Carbon Dioxide Hydrogenation by Means of Plasmonic Resonance Activation in Silica Aerogel Media

Surface Plasmon Resonance can be used to activate zinc oxide/copper catalysts in order to perform the carbon dioxide hydrogenation reaction by means of light energy, avoiding high-temperature processes. The synthesis and impregnation methods have been designed to fill glass microreactors with ZnO/Cu nanoparticles supported on transparent silica aerogels to maximize the light absorbed by the catalyst. A LED device surrounding the glass microreactors provided white light to activate the catalyst homogeneously throughout the reactor. Temperature, pressure, amount of catalyst and gases flow were studied as possible variables to enhance the process trying to maximize CO₂ conversion rates, achieving the best results working at high pressures. The use of transparent SiO₂ Aerogels as supports for photocatalytic gas phase reactions even under high-pressure conditions is demonstrated.

Optically Transparent Thermally Insulating Silica Aerogels for Solar Thermal Insulation

Rooftop solar thermal collectors have the potential to meet residential heating demands if deployed efficiently at low solar irradiance (i.e., 1 sun). The efficiency of solar thermal collectors depends on their ability to absorb incoming solar energy and minimize thermal losses. Most techniques utilize a vacuum gap between the solar absorber and the surroundings to eliminate conduction and convection losses, in combination with surface coatings to minimize reradiation losses. Here, we present an alternative approach that operates at atmospheric pressure with simple, black, absorbing surfaces. Silica based aerogels coated on black surfaces have the potential to act as simple and inexpensive solar thermal collectors because of their high transmission to solar radiation and low transmission to thermal radiation. To demonstrate their heat-trapping properties, we fabricated tetramethyl orthosilicate-based silica aerogels. A hydrophilic aerogel with a thickness of 1 cm exhibited a solar-averaged transmission of 76% and thermally averaged transmission of ≈1% (at 100 °C). To minimize unwanted solar absorption by O-H groups, we functionalized the aerogel to be hydrophobic, resulting in a solar-averaged transmission of 88%. To provide a deeper understanding of the link between aerogel properties and overall efficiency, we developed a coupled radiative-conductive heat transfer model and used it to predict solar thermal performance. Instantaneous solar thermal efficiencies approaching 55% at 1 sun and 80 °C were predicted. This study sheds light on the applicability of silica aerogels on black coatings for solar thermal collectors and offers design priorities for next-generation solar thermal aerogels.