Hydrogen sensing by wet-gasochromic coloring of PdCl2(aq)/WO3 and the role of hydrophilicity of tungsten oxide films

In this study, WO3/glass thin films were prepared by pulsed laser deposition (PLD) at 100 mTorr oxygen pressure and substrate temperatures of 25, 100, 200, 300 and 400 °C for gasochromic investigations. In the presence of H2, a wet-gasochromic switching with an edge-to-center coloring nature was observed when aqueous PdCl2 was used as hydrogen catalyst. A correlation between substrate temperature, hydrophilicity, palladium growth and gasochromic coloring of tungsten oxide films was observed and analyzed by Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscope (FE-SEM) and water contact angle measurement. Results showed that the samples made at 200 °C have the best gasochromic properties; coloring rate and deepness.