Construction of Fully Integrated and Energy Self-Sufficient NO2 Gas Sensors Utilizing Zinc-Air Batteries.

Abstract

Exploration of novel self-powered gas sensors free of external energy supply restrictions, such as light illumination and mechanical vibration, for flexible and wearable applications is in urgent need. Herein, this work constructs a flexible and self-powered NO2 gas sensor based on zinc-air batteries (ZABs) with the cathode of the ZABs also acting as the gas-sensitive layer. Furthermore, the SiO2 coating film, serving as a hydrophobic layer, increases the three-phase interfaces for the NO2 reduction reaction. The constructed sensors exhibit a high sensing response (0.3 V @ 5 ppm), an ultralow detection limit (61 ppb), a fast sensing process (129 and 103 s), and excellent selectivity. Moreover, the sensors also possess a wide working temperature range and a low working temperature tolerance (0.34 V at -15 °C). Simulations indicate that the hydrophobic surface at the cathode-hydrogel interface will accommodate more NO2 gas molecules at the reaction sites and prevent the influence of inner water evaporation and direct dissolution of NO2 in the electrolyte, which is beneficial to the enhanced gas sensing abilities. Finally, the self-powered sensing device is incorporated into a smart sensing system for practical applications. This work will pave a new insight into the construction of integrated and energy self-sufficient smart gas sensing systems.