• Energy Research
• Embargo close
• IT close
• ES close
• EU close
• DK close

Self-organizing nanopatterns can enable economically competitive, industrially applicable light-harvesting platforms for thin-film solar cells. In this work, we present transparent solar cell substrates having quasiperiodic uniaxial nanowrinkle patterns with high optical haze values. The self-organized nanowrinkle template is created by controlled heat-shrinking of metal-deposited pre-stretched polystyrene sheets. A scalable UV nanoimprinting method is used to transfer the nanopatterns to glass substrates on which single-junction hydrogenated amorphous silicon p-i-n solar cells are subsequently fabricated. The structural and optical analyses of the solar cell show that the nanowrinkle pattern is replicated throughout the solar cell structure leading to enhanced absorption of light. The efficient broadband light-trapping in the nanowrinkle solar cells results in very high 18.2 mA/cm2 short-circuit current density and 9.5% energy-conversion efficiency, which respectively are 35.8% and 39.7% higher than the values obtained in flat-substrate solar cells. The cost- and time-efficient technique introduces a promising new approach to customizable light-management strategies in thin-film solar cells.

This study provides the first comprehensive overview of the sustainability performance of the hotel sector in the Himalayan region: Sagarmatha National Park and Buffer Zone, using both environmental, economic, and technical criteria. In particular, the performance of 45 buildings in this region were measured and quantified in terms of life cycle based carbon footprint, life cycle costs, heat loss rate, number of guests, energy consumption, and area. Buildings were classified into three types: traditional, semi-modern and modern. The statistical analysis included testing for significant differences between such categories by means of ANOVA, and determination of the correlation between the same parameters. Results show a significant difference between the buildings’ total carbon footprint and operation stage carbon footprint while, there is no significant difference between the buildings’ life cycle costs. Traditional buildings have on average the largest carbon footprint and life-cycle cost over the typical building lifespan of 50 years of building lifespan. The ANOVA tests highlight how heat loss rate, size of the building and number of tourists in the hotels are significantly different across the building types. A strong positive correlation is observed between environmental impact, economic impact and energy consumption for the household activities, and a negative correlation with the number of guests and building size. By considering several buildings, this study allows to draw new and more general conclusions about effective sustainability strategies in the whole hotel sector in the Himalayan region. In particular, it shows that reducing impacts in the operation stage should be highly prioritized, focusing on reducing energy consumption and heat loss and shifting to the use of renewable energy sources.

Industrial symbiosis (IS) is recognized as an effective practice to support circular economy and sustainable development because it is able to enhance the technical efficiency of production processes, provided IS relationships among companies remain active over the long period. However, although it has been established that IS relationships can be vulnerable to disruptive events that reduce the willingness of companies to cooperate in IS synergies, to date few contributions to the literature focus attention on the events which lead firms to interrupt IS synergies. This paper contributes to the existing literature firstly by highlighting the disruptive events affecting the willingness of companies to cooperate in IS synergies and their causes, and secondly by developing an analytical model to assess the impact of each disruption on physical and monetary flows created among companies by the IS relationship. Specifically, an enterprise input-output (EIO) model is proposed, aimed at mapping the physical and monetary flows resulting from IS synergies among companies. Through this model, disruptive events can be modeled and their impact on the above-mentioned flows can be assessed. A numerical case example illustrates how the model works and how company managers and IS facilitators could use it to evaluate to what degree their current IS relationships may be vulnerable to perturbations. The model could therefore facilitate the design of adequate countermeasures and contribute to the development of perturbation resilient IS relationships. Furthermore, policymakers could adopt the model when designing policy actions to support IS practice.

The data used in "Assessing a Fuel Subsidy: Dynamic Effects on Retailer Pricing and Pass-Through to Consumers" by J. Balaguer and J. Ripollés.

The optical and photovoltaic properties of Si NCs / SiC multilayers (MLs) are investigated using a membrane-based solar cell structure. By removing the Si substrate in the active cell area, the MLs are studied without any bulk Si substrate contribution. The occurrence is confirmed by scanning electron microscopy and light-beam induced current mapping . Optical characterization combined with simulations allows us to determine the absorption within the ML absorber layer, isolated from the other cell stack layers. The results indicate that the absorption at wavelengths longer than 800 nm is only due to the SiC matrix. The measured short-circuit current is significantly lower than that theoretically obtained from absorption within the ML absorber, which is ascribed to losses that limit carrier extraction. The origin of these losses is discussed in terms of the material regions where recombination takes place. Our results indicate that carrier extraction is most efficient from the Si NCs themselves, whereas recombination is strongest in SiC and residual a-Si domains . Together with the observed onset of the external quantum efficiency (EQE) at 700-800 nm, this fact is an evidence of quantum confinement in Si NCs embedded in SiC on device level.

