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Michigan
State
University
Science
at
the
Edge
Engineering
Seminar
September
30th,
2016
11:30 a.m.
Room1400 Biomedical
and Physical
Sciences
Building
Refreshments served
at
11:15 a.m.
Professor
Nathan.
S. Lewis
California
Institute
of Technology
Division
of Chemistry
and Chemical Engineering
Beckman
Institute and
Kavli
Nanoscience
Institute
Sunlight-Driven
Hydrogen
Formation
by
Membrane-Supported
Photoelectrochemical
Water
Splitting
Abstract
We
are
developing
an
artificial
photosynthetic
system
that will
utilize
sunlight
and
water
as inputs
and
will produce
hydrogen
and
oxygen
as
outputs
using a modular,
parallel
development
approach
in which
the
three
distinct
primary
components-the
photoanode,
the photocathode,
and the
product-separating
but
ion-conducting membrane-are
fabricated
and
optimized
separately before
assembly
into
a water-splitting
system.
The
design
principles
incorporate
two separate,
photosensitive
semiconductor/liquid
junctions that
will collectively
generate
the 1.7-1.9
V at
open
circuit
to support both
the oxidation
of H2O
(or OH-)
and
the reduction
of H+
(or
H2O).
The photoanode and
photocathode will
consist
of rod-like semiconductor
components,
with attached heterogeneous
multi-electron
transfer
catalysts,
needed
to drive the oxidation
or reduction reactions
at
low overpotentials.
The
high
aspect-ratio
semiconductor
rod electrode
architecture
allows
for the
use of
low
cost,
earth
abundant
materials
without sacrificing
energy
conversion
efficiency due
to
orthogonalization
of light
absorption
and
charge-carrier
collection. Additionally,
the high
surface-area
design
of the
rod-based
semiconductor
array
electrode inherently lowers
the flux
of charge
carriers
over
the rod
array
surface
relative
to the
projected
geometric
surface
of the
photoelectrode,
lowering
the photocurrent
density
at
the solid/liquid junction and thereby
relaxing
demands on the
activity
(and
cost)
of any
electrocatalysts.
Flexible
composite
polymer
film will
allow
for electron
and
ion conduction
between
the photoanode
and photocathode
while
simultaneously
preventing
mixing
of
the gaseous
products.
Separate
polymeric
materials
will be used to
make electrical
contact
between
the anode
and
cathode
and
also provide
structural
support.
Interspersed
patches
of an
ion conducting
polymer
will maintain
charge
balance
between
the two
half-cells.
The
modularity design
approach
allows
each
piece
to be independently modified,
tested,
and
improved,
as
future
advances
in semiconductor, polymeric,
and
catalytic
materials
are
made.
This
work
will demonstrate
a feasible
and functional
prototype
and
blueprint
for an
artificial
photosynthetic system,
composed
of inexpensive,
earth-abundant
materials
while simultaneously
efficient,
durable,
manufacturably scalable,
and
readily
upgradeable.
Shawna Prater / Secretary
Astrophysics Group
Michigan State University
567 Wilson Road, Room 3261
Biomedical Physical Sciences Bldg
East Lansing, MI 48824-2320
Ph: (517) 884-5601 Fax (517) 432-8802
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