Surface defect passivation and charge redistribution synergistically enhance the room-temperature H2S gas sensing performance of Cs3Cu2I5-based sensors

Hydrogen sulfide (H 2 S) is a highly toxic gas, making its efficient and energy-saving detection at room temperature critical for industrial safety and environmental monitoring. In this work, a Cs 3 Cu 2 I 5 /TiO 2 composite was fabricated via in situ pyrolytic encapsulation. The composite exhibits high sensitivity (0.29 @1 ppm), rapid response (25 s), and excellent selectivity toward H 2 S at room temperature. Theoretical calculations reveal that incorporating TiO 2 narrows the bandgap from 2.260 eV to 1.296 eV, thereby enhancing carrier mobility. Furthermore, TiO 2 passivation elevates the formation energy of iodine vacancies from 4.11 eV to 6.60 eV, suppressing defect migration and improving chemical stability (decay <6.7 % over 15 days). Calculated adsorption energies confirm significantly stronger adsorption of H 2 S (−4.44 eV) on Cs 3 Cu 2 I 5 /TiO 2 compared to CO (−2.39 eV), CH 4 (−2.57 eV), SO 2 (−2.74 eV), and H 2 (−1.93 eV), consistent with experimental selectivity. To mitigate humidity interference, dynamic sensor signals were mapped into two-dimensional images using a Gramian Angular Summation Field (GASF) and processed via an AlexNet-based convolutional neural network. This approach achieves 97 % accuracy in interference elimination through time-series feature extraction. This study establishes a new paradigm for regulating electronic states, defects, and band structures in room-temperature gas sensors, advancing the development of intelligent sensing technologies.