Desenvolupament d’una xarxa autònoma per a bombeig d’aigua mitjançant energia fotovoltaica

El projecte tracta sobre el desenvolupament d’una xarxa per al bombeig d’aigua fent ús d’energia fotovoltaica. En el document es pot trobar tota la informació teòrica relativa a aquest tipus d’instal·lacions, els càlculs necessaris per dimensionar el sistema a partir d’un indret suposat amb una demanda d’aigua suposada, els criteris d’elecció dels components que conformen la xarxa, i alguns aspectes d’interès com el marc legal que l’envolta o l’impacte ambiental que pot causar. També, es realitza un estudi econòmic on s’analitza el pressupost de la implementació de la instal·lació partint des de zero, i es compara la solució fotovoltaica davant d’altres alternatives, com ara, l’eòlica, l’electricitat de la xarxa, o amb el preu d’una factura de subministrament d’aigua. L’energia fotovoltaica com a font d’energia per a un sistema d’aquest tipus és una opció viable per la constància del sol a la zona d’implementació, la possibilitat d’emmagatzemar aigua a un dipòsit per satisfer el consum els dies de baixa radiació i pel baix impacte ambiental. Resulta ser la més barata perquè l’equip fotovoltaic és més econòmic que les altres opcions, i en cas de fer la instal·lació partint des de zero i tenint en compte el preu tarifari del subministrament d’aigua, la inversió inicial es recupera abans del termini de la seva vida útil, que és de 25 anys

Hydrothermal Fabrication of Carbon-Supported Oxide-Derived Copper Heterostructures : A Robust Catalyst System for Enhanced Electro-Reduction of CO2 to C2H4

Anthropogenic CO can be converted to alternative fuels and value-added products by electrocatalytic routes. Copper-based catalysts are found to be the star materials for obtaining longer-chain carbon compounds beyond 2e products. Herein, we report a facile hydrothermal fabrication of a highly robust electrocatalyst: in-situ grown heterostructures of plate-like CuO−CuO on carbon black. Simultaneous synthesis of copper-carbon catalysts with varied amounts of copper was conducted to determine the optimum blend. It is observed that the optimum ratio and structure have aided in achieving the state of art faradaic efficiency for ethylene >45 % at −1.6 V vs. RHE at industrially relevant high current densities over 160 to 200 mA ⋅ cm. It is understood that the in-situ modification of CuO to CuO during the electrolysis is the driving force for the highly selective conversion of CO to ethylene through the *CO intermediates at the onset potentials followed by C−C coupling. The excellent distribution of Cu-based platelets on the carbon structure enables rapid electron transfer and enhanced catalytic efficiency. It is inferred that choosing the right composition of the catalyst by tuning the catalyst layer over the gas diffusion electrode can substantially affect the product selectivity and promote reaching the potential industrial scale

A MOF-Based Spatial-Separation Layer to Enable a Uniform Favorable Microenvironment for Electrochemical CO2 Reduction

Regulating the local microenvironment of active sites to increase their specific CO2 concentration and pH gradient, is a promising approach to optimize the electrochemical CO2 reduction reaction (eCO2RR). However, currently reported morphological strategies display an uncertainty to the compatibility and distribution between catalytic sites and their microenvironment. Here, a uniform spatial-separation metal-organic framework (MOF) layer between active sites and bulk electrolyte is proposed, which enables each active site to locate in a similarly favorable microenvironment. Zinc oxide (ZnO) nanorods (NR), a representative electrocatalyst for eCO2RR, is covered with a Zeolitic imidazolate framework-8 (ZIF-8) thin layer to serve as a model system. The prepared ZnO NR@ZIF-8 exhibits an enhanced Faradaic efficiency toward CO at a wide range of potentials and reaches a maximum FE of CO (85%) at −1.05 V versus reversible hydrogen electrode, which is one of the best records till date. Moreover, the hydrophobic ZIF-8 layer protects ZnO against self-reduction. Such performance benefits from the porous ZIF-8 shell with high CO2 affinity, realizing efficient CO2 access and retaining an increased local pH near ZnO active sites

Flexible and Binder-Free Iron Phosphide Electrodes Using a Three-Dimensional Support for High Hydrogen Productivity

