The Oxygen Reduction Performance of Pt Supported on the Hybrid of Porous Carbon Nanofibers and Carbon Black

Proton exchange membrane fuel cells (PEMFCs) represent an outstanding clean energy alternative for next-generation power sources. The PEMFC’s performance is mainly determined by the sluggish oxygen reduction reaction (ORR) that occurs in its cathode Therefore, the use of electrocatalysts with high electrocatalytic activity and stability for improving the ORR has been a vital direction for the commercialization of PEMFCs. In this article, porous carbon nanofibers (PCNFs) based on a polyacrylonitrile/polymethyl methacrylate (PAN/PMMA) precursor were fabricated by electrospinning followed by carbonization; then, the PCNFs were mixed together with carbon black (CB) in different mass ratios as a hybrid support for Pt nanoparticles. Pt nanoparticles were deposited on the hybrid support by the ethylene glycol reduction method, and the obtained series of Pt/(PCNF + CB) were used as the oxygen reduction electrocatalyst in the cathode. Their electrocatalytic properties, as well as those of Pt/C as a reference, were investigated by cyclic voltammetry scanning (CV) and linear sweep voltammetry (LSV). The results explained that Pt/(PCNF + CB) showed a higher electrochemical activity area and half-wave potential when the PCNF/CB mass ratio was 3/2 than that of commercial Pt/C. Furthermore, the half-wave potential of Pt/(PCNF + CB) only decreased by 4 mV, which was 86 mV lower than that of commercial Pt/C (90 mV) after 2000 ADT cycles, indicating that the incorporation of PCNFs to form a hybrid support could result in corrosion resistance.

Enhanced oxygen reduction and methanol oxidation reaction over self-assembled Pt-M (M = Co, Ni) nanoflowers

Herein, we introduce a facile approach to synthesize a unique class of Pt-M (M = Ni, Co) catalysts with a nanoflower structure for boosting both oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR). By controlling the surface-active agents, we modified the functional groups surrounding the Pt atoms, tuned the alloying of Pt and the transition metals Ni and Co, and prepared two different kinds of nanodendrites. Their successful synthesis depends on the selection and amount of surfactants (hexadecyltrimethylammonium bromide (CTAB), Polyvinylpyrrolidone (PVP)). Besides, by controlling reaction time, we also explored the forming procedures for Pt-Co globularia nanodendrite (Pt-Co GND) and Pt-Ni petalody nanodendrite (Pt-Ni PND). Our investigation highlights the importance of complex nanoarchitecture, which enables surface and interface modification to achieve excellent catalytic performance in fuel cell electrocatalysis. The characterization of the as-prepared catalysts reveals a high electrochemical surface area and mass activity (2041 mAmg_Pt^-1and 950 mAmg_Pt^-1 for Pt-Co GND and Pt-Ni PND, respectively, for ORR). Furthermore, Pt-Co GND showed a high MOR activity, with a mass activity value recorded at 1615 mAmg_Pt^-1 which is far superior to that for Pt/C. Moreover, both catalysts retain high activity after accelerated durability tests (ADTs). The electron transfer number was calculated by performing the rotating ring-disk electrode (RRDE) measurements. Due to abundant active sites of Pt, both Pt-Co GND and Pt-Ni PND exhibit a 4e^- pathway for ORR with electron transfer number of >3.95.

Controlled growth of silver nanoparticles on carbon fibers for reinforcement of both tensile and interfacial strength

We have developed an electro-chemical deposition approach to synthesize various structures of Ag NPs on carbon fibers. This improved both the tensile strength and the interfacial property as much as 57.2% and 27.2%, respectively.