Large-Area Printed Oxide Film Sensors Enabling Ultrasensitive and Dual Electrical/Colorimetric Detection of Hydrogen at Room Temperature.

Commercial hydrogen (H 2 ) sensors operate at high temperatures, which increases power consumption and poses a safety risk owing to the flammable nature of H 2 . Here, a polymer-noble metal-metal oxide film is fabricated using the spin-coating and printing methods to realize a highly sensitive, low-voltage operation, wide-operating-concentration, and near-monoselective H 2 sensor at room temperature. The H 2 sensors with an optimized thickness of Pd nanoparticles and SnO 2 showed an extremely high response of 16,623 with a response time of 6 s and a recovery time of 5 s at room temperature and 2% H 2 . At the same time, printed flexible sensors demonstrate excellent sensitivity, with a response of 2300 at 2% H 2 . The excellent sensing performance at room temperature is due to the optimal SnO 2 thickness, corresponding to the Debye length and the oxygen and H 2 spillover caused by the optimized coverage of the Pd catalyst. Furthermore, multistructures of WO 3 and SnO 2 films are used to fabricate a new type of dual-signal sensor, which demonstrated simultaneous conductance and transmittance, i.e., color change. This work provides an effective strategy to develop robust, flexible, transparent, and long-lasting H 2 sensors through large-area printing processes based on polymer-metal-metal oxide nanostructures.