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A D V A N C E D
M A T E R I A L S
&
P R O C E S S E S |
M A R C H
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EMERGING TECHNOLOGY
CARBON-BASED CATALYST
DECODED
Carbon-based catalysts with add-
ed nitrogen are among the most prom-
ising alternatives to the expensive
precious metals currently used for oxy-
gen reduction in fuel cells. A team of re-
searchers from the University of Tsuku-
ba, Japan, identified the arrangement
of nitrogen and carbon that provides
the catalytic effect in these materials,
and proposed a mechanism by which
the reaction works.
To determine whether the nitro-
gen in the carbon-based catalyst was
pyridinic or graphitic—a question unan-
swered until now—the team fabricated
four model catalyst substrates and an-
alyzed their reaction performance. Be-
cause pyridinic nitrogen occurs mainly
at the edges of the material, the team
manipulated the number of edges on
the samples to adjust these nitrogen
levels, then measured how it affected
catalytic performance. The results? Ac-
tive catalytic sites were associated with
pyridinic nitrogen. After learning that
it was actually the carbon atom next
to the nitrogen that was the active site
rather than the nitrogen atom itself,
investigators were able to hypothesize
the various stages of the reactionmech-
anism. This will enable future research
to focus on ratcheting up catalyst per-
formance. .
BATTERY HEATS UP,
DOESN’T POWER DOWN
Researchers at Pennsylvania State
University, University Park, Pa., and EC
Power, State College, Pa., developed a
lithium-ion battery that self-heats if the
temperature is below 32°F. The most
Patterning nitrogen-doped graphite to create multiple edges increases the amount of
pyridinic nitrogen present. Courtesy of University of Tsukuba.
BRIEF
Scientists at the Energy Department’s National Renewable Energy Laboratory (NREL) and the Swiss Center for
Electronics and Microtechnology (CSEM) jointly set a new world record for converting non-concentrated sunlight
into electricity using a dual-junction III-V/Si solar cell. The team achieved conversion efficiency of 29.8% by using a
top cell made of gallium indium phosphide developed by NREL, and a bottom cell made of crystalline silicon devel-
oped by CSEM using silicon heterojunction technology. .
ENER Y TRE DS
significant impact of this technology
could be reducing winter “range anxi-
ety” for electric vehicle owners—one of
the major barriers to large-scale adop-
tion of all-electric cars.
At below-freezing temperatures,
conventional batteries suffer severe
power loss, leading to slow charging,
restricted regenerative breaking, and
reduction of cruise range by as much as
40%. Larger battery packs, which could
supply adequate power in the cold, are
significantly heavier and more expen-
sive. The all-climate battery, however, is
designed to weigh only 1.5% more and
cost just 0.04% of the base battery. It can
heat from22°F to 32°F in 30 seconds, con-
suming only 5.5% of the cell’s capacity.
In the all-climate battery, one end
of a 50- μm-thick nickel foil is attached
to the negative terminal while the other
end extends outside the cell, creating
a third terminal. A temperature sensor
attached to a switch causes electrons
to flow through the nickel foil when it is
cold, completing the circuit and rapid-
ly warming the foil through resistance
heating. Once the battery reaches 32°F,
the switch turns off, and electric current
flows normally. .
An all-climate battery that rapidly self-
heats battery materials and electrochem-
ical interfaces in cold environments.
Courtesy of Chao-Yang Wang/Penn State.