Search

The primary issue for the commercialization of proton exchange membrane fuel cells (PEMFCs) is the carbon corrosion of support and dissolution agglomeration of platinum nanoparticles under start-up/shut-down (SU/SD) conditions. Carbon nanotubes (CNTs)-supported Pt nanowire (PtNW) catalyst toward the ORR was synthesized via the soft template method. Electrochemical characterization demonstrated that the PtNW/CNTs showed higher activity than Pt/C because the anisotropy of the 1D structure strengthened its ability to transport electrons. An accelerated stressed test between 1.0 and 1.5 V for carbon corrosion was performed to examine durability at a single cell under practical SU/SD conditions. After 5000 cycles, the voltage drop was 0.142 V, and the voltage decay rate was 0.0284 mV cycle−1 for the PtNW/CNTs catalyst at 1600 mA cm−2; the voltage drop was 0.417 V, and the voltage decay rate was 0.0834 mV cycle−1 for the Pt/C catalyst at 1600 mA cm−2. The Pt/C catalyst demonstrated severe Pt nanoparticle aggregation and growth with a wide size distribution, whereas the PtNW/CNTs catalyst showed a slight variation. The PtNW/CNTs catalyst showed remarkable durability after 5000 SU/SD cycles. Consequently, PtNW/CNTs is a promising electrocatalyst, which can replace traditional Pt/C catalyst in PEMFCs. • PtNW/CNTs were synthesized using the soft template method with CNTs as support. • The start-up/shut-down event was analyzed and simulated with a measurable protocol. • The ORR activity and the electrochemical stability of the PtNW/CNTs catalyst were remarkably improved. • The PtNW/CNTs catalyst has better performance and life of single cell than the Pt/C catalyst. [ABSTRACT FROM AUTHOR] more...

The activity of catalyst could be enhanced by the temperature rising, so it is a suitable way to reduce the noble metal loading for the catalyst. However, the corrosion of carbon supports will be remarkable in the high temperature proton exchange membrane fuel cells (HT-PEMFC, >100 °C). This report demonstrated a novel Ti 3 C 2 T x and CNT hybrid material as the catalytic support, and Pt nanowires (Pt NWs) is loaded on the hybrid support to construct the catalyst for HT-PEMFC. The Pt NWs/Ti 3 C 2 T x -CNT performs higher electrochemical activity, better stability than that of commercial Pt/C. The mass activity and specific activity of Pt NWs/Ti 3 C 2 T x -CNT catalysts are 3.89 and 3.02 times as that of Pt/C, respectively. The power densities of HT-PEMFC showed 155.4 mW cm−2 and 182 mW cm−2 at 150 and 180 °C, respectively. • The mass activity of Pt NWs/Ti3C2Tx-CNT is 3.89 times as that of Pt/C. • The catalyst superior performance is mainly ascribed to the synergistic effect. • The peak power density based on Pt NWs/Ti3C2Tx-CNT achieves 182 mW cm-2 at 180 °C. [ABSTRACT FROM AUTHOR] more...

Abstract Improving cathode performance at a lower Pt loading is critical in commercial PEMFC applications. A novel Pt nanowire (Pt-NW) cathode was developed by in-situ growth of Pt nanowires in carbon matrix consisting Pt nanoparticles (Pt-NPs). Characterization of TEM and XRD shows that the pre-existing Pt-NPs from Pt/C affect Pt-NW morphology and crystallinity and Pt profile crossing the matrix thickness. The cathode with Pt-NP loading of 0.005 mg Pt-NP cm−2 and total cathode Pt loading of 0.205 mg Pt cm−2 has the specific current density of 89.56 A g Pt −1 at 0.9 V, which is about 110% higher than that of 42.58 A g Pt −1 of the commercial gas diffusion layer (GDE) with Pt loading of 0.40 mg cm−2. When cell voltage is below 0.48 V, the Pt-NW cathode has better performance than the commercial GDE. It is believed that the excellent performance of the Pt-NW cathode is attributed to Pt-NP induction, therefore producing unique Pt-NW structure and efficient Pt utilization. A Pt-NW growth mechanism was proposed that Pt precursor diffuses into the matrix consisting of pre-existent Pt-NPs by concentration driving, and Pt-NPs provide priority sites for platinum depositing at early stage and facilitate Pt-NW growth. Graphical abstract Pt nanoparticles in carbon matrix enhance growth, uniformity and profile of Pt-NWs, and the Pt-NW electrodes behave high performance. Image 1 Highlights • Pt nanoparticles in the carbon matrix improve uniformity and profile of Pt-NWs. • The novel cathode with 0.205 mg Pt cm−2 is comparable to commercial one. • A Pt-NW growth mechanism in the porous matrix is proposed. • This work provides a strategy for tailoring the electrode architectures. [ABSTRACT FROM AUTHOR] more...

