Reacciones catalíticas mejoradas con plasmones para combustibles renovables

Victoria Golovanova

Prof. Joan Ramón Morante Lleonart Dra. Teresa Andreu Arbella

Prof. Joan Ramón Morante Lleonart, director del Institut de Recerca en Energia de Catalunya IREC i Catedràtic d'Universitat del Departament d'Enginyeria Electrònica i Biomèdica de la Universitat de Barcelona, i la Dra. Teresa Andreu Arbella, Profesora Lectora del Departamento de Ciencia de Materiales y Química Física de la Universitat de Barcelona.

The depletion of fossil fuels and global warming caused by excessive carbon emissions have led to an urgent transition to renewable energy sources, of which only solar energy is capable of meeting the growing global energy demand. In this context, the utilization of sunlight in catalytic reactions for the production of renewable fuels is a great challenge. The hot field of plasmon-assisted catalysis requires inexpensive materials with excellent optical and catalytic properties at the same time. So far, few works have highlighted the importance of plasmon heating as the main consequence of plasmon. Due to the above reasoning, nickel (Ni) is an excellent candidate for plasmon-enhanced catalytic applications, as it is an abundant transition metal with a beneficial combination of excellent catalytic and photothermal properties. The main objectives of this work are i) the design of Ni-based plasmonic catalysts for renewable fuel reactions (CO₂ methanation and hydrogen evolution reaction -HER-), ii) their structural, optical and functional study to identify the optimal reaction conditions and quantify the gain in the light-assisted reaction, and iii) define the mechanisms of reaction improvement. The first chapter of the thesis presents an overview of the problem, includes the description of the fundamental concepts and provides a state of the art in plasmon-enhanced CO2 methanation and HER. The second chapter is dedicated to the development of the highly active Ni/CeO2 catalyst (80% CO₂ conversion and 95% methane selectivity) for light-assisted CO2 methanation. A 2.4-fold increase in the reaction rate was demonstrated, which led to a 20% decrease in energy consumption. In situ characterization techniques revealed a dual effect of solar radiation on the Ni/CeO2 catalyst, confirming the presence of photothermal and electronic effects. The third chapter presents a study on plasmonic Ni nanoparticles with enhanced absorption in the visible light range and their application as a photocathode for HER. The strong photothermal effect of the nanoparticles on the reaction rate allowed to increase the hydrogen production by 27% after finding the optimal conditions. Light-dark and pressed illumination measurements were used to identify the mechanism of the light-induced overpotential drop. The fourth chapter is dedicated to the optical study of Ni nanophore (NHA) arrays and the use of their surface plasmon in the iodate reduction reaction. The tunable hollow mask lithography method used in the fabrication of NHA involved precise adjustment of its geometric parameters and optimization of its optical properties. The study of wavelength-dependent photocurrent under pulsed laser irradiation of planar and structured photocathodes with respect to their optical spectrum demonstrated the photothermal plasmonic nature of the reaction enhancement.

Los catalizadores plasmónicos basados en Ni, desarrollados durante mi tesis doctoral, permiten mejorar la tecnología de conversión de energía a gas, actualmente en desarrollo, mediante la incorporación de luz solar en el proceso. Este catalizador universal puede aplicarse para mejorar las reacciones catódicas y anódicas en la electrólisis del agua, mejorando así la producción de hidrógeno y, por lo tanto, teniendo un gran impacto en la descarbonización del sector energético. Además, se ha demostrado que los catalizadores basados en Ni mejoran significativamente la tasa de metanación del CO2 bajo luz solar débilmente concentrada, lo que se traduce en un aumento significativo del consumo de energía. Los pasos posteriores se centrarán en optimizar el diseño del reactor para obtener altos valores de conversión sin necesidad de reducir el caudal y optimizar la gestión adecuada de la luz y el calor del reactor. Esto se implementará en el proyecto Producte19 (AGAUR, 2019 PROD 00091) y en la planta piloto de metanización IREC, que Naturgy Energy Group pondrá en marcha en 2023. El catalizador plasmónico también se combinará con fotoánodos de última generación para mitigar la reacción de cuello de botella de la oxidación del agua mediante la luz solar. Finalmente, el catalizador fototérmico se aplicará en la desalinización plasmónica de agua de mar, lo que facilitará la captación de agua dulce en condiciones exteriores.

Fossil Fuel Depletion; Global Warming; Carbon Emissions; Renewable Energy Sources; Solar Energy; Sunlight Utilization; Catalytic Reactions; Renewable Fuels; Plasmon-Assisted Catalysis; Inexpensive Materials; Optical Properties; Catalytic Properties; Plasmon Heating; Abundant Transition Metal; Nickel (Ni); Plasmon-Enhanced Catalytic Applications; Photothermal Properties; Ni-based Plasmonic Catalysts; CO₂ Methanation; Hydrogen Evolution Reaction (HER); Structural Study; Optical Study; Functional Study; Optimal Reaction Conditions; Light-Assisted Reaction Gain; Reaction Improvement Mechanisms; Ni/CeO2 Catalyst; High Activity; CO₂ Conversion; Methane Selectivity; Reaction Rate Increase; Energy Consumption Decrease; In situ Characterization; Dual Effect; Solar Radiation; Photothermal Effects; Electronic Effects; Plasmonic Ni Nanoparticles; Enhanced Visible Light Absorption; Photocathode; Hydrogen Production; Optimal Conditions; Light-Dark Measurements; Pressed Illumination Measurements; Light-Induced Overpotential Drop; Ni Nanophore (NHA) Arrays; Surface Plasmon; Iodate Reduction Reaction; Tunable Hollow Mask Lithography; NHA Fabrication; Geometric Parameters; Optical Properties Optimization; Wavelength-Dependent Photocurrent; Pulsed Laser Irradiation; Planar Photocathodes; Structured Photocathodes; Optical Spectrum; Photothermal Plasmonic Nature; Reaction Enhancement.