Spectroscopical Study on Electron Storage in Nano-Sized Tungsten Oxide

Dark photocatalysis is a promising technology for fuel production, which combines light harvesting properties with energy storing materials. The system involved would both work as a photocatalyst and rechargeable solar battery under illumination, so that electrons released during the discharge could be exploited for ‘dark’ reactions, <i>e.g.</i> CO₂ reduction reaction (CO₂RR) and hydrogen evolution reaction (HER). Thus, it also implies the investigation of materials capable of storing electrons for hours [1]. Tungsten(III) oxide (WO₃) has drawn interest owing to its ability of trapping electrons through intercalation of positive ions, accommodating negative charges at W centres [2], and being utilised for prolonged anti-corrosion activity in the dark (<i>i.e.</i> photocathodic protection) [3].<br/>In the work herein presented we investigated the potential use of WO₃ nanoparticles for dark photocatalytic CO₂RR by means of photo-doping process. We analyzed the charge storing properties of the WO₃ colloidal nanoparticles via UV-VIS-NIR spectroscopy, by monitoring absorption changes under illumination. The increase of the LSPR peak and the blue shift of the band gap due to the Moss-Burstein effect indicate that WO₃ undergoes electron accumulation, similar to what has already been reported for indium tin oxide (ITO) and other metal oxide nanocrystals (MO NCs) [4]. The results obtained in our study suggest that these materials can be valid candidates for next generation of photocatalytic systems.<br/><br/>[1] Rogolino and Savateev, <i>Adv. Funct. Mater</i> <b>2023</b> 2305028<br/>[2] Ng et al., <i>Phys. Chem. Chem. Phys</i> <b>2011</b> 13 13421-13426<br/>[3] Zhou et al., <i>Corros. Sci.</i> <b>2009</b> 51 1386-1391<br/>[4] Ghini <i>et al.</i>, <i>Nanoscale </i><b>2021</b> 19 8773-8783