Reduced Graphene Oxide-Wrapped Palladium Nanowires Coated With A Layer Of Zeolitic Imidazolate Framework-8 For Hydrogen Sensing

Rapid and sensitive H-2 detection is important because of its low threshold for the formation of explosive mixtures in air (similar to 4%). Palladium's unique interactions with H-2 make it particularly useful in room-temperature H-2 sensing, but the formation of water by reaction with O-2 at the Pd surface can interfere with sensor response. Here, we report H-2 sensors using networks of high aspect ratio and ultrathin reduced graphene oxide (rGO)-coated palladium nanowires (Pd NWs@rGO) with a coating of zeolite imidazole framework (ZIF-8) that serves as a nanofiltration layer. We first produced Pd NWs in high yield by a hydrothermal method, then sonicated them with GO and added a reducing agent to produce Pd NWs@rGO. Thin Pd NWs promote rapid response and high sensitivity, while rGO prevents the formation of additional conductive channels due to expansion of Pd NWs upon H-2 exposure, ensuring monotonic sensor response. The coating of ZIF-8 reduces the transport of molecules like oxygen and nitrogen to the Pd NWs while allowing H-2 to reach them and H2O to diffuse away from them. The optimized sensors showed a response (relative change in resistance) to 1% H-2 in air of up to 2%, with a response time of 5 s and a lower limit of detection of 20 ppm. Relative to previously reported Pd-based H-2 sensors with fast response, the Pd NWs@rGO@ZIF-8 nanocomposite-based device provides a low-cost, high-performance sensor solution for fuel-cell vehicles and similar applications that require both rapid and sensitive H-2 detection.