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Abstract: The global transition from a coal-based energy economy to a green hydrogen economy, together with the demand for energy utilization efficiency, has intensified interest in ammonia as a carbon-free hydrogen energy carrier which is capable of storing and transporting renewable energy at scale. Efficient regeneration of hydrogen through thermal ammonia decomposition, enabled by advanced downstream technologies such as membrane reactors and purification systems, offers a techno-economically mature and evolving pathway. However, achieving low-temperature, energy-efficient ammonia decomposition remains a fundamental challenge. At the heart of this challenge lies the rational design of heterogeneous thermocatalysts capable of overcoming intrinsic kinetic limitations. Through critical examination of the vast research on catalyst systems and activity studies, we identify that tailored metal-support systems often give rise to multiple reaction pathways that govern the overall kinetics. To scientifically elucidate the origins of enhanced catalytic performance, the precise understandings on the nature of active sites and their coordination environments is the core. This requires precise identification of catalytically relevant sites, rigorous correlation between structure and reactivity, and operando-level insights into dynamic phase evolution. In this review, we reframe ammonia decomposition catalysis through the lens of active-phase chemistry. Based on our current understanding of active centres across different catalyst categories, we highlight strategies for rational catalyst design grounded in active phases and coordination environment. We further discuss advanced characterization methodologies capable of tracking active sites and unravelling their specific mechanistic contributions.

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Abstract: Amid rising global demand for renewable energy and effective plastic waste management, adopting green methods to utilize plastic waste for chemicals is a win–win strategy. Constituting the largest amount of single-use plastic litter worldwide, cellulose diacetate (CDA) based waste cigarette filters urgently require sustainable valorization pathways. However, CDA photoconversion remains highly challenging due to substantial energy barriers for selective bond cleavage, inadequate radical generation capability, and inefficient charge-carrier separation. Herein we propose a strategy to efficiently obtain C2H4 through carbene-mediated CDA photoconversion by using a sulfur vacancy-regulated copper-gallium-zinc-sulfide (VS-CGZS) catalyst. VS-CGZS enhances the thermal effect of light and lowers the energy barrier for acetyl group (*CH3CO) desorption from CDA. VS reduces the adsorption energy of *CH3CO on VS-CGZS and facilitated :CH2 formation. Consumption of photogenerated holes via *CH3CO desorption and VS-enhanced carrier separation synergistically elevate the photogenerated electrons concentration for :CH2 coupling, thereby selectively triggering and boosting C2H4 yield. Therefore, we achieve a record-breaking 14.43 mmol·gcat–1 C2H4 for CDA photoconversion within 4 h, over 6 times exceeding previous reports on photoconverting plastic into C2H4. This work establishes a strategy for efficient ethylene production from photoconversion of cellulose diacetate and carves out a paradigm in solar-driven plastic valorization.

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Abstract: Microfluidics has emerged as a versatile platform for studying biomolecular processes and forming nanoparticles, due to its ability to manipulate fluids with precision at the microscale. This thesis reports the development of two microfluidic platforms: a stopped-flow system for time-resolved small-angle X-ray scattering (TR-SAXS) experiments at synchrotron beamlines, and a fast micromixer for lipid liquid crystalline nanoparticle (LLCN) formation. The stopped-flow device integrates layered microfluidic chips, custom syringe drivers, and automated heating. A control system was developed and fully integrated with the EPICS/GDA environment at the I22 beamline of Diamond Light Source to make the device accessible to beamline users. Computational fluid dynamics (CFD) simulations guided optimisation of the vortex T-mixer geometry and operating conditions before fabrication. The device reduces sample requirements to 15 µl per experiment and achieves rapid and efficient mixing with a mixing index >0.95 and a dead time of 11 ms, validated using the reduction of 2,6-dichlorophenolindophenol (DCIP) reaction. Its performance was evaluated at synchrotron facilities, first by assessing mixing efficiency with an X-ray absorptive solution and then in time-resolved analyses to (i) track structural changes in nanoparticles undergoing cubic-to-hexagonal phase transitions and (ii) monitor the disruption of AdhE spirosomes by the anti-virulence compound ME0054, demonstrating its ability to capture structural dynamics across multiple timescales. The fast mixer was developed for scalable and reproducible LLCN production, optimised through CFD simulations and fabricated using CNC machining. Its performance was tested against a commercial herringbone mixer, showing reliable formation of nanoparticles with controlled size and low polydispersity. Optimal flow conditions yielded cubosomes of ~170 nm with PDI values below 0.15, while SAXS confirmed preservation of the internal structure across operating ranges. The device matched, and in some cases outperformed, the herringbone mixer, demonstrating robustness and suitability for reproducible LLCN production. Together, these developments provide open-source, beamline-compatible microfluidic tools that reduce sample consumption, improve reproducibility, and extend the scope of TR-SAXS experiments and nanoparticle production, contributing practical and accessible platforms for advancing research in soft matter and biomolecular science.

