Here, we report a Pd/PdOx sensing material that achieves 1-s detection of 4% H2 gas (i.e., the lower explosive limit concentration for H2) 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% H2, 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 H2 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.
The work at Wayne State University and the Pacific Northwest National Laboratory was supported by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, through Award # 78705. In addition, L. L. and X. G. acknowledge support from National Science Foundation under award CHE-1943737. L. Z. and S. W. L. acknowledge support from the National Natural Science Foundation of China (No. 22103047) and Hefei National Laboratory for Physical Sciences at the Microscale (No. KF2020107). We also thank Prof. Reg Penner at the University of California, Irvine, for his valuable suggestions.
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