Temperature‐Activated Reverse Sensing Behavior of Pd Nanowire Hydrogen Sensors

Abstract

Hydrogen sensors built with individual palladium nanowires (Pd NWs) have been achieved by integrating Pd NWs across microelectromechanical system (MEMS) electrodes, followed by assembling and bonding them to a chip carrier platform. The sensing measurements reveal that the sensors with individual Pd NWs show reverse sensing behaviors between the temperature zones of (370-263 K) and (263-120 K).

Shape-controlled synthesis of palladium and copper superlattice nanowires for high-stability hydrogen sensors

“…However, when the temperature reached to 259.3 K, weak responses were detected even if 3% H 2 (v/v) was introduced. Accordingly, the temperature dependent resistance change (ΔR) plotted in Figure 5c indicates that the critical temperature where the sensing behavior is reversed occurs at ~259.4 K, which is much lower than the values observed in Pd NWs systems (287 K)5. Similarly, the sensors with NWs of random-gapped shapes were investigated, and the critical temperature in Figure 5d was obtained ~261 K (For detail, see Supplementary Figure S10), which is close to that of the screw-threaded shapes (~259.4 K).…”

“…To build hydrogen sensors with these new materials, inter-digitated electrodes (IDEs) were employed to integrate the PdCu NWs5. The sensor prototypes in Figure 5a were built with multiple NWs, in which PdCu NWs across the IDEs are randomly aligned and overlapped (Supplementary Figure S7).…”

“…The NWs were transferred by first sonicating the bundled NWs in alcohol and then dripping the suspension onto the electrodes arrays; the mounting of the IDE on a chip carrier platform was made by bonding the IDE to aluminum wires using a wire bonder (Kulicke & Soffa 4700). The sensing measurement routine was similar to our previous work5. The testing chamber consisted of a cryostat cooled with liquid nitrogen where the temperature was kept constant for 20 min using a temperature controller (Lake shore, Model 330), with a temperature stability of the order of ±0.2 K. In all cases, a mixed flow of Ar (99.999%) and H 2 (99.9999%) was used to fill the chamber and the H 2 concentration was controlled using gas flow controllers (MKS MASS-FLOW).…”

“…This behavior can be modified in NWs by the α - β phase transition of PdHx that causes their response to change to a percolation controlled one. Recently, temperature-dependence investigations5 within the 120–370 K range showed that at a failing certain critical temperature the sensing behavior changes from the typical bulk response, where the electrical resistance of the NWs increases, to the percolation-type behavior where the resistance decreases instead. Meanwhile, the α - β phase transition267 that occurs above hydrogen 1%–2% volume concentrations8, may reduce their stability and reproducibility.…”

An Ultrasensitive and Ultraselective Hydrogen Sensor Based on Defect‐Dominated Electron Scattering in Pt Nanowire Arrays

“…Palladium (Pd)‐based nanoresistors which are featured with low cost and simplicity have been extensively studied since Hughes and Schubert reported the detection of H 2 by Pd/Ni alloys in 1991 . Specifically, Pd is strongly affinitive to H 2 molecules and will absorb hydrogen to generate PdH x , while the resistivity of PdH x is proportional to x . The features guaranteed superior selectivity to hydrogen and quantitative monitoring of H 2 concentration through the resistance change .…”