Design and optimization of Co3O4 nanostructures for hydrogen sulfide sensing

Metal oxide semiconductors including cobalt oxide (Co 3 O 4 ) have emerged as a pivotal class of materials for high-performance gas-sensing applications due to their intrinsic chemical stability, tunable surface reactivity, and robustness under severe operating environments. Herein Co 3 O 4 thin films were fabricated via a scalable and cost-effective spray-coating process to evaluate their potential as active layers for hydrogen sulfide (H 2 S) detection. The resulting films exhibit a well-defined porous morphology and strong optical absorption, features that collectively enhance surface-gas interactions and charge transport dynamics. The optimized Co 3 O 4 sensors display an impressive and reproducible relative response of 17.59 toward H 2 S, along with rapid response and recovery times of 20 s and 120 s, respectively. Such performance metrics surpass many conventionally processed counterparts, underscoring the efficacy of the spray-coating approach in tailoring surface activity and microstructure. These findings position spray-deposited Co 3 O 4 thin films as promising candidates for next-generation, low-cost, and highly responsive H 2 S gas-sensing devices applicable in industrial safety and environmental monitoring.