(6gz) 3D, Self-Assembled, Membrane-Electrode Assemblies for Advanced Electrochemical Devices

3D, Self-Assembled, Membrane-Electrode
Assemblies for Advanced Electrochemical Devices

Samuel St. John, University of Tennessee

sstjohn1@utk.edu

2^nd
Year Postdoctoral Fellow

Research
Interests

I am interested in
self-assembled anion exchange membranes, meso-structured electrodes, and
alkaline electrocatalysis for electrochemical devices (e.g., fuel cells and
batteries). In general, the area-specific resistance, reactant crossover, and cell
performance are closely related to ion transport across the membrane/catalyst
layer interface and within the membrane electrode assembly. Understanding
electrocatalysis and transport within structured membrane/electrode assemblies
and controlling that transport is the key to realizing high-current-density
devices. The research questions I explore will enable rationally designed
architectures in membranes, electrodes, and their interfaces. Science teaches
us that nature uses hierarchical approaches to overcome the challenge of
assembly across many length-scales. Such a foundational approach underpins the
primary methods I use in my research, which include: self-assembly of
phase-segregated block copolymer membranes; layer-by-layer assembly of blended
membrane/electrode interfaces; and chemical-vapor impregnation of catalysts
onto fully formed electrode supports. This research is well-funded by the NSF
CBET division and the DOE BES program and will result in an outstanding record
of publications, educate many PhD students, and advance the reputation of my
future department.

Proposal
Writing Experience

Funded (Written by S. St.
John):

  -  Graduate
School Distinguished Dissertation Fellowship, University of Cincinnati

Funded (Contributed to by
S. St. John as a graduate student):

  -  NSF
DMR-1410118 Investigator: Angelopoulos, Anastasios: NSF SusChEM:
Sustainable Synthesis of Bismuth-Based Core-Shell Nanoparticles for Alternative
Energy Applications

Contributed to 13
additional unfunded NSF, DOE, and ACS grant applications

Postdoctoral
Project

Alkaline Electrocatalysis
in Anion Exchange Fuel Cells and Batteries

Advisor: Dr. Thomas A.
Zawodzinski, Jr., University of Tennessee

PhD
Dissertation

Hierarchical
Electrocatalyst Structure Control to Study Cathodic and Anodic Overpotential in
Proton Exchange Membrane Fuel Cells

Advisor: Dr. Anastasios
P. Angelopoulos, University of Cincinnati

Research
Experience

My doctoral work focused
on oxygen reduction and ethanol oxidation electrocatalysts, which are critical
to the commercialization of proton exchange membrane fuel cells. By developing
a nanoparticle preparation method that allowed me to study the structure of the
electrocatalyst surface during use, I revealed an unexpected relationship
between catalyst geometry and activity that depended upon the proportion of
stepped surface active sites. These promising results led me to investigate the
ligand-mediated nanoparticle growth mechanism, equilibrated particle size, and
the strength of the metal-ligand interaction using a suite of spectroscopic
techniques. I plan to apply similar methods to investigate the interaction of
ligands with metal electrocatalysts and the binding energy of active
intermediates (e.g., H and OH) during electrode polarization, the understanding
of which is central to my current electrocatalysis research.

My present collaborative
research focuses on catalysis and transport in anion exchange membrane fuel
cells (AEMFCs). These devices are receiving renewed interest because of recent
advances in anion exchange polymer membrane conductivity and stability that
offer the possibility to dramatically reduce the noble metal (Pt) and specialty
polymer (Nafion) content. Identifying suitable alternative hydrogen oxidation
reaction (HOR) catalysts in alkaline pH is foundational for the technological
promise of AEMFCs to be fulfilled. My colleagues and I have just prepared a
paper demonstrating the critical understanding of alkaline HOR needed to
develop low-cost AEMFC anodes. Additionally, I am involved in understanding and
manipulating the structure of a new class of membranes with exceptional
hydroxide conductivity, how this transport correlates with aqueous domain size,
and how directly manipulating the membrane-electrode interface influences
transport across said interface.