[eng] Aqueous zinc ion batteries (AZIBs) have garnered significant research attention due to their remarkably high-volume energy density, reaching up to 5,851 mAh mL-1. This surpasses the capabilities of state-of-the-art lithium-ion batteries (LIBs), making AZIBs a promising candidate for advanced energy storage technology. Additionally, the natural abundance, low cost, and non-toxic nature of zinc offer economic advantages and environmental sustainability, particularly beneficial for large-scale applications. One notable advantage of AZIBs is their ability to be fabricated in an air atmospheric environment, thanks to the air stability of the AZIBs system. This characteristic significantly simplifies the fabrication process, further enhancing the attractiveness of AZIBs for widespread adoption. However, the practical implementation of AZIBs still suffers from several intractable technical challenges, such as limited energy density and inadequate cycle life, which seriously hinder this technology from yielding practically viable energy density and cyclability. Selecting appropriate cathode materials and implementing rational structural design engineering can effectively overcome the aforementioned challenges. In Chapter 1, I summarize the state of the art on advanced cathode materials for AZIBs and particularly detail structural engineering strategies to achieve high energy density and extended cycle life. In Chapter 2, I detail my work on the design and engineering of K+ pre-intercalated MnO2 nanorods (K-MnO2-NR) as an efficient cathode to overcome the limitations of AZIBs. The K-MnO2-NR is synthesized by a facile one-step chemical method with a size of less than 10 nm. Their unique structure provides a large surface area, abundant active sites for ion storage, and a short diffusion path for ion transport. The intercalation of K+ also improves the conductivity of the electrode and stabilizes the tunnel structure. Consequently, this K-MnO2-NR configuration delivers a high capacity of 285 mAh g-1 at 0.1 A g-1, while retaining 222 mAh g-1 at 2 A g-1. Kinetic reaction analysis reveals that even under high charging/discharging rates, ion diffusion-controlled capacity plays a crucial role, which is beneficial for achieving high capacity under such conditions. Assembled pouch cells with K-MnO2-NR also exhibit promising application prospects. This work has been accepted for publication in the journal Ceramics International and it is already available online (https://doi.org/10.1016/j.ceramint.2024.04.324). However, the capacity of the enhanced MnO2 still falls short of expectations, hampering its practical application. The primary reason for this limitation is that the prepared crystalline MnO2 possess few defects, resulting in a reduced ion storage capacity. Hence, there arises a necessity to devise a novel defect engineering methodology to address this issue and obtain materials with high-density active sites, thereby enhancing their performance. In Chapter 3, to further improve MnO2-based cathodes, I introduce a method to obtain manganese oxide materials with high-density active sites through the in situ phase transformation of MnSe, thereby regulating the defect structure. I detail my work on the structural engineering of reduced graphene oxide (rGO)-coated MnSe nanoparticles (MnSe@rGO) as a cathode material for AZIBs. The introduction of rGO provides a surface-confining effect against morphological evolution, thus preventing structural failure of the electrode. Furthermore, the intrinsically high electronic conductivity of rGO facilitates the MnSe phase transition, enabling the utilization of its full capacity potential. The optimized MnSe@rGO-3 cathode demonstrates a significant specific capacity of 290 mAh g-1 at 0.1C and retains a specific capacity of 178 mAh g-1 even at 5C. Through quantitative electrochemical analyses, first-principles calculations, and in situ characterization, the enhanced capacitive zinc-ion storage behavior and phase transformation mechanism of MnSe@rGO cathode materials are elucidated. Moreover, the mechanical stability of rGO ensures the successful electrohydrodynamic (EHD) jet printing of flexible ZIBs into a flexible integrated functional system. As an illustration, a flexible touch-controlled light-emitting diode (LED) array system incorporating as-fabricated MnSe@rGO-3-based ZIBs is developed. This approach showcases effective performance in both flat and bent configurations, offering the added advantages of enhanced safety and environmental sustainability. This work was published in ACS Nano in 2023 (https://doi.org/10.1021/acsnano.3c00672). Despite the significant strides made in enhancing the specific capacity of Mn-based cathode materials through defect engineering, the persisting limitations associated with manganese dissolution and moderate cycle life continue