Photocatalytic, electrochemical, and electrochromic properties of in situ Ag-decorated WO3 nanocuboids synthesized via facile hydrothermal method

Tungsten trioxide (WO3) has been considered for various applications from electronic devices, sensors to antibacterial. Recently, modifying WO3 nanostructures with silver or silver’s compounds has been proved to be an effective route to not only improve the light absorption but also reduce the recombination rate of photogenerated carriers in modified WO3 samples which can further improve and broaden the applicability of WO3. Herein, in situ Ag decorated WO3 nanocuboids were prepared via a facile hydrothermal method using tungstite (WO3·H2O) and silver nitrate (AgNO3) as precursors. The maximum Ag amount that could be in situ decorated on WO3 nanostructures is approximately 6.0 wt.%. The in situ Ag decoration caused the change in both morphology, crystal structure, and optical properties of samples. Pristine sample WO3 had uniform morphology of nanocuboids with single monoclinic crystal structure, while Ag-decorated samples had mixture morphology of nanocuboid and nanobundle with multiphase crystal structure of monoclinic and hexagonal phases. The optical bandgap of Ag-decorated sample abnormally increased with the Ag content due to the appearance of hexagonal structure in nanocomposite sample. The Ag decoration further helps improve photocatalytic, electrochemical, and electrochromic properties of the platform material WO3. The 5 wt.% Ag-decorated sample exhibited the highest methylene blue removal performance of 34% under visible light irradiation, which was enhanced to 85% when using 100 µL H2O2. All Ag-decorated samples showed enhanced electrochemical properties in comparison with pristine sample, particularly, a higher exchanged charge density, ten-time higher Li-ion diffusion coefficient, and more stability. Sample decorated with 15 wt.% Ag exhibited the highest exchange charge density and highest Li-ion diffusion coefficient, while sample decorated with 10 wt.% Ag showed the best stability. The 10wt.% decorated sample also manifested the highest EC properties with an optical modulation of 17%, an optical density of 0.11, and a coloring and bleaching time of 2.6 and 3.9 s at 800 nm, respectively. These results implied a method to manipulate the phase transformation and phase junction in WO3-based nanocomposite.