Ultrafast metal oxide reduction at Pd/PdO2 interface enables one-second hydrogen gas detection under ambient conditions

Here, we report a Pd/PdOx sensing material that achieves 1-s detection of 4% H-2 gas (i.e., the lower explosive limit concentration for H-2) at room temperature in air. The Pd/PdOx material is a network of interconnected nanoscopic domains of Pd, PdO, and PdO2. Upon exposure to 4% H-2, PdO and PdO2 in the Pd/PdOx are immediately reduced to metallic Pd, generating over a > 90% drop in electrical resistance. The mechanistic study reveals that the Pd/PdO2 interface in Pd/PdOx is responsible for the ultrafast PdOx reduction. Metallic Pd at the Pd/PdO2 interface enables fast H-2 dissociation to adsorbed H atoms, significantly lowering the PdO2 reduction barrier. In addition, control experiments suggest that the interconnectivity of Pd, PdO, and PdO2 in our Pd/PdOx sensing material further facilitates the reduction of PdO, which would otherwise not occur. The 1-s response time of Pd/PdOx under ambient conditions makes it an excellent alarm for the timely detection of hydrogen gas leaks.