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Abstract: Polychlorinated aromatic hydrocarbons (PCAHs) in flue gas seriously threaten the environment and human health, and Ru-based catalysts exhibit efficient oxidation property for PCAHs removal. However, the current Ru catalysts either have high Ru loading/non-stable structure or are developed empirically whilst lack of design mechanism. Herein, a robust Ru single atom catalyst (0.5 Ru1/TiO2) was designed based on metal-support interaction for o-DCB (o-dichlorobenzene, a typical PCAHs) degradation, and it revealed significantly better oxidation activity with T50 = 207.4 °C and T90 = 243.5 °C than its contrast with weak metal-support interaction (0.5 RuNP/TiO2, T50 = 247.4 °C, T90 > 300 °C). In addition, 0.5 Ru1/TiO2 exhibited much better chlorine resistance stability, maintaining >90% o-DCB conversion for 700 min versus∼70% on 0.5 RuNP/TiO2. The superior performance of 0.5 Ru1/TiO2 was attributed to its stronger metal-support interaction between Ru and TiO2, verified by H2-TPR, which offered higher active oxygen species (22.4%), more Lewis acid (0.675 mmol/g) and higher exposed Ru ratio (> 90.0%) than 0.5 RuNP/TiO2 (15.0%, 0.068 mmol/g, 28.6%, respectively). The above properties can not only enhance o-DCB adsorption/activation and weaken its Csingle bondCl bonds but also favor partial/deep oxidation and remove deposited chlorine on 0.5 Ru1/TiO2, proved by in situ FT-IR. Moreover, notable higher water resistance under different water vapor and applicability under varied pollutant concentration were observed on the robust Ru1/TiO2. This work reveals insightful function-property study on Ru single atom catalysts for PCAHs oxidative removal.

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Abstract: Crystallization is a key step in drug purification, offering low cost and facile scalability. The thesis investigates the role of heterogeneous nucleation templates in enhancing crystallization efficiency and controllability with a focus on biopharmaceutical applications, and examines the mechanisms of template-mediated nucleation, crystal growth, and morphology control using carbon-based templates, polymeric hydrogel templates, and microbial bio-templates. The interaction between inorganic salt and proteins was investigated and proteins themselves were also applied as the macromolecular templates. Carbon-based materials, including graphite and graphene oxide (GO), were investigated for their influence on lysozyme crystallization. Graphite reduced nucleation time by 57% compared to those without templates and demonstrated edge adsorption. GO exhibited a nonlinear effect, accelerating nucleation at low lysozyme concentrations (30 mg mL-1) while inhibiting it at higher concentrations (over 50 mg mL-1). Furthermore, a second strategy was pursued using heterogeneous templates based on poly (ethylene glycol) diacrylate (PEGDA) hydrogel microspheres (HMS). In contrast to the adsorption mechanism, the PEGDA HMS acts by releasing precipitant (0- 4 M NaCl) to create localized supersaturation gradients, thereby reducing nucleation time by 79%. Based on the mechanisms of templated crystallization observed in the lysozyme system, this work sought to explore the universality of these effects in inorganic systems critical to biomineralization and disease. The interaction between proteins and inorganic salts was further investigated in two model systems: lithium carbonate (Li'CO') and calcium oxalate (CaOx) with proteins (lysozyme, bovine haemoglobin and mRFP). In both systems, inorganic salt crystals serve as templates that influence subsequent protein adsorption and crystallization, leading to the formation of protein-salt composite crystal structures. Elevated salt concentrations consistently promoted nucleation kinetics. Proteins, however, exhibited complex effects: At low supersaturation, proteins like lysozyme inhibited Li'CO' nucleation by chelating Li'. Conversely, at high supersaturation, proteins self-assemble into oligomers or aggregates, providing additional nucleation sites and accelerating nucleation. In the CaOx system, lysozyme enhanced nucleation across its tested concentration range (0-70 mg mL-1). To bridge our findings on artificial templates to biological contexts, in vivo crystallization is further explored. Inspired by nature, the production of intracellular crystals in Bacillus thuringiensis (Bt) was studied, and its Cry1Ac gene was applied to form a crystal scaffold (CS) as the bio-template to generate crystal nanoparticles in Escherichia coli (E. coli). Through adaptive laboratory evolution (ALE) via serial passaging, we achieved a nearly tenfold increase in protein fluorescence level and produced biologically active nanocrystals with high solubility under alkaline conditions. By integrating heterogeneous nucleation theory with biomimetic strategies, our work elucidates diverse templating mechanisms, including surface, the creation of local supersaturation gradients, and inorganic salt templates. These understandings enable the rational design of templates to control crystallization outcomes. Furthermore, we establish a platform that applying the Cry gene from Bt as the crystal scaffold to function as bio-templates inside cells, demonstrating their potential in high-yield production of bioactive nanocrystals.