Amorphous Ag catalytic layer-SnO2 sensitive layer-graphite carbon nitride electron supply layer synergy-enhanced hydrogen gas sensor

Achieving high sensitivity and rapid detection of hydrogen is crucial for effectively preventing thermal runaway accidents in batteries. In this study, a novel sandwich-structured hydrogen gas sensor has been developed, comprising a catalytic sensitization layer (Ag nanoparticles), a gas-sensitive layer (SnO2), and an electron supply layer (g-C3N4), denoted as catalytic sensitization layer-sensitive layer-electron supply layer (CSE). The CSE sandwich structure sensor exhibits optimal gas sensing performance, such as short response/recovery time (3 s/4 s), a low detection limit (30 ppb), outstanding selectivity and excellent long-term stability at 300°C. The variable-temperature HRTEM reveals that the Ag nanoparticles are in an amorphous state at this temperature, possessing abundant crystal defects and higher reactivity compared to the crystalline state. This amorphous state provides numerous active sites for gas adsorption and redox reactions. Additionally, compared to sensors fabricated with other materials, the CSE sandwich gas sensor exhibits the highest response values, attributed to the synergy-enhanced effect arising from three distinct functional layers. The outstanding selectivity of the CSE gas sensor towards H2 is attributed to its highest adsorption energy and significant hybridization between H2 electronic orbitals and SnO2, as revealed by first-principles-based adsorption models and density of states analysis, respectively. In summary, the CSE gas sensor holds the potential to forecast occurrences of thermal runaway in batteries. Simultaneously, it paves the way for innovative research on gas sensors within various functional layers.