High-Performance Humidity Sensor Based on Urchin-Like Composite of Ti₃C₂ MXene-Derived TiO₂ Nanowires

Humidity sensors have broad applications in health monitoring, environmental protection and human-machine interface, and robotics. Here, we developed a humidity sensor using alkali oxidation method to grow in situ TiO₂ nanowires on two-dimensional Ti₃C₂ MXene. With an order of magnitude larger surface area compared to pure Ti₃C₂ or TiO₂ materials, the urchin-like Ti₃C₂/TiO₂ composite demonstrates a record high sensitivity in a low relative humidity (RH) environment (∼280 pF/% RH from 7% RH to 33% RH). Complex impedance spectroscopy and Schottky junction theory were employed to understand the underlying sensing mechanisms of the Ti₃C₂/TiO₂ composite under various humidity conditions. We demonstrate the application of humidity sensors made with the Ti₃C₂/TiO₂ composite for noncontact detection of the presence of various liquids as well as human fingers.