Pd Nanoislands-Modified ZnO Nanowire-Network for Sensitive and Linear Hydrogen Sensing

To facilitate the safety use of hydrogen fuel in aerospace applications and in hydrogen fuel cell vehicles, there is a high demand for hydrogen sensing technology with both merits of high sensitivity and high linearity. However, it is hard to integrate these two advantages together in just one device. Here, we designed and developed a hydrogen-sensitive Pd nanoislands-modified ZnO nanowire-network structure (Pd-ZnO nanoisland structure) for sensitive and linear hydrogen sensing. By optimizing the size-to-gap ratio of Pd nanoislands, we enhanced the response of the Pd-ZnO nanoisland structure sensor (Pd-ZnO sensor) more than 12 times larger than that of the pure ZnO nanowire-network sensor (without Pd nanoislands), and decreased its limit of detection down to 100 ppb at 150 °C low temperature. On the premise of high sensitivity, the sensor also has a remarkable sensing linearity (R² >0.9969) in the whole detecting range and the full operating temperature range as designed. The high sensitivity together with high linearity can maximize the signal-to-noise ratio and facilitate the calibration of sensors. For example, only single calibration at a specific concentration can meet the sensing of Pd-ZnO sensors in whole concentration range. This study of utilizing noble metal nanoislands modifying metal oxide semiconductors provides an opportunity for hydrogen sensors with high sensitivity and high linearity integrated in one device.