Electrostatic spray deposition of chemochromic WO₃-Pd sensor for hydrogen leakage detection at room temperature

We demonstrate the chemochromic sensor, which is used to detect hydrogen leaks at room temperature. The structure of the sensor is fabricated via electrostatic spray deposition (ESD) of a solution of Pd and WO₃ nanoparticles. ESD enables the uniform distribution of Pd nanoparticles on WO₃, with droplets of sub-micron size being generated during the process. With 1% of hydrogen diluted in N₂, the optimized sensor shows a rapid color change at room temperature that can be recognized with the naked eye within 15 s. The sensor exhibits a deep blue color in the presence of hydrogen, and this change is quantified by a color difference value of 18.5 in 10 min. The developed sensor is reversible, implying that it can recover its original color when exposed to air, and its reversibility is maintained over 20 cycles. Moreover, the sensor exhibits long-term stability for 40 d. The sensor is also fabricated on adhesive tape, which enables it to demonstrate prompt color change at the hydrogen leakage site.