High-Performance MEMS Gas Sensors Utilizing an N-CQD/NiCo2O4 Composite for H2S Detection and Concentration Regression Prediction

Abstract

Hydrogen sulfide (H₂S) poses significant risks in industrial settings due to its high toxicity and flammability, making its efficient detection crucial for operational safety. In this study, high-performance MEMS gas sensors based on a nitrogen-doped carbon quantum dot/nickel cobaltite (N-CQD/NiCo₂O₄) nanocomposite were developed, achieving highly sensitive H₂S detection. Characterization techniques such as XRD, XPS, SEM, and TEM confirmed the successful loading of N-CQDs onto the NiCo₂O₄ surface, leading to an increase in oxygen vacancy concentration. The sensor with NCQD/NCO-2 exhibited excellent H₂S selectivity, good repeatability, and long-term stability over 40 days. At low-temperature heating, the response to 1000 ppm H₂S was enhanced by a factor of 6.84, with a theoretical detection limit of 9.42 ppb. Beyond the material-level enhancement, this work integrates N-CQD-mediated surface/interfacial activation, a low-temperature-heated MEMS sensor array, and a lightweight temporal regression model for H₂S quantification. The DCG-Net model achieved accurate concentration prediction with an R² value of 0.9902 and was successfully deployed, offering a compact material–device–algorithm solution for intelligent H₂S monitoring.