Catalyst layers play an important role in direct methanol fuel cells (DMFCs), providing the reaction sites and catalysing the electrochemical reactions. For gas diffusion electrodes with Pt nanowires in-situ grown on gas diffusion layers (GDLs), the hydrophobic property of the GDL surface negatively affects the growth of the Pt nanowire catalysts, leading to the unsatisfied catalysis performance. In this work, the influence of active screen plasma (ASP) treatment temperature and duration on the growth of Pt nanowire catalyst layer was systemically studied. Single cell performance test with in-situ electrochemical surface area (ECSA) measurement were conducted to evaluate the catalysis performance of the Pt nanowire catalyst layer grown on the ASP treated carbon paper; scanning electron microscopy (SEM) was used to observe the surface morphology of the catalyst layer formed. Results revealed that the ASP treatment conducted at 120 °C for 10 min can effectively promote the growth of Pt nanowires on carbon paper gas diffusion layer, which exhibited the best catalysis performance. [ABSTRACT FROM AUTHOR] more...

A gradient Pt nanowire (Pt-NW) cathode with a promoted mass transfer and Pt utilization was developed by decal transfer method. The relationships of Pt loading and ionomer content with electrode performance were investigated by electrode structure characterization and testing in polymer electrolyte membrane fuel cell (PEMFC). The results show that an increasing Pt loading can improve the catalytic kinetic performance of Pt-NW electrode, but too higher a Pt loading leads to serious aggregation and thus low catalyst utilization. A similar trend was found to the ionomer content sprayed onto the Pt-NW cathode. The ionomer extends the triple-phase boundary (TPB), but excessive amount would cover part of the catalyst active sites and hinder the mass transfer. The optimal performance of the Pt-NW cathode is achieved at 0.30 mg Pt cm −2 and 33 wt% ionomer, where a maximum power density of 0.93 W cm −2 is obtained, which is better than the state-of-the-art commercial gas diffusion electrode (GDE) with 0.40 mg Pt cm −2 . [ABSTRACT FROM AUTHOR] more...

Abstract: The effects of ionomer contents were investigated in composite electrodes with in-situ grown single crystal Pt nanowires (Pt-NWs) for PEMFCs, including the amount in the carbon matrix and impregnated on the surface of the electrocatalyst layer. The electrocatalyst layer was prepared by growing Pt-NWs directly on the carbon matrix with a simple one-step wet chemical approach at room temperature. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), polarization curve tests, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) were employed to evaluate the ionomer effects. The experimental results showed that the ionomer in the carbon matrix had an influence on the ionic conductivity and aggregation and distribution of the Pt-NWs, and the ionomer impregnated on the surface of the electrocatalyst layer affected the mass transport and ionic conductivity. The performance of the MEA was improved by optimizing the ionomer contents. [Copyright &y& Elsevier] more...

Abstract: Pt-nanowire (Pt-NW) catalyst layers were prepared by in-situ growing Pt nanowires onto carbon matrix coated on electrolyte membrane surface and used as PEMFC cathodes. The performances of the catalyst layer with various catalyst loadings and carbon matrix thicknesses were evaluated. Scanning electron microscopy (SEM) was employed to observe the morphology and thickness of the Pt-NW catalyst layers, energy-dispersive X-ray spectroscopy (EDS) was used to investigate the Pt distribution along the layers. The polarization curve, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) were performed in fuel cells to check the practical electrochemical activity of the Pt-NW catalyst layers. The results showed that the electrochemical surface area (ECSA) and the cell performance exhibited a volcano-type curve with different Pt loadings, while the carbon matrix thickness had an influence on the Pt-NW gradient distribution, the mass diffusion, and the charge transfer in the electrodes. [Copyright &y& Elsevier] more...

Abstract: The effect of varying Nafion® ionomer loadings coated on the surface of gas diffusion electrodes (GDEs) with in-situ grown single crystal Pt nanowires and their durability in Proton Exchange Membrane Fuel Cells (PEMFCs) were investigated. GDEs were fabricated by growing Pt nanowires directly onto the Gas Diffusion Layer (GDL) surface with a simple one-step wet chemical approach at room temperature, as reported in our previous studies. The samples were then coated with various Nafion® ionomer loadings and tested as cathodes in a 25 cm2 PEMFC hardware with Hydrogen/Air. The data were compared to commercial GDEs (E-TEK ELAT® GDE LT 120E-W). Performance results showed that the as-prepared GDEs with Pt nanowires required higher Nafion® ionomer loading coating compared to the commercial ones. Accelerated ageing tests (500 cycles of voltage scan) were performed in views of evaluating the as-prepared GDE durability. The experimental data showed that the as-prepared GDEs exhibited much larger current densities at 0.7 V but higher degradation rates compared to commercial GDEs, indicating that the as-prepared GDEs gave poor durability. This was due to the difference in GDE surface nanostructures influenced by the electrolyte ionomer loading coating. This effect is further discussed in this paper. [Copyright &y& Elsevier] more...