Enhancement of Platinum Mass Activity on the Surface of Polymer-wrapped Carbon Nanotube-Based Fuel Cell Electrocatalysts

Abstract

Cost reduction and improved durability are the two major targets for accelerating the commercialization of polymer electrolyte membrane fuel cells (PEFCs). To achieve these goals, the development of a novel method to fabricate platinum (Pt)-based electrocatalysts with a high mass activity, deposited on durable conductive support materials, is necessary. In this study, we describe a facile approach to grow homogeneously dispersed Pt nanoparticles (Pt) with a narrow diameter distribution in a highly controllable fashion on polymer-wrapped carbon nanotubes (CNTs). A PEFC cell employing a composite with the smallest Pt nanoparticle size (2.3 nm diameter) exhibited a ~8 times higher mass activity compared to a cell containing Pt with a 3.7 nm diameter. This is the first example of the diamter control of Pt on polymer-wrapped carbon supporting materials, and the study opens the door for the development of a future-generation of PEFCs using a minimal amount of Pt.

Homogeneous coating of ionomer on electrocatalyst assisted by polybenzimidazole as an adhesive layer and its effect on fuel cell performance

“…For the MWNT/PyPBI/Pt (Fig. 3a), the peaks due to the N 1s at~400 eV derived from the imidazole in the PyPBI [22] and Pt 4f at around 72e75 eV were observed. Importantly, new peaks at~689 and 168 eV due to the F 1s and S 2p , respectively [43], were observed after the washing, suggesting successful coating of Nafion on the MWNT/ PyPBI/Pt to provide an ionomer-coated electrocatalyst (MWNT/ PyPBI/Pt-i), On the other hand, both the F 1s and S 2p peaks were not detected from the ox-MWNT/Pt after washing ( Fig.…”

NaOH‐Aided Platinum Nanoparticle Size Regulation on Polybenzimidazole‐Wrapped Carbon Nanotubes for Use as Non‐Humidified Polymer Electrolyte Fuel Cell Catalyst

“…It is clear that uniform Pt‐NPs are homogeneously dispersed on the MWNT/PyPBI as a result of the strong chelating effect of the Pt ion by PyPBI . In the absence of NaOH, the Pt‐NPs size was 3.8±0.4 nm as we previously reported . On the other hand, it was found that the Pt‐NP size decreased with increasing amounts of NaOH; specifically, the Pt‐NP diameters were 3.1±0.3, 2.4±0.2, 2.2±0.2, 2.0±0.2, and 1.7±0.1 nm for the electrocatalysts synthesized with 0.5, 1.0, 2.0, 4.0, and 6.0 m m NaOH, respectively, which correspond to pH values of 4.4, 4.7, 6.2, 7.3, and 10.6, respectively (before the addition of NaOH, the pH was 3.9).…”

“…Thereby, use of a large amount of the electrocatalyst is needed to prepare a membrane electrode assembly (MEA) with a typical Pt loading (0.5–1.0 mg Pt cm −2 ). Thus, the catalyst layer becomes thicker compared with the commercial electrocatalyst containing a Pt loading of approximately 40 wt %, an effect that is a disadvantage in terms of mass transfer, suggesting the electrocatalyst is not suitable for real fuel cell applications …”

Facile Fabrication of Pt‐Ru Nanoparticles Immobilized on Reduced Graphene Oxide Support for the Electrooxidation of Methanol and Ethanol

“…The Pt‐utilization in fuel cell electrocatalysts is believed to be improved by reducing the particle size of platinum or by exploring various Pt‐based bimetallic structures including core – shell,textured Pt‐alloys with Pt‐skins on top of base metals, etc. For example, Hafeez et al have demonstrated that a hydrogen‐fed fuel cell incorporating Pt particles with a size of 2.3 nm as both anode and cathode exhibit an eight‐fold increased mass activity compared to a fuel cell constructed with Pt particles with a size of 3.7 nm as both anode and cathode . Further, homogeneous deposition of Pt‐based nanoparticles on to a suitable conductive carbon supports like carbon black (CB), carbon nanotubes, graphene oxide were also explored as a convenient way to enhance the Pt utilization .…”