Hydrogen safety demands highly sensitive H2 sensors with rapid response (< 30 s) to detect leakage at concentrations far below its explosion limit (40,000 ppm). Nanostructured materials based on palladium (Pd) and its alloys emerged as the most promising candidates that meet the standards set by the U.S. Department of Energy for hydrogen sensors. In this study, we are developing novel robust chemiresistive gas sensors employing single-crystalline mesoporous bimetallic alloys (s-meso PdM) nanocubes (NCs) on ordered mesoporous tin (IV) oxide (m-SnO2) for remote and distributed H2 sensors. We have selected Pd as a metal, an excellent hydrogen host, absorbing 900 times its own volume of H2 at STP, and m-SnO2 support as an n-type semiconductor, which enables readily and reversibly release of oxygen in the presence of gas molecules and its resistance changes before and after gas adsorption. Alloying Pd with copper (Cu) and cobalt (Co) significantly enhances its sensitivity, selectivity and structural stability, and promotes poisoning resistance. Unlike their nanoparticle counterparts, the ordered mesopores in the NCs yield large accessible surface areas and active sites, and facilitate rapid diffusion of gas molecules, while their single crystallinity ensures long-range structural coherence and enhances electron transport. Meanwhile, the porous SnO2 provides a high internal surface area for gas molecules, and the meso-channels embedded in SnO2 give pathways for the gas to pass in and out of the sensor, enhancing sensing performance. The sensor exhibits exceptional sensitivity (~ 5-35) toward extremely low concentrations of H2 (25-1000 ppm) with rapid response (< 10 s) and can detect low concentration of 100 ppm CO2. These metrics are far superior to previously reported Pd-based materials and underscore the structural advantages of our materials. Current efforts aim to elucidate their gas sensing mechanisms through detailed structural, chemical, electrical and optical characterizations. These insights will aid in developing guideposts for further improvements in these sensors and their broader utilization in a variety of applications.
Project is currently funded by: Industry Sponsored Research