Synthesis of Nanohole‐Structured Single‐Crystalline Platinum Nanosheets Using Surfactant‐Liquid‐Crystals and their Electrochemical Characterization

Abstract

Nanohole‐structured single‐crystalline Pt nanosheets have been synthesized by the borohydride reduction of Na2PtCl6 confined to the lyotropic liquid crystals (LLCs) of polyoxyethylene (20) sorbitan monooleate (Tween 80) with or without nonaethylene‐glycol (C12EO9). The Pt nanosheets of around 4–10 nm in central thickness and up to 500 nm or above in diameter have a number of hexagonal‐shaped nanoholes ∼1.8 nm wide. High‐resolution electron microscope images of the nanosheets showed atomic fringes with a spacing of 0.22 nm indicating that the nanosheets are crystallographically continuous through the nanoholed and non‐holed areas. The inner‐angle distributions for the hexagonal nanoholes indicate that the six sides of the nanoholes are walled with each two Pt (111), Pt (1${\bar {1}}$1) and Pt (010) planes. The formation mechanism of nanoholed Pt nanosheets is discussed on the basis of structural and compositional data for the resulting solids and their precursory LLCs, with the aid of similar nanohole growth observed for a Tween 80 free but oleic acid‐incorporated system. It is also demonstrated that the nanoholed Pt nanostructures loaded on carbon exhibit fairly high electrocatalytic activity for oxygen reduction reaction and a high performance as a cathode material for polymer‐electrolyte fuel cells, along with their extremely high thermostability revealed through the effect of electron‐irradiation.

Study on Platinum and Copper Nanosheets Alloys Supported on Mesoporous Titanium Dioxide Doped with Carbon Black as Electrocatalysts in PEM Fuel Cells

“…Figure 6a shows the EDX analysis of the Pt 5 Cu NS/CTiO 2 , the elements distribution well matches with the experiments ratio. Figure 6b shows the EDX analysis of Pt 5 Cu NS/C catalyst, as can be seen from the Figure 6b, the elements distribution also well matches with the experiments ratio. Figure 7 shows the CV curves of Pt 5 Cu nanosheets on carbon support or carbon doped mesoporous TiO 2 support and commercial Pt/C (J. Matthey, 50 wt%) in 0.5 M H 2 SO 4 at the scan rate of 50 mV s…”

“…The mesopores of TiO 2 are about 10 nm and the size dimensions of TiO 2 are about 350nm, which indicates that the carbon black can be doped into the mesoporous TiO 2 . In Figure 5a, it can be found that Pt 5 Cu nanosheets are well dispersed on the surface of the carbon doped TiO 2 . The doped carbon black may provide electrical conductivity to the catalysts.…”

“…Since the Pt 5 Cu nanosheets have the highest ECSA, Pt 5 Cu was used in the following experiments. Carbon and Figure 5a and Figure 5b show the SEM images of the loaded catalysts, from which it can be found that the Pt 5 Cu nanosheets are dispersed on the carbon doped mesoporous TiO 2 support or carbon support, respectively.…”

“…Through electrochemical characterization, the Pt 5 Cu nanosheets showed best hydrogen adsorption/desorption activity and highest electrochemical surface area (ECSA). Then the as-prepared Pt 5 Cu nanosheets were supported on the mesoporous TiO 2 doped with carbon black (C-TiO 2 ). Subsequently, also in accordance with the electrochemical characterization, the Pt 5 Cu NS/C-TiO 2 exhibited lower polarization loss and higher durability than that of the commercial Pt/C catalyst when it was used as the cathode catalyst in the PEM fuel cell.…”

Morphosynthesis of Nanostructured Gold Crystals by Utilizing Interstices in Periodically Arranged Silica Nanoparticles as a Flexible Reaction Field

“…It can be explained by the interstices in the template acting as a flexible reaction field to relax the strain due to structural mismatch between template and gold, which is analogous to morphosynthesis [17] utilizing reaction fields provided by gel matrices [18] and liquid crystals. [19] A single nanoparticle acts as a rigid template on the microscopic scale, while on the macroscopic scale periodically arranged nanoparticles can alter their interstitial nanospaces, as layered crystals accommodate guest species by changing their interlayer spaces. [20] Furthermore, the reduction process was found to be critical to the morphological and nanostructural variation of gold (Scheme 1).…”