Hierarchically porous PdO-functionalized SnO₂ nano-architectures for exclusively selective, sensitive, and fast detection of exhaled hydrogen

Approximately one in 10 people worldwide suffer from irritable bowel syndrome (IBS). Thus, early diagnosis and simple monitoring of chronic diseases will help to improve the patient's quality of life. Herein, we report a chemiresistive-type gas sensor for exhaled hydrogen detection that was fabricated by combining hierarchically porous SnO₂ nano-architectures and PdO. The unique structured PdO-functionalized SnO₂ hydrogen sensor exhibited excellent selectivity (response ratio > 5.2), high response (resistance ratio = 6.3), extremely fast sensing kinetics (response speed: 4.0 s and recovery period: 36.2 s), and low detection limit (0.096 ppm) under high humidity (relative humidity 80%). These exceptional sensing properties toward hydrogen were investigated from multiple perspectives, including effective gas diffusion through multimodal pores, changes in charge-carrier concentration in p-n heterojunctions, and the catalytic effect of PdO. The proposed sensor has a high potential for practical high-performance hydrogen sensor applications and will offer new possibilities for a simple disease diagnosis based on breath analysis.