Microgram-Level Ta₄C₃ Nanosheets Decorated with NiWO₄ Nanoparticles as a High-Performance Humidity Sensor

Rapid and accurate detection capability, miniaturization, and nondirect contact are the research hotspots for the next generation of functional sensing devices. In this study, for the first time, nanoscopic accordion-like Ta₄C₃ MXene nanosheets were used as a sensitive material in a humidity sensor, achieving ultralow load, high response, and rapid response/recovery times performance. Experimental results show that Ta₄C₃ MXene nanosheets have an extremely large specific surface area and excellent conductivity. The first-principles calculations indicate that Ta₄C₃ MXene nanosheets have a strong adsorption capacity for water molecules, which is the key to the excellent performance of the Ta₄C₃ MXene-based humidity sensor. In addition, NiWO₄ nanoparticles were grown on the surface of Ta₄C₃ MXene nanosheets to address the challenges of long recovery time and poor linear correspondence typically associated with MXene-like materials in humidity sensors. The humidity sensor prepared using NiWO₄-Ta₄C₃ achieved an ultrahigh response (1.5 × 10⁵), a rapid response (2.6 s) and recovery time (1.7 s), and high stability. Moreover, this humidity sensor can be applied to human breath detection, noncontact sensing, as well as early diagnosis and prediction of human diseases. Furthermore, the humidity sensor can utilize the photothermal effect of the material to remove difficult-to-desorb water molecules by simple illumination, restoring it to its initial working state. This study expands the new application of Ta₄C₃ MXene nanosheets in humidity sensors for the first time.