Reduced Graphene Oxide-Wrapped Palladium Nanowires Coated with a Layer of Zeolitic Imidazolate Framework-8 for Hydrogen Sensing

Abstract

Rapid and sensitive H2 detection is important because of its low threshold for the formation of explosive mixtures in air (∼4%). Palladium’s unique interactions with H2 make it particularly useful in room-temperature H2 sensing, but the formation of water by reaction with O2 at the Pd surface can interfere with sensor response. Here, we report H2 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 H2 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 H2 to reach them and H2O to diffuse away from them. The optimized sensors showed a response (relative change in resistance) to 1% H2 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 H2 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 H2 detection.

Palladium Nanosheet-Based Dual Gas Sensors for Sensitive Room-Temperature Hydrogen and Carbon Monoxide Detection

“…30 Pd often has a thin layer of oxide formed at its surface when present in air. 7 Thus, when CO comes in contact with the Pd surface, it may react with the −O atom adsorbed on the surface to form CO 2 . To check the reversible response of the sensor to CO, varying concentrations of CO were flowed through the microprobe station without purging with air first and later at 100 ppm for various time durations.…”

“…Pd is an effective oxidation catalyst, and it oxidizes CO into CO 2 at a low temperature . Pd often has a thin layer of oxide formed at its surface when present in air . Thus, when CO comes in contact with the Pd surface, it may react with the −O atom adsorbed on the surface to form CO 2 .…”

“…3,4 Pd nanomaterials are known to provide improved sensing performance compared to bulk Pd due to their increased surface area for H 2 interaction. Various morphologies of Pd have been studied to date, with most work being done on Pd nanoparticles 5 and Pd nanowires, 6,7 yielding some promising results. However two-dimensional Pd nanomaterials have rarely been considered.…”

“…Palladium (Pd) nanoparticles have been widely explored for a variety of sensing applications including hydrogen (H 2 ), volatile organic compounds, and biochemicals. , Pd can selectively absorb a large amount of H 2 to form hydride phases, PdH x , which leads to a change in its electrical and optical properties. , Pd nanomaterials are known to provide improved sensing performance compared to bulk Pd due to their increased surface area for H 2 interaction. Various morphologies of Pd have been studied to date, with most work being done on Pd nanoparticles and Pd nanowires, , yielding some promising results. However two-dimensional Pd nanomaterials have rarely been considered.…”

Pd Alloy Nanosheet Inks for Inkjet‐Printable H2 Sensors on Paper

“…The response time of the sensor was evaluated as the time required for the resistance to change from R 0 to R 0 +0.9Δ R max , and the recovery time was taken as the time required to return from R 0 +Δ R max to R 0 +0.1Δ R max . [ 50 ] Figure S7 (Supporting Information) compares response and recovery times of the PdMoY NS sensors on paper or on an IDE. The PdMoY NS on an IDE had response and recovery times of 60 and 72 s respectively, while the paper‐based sensor had response and recovery times of 73 and 40 s, respectively.…”