Skip to Main Content
 

Global Search Box

 
 
 
 

Files

File List


36600.pdf (6.19 MB)

ETD Abstract Container

Abstract Header

Boosting Reaction Kinetics of N2 Electrocatalysis via Adsorption Enhancement and Confinement of Adsorbates

Tian, Yujing
http://orcid.org/0000-0002-5755-8190
http://rave.ohiolink.edu/etdc/view?acc_num=ucin159239534417192

Abstract Details

2020, MS, University of Cincinnati, Engineering and Applied Science: Chemical Engineering.
The synthesis of ammonia (NH3) from artificial N2 fixation is extremely challenging due to the sluggish reaction kinetics associated with six proton-couple electron transfer steps.4 Currently, the industrial production of NH3 heavily relies on the Haber-Bosch process, which operates at high temperatures (300-550 degree C) and pressure (200-350 atm).1 Therefore, it is highly desired to develop an alternative process to synthesize NH3 with renewable energy sources under ambient conditions. Electrochemical synthesis of NH3 from N2 reduction reaction (NRR) using water as the proton source can potentially become a supplementary route to the Haber-Bosch process. The grand challenge of electrocatalytic NRR is to develop active and selective catalysts that yield NH3 at a rate of industrial relevance.2 The search of such catalysts is hindered by the slow reaction kinetics of electrocatalytic NRR under ambient conditions resulting from the high dissociation energy of N?N triple bond, low N2 solubility in water, and weak N2 adsorption on the catalyst surfaces.2 To overcome these limitations, here we demonstrate two strategies to boost reaction kinetics of N2 electrocatalysis. The first strategy is applying confinement of intermediates in blue TiO2 nanotube arrays to boost the reaction rate of nitrogen reduction. The space confinement effect of reactive intermediates in highly ordered blue TiO2 nanotubes (b-TiO2) encapsulating metal oxide can significantly enhance the electrocatalytic NRR activity and selectivity. The restricted local intermediates inside b-TiO2 nanotube can increase the surface coverage of reactive sites, thus promote the reaction rate of NH3 synthesis. Benefiting from confinement effect of intermediates, the b-TiO2 nanotubes encapsulating metal oxide catalysts show both higher production rate and Faradaic efficiency (FE) of NH3 than the combined ones of individual metal oxide and b-TiO2 electrodes. The second strategy focuses on improving N2 adsorption strength by incorporating boron into Ni/Fe metals in amorphous NiFeB nanoflowers. Recent research indicates that hypovalent boron species can mimic TMs (transition metals) with the electron's “acceptance - donation” process. Some studies reported that boron doping could enhance the NRR performance of graphene, in which boron can break the intrinsic equilibrium of graphene molecular orbitals and the positively charged boron is conducive to the adsorption of N2 to improve the NRR activity. A series of amorphous NiFeB nanoflowers were fabricated with varying atomic ratios of Ni/Fe by a facile chemical- reduction method. The increased catalytic activity of NiFeB nanoflowers can be ascribed to B enhanced N2 adsorption and abundant surface defects.
Jingjie Wu, Ph.D. (Committee Chair)
Joo-Youp Lee, Ph.D. (Committee Member)
Yujie Sun, Ph.D. (Committee Member)
77 p.
Chemical Engineering
nitrogen reduction reaction; TiO2 nanotube array; confinement effect; restricted intermediates; NiFeB nanoflowers; boost reaction kinetics

Recommended Citations

Citations

  • Tian, Y. (2020). Boosting Reaction Kinetics of N2 Electrocatalysis via Adsorption Enhancement and Confinement of Adsorbates [Master's thesis, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin159239534417192

    APA Style (7th edition)

  • Tian, Yujing. Boosting Reaction Kinetics of N2 Electrocatalysis via Adsorption Enhancement and Confinement of Adsorbates. 2020. University of Cincinnati, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin159239534417192.

    MLA Style (8th edition)

  • Tian, Yujing. "Boosting Reaction Kinetics of N2 Electrocatalysis via Adsorption Enhancement and Confinement of Adsorbates." Master's thesis, University of Cincinnati, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin159239534417192

    Chicago Manual of Style (17th edition)

ucin159239534417192
161
© 2020, all rights reserved.
This open access ETD is published by University of Cincinnati and OhioLINK.