ni0.7Al0.3–xZrx(OH)2][CO3](0.3–x)/2, [Ni0.7Co0.3–xZrx(OH)2][CO3](0.3–x)/2; x = 0, 0.1, 0.2, and 0.3. This approach allowed us to exploit the compositional tunability of the LDH framework to control the homogeneous distribution of the active metal centers. We find that Zr incorporation in these MMOs can significantly enhance catalytic PP hydrogenolysis. Our best-performing catalysts, Co2.1Al0.3Zr0.6Oy, delivers, after 1 h at 275 °C and 20 bar of H2, liquid hydrocarbon yields above 75% at a total PP conversion of over 90%, while keeping methane yields below 3%. Mechanistic studies show that these catalysts favor backbone C–C cleavage, delivering C3, C6, and C9 hydrocarbon selectivity. These scalable, highly efficient, and cost-effective catalysts are also efficient for the hydrogenolysis of a mix of commercial PP products. Hydrogenolysis of mixed pipette tips using Co2.1Al0.3Zr0.6Oy (275 °C, 1.5 h, 20 bar H2) produced a liquid hydrocarbon yield of 74%.

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Abstract: Barocaloric (BC) effects at liquid–vapor transitions in hydrofluorocarbons drive most commercial technologies used for heating and cooling in the heating, ventilation and air-conditioning sector. However, these fluids suffer from huge global warming potential and alternative gases are less efficient, toxic or flammable. Solid–solid and solid–liquid BC materials have zero global warming potential and could even improve on current device efficiencies. Whilst solid–liquid BCs typically outperform solid–solid BCs, the latter are advantageous as they avoid leaks and present easier handling and recyclability thus facilitating waste management. Here we confine the solid–liquid BC stearic acid inside the nanopores of a functionalized metal-organic framework (MOF) and demonstrate that the colossal BC properties are retained in a solid-state material. Moreover, the enhanced interactions between the pore surface and the BC material allow a level of active control over the thermal response, as opposed to passive encapsulation. Our results open novel avenues to exploit and tune colossal BC effects in a wide range of combinations of solid–liquid BC materials embedded within functionalized MOFs, without the associated engineering drawbacks.

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Abstract: Air pollution is one of the leading global health risks according to the World Health Organization (WHO). Addressing this problem requires a variety of technological solutions such three-way catalysis (TWC), which reduces the tailpipe emissions of gasoline engines. TWC accomplishes this by catalyzing reactions between CO, NO, unburnt hydrocarbons and remaining O2, converting them into less harmful gaseous products. Despite being a long-established technology, continuous innovation is still required to meet the increasingly stringent legislative standards that aim to limit emissions from cars. Since modern three-way catalysts already operate efficiently at elevated temperatures, research efforts have shifted towards improving the low-temperature activity of such catalysts and decreasing emissions slip during the cold-start phase of the engine. Achieving this goal requires a molecular understanding of the underlying catalytic processes, which provides a basis for the rational design and optimization of improved catalyst systems. A typical three-way catalyst consists of a ceramic monolithic substrate onto which a wash coat containing catalytically active material is applied. These typically contain Pd, Pt and Rh as active metals, a ceria-zirconia based oxygen storage component, and a range of catalytic and structural promoters, all supported on alumina which provides stability and a high internal surface area. During operation, the active metals catalyze various reactions in parallel, most notably CO oxidation, NO reduction and hydrocarbon oxidation. The ceria-based component plays a crucial role by storing and releasing oxygen, thereby providing oxygen buffering under fluctuating exhaust gas compositions. Ceria in contact with active metal sites can directly participate in catalytic reactions by supplying oxygen at the metal-ceria interface, which helps mitigate CO poisoning of the metal. Furthermore, ceria can enhance catalyst durability by stabilizing highly dispersed metal species and preventing their agglomeration. The synergy of these functions makes ceria a highly effective promoter in three-way catalysis. Ceria-based catalysts in which the metal is highly or even atomically dispersed have attracted considerable attention due to their unique catalytic properties and high metal utilization. In these catalysts, precise control over both the metal and ceria speciation was found to be key for optimizing catalytic performance. Although substantial progress has been made in identifying catalytically active species and establishing structure-performance relationships, most studies rely on CO oxidation as a model reaction. This work extended this approach by investigating the behavior of ceria-based model three-way catalysts under more realistic operating conditions. These conditions include complex exhaust gas mixtures, fluctuating gas compositions and high temperatures. Particular emphasis is placed on the dynamic nature of metal speciation, which was studied by operando spectroscopy and transient kinetics. Our results reveal that significantly more complex behaviors emerge under realistic conditions than in simplified model reactions. This highlights the critical importance of understanding and controlling dynamic catalyst behavior, as well as identifying the mechanisms of inhibition and deactivation, for the design of effective three-way catalysts. In Chapter 2, Pd-CeO2 and Pt-CeO2 model three-way catalysts containing highly dispersed metal species were investigated under realistic operating conditions. The study included perturbed experiments with oscillating exhaust gas compositions, as well as cold-start tests that mimic the initial phase of rapid catalyst heating. Using quasi-in situ XPS, reducibility was identified as a key parameter determining activity, as it dictates the temperature at which highly active reduced species are formed under reaction conditions.