In the current context of escalating climate change and all of its related problems, innovative solutions are needed through the whole range of energy related technologies. In its specific field, smart windows devices stand out for their ability to reduce energy consumption and CO₂ emissions by controlling dynamically the light and heat transmittance in buildings. In this context, nanostructured TiO₂ crystals (NCs) emerge as a versatile platform because of its excellent energy conversion and electrochromic properties.

In our group, one of the research lines exploits the aliovalent doping of the nanostructured TiO₂ crystals to improve their electrical conductivity, specific capacitance and their ability to modulate optical transmittance further and in a more selective manner: in previous works V- and Nb-doped TiO₂ nanocrystals have already been successfully synthetized and deeply characterized to unveil the role of the dopants^1,2.

In my contribution, I will present the results coming from the synthesis and in situ characterization of the TiO₂ nanocrystals doped with W: the amount of doping (10%) is based on previous studies where the optimization of the localized surface plasmon resonance (LSPR) properties was addressed3. The successful synthesis was proved by Raman microscopy and XRD, which confirmed the presence of the anatase phase and effective W-doping. An UV-VIS-NIR absorption spectrum showed that the LSPR absorption mechanism is present in NIR region for these NCs. NCs thin films were prepared by doctor blading an organic viscous and then calcinating it. The morphology of the films is characterized by FESEM and also TEM images were taken, from which is clear that the NCs have an average diameter of 5nm.

The electrochemical properties were tested through a set of cyclic voltammetries at different scan rates from which it is evident a change in the current shape of the redox pair and an increase in the charge capacitance of the W doped TiO₂ NCs, resulting in an improvement of the electrochemical behavior.

The spectroelectrochemical behavior was tested through UV-VIS absorption measurements at different applied voltages: the LSPR and plasmonic light absorbing mechanisms characteristic of this W doping are revealed, resulting in a partial filtration of the light spectrum. This suggests its potential in smart windows applications.

Finally, a deep in situ analysis comprehending x-ray absorption spectroscopy (XAS), x-ray photoemission spectroscopy (XPS) spectro-electrochemistry (SEC) electrochemical impedance spectroscopy (EIS) techniques have been used to characterize the real-time electronic and structural changes during operation allowing to give insights into the electrochemical reaction mechanisms.