Flower-like Palladium Nanoclusters Decorated Graphene Electrodes for Ultrasensitive and Flexible Hydrogen Gas Sensing

Abstract

Hydrogen (H 2 ) gas is used extensively in many industrial processes and is an essential fuel source in clean-energy transportations and power generation applications 1,2 . However, it is highly flammable and explosive at volume concentrations higher than ca. 4%. Therefore, hydrogen sensors that have high sensitivity, rapid response, and reversibility are required to detect and/or monitor minute hydrogen leakages in industrial applications 3,4 . In general, commercial hydrogen sensors composed of metal oxide (SnO 2 ) films meet these demand but require an operating temperature of over 200 °C, which increases the overall power consumption of the sensing device [5][6][7] . Palladium (Pd) is an attractive candidate to replace metal oxides, because H 2 molecules are selectively adsorbed onto the surface of Pd by dissociation into hydrogen atoms (H 2 → 2H), and diffused into the interstitial sites of Pd structure. As a result, the phase of Pd transfer a solid solution of Pd/H (α -phase) and a palladium hydride (β -phase), resulted in resistance changes at room temperature. However, materials based on Pd is susceptible to structural changes (such as vacancy and dislocation), which are increased during the phase transition of Pd (α to β ) that occurs at hydrogen concentration higher than 2%, causing have been known to collapse during the sensing reaction due to an irreversible phase change [8][9][10][11][12][13][14] . The shape control of metal nanostructure is important factor to enhance the activity and stability 15 . Numerous research have studied to improve the performance by change the nano-sized morphology such as nanocube 16 . Furthermore, the substrate for the introduction of these shape is also play a critical roles due to the improvement of the charge transport and stability of active materials.

One-step Synthesis of Ordered Pd@TiO2 Nanofibers Array Film as Outstanding NH3 Gas Sensor at Room Temperature

“…As we known, the Pd NPs on the surface of metal oxide material can form electronic sensitization mechanism, that is, oxygen molecules can rapidly dissociate and forming oxygen ions (O 2 − ) because of the catalyticaction of Pd NPs 27,31,33,34,36 . Not only that, the response of the pPTND3 sensor to the NH 3 is 1.43 at the concentration of 100 ppm, it illustrates that interaction between NH 3 molecules and oxygen ions happened with the presence of Pd.…”

Metallic nanoislands on graphene: a metamaterial for chemical, mechanical, optical, and biological applications

“…14,15,16,17,18 Crystallites of metal nucleate and grow directly on the surface of graphene, enabling the controlled growth of single crystals of metal and even complex geometries such as spheres, 19 rods, 20,21 or flower-like nanoparticles (Figure 2a). 15 While a wet chemical method allows some degree of control of the shapes of nanoparticles, along with the crystalline quality (Figure 2b), it also results in an uncontrolled distribution of metal on the surface of graphene. A random distribution of particles may not have deleterious effects on applications such as catalysis, but limits other applications (i.e., electronics and photonics) that require deterministic placement of nanoparticles.…”

“…In this example, the shapes of the nanoparticles and sensitivities to gases were determined by the growth time of the nanoparticles. 15 The sensitivity of these nanoisland-graphene composites is determined by nanoparticle surface area, which limits the chemical kinetics. Shorter reaction times lead to smaller particles with a higher surface area to volume ratio.…”

“…(a) Hydrogen gas sensing performance is depicted for palladium nanoflowers (reprinted with permission from reference 15 . Copyright © 2015, Nature Publishing Group) and (b) nanoislands (Reprinted with permission from reference 35 .…”

Electronic and Magnetic Properties of Two-dimensional Nanomaterials beyond Graphene and Their Gas Sensing Applications: Silicene, Germanene, and Boron Carbide

“…Functionalization of graphene with micro/nanomaterials has been proven to be an effective approach to further improve the sensing performances of the graphene thank to the diverse functionalities and synergistic effects in the composites. To this reason, various functional materials such as metals [224][225][226][267][268][269][270], metal oxides [214,227,228,239,271], CNTs [240], polymers [229-231, 241, 272, 273] have been incorporated into graphene structures. As we know from quantum mechanics, all information about a given system is contained in its wave function, Ψ .…”