Research

Oxidative Molecular Layer Deposition

Controlled Molecular Assembly

Electrically-conductive and redox-active polymers such as polyethylenedioxythiophene, polyaniline, and polypyrrole can be used for electrochemical water desalination, chemical sensing, and energy storage applications. However, conventional synthesis techniques for this class of polymers provide limited control over the local polymer structure. Our group is working to understand and control the electrochemical properties of these polymers through controlled molecular assembly. (See e.g. doi: 10.1021/acsapm.2c00942 and doi: 10.1021/acs.chemmater.2c02923) Moving forward, our focus is to leverage this precision synthesis to understand how the local molecular structure of these polymers impacts electrochemical properties including electron transport, ion transport, and redox-activity.

Cryogenic Electron Diffraction to Measure Atomic Structure

Raw diffraction data (a) and Pair Distribution Functions (b,c) used to derive atomic structure

Measuring the atomic structure of amorphous interfaces promises to help us understand the behavior of materials in semiconductor devices, catalysts, batteries, and other applications. Our recent work has focused on understanding the atomic structure of amorphous materials deposited by atomic layer deposition (ALD) as model systems. Atomic layer deposition (ALD) provides uniform and conformal thin films that are of interest for a range of applications. Initial work demonstrated measurement of how the local atomic structure of ALD-grown aluminum oxide (AlOx) evolves in operando during growth by employing synchrotron high-energy X-ray diffraction (HE-XRD) (doi: 10.1021/acsami.0c01905) In more recent work, we report on efforts to employ electron diffraction pair distribution function (ePDF) measurements using more broadly available transmission electron microscope (TEM) instrumentation (doi: 10.1021/acsomega.0c06124 and doi: 10.1021/acsanm.2c02312). For more information on these efforts, see: From the Noise - Measuring the Atomic Structure in Amorphous Thin Films Grown By Atomic Layer Deposition - 6/18/2020.

Concept for electrode design to study origins of energetic limits in CDI

Compressible Electrode Formed by oMLD of PEDOT

Current seawater desalination technology is energy-intensive and costly, limiting our ability to generate clean water for an increasing global population. In recent years, researchers have explored a new concept based on the removal of salt from seawater using a battery-like device where salt water flows into the device, salt ions bind to electrodes within the device, and fresh water flows out. One would expect this technology, called capacitive deionization (CDI), to maximize the energy efficiency of desalination by recovering input energy through discharge of the electrodes—similar to charging and discharging a battery. However, the performance of CDI devices has not yet been competitive for seawater desalination. We are working to understand the origins of the poor performance of CDI electrodes for seawater desalination and overcome these limitations to boost the energy efficiency of CDI. To accomplish this, we aim to decouple and independently study the two main factors thought to drive CDI inefficiency – low ion uptake capacity and slow ion transport within CDI electrodes. The outcomes of this project will define the most promising avenues for investigation in pursuit of the next generation of desalination technology.

Need novel materials for improved nitrate sensing

Multimodal electrochemical cell to understand materials behavior

Each year over $100 million worth of nitrogen fertilizer is lost to water runoff in Missouri and collects in Missouri water resources, causing harmful algal blooms that damage the environment and leading to economic losses to waterfront communities. In order to mitigate these harmful effects, we need to better understand how nitrogen from fertilizer is lost and transported in the environment. Conventional methods for detecting nitrogen in water or soil samples rely on slow and costly laboratory measurements, most commonly liquid chromatography-mass spectrometry (LC-MS) methods. The sparse data from these measurements cannot provide a clear picture of how nitrogen moves through the environment. We aim to develop low-cost and high accuracy nitrogen sensors based on electrically-conducting polymer thin films. The goal is to enable real-time distributed monitoring of nitrate in the environment in line with efforts such as EARTHDATA from NASA. These polymer films must be stable in the environment to be used in sensors. Recent work (doi: 10.1063/5.0035309) has established a multimodal tool to measure the degradation of polymers in real-time and inform changes to the polymers for improved stability. For more information on these efforts, see: MOWRRC Seminar - 4/30/2021.