to raise concerns. These issues indeed cast doubt on their viability for high-energy-density applications, particularly in application fields like wearables. In Chapter 4, to increase the energy density of AZIBs, I explain my work on the development of a new cathode material based on a layered metal chalcogenide (LMC), bismuth telluride (Bi2Te3) nanodisks, coated with polypyrrole (PPy) as cathode material for aqueous ZIBs, and then explore its storage mechanism. In situ X-ray diffraction (XRD) analysis, X-ray photoelectron spectroscopy (XPS) measurements, and density functional theory (DFT) calculations are employed to elucidate that the energy storage mechanism of Bi2Te3 is the insertion/extraction of protons rather than Zn ions within the (0 0 6) interlayers, coupled with the formation/deposition of Zn4SO4(OH)6·5H2O on the electrode surface. The PPy coating enhances the ionic conductivity of the LMC while preventing surface oxidation. Consequently, the Bi2Te3@PPy cathode exhibits remarkable rate performance and long-term cycling stability with ultra-long lifespans of over 5,000 cycles. They also present outstanding stability even under bending. This work was published in Advanced Materials in 2023 (https://doi.org/10.1002/adma.202305128). Finally, the main conclusions of this thesis, including a comparison chart of the three cathode materials developed in the thesis, and some perspectives for future work are presented. [spa] Las baterías de iones de zinc en electrolito acuoso (AZIBs) han atraído notable atención por su excelente densidad volumétrica de energía, alcanzando hasta 5,851 mAh mL-1, superando a las baterías de iones de litio (LIB). Además, el zinc es abundante, económico y no tóxico, lo que beneficia aplicaciones a gran escala. Las AZIBs pueden fabricarse en un ambiente atmosférico, simplificando significativamente el proceso de fabricación. Sin embargo, enfrentan desafíos técnicos como densidad de energía limitada y vida útil corta. En el Capítulo 1, se revisa el estado del arte sobre materiales catódicos avanzados para AZIBs, y se detallan estrategias para lograr alta densidad de energía y ciclo de vida extendido. En el Capítulo 2, se presenta el diseño e ingeniería de nanobarras de MnO2 preintercaladas con K+ (K-MnO2-NR) como cátodos. Este material, sintetizado mediante un método electroquímico sencillo, ofrece una alta capacidad de 285 mAh g 1 a 0.1 A g-1 y retiene 222 mAh g-1 a 2 A g-1. La intercalación de K+ mejora la conductividad y estabiliza la estructura, proporcionando una gran superficie y sitios activos para el almacenamiento de iones. Este trabajo se ha publicado en International Ceramics. En el Capítulo 3, se introduce un método para mejorar aún más el cátodo a base de MnO2 mediante la transformación de fase de MnSe, creando materiales con alta densidad de sitios activos. Se diseñaron nanopartículas de MnSe recubiertas con óxido de grafeno reducido (rGO) (MnSe@rGO). El recubrimiento de rGO mejora la conductividad y estabiliza la estructura, evitando fallos estructurales. El cátodo MnSe@rGO-3 demuestra una capacidad específica de 290 mAh g-1 a 0.1 C y retiene 178 mAh g-1 a 5C. Este trabajo fue publicado en ACS Nano. En el Capítulo 4, se explora un nuevo material catódico basado en nanodiscos de telururo de bismuto (Bi2Te3) recubiertos con polipirrol (PPy) para ZIBs acuosas. Mediante análisis XRD in situ, mediciones XPS y cálculos DFT, se dilucida que el mecanismo de almacenamiento de Bi2Te3 implica la inserción/extracción de protones y la formación de Zn4SO4(OH)6·5H2O. El recubrimiento de PPy mejora la conductividad iónica y previene la oxidación. El cátodo Bi2Te3@PPy exhibe excelente rendimiento y estabilidad a largo plazo, con una vida útil de más de 5,000 ciclos, incluso bajo flexión. Este trabajo fue publicado en Materiales Avanzados. A pesar de estos avances, persisten desafíos como la disolución del manganeso y la vida útil limitada, cuestionando su viabilidad para aplicaciones de alta densidad de energía. La tesis concluye con una comparación de los tres cátodos desarrollados y ofrece perspectivas para futuros trabajos. Programa de Doctorat en Nanociències / Tesi realitzada a l'Institut de Recerca en Energia de Catalunya (IREC)

