Browsing by Subject "fuel cells"

Now showing 1 - 3 of 3
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    Atomic Structure Evolution of Pt–Co Binary Catalysts: Single Metal Sites versus Intermetallic Nanocrystals
    (Wiley, 2021-12) Li, Xing; He, Yanghua; Cheng, Shaobo; Li, Boyang; Zeng, Yachao; Xie, Zhenhua; Meng, Qingping; Qingping, Lu; Kisslinger, Kim; Tong, Xiao; Hwang, Sooyeon; Yao, Siyu; Li, Chenzhao; Qiao, Zhi; Shan, Chongxin; Zhu, Yimei; Xie, Jian; Wang, Guofeng; Wu, Gang; Su, Dong; Mechanical and Energy Engineering, School of Engineering and Technology
    Due to their exceptional catalytic properties for the oxygen reduction reaction (ORR) and other crucial electrochemical reactions, PtCo intermetallic nanoparticle (NP) and single atomic (SA) Pt metal site catalysts have received considerable attention. However, their formation mechanisms at the atomic level during high-temperature annealing processes remain elusive. Here, the thermally driven structure evolution of Pt–Co binary catalyst systems is investigated using advanced in situ electron microscopy, including PtCo intermetallic alloys and single Pt/Co metal sites. The pre-doping of CoN4 sites in carbon supports and the initial Pt NP sizes play essential roles in forming either Pt3Co intermetallics or single Pt/Co metal sites. Importantly, the initial Pt NP loadings against the carbon support are critical to whether alloying to L12-ordered Pt3Co NPs or atomizing to SA Pt sites at high temperatures. High Pt NP loadings (e.g., 20%) tend to lead to the formation of highly ordered Pt3Co intermetallic NPs with excellent activity and enhanced stability toward the ORR. In contrast, at a relatively low Pt loading (<6 wt%), the formation of single Pt sites in the form of PtC3N is thermodynamically favorable, in which a synergy between the PtC3N and the CoN4 sites could enhance the catalytic activity for the ORR, but showing insufficient stability.
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    Nitrogen-doped carbon nanotubes with encapsulated Fe nanoparticles as efficient oxygen reduction catalyst for alkaline membrane direct ethanol fuel cells
    (Elsevier, 2017-12) Rauf, Muhammad; Chen, Rongrong; Wang, Qiang; Wang, Yu-Cheng; Zhou, Zhi-You; Engineering Technology, School of Engineering and Technology
    Exploring low-cost and highly efficient non-precious metal electrocatalysts toward oxygen reduction reaction is crucial for the development of fuel cells. Herein, we report the synthesis of bamboo-like N-doped carbon nanotubes with encapsulated Fe-nanoparticles through high-temperature pyrolysis of multiple nitrogen complex consisting of benzoguanamine, cyanuric acid, and melamine. As-prepared catalyst exhibits high catalytic activity for oxygen reduction with onset potential of 1.10 V and half-wave potential of 0.93 V, as well as low H2O2 yield (<1%) in alkaline medium. The mass activity of the catalyst at 1.0 V (0.58 A g−1) can reach 43% of state-of-the-art commercial Pt/C. This catalyst also exhibits high durability and ethanol tolerance. When it was applied in alkaline membrane direct ethanol fuel cell, the peak power density could reach to 64 mW cm−2, indicating its attractive application prospect in fuel cells.
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    AN ONBOARD HYDROGEN GENERATION METHOD BASED ON HYDRIDES AND WATER RECOVERY FOR MICRO-FUEL CELLS
    (Office of the Vice Chancellor for Research, 2012-04-13) Edalatnoor, Arash; Qureshi, Mariam; Derry, Matthew D.; Ochung, John; Park, Cho Young; Zhu, Likun
    The purpose of this paper is to conduct experiments to generate hydrogen in a fuel cell by employing hydrides and water recovery methods. Micro-proton exchange membrane fuel cells are the next generation power source for micro-scale applications. The methods presented in the paper make use of the recycled water produced from the cathode reaction to develop high energy density micro fuel cells. The method for this experiment is accomplished by utilizing oxidation-reduction reactions that take place in the cell. These reactants must be constantly replenished through an external source. This paper will introduce the methods and procedures that permit a solution to the small-scale generation of fuel and water byproduct; this is accomplished by implementing a water recovery mechanism. The experiment commenced with designing and manufacturing a Nafion membrane and a fuel cell package. From then the calcium hydride and lithium aluminum hydride was loaded. These hydrides were given controlled amounts of water vapor and the amount of gas production was measured. After the amount of gas is measured, we are able to calculate the most efficient way to receive the greatest amount of hydrogen from the cell. The objective of our experiment is to achieve a higher energy density for micro-fuel cells. Our aim is that the results of our research will replace lithium ion batteries with a high energy density fuel cell that can increase longevity as a source, and is able to be used in multiple environments including pace makers and space exploration. Multidisciplinary Undergraduate Research Institute, CRL Programs