Polyethylene Oxide–Sodium Titanate Composite: A Highly Selective Humidity Sensing Material With Wide Detection Range and Low Hysteresis, and Its Sensing Mechanism

Developing highly-selective humidity sensors with a wide detection range and negligible hysteresis remains a critical challenge for practical implementations. In this study, the polyethylene oxide-sodium titanate (PEO-NTO) composite is proposed as an excellent humidity-sensing material. We demonstrate that the surface modification of PEO and the hierarchically structure of NTO synergistically promote water molecules adsorption/desorption, resulting in a wide detection range (3%-98% RH) and significantly reduced hysteresis (from 10.8% RH for pure NTO to 1.2% RH for PEO-NTO). PEO also acts as a filtration layer that prevents the adsorption of common interfering gases such as NO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>, ensuring an improved selectivity and long-term stability (over 60 days). Moreover, the underlying sensing mechanism is systematically examined through electrochemical impedance analysis. A transition from water-adsorption-induced charge transfer mechanism to proton-conduction mechanism is observed for PEO-NTO composite with the increase of RH. Finally, PEO-NTO is applied for non-contact humidity detection and respiration mode monitoring.