[eng] Developing advanced and efficient electrocatalytic energy conversion systems is of great and practical significance for propelling the efficient development of clean energy for the construction of new low-carbon power systems. Among them, electrocatalytic reduction reactions driven by renewable electricity to transform biomass-derived chemicals into biofuels and high value-added chemicals provide an effective way to improve the H/C ratio of biomass-derived chemicals and the stabilizations of bio-oil systems. However, the electrocatalytic reduction of organic compounds is more intricate compared to the electrocatalytic reduction of water molecules. It involves the adsorption of various organic functional groups, multi-step electron transfer, and the generation of organic intermediates. Meanwhile, organic electrocatalytic reduction calls for designing efficient, highly selective, and cost- effective electrocatalysts. During a series conversion process of raw biomass, aldehydes are believed to be particularly troublesome for the aldol condensation and polymerization reactions. To avoid them, hydrogenation processes are necessary. As an alternative to traditional high-pressure and -temperature processing, we choose electrochemistry that can operate in ambient conditions for the conversion of benzaldehyde (BZH), which was chosen as a typical biomass-derived chemical. Another reason for choosing BZH is that the hydrogenation products benzyl alcohol (BA) and hydrobenzoin (HDB) are important industrial chemicals. Based on the mentioned above, this work seeks to design highly efficient and high selective catalysts for the electrocatalytic conversion of the carbonyl group of BZH into BA, HDB or benzoic acid (BZA) in aqueous solution at pH＞5 (avoiding the deoxygenation product toluene). Additionally, this work screens the optimal reaction conditions for various products and speculates their most probable reaction pathways. Chapter 4 focused on the electrocatalytic reduction of BZH into BA. Pd nanoparticles supported on a nickel metal-organic framework (MOF), Ni-MOF-74, are prepared and their activity towards the ECH of BZH in a 3M sodium acetate-acetic acid (pH 5.2) aqueous electrolyte is explored. An outstanding ECH rate up to 283 µmol cm-2 h-1 with a Faradic efficiency (FE) of 76% is reached. Besides, higher FEs of up to 96% are achieved using a step-function voltage. Materials studio and density functional theory calculations show these outstanding performances to be associated with the Ni- MOF support that promotes H-bond formation, facilitates water desorption, and induces a favorable tilted BZH adsorption on the surface of the Pd nanoparticles. In this configuration, BZH is bonded to the Pd surface by the carbonyl group rather than through the aromatic ring, thus reducing the energy barriers of the elemental reaction steps and increasing the overall reaction efficiency. Chapter 5 focused on the electrochemical reduction of self-coupling of BZH to HDB using semiconductor electrocatalysts with nanosheet morphologies. The effects of electrode potential and electrolyte pH on BZH self-coupling reaction were comprehensively studied on several semiconductor electrocatalysts. A correlation is observed between their band gap and the electrochemical potential necessary to maximize selectivity towards HDB in alkaline medium, which we associate with the charge accumulation at the semiconductor surface. N-type CuInS2 provides the highest conversion rate at 0.3 mmol cm−2 h−1 with a selectivity of 98.5% at -1.3 V vs. Hg/HgO in aqueous alkaline solution pH=14. Additional density functional theory calculations demonstrate a lower kinetic energy barrier at the CuInS2 surface compared with graphitic carbon, proving its catalytic role in the self-coupling reaction of BZH. Based on the previous two works, we realize that even when selecting materials with poor HER performance, different voltages and pH values have a significant impact on the selectivity of HDB. This drives us towards the rational design of electrocatalysts for these two different reaction pathways. Chapter 6 employed material with exposed active sites Cu2S and the material Cu2S-OAm with ligands capped to catalyze the electrocatalytic reduction reaction of the biomass platform molecule BZH convert into BA and HDB. Cu2S particles are used as electrocatalysts for the BZH electrochemical conversion. We particularly analyze the effect of surface ligands, oleylamine (OAm), on the selective conversion of BZH to BA or HDB. The effect of the electrode potential, electrolyte pH, and temperature are studied. Results indicate that bare Cu2S exhibits higher selectivity towards BA, while OAm-capped Cu2S promotes HDB formation. This difference is explained by the competing adsorption of protons and BZH. During the BZH electrochemical conversion, electrons first transfer to the C in the C=O group to form a ketyl radical. Then the radical either couples with surrounding H+ to form BA or self-couple to produce HDB, depending on the available H+ that is in turn affected by the electrocatalyst surface properties. The presence of OAm inhibits the H adsorption on the electrode surface therefore reducing the formation of high-energy state Had and its combination with ketyl radicals to form BA instead promotes the outer sphere reaction for obtaining HDB. Finally, we turn our attention to the anodic reaction in chapter 7. The electrooxidation of organic compounds offers a promising strategy for