Environmental Research Institute - Journal Articles

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    Guanidine functionalized porous SiO2 as heterogeneous catalysts for microwave depolymerization of PET and PLA
    (Royal Society of Chemistry, 2024-03-06) Casey, Éadaoin; Breen, Rachel; Pareras, Gerard; Rimola, Albert; Holmes, Justin D.; Collins, Gillian; Science Foundation Ireland
    Chemical recycling is an important strategy to tackle the growing global problem of plastic waste pollution. The development of metal-free catalysts for depolymerization of plastics is attractive as it avoids the use of metal salts, which are potentially damaging to the environment. Here we report a metal-free heterogeneous catalyst for the glycolysis of polyethylene terephthalate (PET) and methanolysis of polylactic acid (PLA). The catalysts are synthesized by covalent surface modification of mesoporous silica (SiO2) with guanidine ligands and evaluated under conventional thermal and microwave-assisted heating. A surface bound cyanoguanidine ligand was found to be the best catalyst leading to 100% PET conversion with 80% BHET yield. The nature of the catalyst support material influenced the catalytic performance of the guanidine ligands with porous SiO2 supports outperforming activated carbon in conventional thermal glycolysis, while the opposite trend was observed with microwave assisted glycolysis. Dedicated density functional theory (DFT) computations were performed to simulate the depolymerization processes, obtain the free energy profiles of the reaction mechanisms, and identify the important role of hydrogen bonding in the reaction mechanism.
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    A systematic review of the lived experiences of the energy vulnerable: Where are the research gaps?
    (Elsevier Ltd., 2024-05-10) Hihetah, Claudia; Ó Gallachóir , Brian; Dunphy , Niall P.; Harris, Clodagh; Science Foundation Ireland
    The transition to a low-carbon world, coupled with energy supply uncertainties, has heightened the urgency to better understand the experiences of vulnerable groups who lack affordable and adequate energy. Access to energy is crucial for their health, well-being, and social stability. However, there are significant knowledge gaps relating to the lived experiences of energy vulnerable groups that this paper directly addresses. There is a wide body of literature focusing on the quantification of, and policy response to, energy poverty alongside a fast- growing area of research on the lived experience of the energy vulnerable. This paper's systematic review of research on the lived experiences of the energy vulnerable reveals 46 peer-reviewed articles published between 2011 and 2021. Its review highlights diverse approaches to exploring energy vulnerability, the range of vulnerable groups investigated and different motivations for focusing on lived experiences. The results point to a number of key gaps in the literature in terms of definitions and terminologies, geographic coverage, gender, life stage (specifically children), ethnicity (ethnic minorities absent) and ability (people with disabilities are a further gap). It concludes that there is a need for more context-specific, mixed-methods and longitudinal studies in this area. Having identified gaps in the literature, it recommends how some of these can be addressed and reflects on how studies focused on the lived experience of energy poverty should advance.
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    3D printed rechargeable aqueous and non-aqueous lithium-ion batteries: Evolution of design and performance
    (Electrochemical Society, 2023-12-12) Egorov, Vladimir; Gulzar, Umair; O'Dwyer, Colm; Horizon 2020; European Regional Development Fund; Irish Research Council; Enterprise Ireland; Higher Education Authority
    Here we describe the modeling and design evolution of vat polimerized (Vat-P) stereolithographic apparatus (SLA) 3D printed coin cell-type aqueous and non-aqueous rechargeable lithium-ion batteries, cases and current collectors. We detail the rationale for design evolution that improved performance, handling and assembly of the printed batteries. Some guidance into the modeling, 3D printing process, material choice, chemical and electrochemical stability, assembly, sealing, and performance of 3D printed Li-ion batteries is outlined. 3D printed Li-ion batteries demonstrated promising results in terms of gravimetric capacity, rate capability, and capacity per unit footprint area compared to conventional coin cells in both aqueous and non-aqueous systems. For aqueous cells, the cell level capacity is a factor of 2–3x higher than similar metal coin cells due to the lighter weight and better rate response. We also outline design requirements for a Vat-P printed battery that are compatible with organic carbonate-based electrolytes, where the cell provides 115 mAh g−1 specific capacity using an LiCoO2–graphite chemistry, which is only ∼20% less than the maximum reversible capacity of LCO. Despite the challenges faced in optimizing the design and materials for 3D printed Li-ion batteries, this study provides valuable information for future research and development.
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    Asymmetrical optical response of opal photonic crystals with graded thickness
    (IOP Publishing, 2023-11-27) Grant, Alex; O'Dwyer, Colm; Irish Research Council
    The influence of thickness gradient and structural order on the spectral response of opal photonic crystals (PhCs) grown by evaporation-induced self-assembly (EISA) are presented. SEM imaging and angle resolved optical transmission spectroscopy are used to investigate the evolution of the PBG along a thickness gradient for opals grown from five different colloidal sphere concentrations at two different evaporation rates. The degradation of structural order along the thickness gradient is demonstrated, the occurrence of which attenuates the PBG with the thinning of the opal film and results in asymmetrical angle-resolved transmission spectra. The asymmetry in transmission intensity becomes more pronounced for opals grown from lower volume fractions, where secondary Bragg reflections also appear at low incident angles.
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    Operando color-coding of reversible lithiation and cycle life in batteries using photonic crystal materials
    (IOP Publishing, 2023-12-27) Lonergan, Alex; Gulzar, Umair; Zhang, Yan; O'Dwyer, Colm; Horizon 2020; Irish Research Council
    Innovative new materials are consistently emerging as electrode candidates from lithium-ion and emerging alternative battery research, promising high energy densities and high-rate capabilities. Understanding potential structural changes, morphology evolution, degradation mechanisms and side reactions during lithiation is important for designing, optimizing and assessing aspiring electrode materials. In-situ and operando analysis techniques provide a means to investigate these material properties under realistic operating conditions. Here, we demonstrate operando spectroscopic sensing using photonic crystal-structured electrodes that uses the optical transmission spectrum to monitor changes to the state of charge or discharge during lithiation, and the change to electrode structure, in real-time. Photonic crystals possess a signature optical response, with a photonic bandgap (or stopband) presenting as a structural color reflection from the material. We leverage the presence of this photonic stopband, alongside its intricate relationship to the electrode structure and material phase, to correlate electrode lithiation with changes to the optical spectrum during operation. We explore the optical and electrochemical behavior of a TiO2 anode in a lithium-ion battery, structured as a photonic crystal. The operando optical sensing demonstrated here is versatile and applicable to a wide range of electrochemical electrode material candidates when structured with ordered porosity akin to a photonic crystal structure.