Self-Powered Electrochemical Humidity Sensor Based on Hydroxylated Multi-Walled Carbon Nanotubes-Modified CeO2 Nanoparticles

Electrochemical humidity (ECH) sensors with self-generating capability have attracted widespread attention. In this work, a self-powered ECH sensor is developed using hydroxylated multi-walled carbon nanotubes (OH-MWCNTs)-modified CeO2 nanoparticles as the humidity sensing materials. The results show that the OH-MWCNTs are beneficial for improving the humidity sensing performances of the CeO2 nanoparticles. The optimized OH-MWCNTs/CeO2 ECH sensor exhibits a wide detection range (0–91.5% relative humidity (RH)) and fast response and recovery times (18.6 and 6.9 s), attributed to the synergistic effect of OH-MWCNTs and CeO2 nanoparticles. In addition, a single OH-MWCNTs/CeO2 ECH sensor can output a voltage of 0.711 V and a load power of 0.376 μW at 91.5% RH. When applied for respiratory rate monitoring, the OH-MWCNTs/CeO2 ECH sensor can accurately detect respiratory rate by converting exhaled humidity into voltage signal. This work demonstrates that the OH-MWCNTs-modified oxide material of CeO2 nanoparticles is a good candidate for fabricating self-powered ECH sensor.