In this work, an inexpensive and reliable microstructured electrode for the hydrogen evolution reaction (HER) is developed. This cathode is made of Earth-abundant elements consisting of iron phosphide as an electrocatalyst and carbon felt (CF) as a flexible conductive scaffold. Its porous character and binder-free FeP coverage over the carbon fibers generate a high number of accessible active sites for the reaction, achieving a high value of the electrochemically active surface area. The electrode reaches 100 mA ⋅ cm by applying only −53 mV vs RHE at 50 °C in 0.5 M HSO, demonstrating excellent electrocatalytic activity for the HER and outstanding stability in acidic electrolyte. Furthermore, the feasibility of these electrodes for industrial application is evaluated using a PEM electrolyzer. The developed prototype with a cathodic area of 1.8 cm shows a very promising performance, reaching 14.9 mmol H ⋅ h ⋅ cm (corresponding to 800 mA ⋅ cm) at a voltage of only 2.1 V

Disentangling Epitaxial Growth Mechanisms of Solution Derived Functional Oxide Thin Films

Altres ajuts: CSIC E-08-2012-1321248 i E-08-2013-1028356This study investigates the mechanisms of epitaxial development and functional properties of oxide thin films (CeZrO , LaNiO, and BaSrTiO) grown on single crystal substrates (YO:ZrO, LaAlO, and SrTiO) by the chemical solution deposition approach. Rapid thermal annealing furnaces are very powerful tools in this study providing valuable information of the early stages of nucleation, the kinetics of epitaxial film growth, and the coarsening of nanocrystalline phases. Advanced transmission electron microscopies, X-ray diffraction, and atomic force microscopy are employed to investigate the film microstructure and morphology, microstrain relaxation, and epitaxial crystallization. This study demonstrates that the isothermal evolution toward epitaxial film growth follows a self-limited process driven by atomic diffusion, and surface and interface energy minimization. All investigated oxides experience a transformation from the polycrystalline to the epitaxial phase. This study unequivocally evidences that the film thickness highly influences the epitaxial crystallization rate due to the competition between heterogeneous and homogeneous nucleation barriers and the fast coarsening of polycrystalline grains as compared to epitaxial growth. The investigated films possess good functional properties, and this study successfully confirms an improvement at long annealing times that can be correlated with grain boundary healing processes. Thick epitaxial films can be crystallized by growing sequential individual epitaxial layers

Size-Dependent passivation shell and magnetic properties in antiferromagnetic/ferrimagnetic core/shell MnO nanoparticles

The magnetic properties of bimagnetic core/shell nanoparticles consisting of an antiferromagnetic MnO core and a ferrimagnetic passivation shell have been investigated. It is found that the phase of the passivation shell (γ-Mn2O3 or Mn3O4) depends on the size of the nanoparticles. Structural and magnetic characterizations concur that while the smallest nanoparticles have a predominantly γ-Mn2O3 shell, larger ones have increasing amounts of Mn3O4. A considerable enhancement of the Néel temperature, TN, and the magnetic anisotropy of the MnO core for decreasing core sizes has been observed. The size reduction also leads to other phenomena such as persistent magnetic moment in MnO up to high temperatures and an unusual temperature behavior of the magnetic domains

Orientation symmetry breaking in self-assembled Ce1- : XGdxO2- y nanowires derived from chemical solutions

Understanding the growth mechanisms of nanostructures obtained from chemical solutions, a high-throughput production methodology, is essential to correlate precisely the growth conditions with the nanostructures' morphology, dimensions and orientation. It is shown that self-organized (011)-oriented Ce₀.₉Gd₀.₁O₂ᵧ (CGO) nanowires having a single in-plane orientation are achieved when an anisotropic (011)-LaAlO₃ (LAO) substrate is chosen. STEM and AFM images of the epitaxial nanowires reveal the (001)CGO[0-11](011)LAO[100] growth orientation, with the enlargement occurring along the [0-11]CGO direction with (111) lateral facets. The chosen substrate allowed us to study a unique case where the resulting biaxial strain is isotropic, while the dissimilar lateral surface energies are the key factor to obtain an energetically imbalanced and non-degenerated nanowire configuration. Rapid Thermal Annealing (RTA) has allowed sorting of experimental nucleation from coarsening and analysis of the kinetic phenomena of the nanowires. A thermodynamic driving force is shown to exist for a continuous elongation of the nanowires while the coarsening rates are found to be strongly temperature dependent and so kinetic effects are the key factors to control the size and density of the self-organized nanowire system. A remarkably fast nanowire growth rate (14-40 nm min⁻¹) is observed, which we associate with a high atomic mobility probably linked to a high concentration of oxygen vacancies, as detected by XPS. These nanowires are envisaged as model systems pushing forward the study of low energetic and highly oxygen deficient {111} lateral facets useful for catalysis, gas sensors and ionic conductivity applications

