Sonakshi Saini
(Advisor: Prof. Matthew T. McDowell)

will propose a doctoral thesis entitled,

Investigating the Effect of Catalyst Parameters and Impurity Interactions on Electrolysis Reactions for Direct Seawater Splitting 

On 

Monday, March 10, 2025 from 10am - 12pm 

In

MRDC Room 3515
or virtually via Teams: 

Join the meeting now

Meeting ID: 220 947 435 868
Passcode: DW6SN7Cc

Committee:

Prof. Matthew McDowell - School of Materials Science and Engineering (advisor)

Prof. Juan Pablo Correa-Baena - School of Materials Science and Engineering

Prof. Ryan Lively - School of Chemical and Biomolecular Engineering

Prof. Guoxiang (Emma) Hu - School of Materials Science and Engineering

Prof. Erin Ratcliff - School of Materials Science and Engineering

Abstract

Seawater splitting has been put forward as a cost-effective means of producing green hydrogen by eliminating additional costs associated with water purification. One of the most important considerations to successfully implement seawater splitting is to take into account the effect of impurities in seawater, and how they may impact the functioning of an electrolyzer. In this dissertation, I will investigate the effect of certain metal ions as a source of impurity on catalyst materials to study the effect on the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER).

Previously, I demonstrated that copper ions can have significant effects on catalyst operation and HER, even at the relatively low concentration in which they are present in seawater. In particular, understanding how the dynamic deposition of Cu from electrolytes with different concentrations influences HER on various electrocatalyst materials may further be used to understand the behavior of other ionic impurities on electrolyzer behavior. By combining electrochemical techniques and characterization tools including scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS), the competition between copper deposition and HER was studied.

For further proposed work, I will be using in situ AFM to study the process of nucleation and growth of copper impurities in the early stages and how it varies with increasing time of applied potential. I will also study whether this process is dependent on the nature of the electrocatalyst in terms of activity, conducting nature, and lattice mismatch with copper by studying a few different substrates (platinum, gold, graphene, and hexagonal boron nitride), by performing quantitative analyses to get plots of nucleation rate and activation energy with varying concentration and voltage holds to correlate the values obtained from these plots for a substrate with their individual mentioned characteristics. Finally, by applying what I have learned from the first two objectives about impurity deposition interfering with fuel-producing reactions, in the last objective I will be studying this effect on the more complex reaction occurring in water splitting – oxygen evolution reaction (OER). The goal here is to investigate how different metal ion impurities in seawater can affect the structure and performance of nickel (Ni)-based catalyst films for OER. I will compare Ni and some Ni alloy catalyst films (including cobalt and iron) as well as some graphene on Ni foam electrodes for observed structural and performance changes in the presence of silver, copper, nickel, and zinc cations. These are chosen due to their concentration in seawater as well as reduction potentials that can potentially affect OER. Similarly to the above objectives, I will conduct these studies by using electrochemical tests and a variety of ex situ (SEM, XPS) and in situ techniques (AFM, XRD).