Selective hydrogen sensor with fast response/recovery time based on single ZnO/ZnAl2O4 nanowire

Abstract

Hydrogen represents a promising candidate for the replacement of fossil fuels, which have a massive impact on the environment [1]. However, the reliable detection of hydrogen leaks remains challenging due to its intrinsic properties, underscoring the need for solid-state, portable, selective sensors with fast response/recovery time and high response value, working at low operating temperatures. Core ZnO nanowires were synthesized using flame transport synthesis method and covered with Al2O3 layers using atomic layer deposition method [1]. Afterwards, the obtained nanostructures were annealed at 975 °C. The morphological, chemical and structural study revealed the formation of ZnO/ZnAl2O4 nanowires after thermal annealing. Using FIB/SEM, individual core/shell nanowires were integrated into gas sensing devices (Fig. 1a). Multiple devices based on single ZnO/ZnAl2O4 nanowire were tested to a series of gases (hydrogen, methane, ethanol, acetone, n-propanol, 2-butanol and ammonia) with concentration of 100 ppm at different operating temperatures from room temperature up to 150 °C [1]. In Fig. 1b are presented results for a sensor based on ZnO/ZnAl2O4 nanowire, which demonstrated hydrogen selectivity, achieving a maximum response of ~913 at 100 °C and decreased with the increase of operating temperature to ~33 at 150 °C. The response and recovery time to 100 ppm hydrogen at 100 °C were ~6 s and ~1 s, respectively.