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

Commercialhydrogen (H-2) sensors operate at high temperatures,which increases power consumption and poses a safety risk owing tothe flammable nature of H-2. Here, a polymer-noblemetal-metal oxide film is fabricated using the spin-coatingand 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 optimizedthickness of Pd nanoparticles and SnO2 showed an extremelyhigh response of 16,623 with a response time of 6 s and a recoverytime of 5 s at room temperature and 2% H-2. At the sametime, printed flexible sensors demonstrate excellent sensitivity,with a response of 2300 at 2% H-2. The excellent sensingperformance at room temperature is due to the optimal SnO2 thickness, corresponding to the Debye length and the oxygen andH(2) spillover caused by the optimized coverage of the Pdcatalyst. Furthermore, multistructures of WO3 and SnO2 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 developrobust, flexible, transparent, and long-lasting H-2 sensorsthrough large-area printing processes based on polymer-metal-metaloxide nanostructures.