Boosting Photoelectrochemical Water Oxidation of Hematite in Acidic Electrolytes by Surface State Modification

State-of-the-art water-oxidation catalysts (WOCs) in acidic electrolytes usually contain expensive noble metals such as ruthenium and iridium. However, they too expensive to be implemented broadly in semiconductor photoanodes for photoelectrochemical (PEC) water splitting devices. Here, an Earth-abundant CoFe Prussian blue analogue (CoFe-PBA) is incorporated with core-shell FeO/FeTiO type II heterojunction nanowires as composite photoanodes for PEC water splitting. Those deliver a high photocurrent of 1.25 mA cm at 1.23 V versus reversible reference electrode in acidic electrolytes (pH = 1). The enhancement arises from the synergic behavior between the successive decoration of the hematite surface with nanolayers of FeTiO and then, CoFe-PBA. The underlying physical mechanism of performance enhancement through formation of the FeO/FeTiO/CoFe-PBA heterostructure reveals that the surface states' electronic levels of hematite are modified such that an interfacial charge transfer becomes kinetically favorable. These findings open new pathways for the future design of cheap and efficient hematite-based photoanodes in acidic electrolytes

Desenvolupament d’una xarxa autònoma per a bombeig d’aigua mitjançant energia fotovoltaica

El projecte tracta sobre el desenvolupament d’una xarxa per al bombeig d’aigua fent ús d’energia fotovoltaica. En el document es pot trobar tota la informació teòrica relativa a aquest tipus d’instal·lacions, els càlculs necessaris per dimensionar el sistema a partir d’un indret suposat amb una demanda d’aigua suposada, els criteris d’elecció dels components que conformen la xarxa, i alguns aspectes d’interès com el marc legal que l’envolta o l’impacte ambiental que pot causar. També, es realitza un estudi econòmic on s’analitza el pressupost de la implementació de la instal·lació partint des de zero, i es compara la solució fotovoltaica davant d’altres alternatives, com ara, l’eòlica, l’electricitat de la xarxa, o amb el preu d’una factura de subministrament d’aigua. L’energia fotovoltaica com a font d’energia per a un sistema d’aquest tipus és una opció viable per la constància del sol a la zona d’implementació, la possibilitat d’emmagatzemar aigua a un dipòsit per satisfer el consum els dies de baixa radiació i pel baix impacte ambiental. Resulta ser la més barata perquè l’equip fotovoltaic és més econòmic que les altres opcions, i en cas de fer la instal·lació partint des de zero i tenint en compte el preu tarifari del subministrament d’aigua, la inversió inicial es recupera abans del termini de la seva vida útil, que és de 25 anys

Desenvolupament d’una xarxa autònoma per a bombeig d’aigua mitjançant energia fotovoltaica

El projecte tracta sobre el desenvolupament d’una xarxa per al bombeig d’aigua fent ús d’energia fotovoltaica. En el document es pot trobar tota la informació teòrica relativa a aquest tipus d’instal·lacions, els càlculs necessaris per dimensionar el sistema a partir d’un indret suposat amb una demanda d’aigua suposada, els criteris d’elecció dels components que conformen la xarxa, i alguns aspectes d’interès com el marc legal que l’envolta o l’impacte ambiental que pot causar. També, es realitza un estudi econòmic on s’analitza el pressupost de la implementació de la instal·lació partint des de zero, i es compara la solució fotovoltaica davant d’altres alternatives, com ara, l’eòlica, l’electricitat de la xarxa, o amb el preu d’una factura de subministrament d’aigua. L’energia fotovoltaica com a font d’energia per a un sistema d’aquest tipus és una opció viable per la constància del sol a la zona d’implementació, la possibilitat d’emmagatzemar aigua a un dipòsit per satisfer el consum els dies de baixa radiació i pel baix impacte ambiental. Resulta ser la més barata perquè l’equip fotovoltaic és més econòmic que les altres opcions, i en cas de fer la instal·lació partint des de zero i tenint en compte el preu tarifari del subministrament d’aigua, la inversió inicial es recupera abans del termini de la seva vida útil, que és de 25 anys