Skip to main content
eScholarship
Open Access Publications from the University of California

Scholarly Works (4 results)

  • Thesis
  • Peer Reviewed
UCLA Electronic Theses and Dissertations (2018)

Proton exchange membrane fuel cells (PEMFCs) have been regarded as the most promising candidate for fuel cell vehicles and tools. Their broader adaption, however, has been impeded by cost and lifetime, as well as the inability to respond to fluctuations associated with operation conditions, fuel supply, and transient load. In this dissertation, a novel strategy to improve the performance and durability of PEMFCs for automotive application is purposed. Unlike the conventional hybrid strategies, which batteries or capacitors are always integrated with the fuel cell to achieve high fuel efficiency and high-power output, the novel fuel cell is integrated with energy-storage materials to form a hybrid device.

Tungsten oxide is proved to be a promising energy-storage material using in the PEMFC application, which has high chemical stability and excellent electrochemical performance in the fuel cell configuration. By integrating a thin layer of tungsten oxide (WO3) within the anodes, novel PEMFCs shows significantly enhanced power performance for transient operation, as well as improved durability against adverse operating conditions. Meanwhile, the enhanced power performance minimizes the use of auxiliary energy-storage systems and reduces costs.

In addition, the mechanisms of degradation of PEMFCs, as well as the working principles of WO3 in the hybrid cell are studied. The WO3 layer in the hybrid cell serves as a rapid-response hydrogen reservoir, oxygen scavenger, sensor for power demand, and regulator for hydrogen-disassociation reaction, effectively stabilize the anode potential and inhibit rising of the anode potential during the transient conditions.

    Cover page: Material and Device Design for Rapid Response and Long Lifetime Proton Exchange Membrane Fuel Cells (PEMFCs)
    • Article
    • Peer Reviewed
    UCLA Previously Published Works (2018)
    A low-cost and scalable method has been developed to synthesize Fe-decorated N-rich carbon electrocatalysts for the oxygen reduction reaction (ORR) based on pyrolysis of metal carbonyls containing metal-organic frameworks (MOFs). Such a method simultaneously optimizes the Fe-related active sites and the porous structure of the catalysts. Accordingly, the best-performing Fe-NC-900-M catalyst shows excellent ORR activity with a half-wave potential of 0.91 V vs. RHE, exceeding that of the 40% Pt/C catalyst in alkaline media. Furthermore, the zinc-air batteries constructed with Fe-NC-900-M as the cathode catalyst exhibit high open-circuit voltage (1.5 V) and peak power density (271 mW cm-2), and outperform most zinc-air batteries with noble-metal free ORR catalysts.
      Cover page: Iron-decorated nitrogen-rich carbons as efficient oxygen reduction electrocatalysts for Zn–air batteries
      • Article
      • Peer Reviewed
      UCLA Previously Published Works (2019)
      The application of graphene for electrochemical energy storage has received tremendous attention; however, challenges remain in synthesis and other aspects. Here we report the synthesis of high-quality, nitrogen-doped, mesoporous graphene particles through chemical vapor deposition with magnesium-oxide particles as the catalyst and template. Such particles possess excellent structural and electrochemical stability, electronic and ionic conductivity, enabling their use as high-performance anodes with high reversible capacity, outstanding rate performance (e.g., 1,138 mA h g-1 at 0.2 C or 440 mA h g-1 at 60 C with a mass loading of 1 mg cm-2), and excellent cycling stability (e.g., >99% capacity retention for 500 cycles at 2 C with a mass loading of 1 mg cm-2). Interestingly, thick electrodes could be fabricated with high areal capacity and current density (e.g., 6.1 mA h cm-2 at 0.9 mA cm-2), providing an intriguing class of materials for lithium-ion batteries with high energy and power performance.
        Cover page: High-quality mesoporous graphene particles as high-energy and fast-charging anodes for lithium-ion batteries
        • Article
        • Peer Reviewed
        UCLA Previously Published Works (2020)
        Proton exchange membrane fuel cells have been regarded as the most promising candidate for fuel cell vehicles and tools. Their broader adaption, however, has been impeded by cost and lifetime. By integrating a thin layer of tungsten oxide within the anode, which serves as a rapid-response hydrogen reservoir, oxygen scavenger, sensor for power demand, and regulator for hydrogen-disassociation reaction, we herein report proton exchange membrane fuel cells with significantly enhanced power performance for transient operation and low humidified conditions, as well as improved durability against adverse operating conditions. Meanwhile, the enhanced power performance minimizes the use of auxiliary energy-storage systems and reduces costs. Scale fabrication of such devices can be readily achieved based on the current fabrication techniques with negligible extra expense. This work provides proton exchange membrane fuel cells with enhanced power performance, improved durability, prolonged lifetime, and reduced cost for automotive and other applications.
          Cover page: Multi-functional anodes boost the transient power and durability of proton exchange membrane fuel cellsCreative Commons 'BY' version 4.0 license
          Top