Teaching
Experience

I have a robust portfolio of teaching experience. I taught
Material and Energy Balances at the University of Cincinnati and can provide a
detailed teaching evaluation and student feedback. Additionally, I have
experience mentoring both graduate and undergraduate students as a
post-doctoral scholar, graduate student, and employee at The Procter &
Gamble Company. It
is my desire to use my students' own experiences to help them develop an
intuition for chemical engineering concepts, the mastery of which will be
important for making connections between curriculum and contemporary scientific
pursuits in the world at large. My time in academia and industry have taught me
that mastery of chemical engineering concepts in the context of contemporary
challenges is the key to being a successful engineer. My primary teaching
interests include undergraduate courses in all of the transport phenomena,
material and energy balances, as well as reactor engineering. I would be happy
teaching professional development and/or toolkit (e.g., engineering data
analysis with Matlab) courses for graduate students in addition to graduate
transport phenomena, reaction engineering, and electrochemical engineering.

Future
Direction

My research direction seeks
a fundamental understanding of material properties and how they to
electrocatalysis and transport in membrane-electrode assemblies (MEAs). More
broadly, however, ion-conducting membranes are central the to performance of
electrochemical devices and play a large role in technologies related to the
water-energy nexus, e.g., electrodialysis for water purification. I envision
that structured membrane synthesis will lead to the development and
commercialization of thin, durable, and stable structures for these
applications. Block copolymerization is a flexible chemistry for the
development or ordered, self-assembled membranes with tailored material
properties. By precisely understanding the polymerization and membrane
self-assembly conditions, I hypothesize that it is possible to design membranes
and membrane interfaces for a variety of specific applications. This is one
example of how fundamental understanding of structure-property relationships in
electrochemical devices will lead to high impact science across a number of
important technologies.

Selected
Publications

  -  S St. John, RW Atkinson, III, RR
Unocic, AB Papandrew, and TA Zawodzinski. Ruthenium- alloy electrocatalysts
with tunable hydrogen oxidation kinetics in alkaline electrolyte. J. Phys.
Chem. C, Accepted, 2015

  -  S St. John, P Boolchand, and AP
Angelopoulos. Improved electrocatalytic ethanol oxidation activity in acidic
and alkaline electrolytes using size-controlled Pt-Sn nanoparticles. Langmuir,
29:16150-16159, 2013.

  -  S St. John and AP Angelopoulos.
In-situ adatom analysis of optimum surface atom coordination for Pt
nanoparticle oxygen reduction electrocatalysts. Electrochim. Acta,
112:258-268, 2013.

  -  S St. John, Z Nan, N Hu, DW
Schaefer, and AP Angelopoulos. A nanoscale-modified LaMer model for particle
synthesis from inorganic tin-platinum complexes. J. Mater. Chem. A,
1(31):8903-8916, 2013.

  -  S St. John, N Hu, DW Schaefer, and
AP Angelopoulos. Time-resolved, in situ, small- and wide-angle x-ray scattering
to monitor Pt nanoparticle structure evolution stabilized by adsorbed SnCl3^– ligands during synthesis.
J. Phys. Chem. C, 117(15):7924-7933, 2013.

  -  P Turner, L Petzold, A Shiflet, I Vakalis, K
Jordan and S St. John. Undergraduate computational science and
engineering education. SIAM Review, 53(3):561, 2011.

  -  S St. John, I Dutta, and AP
Angelopoulos. Enhanced electrocatalytic oxygen reduction reaction activity
through electrostatic assembly of Pt nanoparticles onto porous carbon supports
from SnCl2-stabilized suspensions. Langmuir,
27(10):5781-5791, 2011.

  -  S St. John, D Lee*, I Dutta, and AP
Angelopoulos. Acceleration of electrocatalytic activity on Pt–Sn
nanoparticles. J. Electrochem. Soc., 157(8):B1245–B1250, 2010.

  -  S St. John, I Dutta, and AP
Angelopoulos. Synthesis and characterization of electrocatalytically active
platinum atom clusters and monodisperse single crystals. J. Phys. Chem. C,
114(32):13515–13525, 2010.