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Active-Site Study of N-Doped Carbon Nanotubes as Electrocatalyst for Oxygen Reduction Reaction in Fuel Cells

Xu, Zhengyu (2018) Active-Site Study of N-Doped Carbon Nanotubes as Electrocatalyst for Oxygen Reduction Reaction in Fuel Cells. Master's Thesis, University of Pittsburgh. (Unpublished)

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Abstract

Platinum (Pt) is the one of the most efficient electrode catalysts for oxygen reduction reaction (ORR) in fuel cells. However, its high-cost and low-storage properties inhibit it become the commercial catalyst for ORR. Heteroatom-doped carbon-based materials are widely applied to fuel cells as electrode catalyst due to the outstanding performance and low-cost feature. Among all of these materials, the efficiency of nitrogen-doped carbon nanomaterials has been improved increasingly in recent years. In nitrogen-doped carbon nanotubes (NCNTs), the N atoms which are doped in carbon matrix will bring electrons to the system as dopants, to promote the performance of ORR. In the thesis, we reported a specific study of nitrogen-doped carbon nanotubes as electrode catalysts in fuel cell. The NCNTs were obtained by a simple-step chemical vapor deposition (CVD) system. The successfully synthesized NCNTs with superior performance comparing to the other materials make us to evaluate the role of different types of nitrogen active site by X-ray photoelectron spectroscopy (XPS) and rotating ring-disk electrode test. Also, the surface morphology and structure of NCNTs forest was characterized by scanning electron microscope (SEM). The number of transferred electrons was calculated by Koutecky-Levich equation. Furthermore, density functional theory (DFT) was used to calculate the free energy of the pyridine nitrogen and graphitic nitrogen in a single carbon nanotube, respectively. Comparing the experimental data and the simulation results from DFT, we demonstrated that graphitic nitrogen are the most effective active sites for ORR in NCNTs. The nitrogen contents of products do not change if we increase the ratio of precursors and catalysts. The content of iron/oxygen in the product does not have influence on the ORR performance.

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Details

Item Type: University of Pittsburgh ETD
Status: Unpublished
Creators/Authors:
CreatorsEmailPitt UsernameORCID
Xu, ZhengyuZHX28@pitt.eduZHX28
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairLeu, Paulpleu@pitt.edupleu
Committee MemberJohnson, Karlkarlj@pitt.edukarlj
Committee MemberWilmer, ChristopherWILMER@pitt.eduWilmer
Date: 29 August 2018
Defense Date: 24 July 2018
Approval Date: 18 June 2019
Submission Date: 29 November 2018
Access Restriction: 5 year -- Restrict access to University of Pittsburgh for a period of 5 years.
Number of Pages: 65
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Chemical Engineering
Degree: MS - Master of Science
Thesis Type: Master's Thesis
Refereed: Yes
Uncontrolled Keywords: Nitrogen-doped carbon nanotubes, electro-catalyst, ORR, active site
Date Deposited: 18 Jun 2019 16:07
Last Modified: 18 Jun 2019 16:07
URI: http://d-scholarship.pitt.edu/id/eprint/35657

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