Interfacial Design Strategies for Enhanced Nitrogen Reduction Electrocatalysis
Open Access
- Author:
- Maheshwari, Sharad
- Graduate Program:
- Chemical Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- November 06, 2020
- Committee Members:
- Michael John Janik, Dissertation Advisor/Co-Advisor
Michael John Janik, Committee Chair/Co-Chair
Scott Thomas Milner, Committee Member
Robert Rioux, Committee Member
Thomas E Mallouk, Outside Member
Ismaila Dabo, Outside Member
Phillip E Savage, Program Head/Chair - Keywords:
- Electrocatalysis
Density Functional Theory
Electrochemical Nitrogen Reduction
Interfacial Effects
Computational Catalysis
Electrokinetics - Abstract:
- With depleting fossil-based energy resources and the necessity of addressing the reality of climate change (which has never been clearer than recent times), there is an extreme need to develop alternatives to fossil-based energy. Electro-chemical devices such as fuel-cells and electrolyzers, utilizing renewably generated electricity, can provide one such alternative to reduce our dependence on fossil energy. The key component towards making these devices feasible is an economically viable electrocatalyst, suitable for the desired chemical transformation. In an electrochemical device, these chemical transformations take place at a complex interface of a catalyst (electrode) and an electrolyte. The chemical reaction taking place at this interface can now be altered not just by the catalyst but also by the composition and structure of the electrolyte-side of electrode/electrolyte interface. In this dissertation, computational modeling based on Density Functional Theory (DFT) is used to investigate how catalytic and interfacial properties can affect the elementary reaction energetics. Electrochemical nitrogen reduction (N2RR) to ammonia is specifically chosen for several of the studies in this dissertation because a distributed electro-chemical alternative to the current industrial process to produce ammonia, i.e. Haber Bosch process, could help generate ammonia efficiently and on-demand. A comprehensive review of DFT models used to study electrocatalytic systems is followed with in-depth analysis of how the model parameters and choices made to represent solvation and electrification for an electrocatalytic DFT calculation affect the calculated activation barrier for an elementary reaction. Elementary kinetics of the possible associative mechanisms for N2RR is investigated on iron (Fe) surfaces. Different strategies to alter the reaction energetics by altering the interfacial properties is investigated by functionalizing the catalytic surface with small amino acid chains and by altering the proton shuttling agent which can act as a co-catalyst to alter the barrier of proton-coupled electron transfer to the surface bound adsorbate.