(327d) Colloidal Nanocrystals As Building Blocks for Electrocatalysis

Colloidal nanocrystals as building blocks for
electrocatalysis

Molly Jhong, Delia Milliron

McKetta Department of Chemical Engineering,
University of Texas at Austin

Email:
mollyjhong@utexas.edu

Catalysts plays a vital role in heterogeneous electrochemical
reactions for energy conversion, energy storage, and chemical synthesis.  For
example, the widespread commercialization of polymer-electrolyte membrane fuel
cells (PEMFCs) has been limited by the cathodic oxygen reduction reaction (ORR)
which requires high loadings of expensive platinum (Pt) catalyst to achieve
performance benchmarks.  Furthermore, the development of economically-feasible
electrochemical reactors to convert molecules in the atmosphere (e.g., water,
carbon dioxide, and nitrogen) into value-added compounds (e.g., hydrogen,
hydrocarbons, and ammonia) using renewable electricity requires the advent of
catalytic material with high activity and selectivity.[1]  Electrocatalysts
are needed in these energy conversion processes because they bind and activate
the reactant molecules in order to reduce the high energy barriers
(overpotentials) typically encountered.  Also, electrocatalysts can drive
selective formation of desired products through engineering their structure and
composition in order to facilitate the adsorption or desorption of key reaction
intermediates.  While significant research efforts have focused on catalyst discovery
and development, today’s electrocatalysts are still inadequate.  Developing an
improved understanding of how size, shape, and composition of nanoscale
materials impacts the catalytic activity and selectivity is often key to
enhancing overall performance of the electrochemical process, which is needed
for widespread penetration of clean energy technologies.

Over the past two decades, recent advances in colloidal nanocrystal
synthesis of metals and metal oxides have led to the precise control over size,
shape, uniformity, and even composition of the nanocrystals.[2]  This control is realized experimentally through tuning macroscopic
thermodynamic parameters (temperature and concentration), coupled with
microscopic chemical considerations (precursor activities and ligand binding
strengths).  These synthetic techniques are now well-suited to prepare
catalytic materials that allow for detailed studies of the structure-property
relationships in an electrochemical process.

This paper will report some of my recent efforts to understand and
improve catalysts based on colloidal nanocrystals for two electrochemical
reactions: (1) electrochemical reduction of CO₂ (CO₂RR)
and (2) oxygen reduction reaction (ORR) in fuel cells.  Together, these studies
will showcase the opportunities and remaining challenges of using colloidal
nanocrystals as building blocks for electrocatalysis.

References:

1.           Seh,
Z.W., et al., Combining theory and experiment in electrocatalysis: Insights
into materials design. Science, 2017. 355(6321): p. eaad4998.

2.           Agrawal,
A., et al., Localized Surface Plasmon Resonance in Semiconductor
Nanocrystals. Chemical Reviews, 2018. 118(6): p. 3121-3207.