SusChEM: Studying Catalysts and Reaction
Intermediates for Water Oxidation by Spectroscopy of
Cryogenic Ions
Overview
The
Weber group will investigate the electronic and
geometric structures of selected ruthenium- and
copper-based catalysts for water oxidation, as well as
of reaction intermediates in the catalytic cycle. Ions
of catalysts and reaction intermediates are
transferred into the gas phase by electrospray
ionization. The ions are cooled in an ion trap, mass
selected and irradiated by pulsed light, which is
tunable throughout the mid-infrared, visible and
near-ultraviolet spectrum. Photon absorption is
monitored by photofragmentation of the target ions,
allowing the measurement of their vibrational and
electronic spectra. Cooling the ions to low
temperatures is crucial to obtain the necessary
spectroscopic detail. Vibrational spectra will result
in structural information on the ions under study,
which is particularly important for reaction
intermediates. Measuring the electronic spectra of
catalysts and reaction intermediates will aid
clarification of speciation in reactive solutions. In
addition, the excited state vibrational structure will
help modeling excited state dynamics and reactivity.
Intellectual
Merit
The
generation of a sustainable energy economy is one of
the most important technological advances to be
attained in the next decades. One of the most
promising avenues towards this goal is the
electrochemical or photoelectrochemical conversion of
carbon dioxide and water into chemically useable
fuels. For this process to be economically viable,
catalysts for the multielectron/multiproton redox
chemistry need to be developed. In many approaches to
this problem, catalytic water oxidation is used to
supply the electrons and protons needed for solar fuel
generation. However, the molecular-level mechanisms
involving the different steps in the catalytic cycle
are often poorly understood, hindering the rational
design of such catalysts.
One
of the main problems on the road to understanding the
mechanisms underlying these catalytic processes is
that many different species are present in reactive
solutions, making condensed phase identification and
study of key molecules and reaction intermediates very
difficult. Since homogeneous catalysts and reaction
intermediates in water oxidation catalysis are often
ions, an elegant way to circumvent this issue is to
selectively prepare and study the species of interest
in the gas phase. Mass spectrometric preparation of
ions from solutions in concert with laser spectroscopy
is a powerful approach to do this.
Broader
Impacts:
The
chemistry explored in the proposed work will be of
considerable benefit to many areas of science,
particularly to chemical energy science and chemical
engineering. Under the assumption that many areas of
technology will continue to depend on the use of
carbon based chemical fuels for the foreseeable
future, environmental as well as economic and
geopolitical pressures call for the development of
fuel sources independent from fossil fuels. The
understanding of the reactions at play in solar fuels
catalysis will aid in the development of new catalysts
for the generation of chemical fuels from sustainable
sources.
Additionally,
the proposed work has important educational aspects.
In addition to the laboratory research, an educational
JAVA applet will be developed to enhance student
understanding of the quantum mechanical treatment of
angular momentum. The experiments, computational
research and the JAVA applet development will be
carried out by graduate student researchers. This will
contribute to the education of the next generation of
scientists who will be trained in a broad range of
laboratory techniques as well as interactive teaching
technology.
The
PI will be involved in the enormously successful CU
Wizards outreach program. This is a continuing
Saturday morning lecture series that treats topics in
astronomy, chemistry, engineering, and physics, and is
intended primarily for students in grades five through
nine. The PI contributes an interactive lecture to
this series with many experimental demonstrations,
introducing the audience to the world of buoyancy and
water displacement.