Platinum Nanostructure Tailoring for Fuel Cell Applications Using Levitated Water Droplets as Green Chemical Reactors

Abstract

Tailoring of nanostructured materials with well-controlled morphologies and their integration into valuable applications in a facile, cheap, and green way remain a key challenge. Herein, platinum nanoparticles as well as Pt–polymer nanocomposites with unique shapes, including flower-, needle-, porous-, and worm-like structures, were synthesized and simultaneously deposited on a three-dimensional carbon substrate and carbon nanofibers in one step using a levitated, overheated water drop as a green, rotating chemical reactor. Sprinkling of a metal aqueous solution on a hot surface results in its sudden evaporation and creates an overheated zone along with the water self-ionization (i.e., charge separation) at the hot interface. These generated Leidenfrost conditions are believed to induce a series of chemical reactions involving the used solvent and counterions, resulting in the nanoparticles formation. Besides, the in situ generated basic conditions in the vicinity of the liquid–vapor interface due to the loss of hydronium ions into the vapor layer could also play a role in the mechanism of the nanoparticles formation, e.g., by discharging. The as-prepared Pt nanostructures exhibited a superior catalytic activity and stability toward the desired direct formic acid oxidation (essential anodic reaction in fuel cells) into CO2 without generating CO poisoning intermediates compared to the state-of-the-art commercial PtC electrode. The addressed nanotailoring technique is believed to be a promising, inexpensive, and scalable way for the sustainable manufacture of well-designed nanomaterials for future applications.

Conformal Solution Deposition of Pt-Pd Titania Nanocomposite Coatings for Light-Assisted Formic Acid Electro-Oxidation

“…Our catalyst also compares favorably to related nanostructured catalyst designs (see Table S1) both in the absence and presence of illumination. 3,4,[6][7][8][9]16,32,58 Additionally, the I direct /I backward ratio increased from 0.3 in the absence of light to 0.98 in the presence of light (3.2-fold). The improvements upon illumination are attributed to the photocatalytic activity of the TiO 2 nanospike support.…”

“…The Pt-Pd@CF and Pt-Pd-TiO 2 @CF electrodes as well as the commercial Pt-C (Figure S10A) exhibited the typical CV of a clean polycrystalline Pt surface and showed well-defined peaks for hydrogen adsorption/desorption (between −0.2 and 0.2 V) and a broad Pt oxidation peak (between 0.6 and 1.2 V), which is coupled with a reduction peak around 0.4 V, and increased in intensity under illumination. 3,[7][8][9]16,32,58 The ECSA of these electrodes was estimated using the associated charge of the hydrogen desorption peak using the standard value 0.21 mC/cm 2 . 2,18 Interestingly, the Pt-Pd-TiO 2 @CF electrode (ECSA, ∼6.38 m 2 ) showed a 7.5 times higher Pt surface compared to the Pt-Pd@CF electrode (ECSA, ∼0.85 m 2 ), highlighting the essential role of the strongly roughened TiO 2 layer in decreasing the average particles size of the deposited Pt particles together with improving their distribution and increasing the overall number of active surface sites.…”

Metal-to-Semimetal Transition in Platinum Nanotubes: Dependence on Thickness

“…1 However, for Pt nanoparticles (NPs), only a few studies have been published, 2−4 and the characterization of Pt nanostructures for solar cells, photo-or electro-catalysts, and semiconductor devices has rarely been reported. 5,6 Few studies of the changes in electrical resistivity as a function of nanosize in metal nanostructures such as NPs and NTs have been reported.…”

“…Finite-size effects on the electrical resistivity of metallic thin films or nanowires have been a topic of research for several decades from both fundamental and applied approaches . However, for Pt nanoparticles (NPs), only a few studies have been published, − and the characterization of Pt nanostructures for solar cells, photo- or electro-catalysts, and semiconductor devices has rarely been reported. , Few studies of the changes in electrical resistivity as a function of nanosize in metal nanostructures such as NPs and NTs have been reported.…”

Polyelectrolyte-Induced Stereoassembly of Grain Boundary-Enriched Platinum Nanoworms on Ti3C2Tx MXene Nanosheets for Efficient Methanol Oxidation

“…On the other hand, it is generally accepted that 0D Pt NP electrocatalysts are vulnerable to various structural evolutions including aggregation and dissolution in the electrocatalytic processes, which should be ascribed to the relatively small contact area between particle and matrix. In view of this point, one-dimensional (1D) Pt nanocrystals, such as Pt nanowire, , Pt nanotube, , Pt nanoneedle, , and Pt nanorod, , have become a hot topic owing to the more stable configuration arising from their larger areas interacting with the supporting materials. Besides, 1D Pt catalysts commonly possess higher aspect ratios, better flexibility, and more abundant grain boundaries in comparison with 0D Pt NPs, which are very beneficial to expose more catalytically active centers and thereby exert their unique methanol oxidation functions. , Nonetheless, up to now, the facile synthesis of 1D noble-metal nanocrystal catalysts on 2D MXene nanosheets still remains a great challenge in this emerging field.…”