▎ 摘　　要

This study aimed to develop highly-sensitive and flexible humidity sensors based on graphitic carbon nitride doped lithium chloride to form sheet-like Li-C3N4 on porous graphene electrodes. Using a large specific surface area as sensing composites, the synthesized Li-C3N4 composites could greatly improve the sensitivity of humidity sensors. The porous graphene was induced on the polyimide film using an ultraviolet laser combined with farinfrared irradiation as a flexible electrode. The Li-C3N4 sensing composites drop-cast on the porous graphene surface formed the Li-C3N4/graphene nanosheets. Surface morphology, structure analysis, and elemental composition of Li-C3N4 and porous graphene were analyzed. Li-C3N4-based humidity sensors showed an outstanding sensing performance in a wide measuring range of 11-97% relative humidity (RH), with small humidity hysteresis (RH of 2.4%), rapid response and short recovery times (4.1 s and 18.7 s, respectively), high response (99.68%), and response stability. Based on the Li-C3N4 humidity sensor with a high sensitivity, the proposed flexible sensors were applied for human breath sensing, skin humidity sensing, and non-contact sensing of a fingertip.