producing value-added chemicals through environmentally sustainable processes. A key challenge in this field is the development of electrocatalysts that are both effective and durable. In this study, we grow gold nanoparticles (Au NPs) on the surface of various phases of titanium dioxide (TiO2) as highly effective electrooxidation catalysts. Subsequently, the samples are tested for the oxidation of BZH to BZA coupled with a hydrogen evolution reaction (HER). We observe the support containing a combination of rutile and anatase phases to provide the highest activity. The excellent electrooxidation performance of this Au-TiO2 sample is correlated with its mixed-phase composition, large surface area, high oxygen vacancy content, and the presence of Lewis acid active sites on its surface. This catalyst demonstrates an overpotential of 0.467 V at 10 mA cm-2 in a 1 M KOH solution containing 20 mM BZH, and 0.387 V in 100 mM BZH, well below the oxygen evolution reaction (OER) overpotential. The electrooxidation of BZH not only serves as OER alternative in applications such as electrochemical hydrogen evolution, enhancing energy efficiency, but simultaneously allows the generation of high-value byproducts such as BZA [spa] El desarrollo de sistemas de conversión de energía electrocatalítica avanzados es crucial para la energía limpia y un sistema energético de bajo carbono. La reducción electrocatalítica de productos químicos de biomasa mejora la relación H/C y estabiliza los aceites biológicos, aunque es compleja debido a la transferencia de electrones y generación de intermediarios. Es esencial diseñar electrocatalizadores eficientes y selectivos. La hidrogenación de aldehídos en la biomasa cruda es necesaria para evitar reacciones no deseadas. Se utilizó la electroquímica para convertir benzaldehído (BZH) en productos industriales valiosos como alcohol bencílico (BA) e hidrobencoína (HDB). Este trabajo diseñó catalizadores eficientes para convertir BZH en BA, HDB o ácido benzoico (BZA) en solución acuosa con pH ＞ 5, optimizando las condiciones de reacción. En el Capítulo 4, se usaron nanopartículas de Pd en un marco metal-orgánico de níquel (Ni-MOF-74) logrando una alta eficiencia faradaica (FE) y mejor adsorción de BZH. El Capítulo 5 estudió el acoplamiento de BZH a HDB con electrocatalizadores semiconductores, destacando el CuInS₂ de tipo N por su alta selectividad y eficiencia. En el Capítulo 6, se usaron partículas de Cu₂S con y sin oleylamine (OAm), mostrando que OAm promueve la formación de HDB al inhibir la adsorción de protones. El Capítulo 7 se enfocó en la electrooxidación de BZH a BZA usando nanopartículas de oro (Au NPs) en dióxido de titanio (TiO₂), logrando alta actividad y eficiencia energética, generando además subproductos valiosos. Programa de Doctorat en Electroquímica. Ciència i Tecnologia

The transition to cleaner energy sources is fundamental for mitigating the effects of climate change. One promising example is lignocellulosic biomass, a renewable and sustainable energy source that serves as a precursor to various compounds, including γ-valerolactone (GVL). GVL can be utilized as a biofuel or biopolymer. This project evaluates the potential use of SrFe12O19/Ni-P and graphite/Ni-P as catalysts for the photo-thermocatalytic and cost-effective production of GVL from levulinic acid, using a laser light as a source of energy. The goal is to scale up this process for future industrial applications. The catalysts were functionalized via a Ni-P electroless deposition process. The impact of temperature, reaction time, and electroless deposition coating time on catalyst efficiency was analysed. For the effective catalysts, different coverages thicknesses were tested. Optimal experimental conditions for reactor experiments with a laser dispositive were previously established by conducting autoclave tests in a conventional oven. Autoclave tests results evidenced that the SrFe12O19/Ni-P material did not exhibit catalytic properties for the production of γ-valerolactone. In contrast, graphite/Ni-P catalysts achieved nearly 100% conversion, with an optimum minimum reaction temperature of 120 ºC. To evaluate the potential of the graphite/Ni-P catalyst as a photo-thermal catalysts for γ-valerolactone production, experiments were conducted using the laser apparatus under the aforementioned conditions. The results showed that the graphite/Ni-P catalyst with a 10-minute deposition time exhibited higher conversion rates at lower reaction times and demonstrated greater durability and stability throughout the reusability cycles. Consequently, the graphite/Ni-P catalyst with a 10-minute deposition time was identifies as a suitable catalyst for GVL production. Treballs Finals de Grau de Química, Facultat de Química, Universitat de Barcelona, Any: 2024, Tutors: Albert Serrà Ramos, Elvira Gómez Valentín